Polypropylene for additive manufacturing

Abstract

Disclosed are methods of additive manufacturing comprising polypropylene, as well as compositions prepared using the methods.

Description

[0001] Cross-reference

[0002] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 428,515, filed on November 29, 2022, entitled "Polypropylenes for Additive Manufacturing", the content of which is incorporated herein by reference in its entirety. Background of the Invention

[0003] A. Field of the Technology

[0004] The present invention generally relates at least to methods of additive manufacturing that include polypropylene, and to compositions that include the polypropylene.

[0005] B. Background Art

[0006] Polypropylene is used in a number of industries. For example, polypropylene-containing compositions are used for packaging of consumer products, plastic parts in various industries including electrical, equipment manufacturing, and motor vehicle industries, household appliances, special equipment such as living hinges, and fabrics. In some applications such as food storage containers, cups, lids, etc., it is desirable for the manufactured products made of polypropylene to have good transparency.

[0007] Typical methods of manufacturing such manufactured articles include: thermoforming an extruded polypropylene sheet within a tool to form a thermoformed article. Typically, after the thermoforming process, a portion of the extruded sheet is removed from the tool to form the final product. Other portions (such as the non-removed portions) can be recycled and extruded again to form additional extruded sheets to avoid waste. However, such traditional methods can result in excessive waste (materials and / or energy), and / or require thermoforming casting. Alternative manufacturing methods are needed to produce products made of polypropylene.

[0008] One such alternative manufacturing method involves additive manufacturing (AM), also known as 3-D printing (these terms are used interchangeably herein). Compared to traditional manufacturing means, the benefits of additive manufacturing can include: lower energy consumption, reduced waste, manufacturing flexibility, and / or better inventory management. However, polypropylene has not been effectively utilized in additive manufacturing processes.

[0009] Problems associated with producing polypropylene-based products using additive manufacturing can include: insufficient weld line strength, weak mechanical properties, sagging, poor surface properties / textured, porosity, shrinkage, warping, and / or debonding. Summary of the Invention

[0010] Discoveries have been made that provide solutions for at least some of the above problems.

[0011] In some embodiments, additively manufactured articles are provided herein that comprise one or more polypropylenes (PPs) having one or more of the following properties: a) a melt temperature ≤ 135 °C, measured according to ASTM D3418-15; b) an onset melt temperature ≤ 125 °C, measured according to ASTM D3418-15; c) an onset crystallization temperature ≤ 105 °C, measured according to ASTM D3418-15; d) a crystallinity ≤ 35%, measured according to ASTM D3418-15; e) an Avrami exponent ≤ 2.10; f) an absolute value of the crystallization activation energy ≤ 550,000 J / mol, determined by Avrami kinetics fitting; and / or g) an absolute value of the crystallization activation energy is less than or equal to 80% of the absolute value of the crystallization activation energy of an un-nucleated Ziegler-Natta homopolymer polypropylene.

[0012] In some embodiments, additively manufactured articles comprise one or more PPs having one or more of the following characteristics: a) a melt temperature ≤ 130 °C, measured according to ASTM D3418-15; b) an onset melt temperature ≤ 120 °C, measured according to ASTM D3418-15; c) an onset crystallization temperature ≤ 100 °C, measured according to ASTM D3418-15; d) a crystallinity ≤ 30%, measured according to ASTM D3418-15; e) an Avrami exponent ≤ 2.05; f) an absolute value of the crystallization activation energy ≤ 500,000 J / mol, determined by Avrami kinetics fitting; and / or g) an absolute value of the crystallization activation energy is less than or equal to 75% of the absolute value of the crystallization activation energy of an un-nucleated Ziegler-Natta homopolymer polypropylene.

[0013] In some embodiments, additively manufactured articles comprise one or more PPs having at least two of the following characteristics: a) a melt temperature ≤ 135 °C, or ≤ 130 °C, measured according to ASTM D3418-15; b) an onset melt temperature ≤ 125 °C, or ≤ 120 °C, measured according to ASTM D3418-15; c) an onset crystallization temperature ≤ 105 °C, or ≤ 100 °C, measured according to ASTM D3418-15; and / or d) a crystallinity ≤ 35%, or ≤ 30%, measured according to ASTM D3418-15.

[0014] In some embodiments, an additively manufactured article comprises at least one polypropylene, the at least one polypropylene being a Ziegler-Natta based random copolymer, a metallocene random copolymer, and / or a syndiotactic polypropylene, and optionally further comprises at least one additive, wherein the additive comprises: silica, antistatic agent, colorant, corrosion inhibitor, antioxidant, acid neutralizer, anti-caking agent, anti-fogging agent, clarifying agent, ultraviolet absorber, lubricant, plasticizer, mineral oil, wax, clay, talc, calcium carbonate, diatomaceous earth, carbon black, mica, glass fiber, filler, slip agent, colorant, ultraviolet stabilizer and / or tolerance agent, flame retardant, release agent, dye, foaming agent, fluorescent agent, surfactant, oil, neutralizer, flow modifier, processing aid, reinforcing agent, stabilizer, impact modifier, nucleating agent, crystallization aid, additional polymer, or any combination thereof.

[0015] In some embodiments, the absolute value of the crystallization activation energy of the at least one PP is between about 300,000 J / mol and about 500,000 J / mol, determined by combining an isothermal differential scanning calorimetry (DSC) test according to ASTM D3418-15 with Avrami kinetics. In some embodiments, the crystallinity of the at least one PP is 35% to 15%, based on a heat of fusion (ΔH 0m ) of 207 J / g for theoretically 100% crystalline polypropylene. In some embodiments, the sintering window of the at least one PP is 30 °C or lower, defined by the onset melting and crystallization temperatures. In some embodiments, the sintering window of the at least one PP is 18 °C to 30 °C. In some embodiments, the density of the at least one PP is 0.8 g / cc to 1 g / cc, measured according to ASTM D1505-18, and / or the melt flow rate (MFR) is 0.1 g / 10 min to 100.0 g / 10 min, measured according to ASTM D1238-20. In some embodiments, the melt flow of the at least one PP is 0.5 g / 10 min to 30 g / min, measured according to ASTM D1238-20.

[0016] In some embodiments, methods of manufacturing additively manufactured articles are disclosed herein, the methods comprising: melting and / or sintering a composition comprising the one or more PPs. In some embodiments, the at least one polypropylene is a Ziegler-Natta based random copolymer, a metallocene random copolymer, and / or a syndiotactic polypropylene, and optionally further comprises at least one additive, wherein the additive comprises: silica, antistatic agent, colorant, corrosion inhibitor, antioxidant, acid neutralizer, anti-caking agent, anti-fogging agent, clarifying agent, UV absorber, lubricant, plasticizer, mineral oil, wax, clay, talc, calcium carbonate, diatomaceous earth, carbon black, mica, glass fiber, filler, slip agent, colorant, UV stabilizer and / or tolerance agent, flame retardant, release agent, dye, foaming agent, fluorescent agent, surfactant, oil, neutralizer, flow modifier, processing aid, reinforcing agent, stabilizer, impact modifier, nucleating agent, crystallization aid, additional polymer, or any combination thereof. In some embodiments, the article is made by sintering particulate matter in the form of PP having an average particle size of 1 μm to 500 μm. In some embodiments, the average particle size of the particulate matter is 15 μm to 100 μm. In some embodiments, the method comprises material extrusion, wherein the composition in a molten state is extruded through a nozzle and deposited in layers. In some embodiments, the method comprises: sintering particulate composition particles in the form of particulate matter in a powder bed sintering (PBS) process. In some embodiments, the PBS process uses a layer thickness of 10 μm to 200 μm, and / or a part bed temperature of 20 °C to 100 °C. In some embodiments, the PBS process uses a layer thickness of 30 μm to 150 μm.

[0017] Also disclosed herein is an article of manufacture comprising an additively manufactured article made by any of the methods described herein. In some embodiments, the article is a motor vehicle part, a building material part, an insulation part, an electronic instrument part, a furniture part, a fabric part, a container part, a household appliance part, a medical part, a prosthesis, a filter medium, and / or a customized toy.

[0018] Also disclosed herein are compositions for additive manufacturing, wherein the compositions comprise at least one polypropylene (PP) and are in contact with at least one component designed to be used in a 3D printer, and wherein the PP comprises one or more of the following properties: a) a melting temperature ≤ 135 °C, measured according to ASTM D3418-15; b) an onset melting temperature ≤ 125 °C, measured according to ASTM D3418-15; c) an onset crystallization temperature ≤ 105 °C, measured according to ASTM D3418-15; d) a crystallinity ≤ 35%, measured according to ASTM D3418-15; e) an Avrami exponent ≤ 2.10; f) an absolute value of the crystallization activation energy ≤ 550,000 J / mol, determined by Avrami kinetics fitting; and / or g) an absolute value of the crystallization activation energy is less than or equal to 80% of the absolute value of the crystallization activation energy of an un-nucleated Ziegler-Natta homopolymer polypropylene.

[0019] In some embodiments, the composition for additive manufacturing comprises at least one PP in contact with at least one component designed to be used in a 3D printer, and the composition comprises one or more PPs having one or more of the following characteristics: a) a melting temperature ≤ 130 °C, measured according to ASTM D3418-15; b) an onset melting temperature ≤ 120 °C, measured according to ASTM D3418-15; c) an onset crystallization temperature ≤ 100 °C, measured according to ASTM D3418-15; g) a crystallinity ≤ 30%, measured according to ASTM D3418-15; d) an Avrami exponent ≤ 2.05; e) an absolute value of the crystallization activation energy ≤ 500,000 J / mol, determined by Avrami kinetics fitting; and / or f) an absolute value of the crystallization activation energy is less than or equal to 75% of the absolute value of the crystallization activation energy of an un-nucleated Ziegler-Natta homopolymer polypropylene.

[0020] In some embodiments, the composition for additive manufacturing comprises at least one PP in contact with at least one component designed to be used in a 3D printer, and the composition comprises one or more PPs having at least two of the following characteristics: a) a melting temperature ≤ 135 °C, or ≤ 130 °C, measured according to ASTM D3418-15; b) an onset melting temperature ≤ 125 °C, or ≤ 120 °C, measured according to ASTM D3418-15; c) an onset crystallization temperature ≤ 105 °C, or ≤ 100 °C, measured according to ASTM D3418-15; and / or d) a crystallinity ≤ 35%, or ≤ 30%, measured according to ASTM D3418-15.

[0021] In some embodiments, the at least one PP is a Ziegler-Natta based random copolymer, a metallocene random copolymer, and / or a syndiotactic PP, and optionally further comprises at least one additive, wherein the additive comprises: silica, antistatic agent, colorant, corrosion inhibitor, antioxidant, acid neutralizer, anti-caking agent, anti-fogging agent, clarifying agent, ultraviolet absorber, lubricant, plasticizer, mineral oil, wax, clay, talc, calcium carbonate, diatomaceous earth, carbon black, mica, glass fiber, filler, slip agent, colorant, ultraviolet stabilizer and / or tolerance agent, flame retardant, mold release agent, dye, foaming agent, fluorescent agent, surfactant, oil, neutralizer, flow modifier, processing aid, reinforcing agent, stabilizer, impact modifier, nucleating agent, crystallization aid, additional polymer, or any combination thereof. In some embodiments, the composition for additive manufacturing comprises at least 95 wt% of at least one PP. In some embodiments, the PP is in contact with: a 0.4 mm extruder nozzle, a 0.35 mm extruder nozzle, a build plate, and / or a heated bed. In some embodiments, the absolute value of the crystallization activation energy of the PP is between about 300,000 J / mol and about 500,000 J / mol, determined by combining an isothermal differential scanning calorimetry (DSC) test according to ASTM D3418-15 with Avrami kinetics. In some embodiments, the crystallinity of the PP is 35% to 15%, based on the heat of fusion (ΔH 0m ) of 207 J / g for theoretically 100% crystalline polypropylene. In some embodiments, the sintering window of the PP is 30 °C or lower, defined by the onset melting and crystallization temperatures. In some embodiments, the sintering window of the PP is 18 °C to 30 °C. In some embodiments, the density of the PP is 0.8 g / cc to 1 g / cc, measured according to ASTM D1505-18, and / or the melt flow is 0.1 g / 10 min to 100 g / 10 min, measured according to ASTM D1238-20. In some embodiments, the melt flow of the PP is 0.5 g / 10 min to 30 g / 10 min. In some embodiments, the PP is in the form of granules with an average particle size of 1 μm to 500 μm. In some embodiments, the average particle size of the granules is 15 μm to 100 μm.

[0022] Other embodiments of the present invention are also discussed in this application. Any embodiment discussed in one aspect of the present invention is applicable to other aspects of the present invention, and vice versa. Each embodiment described herein is understood to be an embodiment of the present invention applicable to other aspects of the present invention. It is contemplated that any embodiment or aspect discussed herein can be combined with other embodiments or aspects discussed herein and / or can be implemented by any method or composition of the present invention, and vice versa. In addition, the compositions and systems of the present invention can be used to implement the methods of the present invention.

[0023] The following includes definitions of various terms and phrases used throughout this specification.

[0024] The term "about" or "approximately" is defined as being close to what is understood by a person skilled in the art. In a non-limiting embodiment, the term is defined as within plus or minus 10%, or plus or minus 5%, or plus or minus 1%, or plus or minus 0.5%.

[0025] The terms "weight %", "volume %", or "mole %" refer, respectively, to the weight percentage, volume percentage, or mole percentage of a component based on the total weight, total volume, or total moles of the material containing the component. In a non-limiting example, 10 grams of a component in 100 grams of material is 10 weight % of the component. The term "ppm" refers to parts per million by weight of a component, based on the total weight including the component.

[0026] The term "substantially" and its variants are defined to include a range within plus or minus 10%, plus or minus 5%, plus or minus 1%, or plus or minus 0.5%.

[0027] When used in the claims and / or the specification, the terms "suppress", "reduce", "prevent", "avoid", or any variants of these terms include any measurable reduction or complete suppression to achieve the desired result.

[0028] The term "effective", when used in the specification and / or the claims, means sufficient to achieve the desired, hoped-for, or intended result.

[0029] When "a" or "an" is used in conjunction with any of the terms "comprising", "including", "containing", or "having" in the claims or the specification, it can mean "one", but is also consistent with the meaning of "one or more", "at least one", and "one or more than one".

[0030] The expression "and / or" can include "and" or "or". For illustration, A, B, and / or C can include: A alone, B alone, C alone, a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B, and C.

[0031] The terms "comprising" (and any form of comprising, such as "comprises" and "containing"), "having" (and any form of having, such as "has" and "owns"), "including" (and any form of including, such as "includes" and "encompassing") or "containing" (and any form of containing, such as "contains" and "comprises") are inclusive or open-ended and do not exclude other unrecited elements or method steps.

[0032] The methods and systems of the present invention may "comprise", "consist essentially of" the specific ingredients, components, compositions, steps disclosed throughout the specification or "consist of the specific ingredients, components, compositions, steps, etc. disclosed throughout the specification". In a non-limiting aspect, with respect to the transitional term "consisting essentially of", the basis and novel characteristics of the compositions and processes of the present invention are that the compositions comprise and / or the methods use one or more polypropylenes (PPs), and the one or more polypropylenes (PPs) have one or more of the following properties: a) a melting temperature ≤ 135 °C, measured according to ASTM D3418-15; b) an onset melting temperature ≤ 125 °C, measured according to ASTM D3418-15; c) an onset crystallization temperature ≤ 105 °C, measured according to ASTM D3418-15; d) a crystallinity ≤ 35%, measured according to ASTM D3418-15; e) an Avrami exponent ≤ 2.10; f) an absolute value of the crystallization activation energy ≤ 550,000 J / mol, determined by fitting Avrami kinetics; and / or g) an absolute value of the crystallization activation energy is less than or equal to 80% of the absolute value of the crystallization activation energy of an un-nucleated Ziegler-Natta homopolymer polypropylene.

[0033] Other objects, features and advantages of the present invention will become apparent from the following drawings, detailed description and examples. However, it should be understood that these drawings, detailed description and examples, although indicating specific embodiments of the present invention, are given by way of illustration only and are not intended to be limiting. In addition, it is contemplated that changes and modifications within the spirit and scope of the present invention will become apparent to those skilled in the art through the detailed description. In other embodiments, the features of specific embodiments may be combined with the features of other embodiments. For example, the features from one embodiment may be combined with the features from any other embodiment. In other embodiments, additional features may be added to the specific embodiments described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The advantages of the present invention will become apparent to those skilled in the art from the following detailed description and with reference to the accompanying drawings.

[0035] Figure 1A-C (Prior Art) —— depicts a schematic diagram of an exemplary additive manufacturing (AM) process. (A) depicts a schematic diagram of an exemplary fused deposition (FD) modeling process. (B) depicts a schematic diagram of interface healing at the weld line during an additive manufacturing process. (C) depicts a schematic diagram of product production and a pant tear test on a product produced by AM.

[0036] Figure 2 (Prior Art) —— depicts a schematic diagram of an exemplary selective laser sintering (SLS) process [also known as powder bed fusion with a laser beam (PBF-LB)].

[0037] Figure 3 (Prior Art) —— depicts a differential scanning calorimetry (DSC) differential thermal analysis graph that shows the "sintering window" of the SLS-processing region between the melting temperature (Tm) and the crystallization temperature (Tc). The sintering window is calculated as ΔT from the starting point of (T m -T c ).

[0038] Figure 4 A-E —— depicts differential thermal analysis data (DSC) represented by the following melting and crystallization traces (A) polypropylene (PP) 3270, (B) PP 3276, (C) PP Z9450, (D) PP M9675, and (E) PP 1251.

[0039] Figure 5 A-E —— depicts Figure 4 the differential thermal analysis data (DSC) provided in A-E that overlaps with the sintering window of each PP, where the sintering window is defined by the onset melting and onset crystallization temperatures. (A) depicts PP 3270, whose sintering window is 158.72 - 117.88 = 40.84 °C. (B) depicts PP 3276, whose sintering window is 149.26 - 114.91 = 34.35 °C. (C) depicts PP Z9450, whose sintering window is 112.48 - 92.94 = 19.54 °C. (D) depicts PP M9675, whose sintering window is 115.44 - 89.92 = 25.52 °C. (E) depicts PP 1251, whose sintering window is 108.67 - 81.18 = 27.49 °C.

[0040] Figure 6 —— depicts a graph showing semi-crystallization time (minutes; Y-axis) versus temperature (°C; X-axis) from isothermal DSC crystallization tests of PP 3270, PP 3276, PP Z9450, PP M9675, and PP 1251, respectively.

[0041] Figure 7 —— The mapping of the PP Avrami exponent relative to temperature. The small left figure depicts graphs showing the Avrami exponent (Y-axis) of calculated PP 3270, PP 3276, PP Z9450, PP M9675, and PP 1251 relative to temperature (°C; X-axis). The small right figure depicts the respective average Avrami exponents of each of PP 3270 (2.21), PP 3276 (2.30), PP Z9450 (1.89), PP M9675 (2.20), and PP 1251.

[0042] Figure 8 —— Depicts graphs showing Ln(k a )(Y-axis) of each of PP 3270, PP 3276, PP Z9450, PP M9675, and PP 1251 relative to 1 / (RT) (X-axis). The linear best-fit curves for each PP and the associated R 2 values are determined. Detailed Description

[0043] The discovery has been made to provide solutions to at least some of the above problems associated with the use of polypropylene for additive manufacturing. These and other non-limiting aspects of the present invention will be discussed in further detail in the following sections.

[0044] A. Additive Manufacturing

[0045] Additive manufacturing (AM) (also commonly referred to as three-dimensional (3-D) printing, and these terms may be used interchangeably herein) is a process of custom-making articles by selectively depositing materials. Starting from Charles Hull, his company (3D Systems) in the 1980s, and patent application 4575330A (Apparatus for producing three-dimensional objects by stereolithography), the industry has grown.

[0046] Over the past few decades, a variety of mainstream additive manufacturing methods have been developed. ISO / ASTM 59000 has defined seven process classifications, which include: binder jetting (depositing a liquid binder to bind powders), directed energy deposition (thermal energy melts the just-deposited material), material extrusion (selectively dispensing materials from one or more nozzles and / or orifices), material jetting (thermal energy selectively melts areas of a powder bed), sheet lamination (bonding sheets of material), and vat polymerization (selectively curing a liquid photosensitive polymer in a vat by photoactivated polymerization).

[0047] Compared with traditional manufacturing means, additive manufacturing can have multiple benefits. In some embodiments, the benefits of additive manufacturing include: lower energy consumption, reduced waste, reduced time to market, ability to be flexible / innovative, part consolidation, lighter materials, distributed manufacturing, and / or improved inventory management. These and other features have generated widespread interest in using 3D printing (also alternatively referred to herein as "additive manufacturing") for a wide range of applications, including but not limited to: medicine, life science research and development, food manufacturing, organ replacement, medical prosthetics, furniture, consumer electronics, clothing, aerospace, power tools, retail hardware, residential and / or commercial building materials, firearms, ammunition, military / defense, motor vehicles and / or motor vehicle parts, sports equipment, and consumer goods (such as toys, hobby materials, animation products, games, etc.).

[0048] 1. Fused Deposition Modeling (FDM)

[0049] Fused Deposition Modeling (FDM) is an AM technology reported to have the largest market share. As described in ISO / ASTM 59000, it is a type of material extrusion process. Fused Deposition Modeling (FDM) can also be referred to as Fused Filament Fabrication (FFF). In some embodiments, the process starts with a polymer monofilament. In some embodiments, the filament is heated in a die assembly and extruded as a polymer melt from a nozzle. In some embodiments, the melt is deposited one layer at a time to build the final part. In some embodiments, as each layer is built, the print head indexes up by one layer height and then continues with the next layer (alternatively, the build plate indexes down by one layer height). The flexibility and low entry cost associated with the process have made FDM a popular approach for hobbyists up to high-end manufacturing uses. Figure 1 A schematic depiction of the FDM process is provided in A (source: Druckwege 3D printing).

[0050] An important characteristic of FDM is that each successive layer needs to bond to the previous layer. This involves having sufficient molecular diffusion at the interface between two successive layers in order to knit together and form a strong weld line. This characteristic is in Figure 1Schematically depicted in B (source: Fatemah Mashayekhi et al., Fused Filament Fabrication of Polymers and Continuous Fiber-Reinforced Polymer Composites: Advances in Structure Optimization and Health Monitoring. Polymers (Basel), March 4, 2021). In some cases, the interlayer weld line can be a potential weakness inherent in FDM. For example, if voids form at the interface, and / or if sufficient molecular diffusion does not occur, the additively manufactured product can be damaged. Davis and colleagues (Davis et al., Mechanical strength of welding zones produced by material extrusion additive manufacturing. Additive Manufacturing, June 17, 2017) explored the weld line strength in acrylonitrile-butadiene-styrene (ABS) printed parts. Davis et al. showed the process, sample preparation, and tensile testing via "trousers testing" of additively manufactured articles, schematically described in Figure 1 C. The trousers testing conducted in this way is a modified form of ASTM D1938-14 Mode III. Migler and colleagues described the problems associated with weld line knitting as "a race against time" (see, for example, Migler et al., Presentation-Challenges in Additive Manufacturing of Soft Materials: Polymer-based Fused Deposition Modeling. Department of Physics, Institute for Soft matter Synthesis and Metrology, NIST Polymers and Complex Fluids Group).

[0051] In semi-crystalline polymers, the weld line strength can become more complex (see, e.g., Andrea Costanzo et al., Light scattering approach to the in situ measurement of polymer crystallization during 3D printing: A feasibility study. Polymer Crystallization. 2021;4:e10182). In amorphous polymers, the inter-chain diffusion process is hindered by cooling and stops when the glass transition temperature is reached. For semi-crystalline polymers, the welding efficiency is related to the competition between the chain diffusion kinetics (or "reptation" in de Gennes' terms) and the crystallization kinetics. If the crystallization rate occurs too quickly, there is insufficient time for the polymer chains to diffuse and entangle with each other to heal the weld line. This can result in a weak final additive manufactured product.

[0052] In addition to the weak mechanical properties, there are other difficulties in FDM, as summarized by Migler and co-workers. For example, polymer FDM can result in products with weak mechanical properties, sagging, poor surface properties / non-uniform texture, porosity, shrinkage, warping, and / or delamination. The unique melt process method and the inherent layer-by-layer part manufacturing cause its unique difficulties. Those skilled in the art are interested in new ways and techniques to mitigate and / or overcome these problems.

[0053] When used in FDM, semi-crystalline polymers can exacerbate one or more of these negative characteristics. For example, Fitzharris and colleagues (see, e.g., Fitzharris et al., Effects of material properties on warpage in fused deposition modeling parts. International Journal of Advanced Manufacturing Technology. November 18, 2017) stated that "extending FDM technology to semi-crystalline polymers has been challenging because crystallization occurs during cooling, resulting in warping of FDM parts." In addition, Spoerk, Holzer, and Gonzalez-Gutierrez (see, e.g., Spoerk et al., Material extrusion-based additive manufacturing of polypropylene: A review on how to improve dimensional inaccuracy and warpage. Journal of Applied Polymer Science. October 15, 2019) emphasized that warping is a major problem for polypropylene-based FDM parts. In addition, Spoerk et al. noted that there can be competition in the types of crystals formed in PP - where specific process conditions favor the formation of more β-crystals relative to α-crystals, creating another variable that must be controlled from the perspective of product quality and consistency. In addition, in the 2021 Ph.D. thesis of Agbelenko Koffi, the current understanding in the field was summarized as follows: "Basic semi-crystalline plastics, namely low-density polyethylene (LDPE), linear LDPE, high-density polyethylene (HDPE), polypropylene, etc., and certain types of polyamides are particularly difficult to process using material extrusion-additive manufacturing (ME-AM); and although these materials have excellent and unique properties, their application in ME-AM has not been deepened and has not been studied in the literature." (Agbelenko Koffi, Study of injection parameters of fiber composites natural and performance enhancement material mechanics for 3D printing. University of Quebec, February 2021).

[0054] Meanwhile, the art has recognized that semi-crystalline polymers can offer certain attractive advantages in particles produced by FDM compared to amorphous thermoplastics. For example, the advantages can include, but are not limited to: a higher continuous use temperature range, the ability to be used above the glass transition temperature, greater tolerance to creep deformation, and / or excellent chemical and wear resistance (see, e.g., Kishore et al., Additive manufacturing of high performance semi-crystalline thermoplastics and their composites. Proceedings of the 27th Annual International Solid Freeform Fabrication Symposium. 2016). In certain scenarios, polypropylene can be particularly advantageous relative to other suitable materials. For example, in certain embodiments, polypropylene can be advantageous in terms of living hinge performance, weight (e.g., lightweight), toughness, flexibility, chemical resistance, heat resistance (e.g., good stability in boiling water), and / or other properties (see, e.g., Encyclopedia Britannica, definition of polypropylene chemical compound (December 06, 2017); Engineering ToolBox, (2003). PP Polypropylene - Chemical Resistance.; and / or Marline Steel, 7 Need-to-know polypropylene material properties (January 16, 2020)).

[0055] Challenges in FDM associated with the use of semi-crystalline polymers, particularly polypropylene, need to be overcome so that the benefits of these useful polymers can be more fully realized.

[0056] Methods and compositions that overcome any subset of these problems are particularly described herein, for example, where additively manufactured products (such as compositions, articles, etc.) have improved properties compared to conventional additively manufactured products, and the additively manufactured products comprise polypropylene having specific properties as described herein (such specific properties as: melting temperature, onset melting temperature, onset crystallization temperature, crystallinity, Avrami index value, absolute value of crystallization activation energy, and / or relative absolute value of crystallization activation energy). In certain embodiments, additively manufactured compositions and methods of making the same are disclosed herein, wherein mechanical properties are improved, rigidity is improved, texture and / or other surface properties are improved, porosity is reduced, stability is improved, warpage tolerance is improved, tear strength tolerance is improved, and / or bond strength is improved. In certain embodiments, additively manufactured compositions with improved rigidity (such as reduced sagging level) are disclosed herein. In certain embodiments, additively manufactured compositions with improved texture and / or other surface properties are disclosed herein. In certain embodiments, additively manufactured compositions with reduced porosity are disclosed herein. In certain embodiments, additively manufactured compositions with improved stability (such as less shrinkage) are disclosed herein. In certain embodiments, additively manufactured compositions with improved warpage tolerance are disclosed herein. In certain embodiments, additively manufactured compositions with improved tear strength tolerance are disclosed herein. In certain embodiments, additively manufactured compositions with improved bond strength are disclosed herein.

[0057] 2. Selective Laser Sintering (SLS)

[0058] Another common additive manufacturing technique using polymers is Selective Laser Sintering (SLS), also known as Powder Bed Fusion - Laser Beam (PBF - LB), or Powder Bed Sintering (PBS) process. A schematic diagram of SLS is as Figure 2As shown (adapted from Alghamdi et al., Additive Manufacturing of Polymer Materials: Progress, Promise, and Challenges. Polymers (Basel), February 28, 2021). SLS uses polymer powder as a substrate component. Polymer powder substrates generally use a certain level of particle size consistency to ensure optimal functional performance. Some advantages associated with this technology may include: low cost per part, high productivity, and / or excellent mechanical properties, similar to injection-molded parts (see, e.g., FormLabs, Guide to selective laser sintering (SLS) 3D printing. Formalbs.com (2022)). Generally, the most commonly used polymer in SLS is polyamide 12; it can account for ~90% of the market share (see, e.g., Schmid et al., Polymer powders for selective laser sintering (SLS). Conference: Proceedings of PPS-30: The 30th international conference of the polymer processing society – conference paper. May 22, 2015; and / or Mwania et al., Mixing and Reuse of Polymer Laser Sintering Powders to Ensure Homogeneity – A Review. International Journal of Engineering Research and Technology. 2020).

[0059] There are reasons to expand SLS additive manufacturing to other polymers different from the dominant polyamide 12, such as polypropylene. In certain embodiments, polypropylene provides an attractive alternative substrate to polyamide 12 (see, e.g., Advanc3dMaterials AdSint PP flex polypropylene powder, which claims an elongation rate of 29% in SLS, and / or the product PP400 (2020) of Advanced laser Materials (ALM) and Braskemde, which claims an elongation at break of 50%, thus providing impact tolerance in dynamic environments).

[0060] However, current methods of using polypropylene in SLS-based additive manufacturing can result in products having one or more undesirable characteristics. For example, FormLabs acknowledges that 3D printed parts can have a slightly granular surface finish, which under certain conditions can be mitigated by post-manufacturing processing of the article (see, e.g., FormLabs, Guide to selective laser sintering (SLS) 3D printing. Formalbs.com (2022)). In some cases, the powder substrate can present handling and storage difficulties, and the system typically requires dust-free and / or airtight containers to prevent sudden spillage and / or leakage of the usually flammable substrate (see, e.g., LyondellBasell, Handling and storage of polymers (Document 9416 / 1204)). In some situations, static electricity can impede powder flow and distribution (see, e.g., PowderProcess.net, Static electricity influence on powder flow (2022)). In some situations, for production consistency, the powder morphology and particle size distribution must be carefully controlled (see, e.g., Berretta et al., Size, shape and flow of powders for use in Selective Laser Sintering (SLS). University of Exeter Open Research. July 18, 2014). In some situations, when using polypropylene, particle size control can involve a somewhat cumbersome cryogenic milling step followed by precipitation to effectively control the particle size. In some situations, the wavelength-dependent absorption properties of the polymer (which limit which polymers sinter well at typical wavelengths) may require the addition of absorptive additives.

[0061] There is a need to overcome the challenges in SLS posed by the use of semi-crystalline polymers, particularly polypropylene, such that the benefits of these useful polymers can be more fully realized. Descriptions, data, examples, etc. are provided herein that illustrate which polypropylenes are most suitable for SLS-based additive manufacturing.

[0062] B. Polymer-based compositions

[0063] In some embodiments, the compositions of the present invention contain at least 90 wt% polypropylene, such as 90 wt% to 99.9 wt% polypropylene, or at least any one of the following, equal to any one of the following, or between any two of the following: 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%, 99.1 wt%, 99.2 wt%, 99.3 wt%, 99.4 wt%, 99.5 wt%, 99.6 wt%, 99.7 wt%, 99.8 wt%, and 99.9 wt% polypropylene. In some aspects, the polymeric compositions of the present invention may contain at least 95 wt% polypropylene, such as 95 wt% to 99.9 wt%, or 96 wt% to 99.9 wt%, or 97 wt% to 99.9 wt%, or 98 wt% to 99.9 wt%, or 99 wt% to 99.9 wt% of said polypropylene.

[0064] 1. Polypropylene and Its Properties

[0065] In certain embodiments, polypropylene having certain properties is provided herein, and said properties enable the polypropylene to be used as a substrate in an additive manufacturing process.

[0066] In certain embodiments, the melting temperature of the polypropylene is less than or equal to about 155 °C, 154 °C, 153 °C, 152 °C, 151 °C, 150 °C, 149 °C, 148 °C, 147 °C, 146 °C, 145 °C, 144 °C, 143 °C, 142 °C, 141 °C, 140 °C, 139 °C, 138 °C, 137 °C, 136 °C, 135 °C, 134 °C, 133 °C, 132 °C, 131 °C, 130 °C, 129 °C, 128 °C, 127 °C, 126 °C, 125 °C, 124 °C, 123 °C, 122 °C, 121 °C, 120 °C, 119 °C, 118 °C, 117 °C, 116 °C, 115 °C, 114 °C, 113 °C, 112 °C, 111 °C, 110 °C, 109 °C, 108 °C, 107 °C, 106 °C, 105 °C, 104 °C, 103 °C, 102 °C, 101 °C, or 100 °C, or any range derivable therefrom, as measured according to ASTM D3418 - 15.

[0067] In certain embodiments, the starting melting temperature of the polypropylene is less than or equal to about 145 °C, 144 °C, 143 °C, 142 °C, 141 °C, 140 °C, 139 °C, 138 °C, 137 °C, 136 °C, 135 °C, 134 °C, 133 °C, 132 °C, 131 °C, 130 °C, 129 °C, 128 °C, 127 °C, 126 °C, 125 °C, 124 °C, 123 °C, 122 °C, 121 °C, 120 °C, 119 °C, 118 °C, 117 °C, 116 °C, 115 °C, 114 °C, 113 °C, 112 °C, 111 °C, 110 °C, 109 °C, 108 °C, 107 °C, 106 °C, 105 °C, 104 °C, 103 °C, 102 °C, 101 °C, or 100 °C, or any range derivable therefrom, as measured according to ASTM D3418-15.

[0068] In certain embodiments, the starting crystallization temperature of the polypropylene is less than or equal to about 115 °C, 114 °C, 113 °C, 112 °C, 111 °C, 110 °C, 109 °C, 108 °C, 107 °C, 106 °C, 105 °C, 104 °C, 103 °C, 102 °C, 101 °C, 100 °C, 99 °C, 98 °C, 97 °C, 96 °C, 95 °C, 94 °C, 93 °C, 92 °C, 91 °C, 90 °C, 89 °C, 88 °C, 87 °C, 86 °C, 85 °C, 84 °C, 83 °C, 82 °C, 81 °C, 80 °C, 79 °C, 78 °C, 77 °C, 76 °C, 75 °C, 74 °C, 73 °C, 72 °C, 71 °C, or 70 °C, or any range derivable therefrom, as measured according to ASTM D3418-15.

[0069] In certain embodiments, the crystallinity of the polypropylene is less than or equal to about 45%, 44%, 43%, 42%, 41%, 40%, 39%, 38%, 37%, 36%, 35%, 34%, 33%, 32%, 31%, 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, or 20%, or any range derivable therefrom, as measured according to ASTM D3418-15.

[0070] In certain embodiments, the polypropylene satisfies two or more of the following: a melting temperature less than or equal to about 155 °C, 154 °C, 153 °C, 152 °C, 151 °C, 150 °C, 149 °C, 148 °C, 147 °C, 146 °C, 145 °C, 144 °C, 143 °C, 142 °C, 141 °C, 140 °C, 139 °C, 138 °C, 137 °C, 136 °C, 135 °C, 134 °C, 133 °C, 132 °C, 131 °C, 130 °C, 129 °C, 128 °C, 127 °C, 126 °C, 125 °C, 124 °C, 123 °C, 122 °C, 121 °C, 120 °C, 119 °C, 118 °C, 117 °C, 116 °C, 115 °C, 114 °C, 113 °C, 112 °C, 111 °C, 110 °C, 109 °C, 108 °C, 107 °C, 106 °C, 105 °C, 104 °C, 103 °C, 102 °C, 101 °C, or 100 °C, or any range derivable therefrom, as measured according to ASTM D3418-15; an onset melting temperature less than or equal to about 145 °C, 144 °C, 143 °C, 142 °C, 141 °C, 140 °C, 139 °C, 138 °C, 137 °C, 136 °C, 135 °C, 134 °C, 133 °C, 132 °C, 131 °C, 130 °C, 129 °C, 128 °C, 127 °C, 126 °C, 125 °C, 124 °C, 123 °C, 122 °C, 121 °C, 120 °C, 119 °C, 118 °C, 117 °C, 116 °C, 115 °C, 114 °C, 113 °C, 112 °C, 111 °C, 110 °C, 109 °C, 108 °C, 107 °C, 106 °C, 105 °C, 104 °C, 103 °C, 102 °C, 101 °C, or 100 °C, or any range derivable therefrom, as measured according to ASTM D3418-15; an onset crystallization temperature less than or equal to about 115 °C, 114 °C, 113 °C, 112 °C, 111 °C, 110 °C, 109 °C, 108 °C, 107 °C, 106 °C, 105 °C, 104 °C, 103 °C, 102 °C, 101 °C, 100 °C, 99 °C, 98 °C, 97 °C, 96 °C, 95 °C, 94 °C, 93 °C, 92 °C, 91 °C, 90 °C, 89 °C, 88 °C, 87 °C, 86 °C, 85 °C, 84 °C, 83 °C, 82 °C, 81 °C, 80 °C, 79 °C, 78 °C, 77 °C, 76 °C, 75 °C, 74 °C, 73 °C, 72 °C, 71 °C, or 70 °C, or any range derivable therefrom, as measured according to ASTM D3418-15;and / or a crystallinity less than or equal to about 45%, 44%, 43%, 42%, 41%, 40%, 39%, 38%, 37%, 36%, 35%, 34%, 33%, 32%, 31%, 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, or 20%, or any range derivable therefrom, as measured according to ASTM D3418-15.;

[0071] In certain embodiments, the Avrami exponent of the polypropylene is less than or equal to about 2.20, 2.19, 2.18, 2.17, 2.16, 2.15, 2.14, 2.13, 2.12, 2.11, 2.10, 2.09, 2.08, 2.07, 2.06, 2.05, 2.04, 2.03, 2.02, 2.01, 2, 1.99, 1.98, 1.97, 1.96, 1.95, 1.94, 1.93, 1.92, 1.91, 1.90, 1.89, 1.88, 1.87, 1.86, 1.85, 1.84, 1.83, 1.82, 1.81, or 1.80, or any range derivable therefrom, as calculated as described herein (see, e.g., Example 4).

[0072] In certain embodiments, the absolute value of the crystallization activation energy of the polypropylene is less than or equal to about 600,000, 590,000, 580,000, 570,000, 560,000, 550,000, 540,000, 530,000, 520,000, 510,000, 500,000, 490,000, 480,000, 470,000, 460,000, 450,000, 440,000, 430,000, 420,000, 410,000, 400,000, 390,000, 380,000, 370,000, 360,000, 350,000, 340,000, 330,000, 320,000, 310,000, 300,000, 290,000, 280,000, 270,000, 260,000, or 250,000 J / mol, or any range derivable therefrom, determined by fitting to Avrami kinetics with an isothermal differential scanning calorimetry (DSC) test as described in ASTM D3418-15 (see, e.g., Example 4).

[0073] In some embodiments, the absolute value of the crystallization activation energy of the polypropylene is less than or equal to 90%, 89%, 88%, 87%, 86%, 85%, 84%, 83%, 82%, 81%, 80%, 79%, 78%, 77%, 76%, 75%, 74%, 73%, 72%, 71%, 70%, 69%, 68%, 67%, 66%, or 65% of the absolute value of the crystallization activation energy of the non-nucleated Ziegler-Natta homopolymer polypropylene, or any range derivable therefrom (see, for example, Example 4).

[0074] In some embodiments, the polypropylene is a polypropylene copolymer. In some embodiments, the polypropylene is a random propylene-ethylene copolymer. In some specific aspects, the polypropylene copolymer can be an isotactic propylene-ethylene random copolymer. In some specific aspects, the polypropylene copolymer can be a syndiotactic homopolymer polypropylene.

[0075] In some embodiments, the propylene copolymer can comprise: 0.1 wt% to 10 wt%, or 0.1 wt% to 9 wt%, or 0.1 wt% to 8 wt%, or 0.1 wt% to 7 wt%, or 0.1 wt% to 6 wt%, or 0.1 wt% to 5 wt%, or 0.1 wt% to 4 wt%, or 0.1 wt% to 3 wt%, or 0.1 wt% to 2 wt% of ethylene units, or at least any one of the following, equal to any one of the following, or between any two of the following ethylene units: 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10 wt% of ethylene units, and 90 wt% to 99.9 wt%, or 91 wt% to 99.9 wt%, or 92 wt% to 99.9 wt%, or 93 wt% to 99.9 wt%, or 94 wt% to 99.9 wt%, or 95 wt% to 99.9 wt%, or 96 wt% to 99.9 wt%, or 97 wt% to 99.9 wt%, or 98 wt% to 99.9 wt% of propylene units, or at least any one of the following, equal to any one of the following, or between any two of the following propylene units: 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.2%, 99.4%, 99.6%, 99.8%, and 99.9 wt% of propylene units, based on the total weight of the copolymer.

[0076] In some aspects, the polypropylene copolymer may have a xylene-soluble component of less than 8 wt%, such as 1 wt% to 8 wt% of the xylene-soluble component, or at least any one of the following, equal to any one of the following, or between any two of the following: 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, and 8 wt%.

[0077] In some aspects, the polydispersity (Mw / Mn) of the polypropylene may be 3 to 15, or at least any one of the following, equal to any one of the following, or between any two of the following: 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15, wherein the polydispersity is measured using gel permeation chromatography (GPC).

[0078] In some aspects, the melt flow rate (MFR) of the polypropylene can be from 0.1 g / 10 min to 150 g / 10 min, or from 1 to 60 g / 10 min, or from 1 to about 30 g / 10 min, or from 1 to about 10 g / 10 min, or from 1 to about 7 g / 10 min, at 230 °C and 2.16 kg, or at least any one of the following, equal to any one of the following, or between any two of the following: 0.1 g / 10 min, 1 g / 10 min, 2 g / 10 min, 3 g / 10 min, 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min, 9 g / 10 min, 10 g / 10 min, 20 g / 10 min, 30 g / 10 min, 40 g / 10 min, 50 g / 10 min, 60 g / 10 min, 70 g / 10 min, 80 g / 10 min, 90 g / 10 min, 100 g / 10 min, 110 g / 10 min, 120 g / 10 min, 130 g / 10 min, 140 g / 10 min, 150 g / 10 min, and 160 g / 10 min, measured according to ASTM D-1238-20. In some aspects, the density of the polypropylene can be from 0.90 g / cc to 1 g / cc, or from 0.90 to 0.93 g / cc, or from 0.90 g / cc to 0.92 g / cc, or from 0.90 g / cc to 0.91, or at least any one of the following, equal to any one of the following, or between any two of the following: 0.9 g / cc, 0.902 g / cc, 0.904 g / cc, 0.906 g / cc, 0.908 g / cc, 0.91 g / cc, 0.915 g / cc, 0.92 g / cc, 0.925 g / cc, 0.93 g / cc, 0.935 g / cc, 0.94 g / cc, 0.945 g / cc, 0.95 g / cc, 0.955 g / cc, 0.96 g / cc, 0.965 g / cc, 0.97 g / cc, 0.975 g / cc, 0.98 g / cc, 0.985 g / cc, 0.99 g / cc, 0.995 g / cc, and 1 g / cc, measured according to ASTM D1505-18. In some aspects, the polypropylene can have any combination of any or all of the properties described herein.

[0079] In some embodiments, the flexural modulus of the polypropylene may be from 100 Kpsi to 300 Kpsi at 4 - 8 N, as determined by ASTM D790 - 97. In some aspects, the notched Izod impact strength of the polypropylene may be greater than 0.9 ft - lb / in at 23 °C, such as from 1 ft - lb / in to 1.5 ft - lb / in, as measured according to D638. In some aspects, the tensile modulus of the polypropylene may be greater than 210 Kpsi at 23 °C, such as from 211 Kpsi to 300 Kpsi, as measured according to D638. In some embodiments, the elongation at break of the polypropylene may be greater than, equal to, or less than 10% at 23 °C, such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 120%, 140%, 160%, 180%, 200%, 250%, 300%, 350%, 400%, 450%, 500%, 550%, 600%, 650%, 700%, 750% at 23 °C, or any range derivable therefrom, as measured according to D - 638.

[0080] In some embodiments, the polypropylene copolymer can be prepared via conventional polymerization processes, such as those known in the art. Examples of such polymerization processes include, but are not limited to: slurry polymerization, bulk liquid polymerization, and gas phase polymerization. In some embodiments, in the slurry polymerization process, the polymerization is carried out in a loop reactor or a continuous stirred tank reactor in the presence of a solvent (e.g., hexane). In some embodiments, the polymerization can also be carried out by bulk phase polymerization, where liquid propylene and ethylene act as both monomers and diluents. In some embodiments, in a typical bulk process, one or more loop reactors are generally employed. In other aspects, the copolymer can be produced by gas phase polymerization of propylene and ethylene, which is typically carried out in a fluidized bed reactor. In some embodiments, the polymer fluff or powder produced by the polymerization reaction can be removed from the reactor and subsequently processed by conventional techniques (e.g., by extrusion) to obtain the desired copolymer pellets. Desirably, the amount of ethylene monomer used during the copolymer polymerization is proportional to the desired final ethylene content of the target propylene copolymer. In some embodiments, the ethylene content during polymerization can range from 0.1 to 10 wt%, or 0.1 to 9 wt%, or 0.1 to 8 wt%, or 0.1 to 7 wt%, or 0.1 to 6 wt%, or 0.1 to 5 wt%, or 0.1 to 4 wt%, or 0.1 to about 3 wt%, or 0.1 to about 2 wt%, or 0.1 to about 1 wt%, based on the total weight of the monomers (e.g., ethylene and propylene) present during polymerization. In some aspects, metallocene catalysts or Ziegler-Natta catalysts can be used to prepare polypropylene copolymers, such as propylene-ethylene random copolymers. In some embodiments, the polypropylene does not have a nucleating agent. In some embodiments, excluding the nucleating agent avoids interfering with the behavior of the base resin, where the additive enhances such behavior.

[0081] In some embodiments, Ziegler-Natta catalysts can be used to prepare isotactic polypropylene. In some embodiments, these catalysts can be derived from halides of transition metals such as titanium, chromium, or vanadium, where metal hydrides and / or alkyl metals (typically organoaluminum compounds) are used as co-catalysts. In some aspects, the catalyst can contain titanium halide supported on a magnesium compound. In some embodiments, the Ziegler-Natta catalyst is a supported catalyst, such as titanium tetrachloride (TiCl4) supported on activated magnesium dihalide (such as magnesium dichloride or magnesium dibromide) as disclosed in U.S. Patent Nos. 4,298,718 and 4,544,717, both assigned to Mayr et al., the contents of which are incorporated herein by reference. In some embodiments, silica can also be used as a support. In some embodiments, the supported catalyst can be used in combination with a co-catalyst or an electron donor such as an alkylaluminum compound, such as triethylaluminum (TEAL), trimethylaluminum (TMA), and triisobutylaluminum (TIBAL).

[0082] 2. Polypropylene 3270

[0083] In certain embodiments, the polypropylene is polypropylene 3270. In certain embodiments, the polypropylene is not polypropylene 3270. In certain embodiments, polypropylene 3270 is a reference polypropylene. Polypropylene 3270 is produced by TotalEnergies, which uses proprietary process technology to obtain extremely low residues for excellent hardness. Polypropylene 3270 is a highly crystalline homopolymer polypropylene. The polymer is prepared by a Ziegler-Natta catalyst and has a xylene solubles of <1%.

[0084] Table 1 - Properties of Polypropylene 3270

[0085]

[0086] 3. Polypropylene 3276

[0087] In certain embodiments, the polypropylene is polypropylene 3276. In certain embodiments, the polypropylene is not polypropylene 3276. In certain embodiments, polypropylene 3276 is a reference polypropylene. Polypropylene 3276 is produced by TotalEnergies, which uses proprietary process technology to obtain extremely low residues for improved color stability and transparency. Polypropylene 3276 is a homopolymer polypropylene prepared by a Ziegler-Natta catalyst. The polymer has a lower stereoregularity than 3270, as indicated by a typical xylene solubles level of about 4%.

[0088] Table 2 - Properties of Polypropylene 3276

[0089]

[0090]

[0091] 4. Polypropylene Z9450

[0092] In certain embodiments, the polypropylene is polypropylene Z9450. In certain embodiments, the polypropylene is not polypropylene Z9450. In certain embodiments, polypropylene Z9450 is a reference polypropylene. Polypropylene Z9450 is produced by TotalEnergies and is a low melting point, high ethylene random copolymer with improved color, optical, and impact properties. Polypropylene Z9450 has a low melting point, which makes it an excellent heat-sealing layer in some embodiments. Polypropylene Z9450 is a random copolymer. The comonomer is ethylene and is typically incorporated at a level of about 6 wt%. The melting point is typically about 129 °C. The polymer is prepared by a Ziegler-Natta catalyst.

[0093] Table 3 - Properties of Polypropylene Z9450

[0094]

[0095] 5. Polypropylene M9675

[0096] In certain embodiments, the polypropylene is polypropylene M9675. In certain embodiments, the polypropylene is not polypropylene M9675. In certain embodiments, polypropylene M9675 is a reference polypropylene. Polypropylene M9675 is produced by TotalEnergies and is an isotactic propylene copolymer produced using a metallocene catalyst. Polypropylene M9675 results in a film with excellent heat-sealing performance and excellent optical properties. Polypropylene M9675 is a random copolymer. The comonomer is ethylene and is typically incorporated at a level of about 3 wt%. The melting point is typically about 119 °C and the xylene solubles are typically <1%.

[0097] Table 4 - Properties of Polypropylene M9675

[0098]

[0099] 6. Polypropylene 1251

[0100] In certain embodiments, the polypropylene is polypropylene 1251. In certain embodiments, the polypropylene is not polypropylene 1251. In certain embodiments, polypropylene 1251 is a reference polypropylene. Polypropylene 1251 is produced by TotalEnergies and is a syndiotactic copolymer polypropylene. In some embodiments, syndiotactic polypropylene has a lower melting point and / or lower crystallinity compared to other types of polypropylene. Polypropylene 1251 is a syndiotactic homopolymer polypropylene. The melting point is typically about 130 °C and the polymer is prepared by a metallocene catalyst.

[0101] Table 5 - Properties of Polypropylene 1251

[0102]

[0103]

[0104] 7. Clarifying Agent

[0105] In some embodiments, the compositions of the present disclosure include a clarifying agent containing phosphate salt and / or a clarifying agent containing arylamide.

[0106] Non-limiting examples of the clarifying agent containing phosphate salt include: 2,2 - methylene - bis(4,6 - di - tert - butylphenyl) phosphate, and / or hydroxybis(2,4,8,10 - tetra(1,1 - dimethyl)6 - hydroxy - 12H - dibenzo[d,g][1,2,3][dioxaphophocin]6 - oxide)aluminum. In some specific aspects, the clarifying agent may be 2,2 - methylene bis(4,6 - di - tert - butylphenyl) phosphate. Examples of commercially available clarifying agents containing phosphate salt include, but are not limited to: ADK STABILIZER NA - 71 and ADK STABILIZER NA - 21, both of which are available from Amfine Chemical Co., Allendale, N.J.

[0107] Non - limiting examples of the clarifying agent containing arylamide may be: amide derivatives of 1,3,5 - benzenetricarboxamide. In some aspects, the clarifying agent containing arylamide may be: (1,3,5 - tris(2,2 - dimethylpropionamido)benzene. Examples of commercially available clarifying agents containing arylamide include, but are not limited to: IRGACLEAR XT386 available from BASF Corporation.

[0108] In some embodiments, the compositions of the present disclosure may be free of or substantially free of a clarifying agent, such as containing less than 100 ppm, or less than 50 ppm, or less than 10 ppm of a clarifying agent, which contains sorbitol or sorbitol derivatives, nonanol or nonanol derivatives, and / or xylitol or xylitol derivatives.

[0109] 8. Additives

[0110] In some embodiments, the composition may further comprise one or more additives selected from antioxidants, stabilizers, neutralizing agents, processing aids, peroxides, slip agents, and / or antistatic agents. In some embodiments, the one or more additives may be selected from (but are not limited to): antioxidants, acid neutralizing agents, antistatic agents, anti-caking agents, anti-fogging agents, corrosion inhibitors, clarifying agents, UV absorbers, lubricants, plasticizers, mineral oils, waxes, clays, talc, calcium carbonate, diatomaceous earth, carbon black, mica, glass fibers, fillers, slip agents, colorants, UV stabilizers and / or tolerance agents, flame retardants, mold release agents, dyes, foaming agents, fluorescent agents, surfactants, oils, neutralizing agents, flow modifiers, processing aids, reinforcing agents, stabilizers, impact modifiers, nucleating agents, crystallization aids, additional polymers, or any combination thereof. The additives are available from various commercial suppliers. Non-limiting examples of commercial additive suppliers include: BASF (Germany), Dover Chemical Corporation (USA), AkzoNobel (Netherlands), (Sigma-Aldrich, USA), Atofina Chemicals, and the like.

[0111] In some embodiments, the composition may contain: i) an antioxidant in an amount of 50 ppm to 500 ppm, or at least any one of, equal to any one of, or between any two of the following: 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, and 500 ppm of the antioxidant, ii) a stabilizer in an amount of 200 ppm to 2000 ppm, or at least any one of, equal to any one of, or between any two of the following: 200 ppm, 400 ppm, 600 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1400 ppm, 1600 ppm, 1800 ppm, and 2000 ppm of the stabilizer, iii) an antistatic agent in an amount of 200 ppm to 2000 ppm, or at least any one of, equal to any one of, or between any two of the following: 200 ppm, 400 ppm, 600 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1400 ppm, 1600 ppm, 1800 ppm, and 2000 ppm of the antistatic agent, and iv) a neutralizing agent in an amount of 100 ppm to 1000 ppm, or at least any one of, equal to any one of, or between any two of the following: 100 ppm, 200 ppm, 400 ppm, 600 ppm, 800 ppm, and 1000 ppm of the neutralizing agent, or any combination thereof.

[0112] In some embodiments, the antioxidant can be a sterically hindered phenol and / or a phosphite / phosphonate-containing antioxidant. In some embodiments, a combination of antioxidants can be used. In some aspects, the sterically hindered phenol antioxidant can be: pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], or 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, or any combination thereof. In some aspects, the phosphite-containing antioxidant can be: tris(2,4-di-tert-butylphenyl) phosphite, bis(2,4-di-cumylphenyl)pentaerythritol diphosphite, or bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, or any combination thereof. In some specific aspects, the antioxidant can be pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. In some embodiments, the stabilizer can be a phosphite / phosphonate-containing stabilizer and / or an oligomeric hindered amine-containing stabilizer. In some aspects, the phosphite / phosphonate-containing stabilizer can be tris(2,4-di-tert-butylphenyl) phosphite. In some aspects, the oligomeric hindered amine-containing stabilizer can be a polymer of succinic acid, dimethyl ester, and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidylethanol. In some specific aspects, the stabilizer can be tris(2,4-di-tert-butylphenyl) phosphite. In some aspects, the antistatic agent can be glycerol monostearate. In some embodiments, the monoester content of glycerol monostearate can be 45 to 90 wt%, or at least any one of the following, equal to any one of the following, or between any two of the following: 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, and 90 wt%. In some embodiments, the neutralizer can be a stearate / phosphonate-containing neutralizer, hydrotalcite, zinc oxide, or sodium benzoate, or any combination thereof. In some embodiments, the stearate / phosphonate-containing neutralizer can be calcium stearate and / or zinc stearate. In some specific aspects, the neutralizer can be a stearate / phosphonate-containing neutralizer such as calcium stearate, and / or zinc stearate.

[0113] In some aspects, the composition may contain from 50 ppm to 500 ppm of a sterically hindered phenol such as pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], from 200 ppm to 2000 ppm of a phosphite / phosphonate-containing stabilizer such as tris(2,4-di-tert-butylphenyl) phosphite, from 200 ppm to 2000 ppm of an ester-containing antistatic agent such as glycerol monostearate, or from 100 ppm to 1000 ppm of a stearate / phosphonate such as calcium stearate and / or zinc stearate, or any combination thereof.

[0114] C. Method for Preparing a Polypropylene AM Product Comprising Polypropylene

[0115] Methods for producing the polypropylene used in the present disclosure include various methods known in the art such as, but not limited to: "high pressure" processes, slurry processes, solution processes, gas phase processes, or combinations thereof. In some embodiments, the process for preparing polypropylene involves the use of heat, pressure, one or more monomers, and one or more catalysts, as well as optionally additional additives and / or optionally cross-polymers. For example, components such as monomers (e.g., propylene, ethylene, xylene, etc.), optionally in combination with one or more catalysts (e.g., including but not limited to Ziegler Natta catalysts, chromium or Phillips catalysts, single site catalysts, metallocene catalysts, etc.), and optionally in combination with one or more additives, may be mixed (such as, but not limited to, dry blending) and then melt blended (such as, but not limited to, extrusion) to form a polymeric composition. In some embodiments, the polypropylene is produced using: high pressure processes, slurry processes, solution processes, gas phase processes, or combinations thereof. In some embodiments, the reactor powder may subsequently be subjected to downstream processing to introduce additives. In some embodiments, the reactor powder is formed into polypropylene pellets via an extrusion process, injection molding, and / or thermoforming.

[0116] In some embodiments, polypropylene can be formed by placing one or more monomers (e.g., propylene) alone or with other monomers and / or additives in a suitable reaction vessel in the presence of a catalyst (e.g., Ziegler-Natta, metallocene, etc.) and under reaction conditions suitable for monomer polymerization. Any suitable equipment and process can be used to polymerize propylene into a polymer. For example, the process can include: solution phase, gas phase, slurry phase, bulk phase, high pressure processing, or a combination thereof. The process is described in detail in U.S. Patent Nos. 5,525,678; 6,420,580; 6,380,328; 6,359,072; 6,346,586; 6,340,730; 6,339,134; 6,300,436; 6,274,684; 6,271,323; 6,248,845; 6,245,868; 6,245,705; 6,242,545; 6,211,105; 6,207,606; 6,180,735; and 6,147,173, which are incorporated herein by reference in their entirety.

[0117] In some embodiments, polypropylene can be formed by a gas phase polymerization process. A non-limiting example of a gas phase polymerization process includes a continuous recycle system where a recycle gas stream (also referred to as a recycle stream or a fluidizing medium) is heated in a reactor by the heat of polymerization. In another part of the cycle, heat is removed from the recycle gas stream by a cooling system external to the reactor. A recycle gas stream containing one or more monomers can be continuously recycled through a fluidized bed in the presence of a catalyst and under reaction conditions. Generally, the recycle gas stream is withdrawn from the fluidized bed and recycled back to the reactor. At the same time, the polymer product can be withdrawn from the reactor and fresh monomers added to replace the polymerized monomers. The reactor pressure in the gas phase process can vary as follows: 100 psig to 500 psig, or 200 psig to 400 psig, or 250 psig to 350 psig. The reactor temperature in the gas phase process can be 30°C to 120°C, or 60°C to 115°C, or 70°C to 110°C, or 70°C to 95°C. Non-limiting examples of polymer processes are described in U.S. Patent Nos. 4,543,399; 4,588,790; 5,028,670; 5,317,036; 5,352,749; 5,405,922; 5,436,304; 5,456,471; 5,462,999; 5,616,661; 5,627,242; 5,665,818; 5,677,375; and 5,668,228, which are incorporated herein by reference in their entirety.

[0118] In some aspects, the polypropylene to be included in the AM article and / or the method of fabricating the AM article can be formed by extruding a molten polymeric composition through a slot or die and cooling (e.g., quenching) the extrudate to form an initial article, such as an extruded sheet (e.g., but not limited to an extruded tape). In some embodiments, the extrusion of the molten polypropylene can occur at a temperature in the range of 120°C to 315°C, or at least any one of the following, equal to any one of the following, or between any two of the following: 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, and 315°C. In some aspects, the thickness of the extruded sheet can be 0.5 to 100 mm, 12 to 20 mm, 12 to 16 mm, or 16 to 20 mm, at least any one of the following, equal to any one of the following, or between any two of the following: 0.5 mm, 1 mm, 2 mm, 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, and 100 mm. In some aspects, the initial article can be a multi-layer extruded sheet, and the thickness of each layer of the multi-layer extruded sheet can independently be 0.5 to 100 mm, 12 to 20 mm, 12 to 16 mm, or 16 to 20 mm, or at least any one of the following, equal to any one of the following, or between any two of the following 0.5 mm, 1 mm, 2 mm, 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, and 100 mm.

[0119] In some aspects, an additively manufactured product comprising polypropylene and / or a method of preparing an additively manufactured product comprising polypropylene involves using polypropylene in the form of filaments. In some embodiments, the diameter of the polypropylene filaments can be 1.75 mm. In some embodiments, the diameter of the polypropylene filaments can be 2.85 mm. In some embodiments, the polypropylene filaments are greater than, less than, or about 1.5 mm, 1.55 mm, 1.6 mm, 1.65 mm, 1.7 mm, 1.75 mm, 1.8 mm, 1.85 mm, 1.9 mm, 1.95 mm, 2.0 mm, 2.05 mm, 2.1 mm, 2.15 mm, 2.2 mm, 2.25 mm, 2.3 mm, 2.35 mm, 2.4 mm, 2.45 mm, 2.5 mm, 2.55 mm, 2.6 mm, 2.65 mm, 2.7 mm, 2.75 mm, 2.8 mm, 2.85 mm, 2.9 mm, 2.95 mm, 3 mm, 3.05 mm, 3.1 mm, 3.15 mm, 3.2 mm, 3.25 mm, 3.3 mm, 3.35 mm, 3.4 mm, 3.45 mm, or 3.5 mm, or any range derivable therefrom.

[0120] In some aspects, an additively manufactured product comprising polypropylene and / or a method of preparing an additively manufactured product comprising polypropylene involves using polypropylene in the form of powder and / or granules. In some embodiments, the average particle size of the polypropylene powder and / or granules is from 1 μm to 500 μm. In some embodiments, the average particle size of the polypropylene powder and / or granules is from 15 μm to 100 μm. In some embodiments, the average particle size of the polypropylene powder and / or granules is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, 250 μm, 260 μm, 270 μm, 280 μm, 290 μm, 300 μm, 310 μm, 320 μm, 330 μm, 340 μm, 350 μm, 360 μm, 370 μm, 380 μm, 390 μm, 400 μm, 410 μm, 420 μm, 430 μm, 440 μm, 450 μm, 460 μm, 470 μm, 480 μm, 490 μm, or 500 μm, or any range derivable therefrom.

[0121] D. AM Products Comprising Polypropylene and Methods for Preparing the Same

[0122] Additively manufactured products containing polypropylene, methods of using polypropylene, and methods of preparing additively manufactured products containing polypropylene are described herein. In some embodiments, the additively manufactured products containing polypropylene, and / or the methods of preparing additively manufactured products may include any of the additive manufacturing methods described herein, such as but not limited to fused deposition modeling and / or selective laser sintering. The polypropylene described in this disclosure may be included in an article of manufacture. As described above, the article of manufacture is produced by additive manufacturing. In some aspects, the article of manufacture may be transparent, translucent, and / or opaque.

[0123] In some aspects, the additively manufactured products containing polypropylene, the methods of using polypropylene, and the methods of preparing additively manufactured products containing polypropylene include extruding polypropylene from a nozzle. In some embodiments, the nozzle diameter is greater than, less than, or about 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1.0 mm, 1.1 mm, 1.15 mm, 1.2 mm, 1.25 mm, 1.3 mm, 1.35 mm, 1.4 mm, 1.45 mm, 1.5 mm, 1.55 mm, 1.6 mm, 1.65 mm, 1.7 mm, 1.75 mm, 1.8 mm, 1.85 mm, 1.9 mm, 1.95 mm, or 2.0 mm, or any range derivable therefrom. In some embodiments, the polypropylene nozzle diameter is greater than 2.0 mm. In some embodiments, the polypropylene is in contact with a heated plate. In some embodiments, the polypropylene is in contact with a build plate.

[0124] In some aspects, additively manufactured products that include polypropylene, methods of using polypropylene, and methods of preparing additively manufactured products that include polypropylene include layering polypropylene powder and / or particulate matter. In some embodiments, the average particle size of the polypropylene powder and / or particulate matter is from 1 μm to 500 μm. In some embodiments, the average particle size of the polypropylene powder and / or particulate matter is from 15 μm to 100 μm. In some embodiments, the average particle size of the polypropylene powder and / or particulate matter is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, 250 μm, 260 μm, 270 μm, 280 μm, 290 μm, 300 μm, 310 μm, 320 μm, 330 μm, 340 μm, 350 μm, 360 μm, 370 μm, 380 μm, 390 μm, 400 μm, 410 μm, 420 μm, 430 μm, 440 μm, 450 μm, 460 μm, 470 μm, 480 μm, 490 μm, or 500 μm, or any range derivable therefrom. In some embodiments, the polypropylene powder and / or particulate matter is contained in a dust-free and / or airtight container to prevent accidental spillage and / or leakage. In some embodiments, the polypropylene powder and / or particulate matter includes an additive for alleviating static electricity. In some embodiments, the morphology and particle size distribution of the polypropylene powder and / or particulate matter are carefully controlled to facilitate production consistency. In some embodiments, the polypropylene powder and / or particulate matter is cryogenically milled and then dissolved-precipitated to effectively control the particle size.

[0125] Non-limiting examples of the manufactured articles include: household goods, food storage containers, cooking utensils, plates, cups, measuring cups, drinking glasses, strainers, turkey roasters, non-food storage devices, filing cabinets, particularly transparent drawers used in such cabinets, general storage devices such as organizers, totes, sweater boxes, films, coatings and fibers, bags, adhesives, yarns, fabrics, bottles, jars, plates and cups, clamshells, and the like. In certain embodiments, the manufactured article can be rigid packaging such as deli containers and lids, including those for dips, spreads, and pasta salads, dairy containers and lids, including those for storing cottage cheese, butter, and yogurt, personal care products, and bottles and jars. In certain embodiments, the manufactured article can be a motor vehicle component, a building materials component, an insulation component, an electronic instrument component, a furniture component, a fabric component, a container component, a household appliance component, a medical component, sports equipment, a prosthesis, a filter medium, and / or a custom toy.

[0126] In these and other uses, the polypropylene can be combined with other materials such as particulate materials including talc, calcium carbonate, wood, and fibers such as glass or graphite fibers, etc., to form a composite material. Examples of such composite materials include components for furniture, automotive components, and building materials, particularly those used as wood substitutes.

[0127] E. Recitation of Aspects

[0128] Certain aspects of the invention are set forth by the following numbered aspects.

[0129] Aspect 1 is an additively manufactured article comprising one or more polypropylenes (PP) having one or more of the following properties: a) a melt temperature ≤ 135 °C, measured according to ASTM D3418-15; b) an onset melt temperature ≤ 125 °C, measured according to ASTM D3418-15; c) an onset crystallization temperature ≤ 105 °C, measured according to ASTM D3418-15; d) a crystallinity ≤ 35%, measured according to ASTM D3418-15; e) an Avrami exponent ≤ 2.10; f) an absolute value of the crystallization activation energy ≤ 550,000 J / mol, determined by fitting to Avrami kinetics; and / or g) an absolute value of the crystallization activation energy less than or equal to 80% of the absolute value of the crystallization activation energy of an un-nucleated Ziegler-Natta homopolymer polypropylene.

[0130] Aspect 2 is an additively manufactured article as described in Aspect 1, comprising one or more PPs having one or more of the following properties: a) a melting temperature ≤ 130 °C, measured according to ASTM D3418-15; b) an onset melting temperature ≤ 120 °C, measured according to ASTM D3418-15; c) an onset crystallization temperature ≤ 100 °C, measured according to ASTM D3418-15; d) a crystallinity ≤ 30%, measured according to ASTM D3418-15; e) an Avrami exponent ≤ 2.05; f) an absolute value of the crystallization activation energy ≤ 500,000 J / mol, determined by fitting to Avrami kinetics; and / or g) an absolute value of the crystallization activation energy less than or equal to 75% of the absolute value of the crystallization activation energy of an un-nucleated Ziegler-Natta homopolymer polypropylene.

[0131] Aspect 3 is an additively manufactured article as described in Aspect 1 or 2, comprising one or more PPs having at least two of the following properties: a) a melting temperature ≤ 135 °C, or ≤ 130 °C, measured according to ASTM D3418-15; b) an onset melting temperature ≤ 125 °C, or ≤ 120 °C, measured according to ASTM D3418-15; c) an onset crystallization temperature ≤ 105 °C, or ≤ 100 °C, measured according to ASTM D3418-15; and / or d) a crystallinity ≤ 35%, or ≤ 30%, measured according to ASTM D3418-15.

[0132] Aspect 4 is an additively manufactured article as described in any one of Aspects 1 to 3, wherein the at least one polypropylene is a Ziegler-Natta based random copolymer, a metallocene random copolymer, and / or a syndiotactic polypropylene, and optionally further comprises at least one additive, wherein the additive comprises: silica, antistatic agent, colorant, corrosion inhibitor, antioxidant, acid neutralizer, anti-caking agent, anti-fogging agent, clarifying agent, UV absorber, lubricant, plasticizer, mineral oil, wax, clay, talc, calcium carbonate, diatomaceous earth, carbon black, mica, glass fiber, filler, slip agent, colorant, UV stabilizer and / or tolerance agent, flame retardant, release agent, dye, foaming agent, fluorescent agent, surfactant, oil, neutralizer, flow modifier, processing aid, reinforcing agent, stabilizer, impact modifier, nucleating agent, crystallization aid, additional polymer, or any combination thereof.

[0133] Aspect 5 is an additively manufactured article as described in any one of Aspects 1 to 4, wherein the absolute value of the crystallization activation energy of the PP is between about 300,000 J / mol and about 500,000 J / mol, determined by combining an isothermal differential scanning calorimetry (DSC) test according to ASTM D3418-15 with fitting to Avrami kinetics.

[0134] Aspect 6 is an additively manufactured article as described in any one of Aspects 1 to 5, wherein the crystallinity of the PP is from 35% to 15%, based on a heat of fusion (ΔH 0m ) of 207 J / g for theoretically 100% crystalline polypropylene.

[0135] Aspect 7 is an additively manufactured article as described in any one of Aspects 1 to 6, wherein the sintering window of the PP is 30 °C or lower, defined by the onset melting and crystallization temperatures.

[0136] Aspect 8 is an additively manufactured article as described in Aspect 7, wherein the sintering window of the PP is from 18 °C to 30 °C.

[0137] Aspect 9 is an additively manufactured article as described in any one of Aspects 1 to 8, wherein the PP density is from 0.8 g / cc to 1 g / cc, measured according to ASTM D1505-18, and / or the melt flow rate (MFR) is from 0.1 g / 10 min to 100.0 g / 10 min, measured according to ASTM D1238-20.

[0138] Aspect 10 is an additively manufactured article as described in any one of Aspects 1 to 9, wherein the melt flow of the PP is from 0.5 g / 10 min to 30 g / min, measured according to ASTM D1238-20.

[0139] Aspect 11 is a method of preparing an additively manufactured article as described in any one of Aspects 1 to 10, the method comprising melting and / or sintering a composition comprising the one or more PPs.

[0140] Aspect 12 is the method as described in Aspect 11, wherein the at least one polypropylene is a Ziegler-Natta based random copolymer, a metallocene random copolymer, and / or a syndiotactic polypropylene, and optionally further comprises at least one additive, wherein the additive comprises: silica, antistatic agent, colorant, corrosion inhibitor, antioxidant, acid neutralizer, anti-caking agent, anti-fogging agent, clarifying agent, UV absorber, lubricant, plasticizer, mineral oil, wax, clay, talc, calcium carbonate, diatomaceous earth, carbon black, mica, glass fiber, filler, slip agent, colorant, UV stabilizer and / or tolerance agent, flame retardant, release agent, dye, foaming agent, fluorescent agent, surfactant, oil, neutralizer, flow modifier, processing aid, reinforcing agent, stabilizer, impact modifier, nucleating agent, crystallization aid, additional polymer, or any combination thereof.

[0141] Aspect 13 is the method as described in Aspect 11 or 12, wherein the article is made by sintering the PP in the form of particulate matter having an average particle size of from 1 μm to 500 μm.

[0142] Aspect 14 is the method as described in aspect 13, wherein the average particle size of the particulate matter is 15 μm to 100 μm.

[0143] Aspect 15 is the method as described in any one of aspects 11 to 14, wherein the method comprises material extrusion, wherein the composition in a molten state is extruded through a nozzle and deposited in layers.

[0144] Aspect 16 is the method as described in any one of aspects 11 to 14, wherein the method comprises sintering the particles as described in the aspect of sintering a composition in the form of particulate matter in a powder bed sintering (PBS) process.

[0145] Aspect 17 is the method as described in aspect 16, wherein the PBS process uses a layer thickness of 10 μm to 200 μm and / or a component bed temperature of 20 °C to 100 °C.

[0146] Aspect 18 is the method as described in aspect 17, wherein the PBS process uses a layer thickness of 30 μm to 150 μm.

[0147] Aspect 19 is an additively manufactured article comprising the article as described in any one of aspects 1 - 10, or a manufactured article obtained by the method as described in any one of aspects 11 - 18.

[0148] Aspect 20 is the article as described in aspect 19, wherein the article is: a motor vehicle component, a building material component, an insulation component, an electronic instrument component, a furniture component, a fabric component, a container component, a household appliance component, a medical component, a prosthesis, a filter medium, and / or a customized toy.

[0149] Aspect 21 is a composition for additive manufacturing, wherein the composition comprises at least one polypropylene (PP) and is designed to contact at least one component used in a 3D printer, wherein the PP comprises one or more of the following properties: a) a melting temperature ≤ 135 °C, measured according to ASTM D3418 - 15; b) an onset melting temperature ≤ 125 °C, measured according to ASTM D3418 - 15; c) an onset crystallization temperature ≤ 105 °C, measured according to ASTM D3418 - 15; d) a crystallinity ≤ 35%, measured according to ASTM D3418 - 15; e) an Avrami exponent ≤ 2.10; f) an absolute value of the crystallization activation energy ≤ 550,000 J / mol, determined by fitting Avrami kinetics; and / or g) an absolute value of the crystallization activation energy is less than or equal to 80% of the absolute value of the crystallization activation energy of an un-nucleated Ziegler - Natta homopolymer polypropylene.

[0150] Aspect 22 is a composition as described in aspect 21, the composition comprising one or more polypropylenes (PPs) having one or more of the following properties: a) a melting temperature ≤ 130 °C, measured according to ASTM D3418-15; b) an onset melting temperature ≤ 120 °C, measured according to ASTM D3418-15; c) an onset crystallization temperature ≤ 100 °C, measured according to ASTM D3418-15; g) a crystallinity ≤ 30%, measured according to ASTM D3418-15; d) an Avrami exponent ≤ 2.05; e) an absolute value of the crystallization activation energy ≤ 500,000 J / mol, determined by fitting Avrami kinetics; and / or f) an absolute value of the crystallization activation energy less than or equal to 75% of the absolute value of the crystallization activation energy of an un-nucleated Ziegler-Natta homopolymer polypropylene.

[0151] Aspect 23 is a composition as described in aspect 21 or 22, the composition comprising one or more PPs having at least two of the following properties: a) a melting temperature ≤ 135 °C, or ≤ 130 °C, measured according to ASTM D3418-15; b) an onset melting temperature ≤ 125 °C, or ≤ 120 °C, measured according to ASTM D3418-15; c) an onset crystallization temperature ≤ 105 °C, or ≤ 100 °C, measured according to ASTM D3418-15; and / or d) a crystallinity ≤ 35%, or ≤ 30%, measured according to ASTM D3418-15.

[0152] Aspect 24 is an additively manufactured article as described in any one of aspects 21 to 23, wherein the at least one PP is a Ziegler-Natta based random copolymer, a metallocene random copolymer, and / or a syndiotactic PP, and optionally further comprises at least one additive, wherein the additive comprises: silica, antistatic agent, colorant, corrosion inhibitor, antioxidant, acid neutralizer, anticaking agent, antifogging agent, clarifying agent, ultraviolet absorber, lubricant, plasticizer, mineral oil, wax, clay, talc, calcium carbonate, diatomaceous earth, carbon black, mica, glass fiber, filler, slip agent, colorant, ultraviolet stabilizer and / or tolerance agent, flame retardant, mold release agent, dye, foaming agent, fluorescent agent, surfactant, oil, neutralizer, flow modifier, processing aid, reinforcing agent, stabilizer, impact modifier, nucleating agent, crystallization aid, additional polymer, or any combination thereof.

[0153] Aspect 25 is a composition as described in any one of aspects 21 to 24, which comprises at least 95 wt% of at least one PP.

[0154] Aspect 26 is a composition as described in any one of aspects 21 to 25, wherein the PP is in contact with: a 0.4 mm extruder nozzle, a 0.35 mm extruder nozzle, a build plate, and / or a heated bed.

[0155] Aspect 27 is a composition as described in any one of aspects 21 to 26, wherein the absolute value of the crystallization activation energy of the PP is between about 300,000 J / mol and about 500,000 J / mol, which is determined by combining an isothermal differential scanning calorimetry (DSC) test according to ASTM D3418-15 with Avrami kinetics fitting.

[0156] Aspect 28 is a composition as described in any one of aspects 21 to 27, wherein the crystallinity of the PP is 35% to 15%, based on a heat of fusion (ΔH 0m ) of 207 J / g for theoretically 100% crystalline polypropylene.

[0157] Aspect 29 is a composition as described in any one of aspects 21 to 28, wherein the sintering window of the PP is 30 °C or lower, defined by the onset melting and crystallization temperatures.

[0158] Aspect 30 is a composition as described in aspect 29, wherein the sintering window of the PP is 18 °C to 30 °C.

[0159] Aspect 31 is a composition as described in any one of aspects 21 to 30, wherein the density of the PP is 0.8 g / cc to 1 g / cc, measured according to ASTM D1505-18, and / or the melt flow is 0.1 g / 10 min to 100 g / 10 min, measured according to ASTM D1238-20.

[0160] Aspect 32 is a composition as described in aspect 31, wherein the melt flow of the PP is 0.5 g / 10 min to 30 g / 10 min.

[0161] Aspect 33 is a composition as described in any one of aspects 21 to 32, wherein the PP is in the form of granules having an average particle size of 1 μm to 500 μm.

[0162] Aspect 34 is a composition as described in aspect 33, wherein the average particle size of the granules is 15 μm to 100 μm.

[0163] Examples

[0164] The present invention will be described in more detail by way of specific examples. The examples provided below are for illustrative purposes only and are not intended to limit the present invention in any way. Those skilled in the art will readily identify various non-critical parameters that can be varied or modified to produce substantially the same results.

[0165] A. Example 1 - Melting and Crystallization Temperatures

[0166] The typical melting temperatures (T m ) and crystallization temperatures (T c ) of polypropylenes 3270, 3276, Z9450, M9675, and 1251 were determined (see Table 6); these data are representative averages of 10 or more different tests). Non-uniform melting behavior was observed, which reflects the malleability of the thermal behavior traced back to the molecular structure of each polypropylene. The melting behavior is also related to the overall crystallinity, as listed in the crystallization enthalpy and melting enthalpy (see Table 7; these data are representative averages of 10 or more different tests). Such diverse melting and crystallization temperatures provide advantages for certain polypropylenes in additive manufacturing.

[0167] Table 6 - Melting Temperature (T m ), Crystallization Temperature (T c ), and Temperature Difference between PP Grades

[0168]

[0169] Melting Temperature = T m ; Crystallization Temperature = T c ; Isotactic Ziegler-Natta highly crystalline homopolymer = IZNHCH; Isotactic Ziegler-Natta homopolymer = IZNH; Ziegler-Natta random copolymer = ZNRC; Metallocene random copolymer = MRC; Syndiotactic metallocene homopolymer = SMH; Standard Deviation = Std Dev.

[0170] Table 7 - Crystallization Enthalpy (-ΔH c ) and Melting Enthalpy (ΔH m ) between PP Grades

[0171]

[0172] Crystallization Enthalpy = -ΔH c ; Melting Enthalpy = -ΔH m ; J / g = joules per gram; Isotactic Ziegler-Natta highly crystalline homopolymer = IZNHCH; Isotactic Ziegler-Natta homopolymer = IZNH; Ziegler-Natta random copolymer = ZNRC; Metallocene random copolymer = MRC; Syndiotactic metallocene homopolymer = SMH; Standard Deviation = Std Dev.; *Based on a melting heat (ΔH 0m ) of 207 J / g for theoretically 100% crystalline polypropylene.

[0173] Three homopolymer grades: 3270, 3276, and 1251 are listed in Tables 6 and 7. Evaluating these three grades highlights how the syndiotactic PP (1251) among the homopolymer grades provides advantages for AM over isotactic PP, such as T m lower, T c lower, and / or a larger T m -T c range. Regarding the lower T m , the melting point of 1251 is 35 to 40 °C lower. At the same time, the melt temperature of 127 °C is significantly higher than the boiling temperature of water, which is a typical lower limit for many applications. Compared with 3270 and 3276 or other alternative polypropylenes, this lower T m can provide the advantage of using less energy for FDM and SLS processes. Regarding the lower T c , 1251 crystallizes at a temperature approximately 50 °C lower than alternative polypropylenes. A crystallization temperature of 67 °C is beneficial, especially when printing in an ambient environment where the temperature is 25 °C. This low crystallization temperature allows for a longer time for proper adhesion between adjacent layers in AM parts. Strong adhesion can be beneficial for maximizing physical property performance. This lower T c is expected to allow for a lower bed temperature and less stringent requirements for enclosing the printed area to maintain thermal consistency. Regarding the larger T m -T c range, the range between the melting and crystallization temperatures of 1251 is 60 °C, which is >10 °C higher than any of the Ziegler-Natta homopolymers.

[0174] A wider range can be advantageous as it can create a larger metastable regime, thus enhancing AM processing. This wider range can provide more control for the processor in manufacturing products, contribute to product consistency, and resilience to natural manufacturing variations.

[0175] Similar statements can also be made when comparing isotactic homopolymers with random copolymers (RCPs) with significantly lower melting points. In particular, both Z9450 and M9675 provide several advantages over isotactic PP, such as a lower T m and a lower T c . Regarding the lower T m , the melt temperature of the RCP is >30 °C lower, but still significantly higher than the boiling temperature of water. Compared with polypropylene 3270 and / or 3276, this lower Tm provides the advantage of using less energy for FDM and / or SLS processes. Regarding the lower T c , the RCP crystallizes at a temperature ≥25 °C lower than the compared isotactic PP.

[0176] This lower crystallization temperature allows adjacent layers in the AM part to adhere properly for a longer time and provides optimal physical properties.

[0177] Analysis of Tc and Tm can be considered a complementary way to quantify the onset crystallization temperature and onset melting temperature [as described by Schmid and colleagues (see, for example, Figure 3 ) and used to evaluate the AM processing window]. For example, 3DEvaluate (3D Alliance Corporation) uses this approach to explore the processing window of SLS, as done by Kuehnlein and colleagues (see, for example, “3D Evaluate - September 21, 2020, Yehiel Shaham's ‘Why don’t we see more polymers in SLS?’”; and Kuehnlein et al., Degradation behavior and material properties of PA12 - Plastic powders processed by powder based additive manufacturing technologies. Annals of DAAAM, 2010).

[0178] There are multiple factors that favor the use of T c and T m to screen polymers for AM. For example, the peak melting and crystallization temperatures are more straightforward and contribute to test consistency. In some cases, measuring the onset temperature requires fitting a tangent to the peak; in cases where the melting or crystallization behavior is diffuse and / or complex, this tangent can prove challenging and / or result in higher deviation. Another advantage is that quantifying the peak temperature is a more common practice compared to quantifying the onset temperature. The onset temperature can capture important salient points of early phase transitions, but may require additional training for those not familiar with metrology. For the purpose of screening and evaluating PP types by comparison, the T c and T m measurements are instructive and useful.

[0179] B. Example 2 - Melting and Crystallization DSC Traces

[0180] Representative DSC melting and crystallization traces were generated for a more subtle observation of the crystallization and melting behavior (see Figure 4 A - E). Several overall observations can be made from the data.

[0181] It was observed that the shape of the melting peak can vary widely. The most extreme case is 1251, which exhibits bimodal behavior. This illustrates the limitation of using a single data point (e.g., melting point) to characterize the melting behavior.

[0182] It was observed that as the temperature increases, the melting peak can have a long lower-temperature tail. For any PP measured, the melting peak is not neatly symmetric. All PPs measured have a lower melting point species, which is reflected as an initially gradually rising peak shape. This rise increases with increasing temperature, accelerating until an inflection point near the peak melting temperature is reached.

[0183] It was observed that the shape of the crystallization peak can vary similarly. Although no clear bimodality was confirmed, it seems that the process from early crystallization to bulk crystallization as T c differs between polymers. It was noted that 1251 in particular seems to have a wider temperature range from early crystallization to broad bulk crystallization.

[0184] C. Example 3 - Starting Temperature and Metastable Zone

[0185] By defining a metastable processing window [calculated between the starting melting temperature (Tm - start) and the starting crystallization temperature (Tc - start)], the subtle variations described in Example 2 are further illustrated and characterized (see Figure 5 A - E). For convenience, this metastable zone will follow the SLS convention and be called the "sintering window". However, this metastable zone has a broader use for AM processes and is not limited to SLS. For example, in the FDM process, both starting temperatures can have practical processing importance.

[0186] For Tc-onset, Pogodina and Winter explored polypropylene crystallization as a physical gelation process, where gelation occurs at 2% crystallinity or less (see, e.g., Natalia V. Pogodina and H. Henning Winter, Polypropylene Crystallization as a Physical Gelation Process. Macromolecules, 1998). This gelation process is the transition point where the bulk flow of the melt ceases. The early formed grains act as physical crosslinks, leading to a significant increase in viscosity. This physical change means that any further layer-by-layer bonding will be dominated by the intermolecular diffusion (creep) of polymer chains at the boundaries, and this intermolecular diffusion competes with further crystallization where the polymer chains fold into grains. To the extent that any physical mechanism (such as crystallization) hinders further interfacial chain diffusion, it can result in weak layer-by-layer bonding (see, e.g., Rhugdhrivya Rane. Enhancing tensile Strength of FDM parts using Thermal Annealing and Uniaxial Pressure. Master of Science in Mechanical Engineering Thesis, December 2018, University of Texas, Arlington).

[0187] For Tm-onset, as each layer is deposited, a portion of the adjacent layer must be melted to enable bonding (see, e.g., "Fused Deposition Modeling (FDM) 3D Printing - Simply Explained" at pick3dprinter.com). Typically, the previous layer is in a transitional state where the melt is at least at or beyond physical gelation, where thin crystalline layers are undergoing primary crystallization on a metastable core layer. This previous layer may need to have sufficient load-bearing capacity to resist the flow associated with the addition of the new layer. Otherwise, subsequent deposition of layers can result in creeping flow and cause severe distortion of the part. In view of this, at the layer-by-layer interface, the temperature should exceed the Tm-onset temperature. The freshly melted extrudate should reach at least this temperature so that both sides of the layer-by-layer interface are molten material. Labile chains can then undergo molecular diffusion across the interface, resulting in bonding strength. In this context, in some cases, the Tm-onset can be regarded as the minimum boundary in FDM processing.

[0188] Evaluating the sintering window (see Figure 5A - E) provide a new perspective on the immediate characterization of the resin compared to the prior evaluation that generally only considers the melting and crystallization temperatures. The immediate approach provides a perspective on the early phase transitions and how physics dominates aspects closely related to AM processing and properties.

[0189] Polypropylene 3270 illustrates a more crystalline polypropylene homopolymer (see Figure 5 A). The melting and crystallization peaks are stronger and more prominent compared to the other polymers studied, meaning that the peak melting and crystallization temperatures are closer to the onset temperature. This, combined with a melting supercooling significantly lower than the melting temperature, results in a wide sintering window. Figure 5 The corresponding DSC trace in A gives a sintering window of >40 °C. Polypropylene 3276 represents a less crystalline polypropylene homopolymer (see Figure 5 B). The peaks are not as sharp as those of 3270, especially the melting peak. The broader melting peak, compared to 3270, particularly shifts Tm - onset to a lower temperature and narrows the sintering window.

[0190] For the random copolymers (Z9450 and M9675), the melting peak behavior enhances the trend observed when comparing 3276 with 3270. The melting peaks are flatter compared to 3276 or 3270 (see Figure 5 C and D). In particular, the melting peak of Z9450 is very broad, shifting the Tm - onset temperature to 112.48 °C. The DSC traces of Z9450 and M9675 each give a narrower sintering window, 19.54 °C and 25.52 °C respectively.

[0191] The behavior of syndiotactic polypropylene (1251) deserves a separate overview. As a homopolymer, its sintering window is significantly narrower compared to those of 3270 and 3276, at 27.49 °C (see Figure 5 E). This narrowness may be due to its bimodal melting endotherm, with a small peak appearing before the main peak, which shifts Tm - onset to 108.67 °C. Also important is the shape of the crystallization peak. It is significantly broader compared to the other homopolymers, meaning that initial grains form at slightly below 85 °C.

[0192] The foregoing qualitative descriptions are quantified in Table 8. The relevant discussion is outlined below.

[0193] The difference between the peak melting temperature and onset melting is smallest for 3270 and M9675. This result is consistent with the molecular structure. 3270 is a highly crystalline homopolymer with high stereoregularity. M9675 is a metallocene random copolymer with high regularity in the ethylene insertion. In both cases, the consistency in the molecular structure helps drive fast crystallization kinetics. Once incipient crystallites are formed, they quickly lead to extensive self-nucleation in the melt.

[0194] The difference between the peak melting temperature and onset melting is largest for Z9450 and 1251. This result is also consistent with the molecular structure. Z9450 is a high-ethylene Ziegler-Natta random copolymer with significantly lower consistency in the ethylene insertion (e.g., the ethylene insertion results in blocks of multiple ethylene units rather than a uniform dispersion with rare ethylene-ethylene linkages). 1251 is a syndiotactic polypropylene with lower consistency in the syndiotactic blocks compared to the consistency present in isotactic polypropylene. This molecular structure favors a continuum of crystals with a wider range of imperfections, resulting in a generally broader melting endotherm.

[0195] 1251 is crystallographically distinct, with the widest difference between onset crystallization and peak crystallization temperatures. For 1251, this difference is 9.56 °C, while for the other four polypropylenes, this difference ranges from 3.73 to 5.01 °C.

[0196] Schmid et al. showed that efforts should be made to make the sintering window as wide as possible. However, as observed herein, such a one-sided statement may not be accurate for polypropylene. In some cases, there is a compromise in favor of random copolymers and sPP compared to homopolymer polypropylene. Such a compromise is outlined below.

[0197] In some cases, slower crystallization kinetics (T c onset - T c larger) are preferred. A melt that crystallizes more slowly allows more time for stress relaxation and more time for polymer chains to diffuse across layer-layer boundaries. This factor particularly favors syndiotactic polypropylene in AM, although the sintering window for syndiotactic polypropylene is narrower compared to conventional Ziegler-Natta homopolymer polypropylenes such as 3270 and 3276.

[0198] In some cases, a lower T cInitiation. A lower crystallization initiation temperature provides more time for the molten extrudate to cool before crystallization begins, which helps to relax stress and maximize layer-to-layer polymer diffusion. This factor particularly favors random copolymers and syndiotactic polypropylenes over conventional Ziegler-Natta homopolymer polypropylenes (such as 3270 and 3276) in AM.

[0199] In some cases, a wider T m -T m initiation is preferred. The balance between the extrudate temperature and the layer temperature in FDM can be delicate. If the extrudate temperature is too high, it can melt the previous layer and disrupt the part geometry. To avoid this problem, a wider heat of fusion is particularly desirable. The physical gelation concept of Pogodina and Winter is also effective in reverse - the remaining higher melting point crystalline species can act as physical crosslinks and impede flow. In this regard, syndiotactic PP and Z9450 are advantageous compared to conventional homopolymer polypropylenes (such as 3270 and 3276).

[0200] In some cases, a lower crystallinity is preferred. For FDM, the trend is that this technology favors amorphous polymers over semi - crystalline polymers because amorphous polymers tend to shrink less, warp less, and distort less (see, for example, Abishek Kafle et al., 3D / 4D Printing of Polymers: Fused Deposition Modelling (FDM), Selective Laser Sintering (SLS), and Stereolithography (SLA). Polymers. September 15, 2021). In a continuum view, this means that lower crystalline polypropylenes should tend to shrink less, warp less, and distort less. Lower melting point random copolymers (such as M9675 and Z9450) and syndiotactic polypropylenes (such as 1271) match this description (see Table 8). These polypropylenes are less crystalline compared to conventional homopolymer polypropylenes (such as 3270 and 3276).

[0201] Table 8 - Initiation Temperature, Melting Temperature, and Crystallization Temperature

[0202]

[0203] Melting temperature = Tm; Crystallization temperature = Tc; Isotactic Ziegler - Natta highly crystalline homopolymer = IZNHCH; Isotactic Ziegler - Natta homopolymer = IZNH; Ziegler - Natta random copolymer = ZNRC; Metallocene random copolymer = MRC; Syndiotactic metallocene homopolymer = SMH

[0204] D. Example 4 - Isothermal Crystallization and Avrami Kinetics

[0205] The following idea was investigated by isothermal DSC testing: various polypropylenes may have different crystallization kinetics. Historically, for this purpose, the Avrami equation has been used (see, for example, Catherine A. Kelly and Mike J. Jenkins, Modeling the crystallization kinetics of polymers displaying high levels of secondary crystallization. Polymer Journal, November 19, 2021; TA393 Comparison of Crystallization Behavior of Different Colored Parts Made from Polypropylene Using a Single DSC Experiment, TA Instruments; and TA222 by J. A. Foreman and R. L. Blaine, Isothermal Crystallization Made Easy: A Simple Model and Modest Cooling Rates, TA Instruments.).

[0206] Equation 1 Avrami Equation

[0207]

[0208] The parameters of the Avrami equation can be determined from the inverse logarithm of the slope (n t ) and the y - intercept (k a ) of the double - logarithmic plot of log(−ln(1 - X a )) versus log time. For this purpose, the Avrami equation (Equation 1) can be rearranged as shown in the linear form of the Avrami equation (Equation 2). The Avrami equation parameters are defined as follows: X t = the fraction of crystallinity at time t; K a = the Avrami rate constant; n a = the Avrami exponent, which should theoretically be an integer between 1 and 4. It represents the nucleation mechanism for the growth geometry.

[0209] Linear form and simplified explanation of the Avrami equation of type 2 (see, for example, TA393 Comparison of Crystallization Behavior of Different Colored Parts Made from Polypropylene Using a Single DSC Experiment, TA Instruments).

[0210] log(-ln(1-X(t)) = logk a +n a logt

[0211] log(-ln(1-X t )) The curve of logt is linear, and the Avrami parameter K a (inverse logarithm of the intercept) and n a (slope) are obtained. The Avrami exponent is associated with the nucleation growth geometry and is summarized as follows (simplified Avrami exponent description): Avrami exponent 1 ≤ n ≤ 2 gives a 1-dimensional growth geometry, rod-shaped; Avrami exponent 2 ≤ n ≤ 3 gives a 2-dimensional growth geometry, disk-shaped; and Avrami exponent 3 ≤ n ≤ 4 gives a 3-dimensional growth geometry, spherical.

[0212] The rate constant and temperature usually follow the Arrhenius relationship (see, for example, Luljeta Raka and Gordana Bogoeva-Gaceva, Crystallization of polypropylene: Application of Differential Scanning Colorimetry, Part 1. Isothermal and non-isothermal crystallization, 2008).

[0213] Arrhenius relationship of the Avrami rate constant K a of Equation 3

[0214]

[0215] The Arrhenius equation parameters are defined as follows: K a = Avrami rate constant; A = pre-exponential factor; E a = activation energy; R = gas constant = 8.314 J / (mol·K); and T = temperature (in Kelvin).

[0216] Arrhenius relationship for the Avrami rate constant Ka in its linearized form of Equation 4

[0217]

[0218] Isothermal DSC scans were performed on each polypropylene (3270, 3276, Z9450, M9675, and 1251), and each scan was fitted to the Avrami equation. The coefficient of determination (r 2 ) of the fit was excellent, usually exceeding 0.995.

[0219] The isothermal temperatures used for each polypropylene were compared with the typical crystallization temperatures in the non-isothermal DSC tests (see Table 9). The comparison results revealed good ordering consistency. The T c of 3270 was the highest, and the isothermal temperature range was the highest. At the other end of the spectrum, the T c of 1251 was the lowest, and the isothermal temperature range was the lowest. The consistency of these results, together with the r 2 values, ensured that the isothermal test data captured the nuances in the crystallization kinetics.

[0220] The data were visually inspected by plotting the semi-crystallization time (t1 / 2) against temperature (see Figure 6 ). The shape followed the expected trend. The half-times of 3270 and 3276 seemed to be more sensitive to temperature compared to the random copolymer or syndiotactic polypropylene. Again, 3270 and 3276 crystallized more rapidly as the isothermal temperature decreased.

[0221] Table 9 - Typical non-isothermal crystallization temperatures and isothermal crystallization temperature ranges for each PP

[0222] Level PP Type Tc (°C) Isothermal Temperature Range (°C) 3270 IZNHCH 117.47 130-140 3276 IZNH 114.76 118-128 Z9450 ZNRC 90.57 92-104 M9675 MRC 82.38 90-100 1251 SMH 67.16 84-94

[0223] Melting temperature = Tm; Crystallization temperature = Tc; Isotactic Ziegler-Natta highly crystalline homopolymer = IZNHCH; Isotactic Ziegler-Natta homopolymer = IZNH; Ziegler-Natta random copolymer = ZNRC; Metallocene random copolymer = MRC; Syndiotactic metallocene homopolymer = SMH

[0224] For polypropylene, the typical literature Avrami exponents generally fall between 2 and 3 (see, e.g., TA393 Comparison of Crystallization Behavior of Different Colored Parts Made from Polypropylene Using a Single DSC Experiment, TA Instruments; TA425 Applying the Avrami and Malkin Macrokinetic Models for Evaluating Isothermal Crystallization Kinetics of Polypropylene with and without a Chemical Nucleator, TA Instruments; and Pitt Supaphol, Application of the Avrami, Tobin, Malkin, and Urbanovici-Segal microkinetic models to isothermal crystallization of syndiotactic polypropylene. Thermochimica Acta, 2001). The results of these fits follow this trend (see Figure 7 ). Of note is the result that the Avrami exponents for Z9450 and 1251 are lower than those of the other polymers. This indicates that these crystallization processes deviate most from spherical growth; as the melt crystallizes, there is a stronger preference for crystal orientation compared to 3270, 3276, and Z9450. The broader crystallization exotherm for Z9450 and 1251 can reflect this aspect of their kinetics. To the extent that this correlation exists for non-nucleated polypropylene, in some cases, polypropylene with a lower Avrami exponent will be preferred for AM.

[0225] When plotting lnk a versus (1 / RT), the slope corresponding to the activation energy (Ea) is obtained using Equation 4 (the linearized Arrhenius relationship). The activation energy indicates how sensitive the crystallization temperature is to temperature; a higher slope is equivalent to being more sensitive, while a smaller slope is equivalent to being less sensitive. From the perspective of AM, in some cases, polypropylene with a lower slope is advantageous because the crystallization process accelerates more slowly as the temperature decreases. The slow kinetics is beneficial for more interlaminar polymer chain diffusion time and better flexibility to processing temperature variations.

[0226] The linearized Arrhenius relationships for each polypropylene are presented in Figure 8 which includes the best linear fit where the slope = -E a (J / mol). Calculate the crystallization activation energy for each PP and record its relative crystallization activation energy (see Table 10).

[0227] Table 10 - Crystallization Activation Energies of Each Polypropylene

[0228]

[0229] Activation energy = Ea; Isotactic Ziegler-Natta highly crystalline homopolymer = IZNHCH; Isotactic Ziegler-Natta homopolymer = IZNH; Ziegler-Natta random copolymer = ZNRC; Metallocene random copolymer = MRC; Syndiotactic metallocene homopolymer = SMH

[0230] These crystallization activation energy results quantify the observations from Figure 6 There are differences among polypropylenes where the E of syndiotactic polypropylene a is ~50% lower than 3270 and 3276. Also, the E of Z9450 a and the E of M9675 a are ~40% and ~22.5% lower than 3270 and 3276, respectively.

[0231] The findings described throughout this disclosure teach that polypropylenes cannot be examined in a one-size-fits-all manner for additive manufacturing (AM). Some traditional metrics for AM (such as the sintering window) may not provide a complete assessment of AM usability. A complete assessment of the thermal behavior using both non-isothermal and isothermal tests provides a basis for which polypropylene properties are preferred in AM.

[0232] Although the embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made to this document without departing from the spirit and scope of the embodiments defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the specific embodiments of the processes, machines, manufactures, compositions of matter, means, methods, and steps described in the specification. As will be readily understood by those of ordinary skill in the art from the foregoing disclosure, processes, machines, manufactures, compositions of matter, means, methods, or steps that currently exist or will be developed in the future and perform substantially the same function or achieve substantially the same result as the corresponding embodiments herein can be utilized. Accordingly, the appended claims are intended to include such processes, machines, manufactures, compositions of matter, means, methods, or steps within their scope.

Claims

1. An article produced by additive manufacturing, the article comprising one or more polypropylenes (PPs) having one or more of the following properties: a) A melting temperature ≤ 135 °C, measured according to ASTM D3418-15; b) An onset melting temperature ≤ 125 °C, measured according to ASTM D3418-15; c) An onset crystallization temperature ≤ 105 °C, measured according to ASTM D3418-15; d) A crystallinity ≤ 35%, measured according to ASTM D3418-15; e) An Avrami exponent ≤ 2.10; f) An absolute value of the crystallization activation energy ≤ 550,000 J / mol, determined by Avrami kinetics fitting; and / or g) An absolute value of the crystallization activation energy is less than or equal to 80% of the absolute value of the crystallization activation energy of an un-nucleated Ziegler-Natta homopolymer polypropylene.

2. The article produced by additive manufacturing according to claim 1, the article comprising one or more PPs having one or more of the following characteristics: a) A melting temperature ≤ 130 °C, measured according to ASTM D3418-15; b) An onset melting temperature ≤ 120 °C, measured according to ASTM D3418-15; c) An onset crystallization temperature ≤ 100 °C, measured according to ASTM D3418-15; d) A crystallinity ≤ 30%, measured according to ASTM D3418-15; e) An Avrami exponent ≤ 2.05; f) An absolute value of the crystallization activation energy ≤ 500,000 J / mol, determined by Avrami kinetics fitting; and / or g) An absolute value of the crystallization activation energy is less than or equal to 75% of the absolute value of the crystallization activation energy of an un-nucleated Ziegler-Natta homopolymer polypropylene.

3. The article produced by additive manufacturing according to claim 1, the article comprising one or more PPs having at least two of the following characteristics: a) A melting temperature ≤ 135 °C, or ≤ 130 °C, measured according to ASTM D3418-15; b) An onset melting temperature ≤ 125 °C, or ≤ 120 °C, measured according to ASTM D3418-15; c) An onset crystallization temperature ≤ 105 °C, or ≤ 100 °C, measured according to ASTM D3418-15; and / or d) Crystallinity ≤ 35% or ≤ 30%, measured according to ASTM D3418-15.

4. An additively manufactured article according to any one of claims 1 to 3, wherein the at least one polypropylene is a Ziegler-Natta based random copolymer, a metallocene random copolymer, and / or a syndiotactic polypropylene, and optionally further comprises at least one additive, wherein the additive comprises: silica, antistatic agent, colorant, corrosion inhibitor, antioxidant, acid neutralizer, anticaking agent, antifogging agent, clarifying agent, UV absorber, lubricant, plasticizer, mineral oil, wax, clay, talc, calcium carbonate, diatomaceous earth, carbon black, mica, glass fiber, filler, slip agent, colorant, UV stabilizer and / or tolerance agent, flame retardant, release agent, dye, foaming agent, fluorescent agent, surfactant, oil, neutralizer, flow modifier, processing aid, reinforcing agent, stabilizer, impact modifier, nucleating agent, crystallization aid, additional polymer, or any combination thereof.

5. An additively manufactured article according to any one of claims 1 to 3, wherein the absolute value of the crystallization activation energy of the PP is between about 300,000 J / mol and about 500,000 J / mol, determined by combining an isothermal differential scanning calorimetry (DSC) test according to ASTM D3418-15 with Avrami kinetics fitting.

6. An additively manufactured article according to any one of claims 1 to 3, wherein the crystallinity of the PP is 35% to 15%, based on a heat of fusion (ΔH 0m ) of 207 J / g for theoretically 100% crystalline polypropylene.

7. An additively manufactured article according to any one of claims 1 to 3, wherein the sintering window of the PP is 30 °C or lower, defined by the onset melting and crystallization temperatures.

8. An additively manufactured article according to claim 7, wherein the sintering window of the PP is 18 °C to 30 °C.

9. An additively manufactured article according to any one of claims 1 to 3, wherein the density of the PP is 0.8 g / cc to 1 g / cc, measured according to ASTM D1505-18, and / or the melt flow rate (MFR) is 0.1 g / 10 min to 100.0 g / 10 min, measured according to ASTM D1238-20.

10. An additively manufactured article according to any one of claims 1 to 3, wherein the melt flow of the PP is 0.5 g / 10 min to 30 g / min, measured according to ASTM D1238-20.

11. A method of manufacturing an additively manufactured article as claimed in any one of claims 1 to 3, the method comprising: melting and / or sintering a composition comprising said one or more PPs.

12. The method as claimed in claim 11, wherein said at least one polypropylene is a Ziegler-Natta based random copolymer, a metallocene random copolymer, and / or a syndiotactic polypropylene, and optionally further comprises at least one additive, wherein said additive comprises: silica, antistatic agent, colorant, corrosion inhibitor, antioxidant, acid neutralizer, anti-caking agent, anti-fogging agent, clarifying agent, UV absorber, lubricant, plasticizer, mineral oil, wax, clay, talc, calcium carbonate, diatomaceous earth, carbon black, mica, glass fiber, filler, slip agent, colorant, UV stabilizer and / or tolerance agent, flame retardant, release agent, dye, foaming agent, fluorescent agent, surfactant, oil, neutralizer, flow modifier, processing aid, reinforcing agent, stabilizer, impact modifier, nucleating agent, crystallization aid, additional polymer, or any combination thereof.

13. The method as claimed in claim 11, wherein the article is manufactured by: sintering PPs in the form of particulate matter having an average particle size of 1 μm to 500 μm.

14. The method as claimed in claim 13, wherein the average particle size of the particulate matter is 15 μm to 100 μm.

15. The method as claimed in claim 11, wherein the method comprises material extrusion, wherein the composition in a molten state is extruded through a nozzle and deposited in layers.

16. The method as claimed in claim 11, wherein the method comprises: sintering particulate composition particles in a powder bed sintering (PBS) process.

17. The method as claimed in claim 16, wherein the PBS process uses a layer thickness of 10 μm to 200 μm and / or a component bed temperature of 20 °C to 100 °C.

18. The method as claimed in claim 17, wherein the PBS process uses a layer thickness of 30 μm to 150 μm.

19. A manufactured article comprising an additively manufactured article as claimed in any one of claims 1 - 3, or made by the method as claimed in claim 11.

20. The article as claimed in claim 19, wherein the article is: a motor vehicle component, a building material component, an insulation component, an electronic instrument component, a furniture component, a fabric component, a container component, a household appliance component, a medical component, a prosthesis, a filter medium, and / or a customized toy.

21. A composition for additive manufacturing, wherein the composition comprises at least one polypropylene (PP) and is in contact with at least one component designed to be used in a 3D printer, and wherein the PP comprises one or more of the following properties: a) The melting temperature ≤ 135 °C, measured according to ASTM D3418-15; b) The onset of the melting temperature ≤ 125 °C, measured according to ASTM D3418-15; c) The onset of the crystallization temperature ≤ 105 °C, measured according to ASTM D3418-15; d) The crystallinity ≤ 35%, measured according to ASTM D3418-15; e) The Avrami exponent ≤ 2.10; f) The absolute value of the crystallization activation energy ≤ 550,000 J / mol, determined by Avrami kinetics fitting; and / or g) The absolute value of the crystallization activation energy is less than or equal to 80% of the absolute value of the crystallization activation energy of an un-nucleated Ziegler-Natta homopolymer polypropylene.

22. The composition according to claim 21, wherein the composition comprises one or more polypropylenes (PPs) having one or more of the following characteristics: a) The melting temperature ≤ 130 °C, measured according to ASTM D3418-15; b) The onset of the melting temperature ≤ 120 °C, measured according to ASTM D3418-15; c) The onset of the crystallization temperature ≤ 100 °C, measured according to ASTM D3418-15; d) The crystallinity ≤ 30%, measured according to ASTM D3418-15; d) The Avrami exponent ≤ 2.05; e) The absolute value of the crystallization activation energy ≤ 500,000 J / mol, determined by Avrami kinetics fitting; and / or f) The absolute value of the crystallization activation energy is less than or equal to 75% of the absolute value of the crystallization activation energy of an un-nucleated Ziegler-Natta homopolymer polypropylene.

23. The composition according to claim 21, wherein the composition comprises one or more PPs having at least two of the following characteristics: a) The melting temperature ≤ 135 °C or ≤ 130 °C, measured according to ASTM D3418-15; b) The onset of the melting temperature ≤ 125 °C or ≤ 120 °C, measured according to ASTM D3418-15; c) The starting point of the crystallization temperature ≤ 105 °C, or ≤ 100 °C, measured according to ASTM D3418-15; and / or d) The crystallinity ≤ 35%, or ≤ 30%, measured according to ASTM D3418-15.

24. The composition according to any one of claims 21 to 23, wherein the at least one PP is a Ziegler-Natta based random copolymer, a metallocene random copolymer, and / or a syndiotactic PP, and optionally further comprises at least one additive, wherein the additive comprises: silica, antistatic agent, colorant, corrosion inhibitor, antioxidant, acid neutralizer, anti-caking agent, anti-fogging agent, clarifying agent, UV absorber, lubricant, plasticizer, mineral oil, wax, clay, talc, calcium carbonate, diatomaceous earth, carbon black, mica, glass fiber, filler, slip agent, colorant, UV stabilizer and / or tolerance agent, flame retardant, mold release agent, dye, foaming agent, fluorescent agent, surfactant, oil, neutralizer, flow modifier, processing aid, reinforcing agent, stabilizer, impact modifier, nucleating agent, crystallization aid, additional polymer, or any combination thereof.

25. The composition according to any one of claims 21 to 23, wherein the composition comprises at least 95 wt% of at least one PP.

26. The composition according to any one of claims 21 to 23, wherein the PP is in contact with: a 0.4 mm extruder nozzle, a 0.35 mm extruder nozzle, a building panel, and / or a heated bed.

27. The composition according to any one of claims 21 to 23, wherein the absolute value of the crystallization activation energy of the PP is between about 300,000 J / mol and about 500,000 J / mol, determined by combining an isothermal differential scanning calorimetry (DSC) test according to ASTM D3418-15 with Avrami kinetics fitting.

28. The composition according to any one of claims 21 to 23, wherein the crystallinity of the PP is 35% to 15%, based on a heat of fusion (ΔH 0m ) of 207 J / g for theoretically 100% crystalline polypropylene.

29. The composition according to any one of claims 21 to 23, wherein the sintering window of the PP is 30 °C or lower, defined by the starting melting and crystallization temperatures.

30. The composition according to claim 29, wherein the sintering window of the PP is 18 °C to 30 °C.

31. The composition according to any one of claims 21 to 23, wherein the density of the PP is from 0.8 g / cc to 1 g / cc, measured according to ASTM D1505-18, and / or the melt flow is from 0.1 g / 10 min to 100 g / 10 min, measured according to ASTM D1238-20.

32. The composition according to claim 31, wherein the melt flow of the PP is from 0.5 g / 10 min to 30 g / 10 min.

33. The composition according to any one of claims 21 to 23, wherein the PP is in the form of granules having an average particle size of from 1 μm to 500 μm.

34. The composition according to claim 33, wherein the average particle size of the granules is from 15 μm to 100 μm.

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