Crosslinkable polymer compositions comprising propylene-based polymer and bifunctional disulfide crosslinker

Abstract

Embodiments are directed to a crosslinkable polymer composition. In embodiments, the crosslinkable polymer composition includes a propylene-based polymer, a free radical initiator, and a bifunctional disulfide crosslinker. The crosslinker comprises Structure 1. Each R is independently selected from the group comprising: methyl, phenyl, aryl, heteroaryl, and hydrogen. Further embodiments are directed to crosslinked compositions formed from the crosslinkable polymer compositions.

Description

CROSSLINKABLE POLYMER COMPOSITIONS COMPRISING PROPYLENE-BASED POLYMER AND BIFUNCTIONAL DISULFIDE CROSSLINKERCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 669,770 filed July 11, 2024, the contents of which are incorporated in their entirety herein.TECHNICAL FIELD

[0002] Embodiments of the present disclosure generally relate to crosslinkable polymer compositions and specifically relate to crosslinkable polymer compositions with propylene- based polymer and bifunctional disulfide crosslinker.BACKGROUND

[0003] Crosslinked olefin-based polymers, and crosslinked propylene-based polymers, in particular, are desirable in a myriad of applications because of their mechanical properties, heat stability, and chemical resistance. Unfortunately, using conventional processes, such as radical crosslinking processes, to crosslink propylene-based polymers leads to difficulties, such as chain scission that occurs in the presence of radicals, thereby resulting in undesirable properties, such as undesirable mechanical or rheological properties.

[0004] Accordingly, there is a need for improved crosslinked propylene-based polymers that exhibit desirable properties, such as desirable mechanical or rheological properties.SUMMARY

[0005] The embodiments of the present disclosure meet this need by utilizing a bifunctional disulfide crosslinker. This results in crosslinkable polymer compositions that may be crosslinked to produce a crosslinked composition that exhibits desirable properties (e.g., a lower intrinsic viscosity at LOG 6.5 (Mw(abs)), a higher complex viscosity at 0.1 rad / s, and a lower tan 8 at 0.1 rad / s as compared to a similar composition lacking a bifunctional disulfide crosslinker).

[0006] According to some embodiments, a crosslinkable polymer composition comprises: a propylene-based polymer; a free radical initiator; and a bifunctional disulfide crosslinker. The crosslinker comprises Structure 1 :STRUCTURE 1.

[0007] Each R is independently selected from the group comprising: methyl, phenyl, aryl, heteroaryl, and hydrogen (H).

[0008] According to other embodiments, a crosslinked composition comprises: a propylene based polymer; and a bifunctional disulfide crosslinker, wherein the crosslinker comprises Structure 1 :STRUCTURE 1.

[0009] Each R is independently selected from the group comprising: methyl, phenyl, aryl, heteroaryl, and hydrogen (El).

[0010] Additional features and advantages will be set forth in the detailed description, which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows and the claims.

[0011] It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

[0013] The Figure is a plot of normalized molecular weight distribution (left-hand y-axis) and intrinsic viscosity (right-hand y-axis) versus normalized MW (x-axis) of comparative and inventive compositions, according to one or more embodiments described herein.

[0014] Reference will now be made in detail to various embodiments, some embodiments of which are illustrated in the accompanying drawing.DETAILED DESCRIPTION

[0015] Specific embodiments of the present application will now be described. The disclosure may be embodied in different forms and should not be construed as limited to the embodiments set forth in this disclosure. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art.

[0016] DEFINITIONS

[0017] Unless stated to the contrary, implicit from the context, or customary in the art, all test methods are current as of the filing date of this disclosure.

[0018] The amount of a component (e.g., propylene-based polymer, bifunctional disulfide crosslinker, coagent, and free-radical initiator) in a crosslinkable polymer composition or a crosslinked composition is provided herein in weight percent (wt%), based on a total weight of the crosslinkable polymer composition or the crosslinked composition, unless otherwise noted.

[0019] Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0020] The terms "comprising", "including", "having”, and their derivatives, are not intended to exclude the presence of any additional component, step or procedure, whether the same is specifically disclosed. In order to avoid any doubt, all compositions claimed through use of the term "comprising" may include any additional additive, adjuvant, or compound,whether polymeric or otherwise, unless stated to the contrary. In contrast, the term, "consisting essentially of’ excludes from the scope of any succeeding recitation any other component, step or procedure, excepting those that are not essential to operability. The term "consisting of’ excludes any component, step or procedure, not specifically delineated or listed.

[0021] Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percentages are based on weight.

[0022] The term “composition,” as used herein, refers to a mixture of materials that comprise the composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0023] The term "propylene-based polymer," as used herein, refers to a polymer that contains more than 50 mole percent polymerized propylene monomer (based on the total amount of polymerizable monomers) and, optionally, may contain at least one comonomer. Propylene-based polymer includes propylene homopolymer, and propylene copolymer (meaning units derived from propylene and one or more comonomers). The terms "propylene- based polymer" and "polypropylene" may be used interchangeably.

[0024] The term “polymer,” as used herein, refers to a compound prepared by polymerizing monomers, whether of the same or a different type, that in polymerized form provide the multiple and / or repeating “units” or “mer units” that make up a polymer. The generic term polymer thus embraces the term homopolymer, usually employed to refer to polymers prepared from only one type of monomer, and the term copolymer, usually employed to refer to polymers prepared from at least two types of monomers. It also embraces all forms of copolymer, e.g., random, block, etc. The term “propylene / a-olefin polymer” is indicative of copolymer as described above prepared from polymerizing propylene respectively and one or more additional, polymerizable a-olefin monomer. It is noted that although a polymer is often referred to as being “made of’ one or more specified monomers, “based on” a specified monomer or monomer type, “containing” a specified monomer content, or the like, in this context, the term “monomer” is understood to be referring to the polymerized remnant of the specified monomer and not to the unpolymerized species. In general, polymers herein are referred to as being based on “units” that are the polymerized form of a corresponding monomer.

[0025] "Crystalline" refers to a polymer or polymer block that possesses a first order transition or crystalline melting point (Tm) as determined by differential scanning calorimetry (DSC) or equivalent technique. The term may be used interchangeably with the term "semicrystalline".

[0026] The term "crystallizable" refers to a monomer that can polymerize such that the resulting polymer is crystalline. Crystalline ethylene polymers typically have, but are not limited to, densities of 0.89 g / cc to 0.97 g / cc and melting points of 75°C to 140°C. Crystalline propylene polymers may have, but are not limited to, densities of 0.88 g / cc to 0.91 g / cc and melting points of 100 °C to 170°C.

[0027] "Amorphous" refers to a polymer lacking a crystalline melting point as determined by differential scanning calorimetry (DSC) or equivalent technique.

[0028] " Isotactic" is defined as polymer repeat units having at least 70 percent isotactic pentads as determined by 13C-NMR analysis. "Highly isotactic" is defined as polymers having at least 90 percent isotactic pentads.

[0029] “Impact modified propylene-based copolymer” and the like terms mean a propylene based polymer composition that has been impact-modified such that the composition's impact strength at room temperature or below is maintained or increased as compared to said given composition's impact strength at the same temperature without the added impact modifier.

[0030] " Block copolymer" or “segmented copolymer” refers to a polymer comprising two or more chemically distinct regions or segments (referred to as "blocks") joined in a linear manner, that is, a polymer comprising chemically differentiated units that are joined (covalently bonded) end-to-end with respect to polymerized functionality (e.g., polymerized propylenic functionality), rather than in pendent or grafted fashion. Block copolymers comprise sequences ("blocks") of the same monomer unit, covalently bound to sequences of unlike type. The blocks can be connected in a variety of ways, such as A — B in diblock and A — B — A triblock structures, where A represents one block and B represents a different block. In a multi-block copolymer, A and B can be connected in a number of different ways and be repeated multiply. It may further comprise additional blocks of different type. Multiblock copolymers may be linear multi-block, multi block star polymers (in which all blocks bond to the same atom or chemical moiety) or comb-like polymers where the B blocks are attached at one end to an A backbone. The block copolymers can be linear or branched. Withrespect to the block copolymers, the blocks may differ in the amount of comonomer incorporated therein. The blocks may also differ in the type of comonomer, density, the amount of crystallinity, the crystallite size attributable to a polymer of such composition, the type or degree of tacticity (isotactic or syndiotactic), regio-regularity or regio-irregularity, the amount of branching, including long chain branching or hyper-branching, the homogeneity, or any other chemical or physical property. The block copolymers are characterized by unique distributions of polymer polydispersity (PDI or Mw / Mn), block length distribution, and / or block number distribution, e.g., due to the effect of the shuttling agent(s) in combination with the catalyst(s).

[0031] The term “block composite” (BC) refers to polymers comprising an ethylene based polymer (EP) having an ethylene content of from 10 mol% to 90 mol%, an alpha-olefin based polymer (AOP) having an alpha-olefin content of greater than 90 mol%, and a block copolymer having an ethylene block (EB) and an alpha-olefin block (AOB), wherein the ethylene block of the block copolymer is the same composition as the ethylene based polymer of the block composite and the alpha-olefin block of the block copolymer is the same composition as the alpha-olefin based polymer of the block composite. The compositional split between the amount of ethylene based polymer and alpha-olefin based polymer will be essentially the same as that between the corresponding blocks in the block copolymer. In certain embodiments, the alpha-olefin is propylene. In further embodiments, the AOB and EB may be an iPP-EP diblock copolymer.

[0032] The term “crystalline block composite” (CBC) refers to polymers comprising a crystalline ethylene based polymer (CEP) having an ethylene content of greater than 90 mol%, a crystalline alpha-olefin based polymer (CAOP) having an alpha-olefin content of greater than 90 mol%, and a block copolymer having a crystalline ethylene block (CEB) and a crystalline alpha-olefin block (CAOB), wherein the CEB of the block copolymer is the same composition as the CEP of the crystalline block composite and the CAOB of the block copolymer is the same composition as the CAOP of the crystalline block composite. The compositional split between the amount of CEP and CAOP will be essentially the same as that between the corresponding blocks in the block copolymer. In embodiments, the alphaolefin is propylene. In further embodiments, the CAOB and the CEB may be an iPP-EP (isotactic polypropylene and ethylene-propylene) diblock copolymer.

[0033] The block composite and crystalline block composite (“the composites”) may be differentiated from conventional, random copolymers, physical blends of polymers, and block copolymers prepared via sequential monomer addition. The composites may be differentiated from random copolymers by characteristics such as higher melting temperatures for a comparable amount of comonomer, BCI, CBCI, and microstructure index; from a physical blend by characteristics such as BCI, CBCI, microstructure index, better tensile strength, improved fracture strength, finer morphology, improved optics, and / or greater impact strength at lower temperature; and from block copolymers prepared by sequential monomer addition by molecular weight distribution, rheology, shear thinning, rheology ratio, and in that there is block poly dispersity. For example, the composites include block copolymers having distinct regions or segments (referred to as “blocks”) joined in a linear manner. The blocks differ, e.g., in the type of crystallinity such as polyethylene (PE) versus polypropylene (PP). The block copolymers can be linear or branched. When produced in a continuous process, the composites may possess PDI from 1.7 to 15 (e.g., from 1.8 to 10, from 1.8 to 5, and / or from 1.8 to 3.5). When produced in a batch or semi-batch process, the composites may possess PDI from 1.0 to 2.9 (e.g., from 1.3 to 2.5, from 1.4 to 2.0, and / or from 1.4 to 1.8). Examples of composites are described in, e.g., U.S. Patent Nos. 8,716,400, 8,802,774, and 8,822,598, which are incorporated herein by reference with respect to, for example, processes to make them and methods of analyzing them.

[0034] The composites include the block copolymers possessing a most probable distribution of block lengths. The block copolymers may contain 2 or 3 blocks or segments. In a process for making the polymers of the composites, chain shuttling is used as a way to prolong the lifetime of a polymer chain such that a substantial fraction of the polymer chains exit at least the first reactor of a multiple reactor series or the first reactor zone in a multiple zoned reactor operating substantially under plug flow conditions in the form of polymer terminated with a chain shuttling agent, and the polymer chain experiences different polymerization conditions in the next reactor or polymerization zone. Different polymerization conditions in the respective reactors or zones include the use of different monomers, comonomers, or monomer / comonomer(s) ratio, different polymerization temperatures, pressures or partial pressures of various monomers, different catalysts, differing monomer gradients, or any other difference leading to formation of a distinguishablepolymer segment. Thus, at least a portion of the polymer comprises two, three, or more, preferably two or three, differentiated polymer segments arranged intramolecularly.

[0035] The composites are prepared, e.g., by a process comprising contacting an addition polymerizable monomer or mixture of monomers under addition polymerization conditions with a composition comprising at least one addition polymerization catalyst, a cocatalyst, and a chain shuttling agent. The process is characterized by formation of at least some of the growing polymer chains under differentiated process conditions in two or more reactors operating under steady state polymerization conditions or in two or more zones of a reactor operating under plug flow polymerization conditions.

[0036] Suitable processes useful in producing the composites may be found in, e.g. example, U.S. Patent Nos. 8,053,529, 8,686,087, and 8,716,400. The polymerization may be carried out as a continuous polymerization, e.g., a continuous-solution polymerization, in which catalyst components, monomers, and optionally solvent, adjuvants, scavengers, and / or polymerization aids are continuously supplied to one or more reactors or zones and polymer product continuously removed therefrom. Within the scope of the terms “continuous” and “continuously” as used in this context are those processes in which there are intermittent additions of reactants and removal of products at small regular or irregular intervals, so that, over time, the overall process is substantially continuous. Further, a chain shuttling agent(s) may be added at any point during the polymerization including in a first reactor or zone, at the exit or slightly before the exit of the first reactor, between the first reactor or zone and a second or any subsequent reactor or zone, or even solely to the second or any subsequent reactor or zone. Examples of chain shuttling agents, catalysts, and cocatalysts are those disclosed in, e.g., U.S. Patent No. 7,951,882. For example, chain shuttling agents that are dialkyl zinc compounds may be used.

[0037] The catalyst may be prepared as a homogeneous composition by addition of the requisite metal complex or multiple complexes to a solvent in which the polymerization will be conducted or in a diluent compatible with the ultimate reaction mixture. The desired cocatalyst or activator and, optionally, the shuttling agent may be combined with the catalyst composition either prior to, simultaneously with, or after combination of the catalyst with the monomers to be polymerized and any additional reaction diluent.

[0038] Due to the difference in monomers, temperatures, pressures, or other differences in polymerization conditions between at least two of the reactors or zones connected in series, polymer segments of differing composition such as comonomer content, crystallinity, density, tacticity, regio-regularity, or other chemical or physical difference, within the same molecule are formed in the different reactors or zones. The size of each segment or block is determined by continuous polymer reaction conditions, and preferably is a most probable distribution of polymer sizes. Each reactor in the series can be operated under high pressure, solution, slurry, or gas phase polymerization conditions.

[0039] EMBODIMENTS

[0040] Embodiments of the present disclosure are related to crosslinkable polymer compositions comprising a propylene-based polymer, a free radical initiator, and a bifunctional disulfide crosslinker. Crosslinked compositions may be formed from the crosslinkable polymer composition comprising the propylene-based polymer, the free radical initiator, and the bifunctional disulfide crosslinker. That is, the crosslinked composition may be the reaction product of crosslinking the crosslinkable polymer composition.

[0041] Propylene-based Polymer

[0042] Propylene-based polymer imparts desirable mechanical properties, heat stability, and chemical resistance to the crosslinkable polymer compositions described herein.

[0043] Nonlimiting examples of suitable propylene-based polymer may include polypropylene homopolymer, polypropylene-based elastomer, polypropylene-based block copolymer, propylene-based impact copolymer, and combinations thereof.

[0044] In embodiments, the propylene-based polymer includes a propylene / ethylene copolymer, apropylene / a-olefin copolymer, or combinations thereof. In embodiments, the etale fm comprises 1 -butene, 1 -hexene, 1 -octene, or combinations thereof.

[0045] In embodiments, the propylene-based polymer is selected from the group comprising polypropylene homopolymer, polypropylene-based elastomer, polypropylene-based block copolymer, propylene-based impact copolymer, and combinations thereof.

[0046] In embodiments, the propylene-based polymer comprises polypropylene-based elastomer. “Propylene-based elastomer” comprise at least one copolymer with at least about 50 weight percent of units derived from propylene and at least about 4 weight percent of units derived from a comonomer other than propylene. Suitable propylene-based elastomers aretaught in US Patent Nos. 6,906,160; 6,919,407; 6,927,256; 6,960,535; 7,250,470; 7,250,471; and 7,344,775, each of which are incorporated by reference in their entireties. In embodiments, the propylene-based elastomer may comprise propylene-ethylene elastomer.

[0047] In embodiments, the propylene-based polymer may comprise a melt flow rate (MFR) from 0.1 g / 10 min to 50 g / 10 min, from 0.1 g / 10 min to 25 g / 10 min, from 0.1 g / 10 min to 10 g / 10 min, from 0.1 g / 10 min to 5 g / 10 min, from 1 g / 10 min to 50 g / 10 min, from 1 g / 10 min to 25 g / 10 min, from 1 g / 10 min to 10 g / 10 min, from 1 g / 10 min to 5 g / 10 min, from 10 g / 10 min to 50 g / 10 min, from 10 g / 10 min to 25 g / 10 min, or even from 25 g / 10 min to 50 g / 10 min, , or any and all sub-ranges formed from any of these endpoints.

[0048] In certain embodiments, the propylene-based polymer may comprise from 0.5 wt% to 20 wt% (e.g., from 0.5 wt% to 15 wt%, from 0.5 wt% to 10 wt%, from 0.5 wt% to 6 wt%, from 1.5 wt% to 3 wt, etc.) of a composite component comprising a block composite. In embodiments, the block composite may have a total ethylene content that is from 25 wt% to 70 wt% (e.g., from 25 wt% to 60 wt%, from 25 wt% to 55 wt%, and from 30 wt% to 50 wt%) based on the total weight of the block composite. The remainder of the total weight of the block composite may be accounted for by units derived from at least one C3-10 alpha-olefin. For example, the remainder of the total weight of the block composite may be accounted for by units derived from propylene.

[0049] In embodiments, the block composite refers to polymers comprising an ethylene based polymer (EP) (soft copolymer) having an ethylene content of from 10 mol% to 90 mol%, an alpha-olefin based polymer (AOP) (hard copolymer) having an alpha-olefin content of greater than 90 mol%, and a block copolymer having an ethylene block / segment (EB) and an alpha-olefin block / segment (AOB), wherein the ethylene block of the block copolymer is the same composition as the ethylene based polymer of the block composite and the alphaolefin block of the block copolymer is the same composition as the alpha-olefin based polymer of the block composite. The compositional split between the amount of ethylene based polymer and alpha-olefin based polymer will be essentially the same as that between the corresponding blocks in the block copolymer.

[0050] In further embodiments, the block composite refers to polymers comprising an EP having an ethylene content that is greater than 10 wt% and less than 95 wt%, an AOP having a propylene content that is greater than 90 wt% and up to 100 wt%, and a block copolymer(e.g., a diblock) having an EB (i.e., soft block) and an AOB (i.e., hard block), wherein the AOB of the block copolymer is the same composition as the AOP of the block composite and the EB of the block copolymer is the same composition as the EP of the block composite. The compositional split between the amount of EP and AOP will be essentially the same as that between the corresponding blocks in the block copolymer.

[0051] In embodiments, the hard blocks refer to highly crystalline blocks of polymerized alpha-olefin units (e.g., propylene). In the hard blocks, the monomer (i.e., propylene) may be present in an amount greater than 90 wt%. The remainder of the hard block may be the comonomer (e.g., ethylene) in an amount of less than 10 wt%. In embodiments, the hard blocks comprise all or substantially all propylene units, such as an iPP (isotactic) homopolymer block or an iPP copolymer block with less than 10 wt% of ethylene. In embodiments, the soft blocks refer to amorphous, substantially amorphous, or elastomeric blocks of polymerized ethylene units. In the soft blocks, the monomer (i.e., ethylene) may be present in an amount of greater than 20 wt% and equal to or less than 100 wt% (e.g., from 40 wt% to 99 wt%, from 45 wt% to 90 wt%, and / or from 50 wt% to 80 wt%). The remainder of the soft block may be the comonomer (e.g., propylene).

[0052] According to an embodiment, the block composite includes a block copolymer having 30-70 wt% hard block and 30-70 wt% soft block. In other words, the block composite includes a block copolymer having 30-70 wt% hard block and 30-70 wt% soft block based on the weight of the block copolymer.

[0053] According to an embodiment, the block copolymer of the block composite has the formula (EP)-(iPP), in which EP represents the soft block of polymerized ethylene and propylene monomeric units (e.g., 50-80 wt% of ethylene and remainder propylene) and iPP represents a hard block of isotactic propylene homopolymer or isotactic propylene copolymer (e.g., less than 10 wt% of ethylene and remainder propylene).

[0054] The block composites may include from 0.5 wt% to 95.0 wt% EP, from 0.5 to 95.0 wt% iPP, and from 5.0 wt% to 99.0 wt% of the block copolymer. Weight percents are based on total weight of block composite. The sum of the weight percents of EP, iPP, and the block copolymer equals 100%. An example of a measurement of the relative amount of the block copolymer is referred to as the Block Composite Index (BCI), as further discussed below. The BCI for the block composite is greater than 0 and less than 1.0.

[0055] In some embodiments, the block composites may have a microstructure index greater than 1 and equal to or less than 20. The microstructure index is an estimation using solvent gradient interaction chromatography (SGIC) separation to differentiate between block copolymers from random copolymers. In particular, microstructure index estimation relies on differentiating between two fractions, i.e., a higher random copolymer content fraction and a higher block copolymer content fraction, of which the random copolymer and the block copolymer have essentially the same chemical composition. The early eluting fraction (i.e., the first fraction) correlates to random copolymers and the late eluting component (i.e., the second fraction) correlates to block copolymers. The calculation of the microstructure index is discussed below.

[0056] The block composites may have a weight-average molecular weight (Mw) from 10,000 g / mol to 2,500,00 g / mol, from 35,000 g / mol to 1,000,000 g / mol, from 50,000 g / mol to 300,000 g / mol, and / or from 50,000 g / mol to 200,000 g / mol. For example, the Mw may be from 20 kg / mol to 1,000 kg / mol, from 50 kg / mol to 500 kg / mol, and / or from 80 kg / mol to 200 kg / mol. The molecular weight distribution (Mw / Mn) or polydispersity of the block composites may be less than 5, between 1 and 5, and / or between 1.5 and 4. Weight-average molecular weight (Mw), number-average molecular weight (Mn), peak molecular weight (Mp), z-average molecular weight Mz, and Polydispersity Index (PDI) (Mw / Mn) are well-known in polymer art and can be determined by methods known to a person of ordinary skill in the art.

[0057] The melt flow rate (MFR) of the block composites may be from 0.1 g / 10 min to 1,000 g / 10 min measured in accordance with ASTM D-1238 (230°C; 2.16 kg). For example, the melt flow rate of the block composites may be from 1 g / 10 min to 50 g / 10 min, from 1 g / 10 min to 25 g / 10 min, from 3 g / 10 min to 15 g / 10 min, and / or from 5 g / 10 min to 10 g / 10 min.

[0058] The density of the block composites may be between 0.850 and 0.900 g / cc. In embodiments, the density of the block composites is from 0.860 to 0.895, from 0.865 to 0.895, and / or from 0.865 to 0.890 g / cc. Density is measured in accordance with ASTM D792.

[0059] The block composites may have a second peak Tm of greater than 90 °C (e.g., greater than 100 °C). According to an embodiment, the block composites exhibit a second peak Tm in a range from 100 °C to 150 °C).

[0060] In certain embodiments, the propylene-based polymer may comprise from 0.5 wt% to 20 wt% (e.g., from 0.5 wt% to 15 wt%, from 0.5 wt% to 10 wt%, from 0.5 wt% to 6 wt%, from 1.5 wt% to 3 wt, etc.) of a composite component comprising a crystalline block composite. In embodiments, the crystalline block composite may have a total ethylene content that is from 40 wt% to 70 wt% based on the total weight of the crystalline block composite. The remainder of the total weight of the crystalline block composite may be accounted for by units derived from at least one C3-10 alpha-olefin. For example, the remainder of the total weight of the crystalline block composite may be accounted for by units derived from propylene.

[0061] The crystalline block composite (CBC) refers to polymers having a crystalline ethylene based polymer (CEP), a crystalline alpha-olefin based polymer (CAOP), and a block copolymer comprising a crystalline ethylene block / segment (CEB) and a crystalline alphaolefin block / segment (CAOB), wherein the CEB of the block copolymer is the same composition as the CEP of the crystalline block composite and the CAOB of the block copolymer is the same composition as the CAOP of the crystalline block composite. Additionally, the compositional split between the amount of CEP and CAOP will be essentially the same as that between the corresponding blocks in the block copolymer.

[0062] The crystalline block composite (CBC) includes the crystalline ethylene based polymer (CEP), the crystalline alpha-olefin based polymer (CAOP), and the block copolymer having the crystalline ethylene block (CEB) and the crystalline alpha-olefin block (CAOB), where the CEB is the same composition as the CEP and the CAOB is the same composition as the CAOP. In the crystalline block composite, the alpha-olefin is at least one selected from the group of C3-10 a-olefins (e.g., may be propylene and / or butylene). The CAOP and the CAOB may have an alpha-olefin content that is greater than 90 mol%. The CEP and CEB comprise greater than 90 mol% of units derived from ethylene (i.e., ethylene content), and any remainder may be at least one of selected from the group of C3-10 a-olefins as a comonomer (in an amount less than 10 mol%, less than 7 mol%, less than 5 mol%, less than 3 mol%, etc.).

[0063] In embodiments, the CAOP and CAOB include propylene, e.g., greater than 90 mol% units derived from propylene and any remainder may be ethylene and / or at least one of selected from the group of C4-10 a-olefins as a comonomer (in an amount less than 10 mol%, less than 7 mol%, less than 5 mol%, less than 4 mol%, less than 4 mol%, etc.). The CEP andCEB include ethylene, e.g., greater than 90 mol% units derived from ethylene and any remainder may be propylene and / or at least one of selected from the group of C4-10 a-olefins as a comonomer (in an amount less than 10 mol%, less than 7 mol%, less than 5 mol%, less than 4 mol%, less than 4 mol%, etc.). The compositional split between the amount of CEP and CAOP will be essentially the same as that between the corresponding blocks in the block copolymer. The CEB and the CAOB may be referred to as hard (crystalline) segments / blocks.

[0064] In embodiments, the CAOB refers to highly crystalline blocks of polymerized alpha olefin units in which units derived from the monomer that is one of C3-10 a-olefins are present in an amount greater than 90 mol%, greater than 93 mol%, greater than 95 mol%, and / or greater than 96 mol%. In other words, the comonomer content in the CAOB is less than 10 mol%, less than 7 mol%, less than 5 mol%, and / or less than 4 mol%. A CAOB with propylene crystallinity may have corresponding melting points that are 80°C and above, 100°C and above, 115°C and above, and / or 120°C and above. In some embodiments, the CAOB comprises all or substantially all propylene units. CEB refers to blocks of polymerized ethylene units in which the comonomer content (such as propylene) is 10 mol% or less, between 0 mol% and 10 mol%, between 0 mol% and 7 mol%, and / or between 0 mol% and 5 mol%. Said in another way, the CEB is derived from at least 90 mol% ethylene, greater than 90 mol% ethylene, greater than 93 mol% ethylene, and / or greater than 95 mol% ethylene. Such CEBs have corresponding melting points that may be 75°C and above, 90°C and above, and / or 100°C and above.

[0065] In embodiments, the CAOB may refer to highly crystalline blocks of polymerized alpha olefin units in which the monomer that is one of C3-10 a-olefins is present in an amount of at least 88 wt% and / or at least 90 wt%. In other words, the comonomer content in the CAOBs is less than 10 wt%. CEB may refer to blocks of polymerized ethylene units in which the comonomer content (such as propylene) is 10 wt% or less.

[0066] The crystalline block composite may include from 0.5 wt% to 95.0 wt% CEP, from 0.5 wt% to 95.0 wt% CAOP, and from 5.0 wt% to 99.0 wt% of the crystalline block copolymer. For example, the crystalline block composite may include from 5.0 wt% to 80.0 wt% CEP, from 5.0 wt% to 80.0 wt% CAOP, and from 20.0 wt% to 90.0 wt% of the crystalline block copolymer. Weight percents are based on total weight of crystalline block composite. The sum of the weight percents of CEP, CAOP, and the crystalline block copolymer equals 100%. An example of a measurement of the relative amount of thecrystalline block copolymer is referred to as the Crystalline Block Composite Index (CBCI). The CBCI for the crystalline block composite is greater than 0 and less than 1.0. For example, the CBCI is from 0.20 to 0.99, from 0.30 to 0.99, from 0.40 to 0.99, from 0.40 to 0.90, from 0.40 to 0.85, and / or from 0.50 to 0.80.

[0067] The crystalline block composite may have, a Tm greater than 90 °C (e.g., for both a first peak and a second peak), a Tm greater than 100 °C (e.g., for both a first peak and a second peak), and / or greater than 120 °C (e.g., for at least one of a first peak and a second peak). For example, the Tm is in the range of from 100 °C to 250 °C, from 110 °C to 220 °C, and / or from 115 °C to 220 °C. According to an embodiment, the crystalline block composite exhibits a second peak Tm in a range from 100 °C to 130 °C (e.g., 100 °C to 120 °C, 100 °C to 110 °C, etc.) and a first peak Tm in a range from 110 °C to 150 °C (e.g., 110 °C to 140 °C, 115 °C to 130 °C, 115 °C to 125 °C, etc.), in which the second peak Tm is less than the first peak Tm.

[0068] The crystalline block composite may have a weight-average molecular weight (Mw) from 10,000 g / mol to 2,500,000 g / mol, from 35000 g / mol to 1,000,000 g / mol, from 50,000 g / mol to 300,000 g / mol, and / or from 50,000 g / mol to 200,000 g / mol. For example, the Mw may be from 20 kg / mol to 1000 kg / mol, from 50 kg / mol to 500 kg / mol, and / or from 80 kg / mol to 125 kg / mol. The molecular weight distribution (Mw / Mn) or polydispersity of the crystalline block composites may be less than 5, between 1 and 5, and / or between 1.5 and 4. Weightaverage molecular weight (Mw) and number-average molecular weight (Mn) are well-known in polymer art and can be determined by methods known to a person of ordinary skill in the art.

[0069] The MFR (melt flow rate) of the crystalline block composites may be from 0.1 to 1000 dg / min (230 °C / 2.16 kg), from 1 to 500 g / 10 min (230 °C / 2.16 kg), from 3 to 30 g / 10 min (230 °C / 2.16 kg), and / or from 5 to 11 g / 10 min (230 °C / 2.16 kg).

[0070] In accordance with ASTM D792, the density of the crystalline block composite may be between 0.850 and 0.920 g / cc (e.g., from 0.860 g / cc to 0.915 g / cc, from 0.875 g / cc to 0.910 g / cc, and / or from 0.890 g / cc to 0.910 g / cc).

[0071] In embodiments, the propylene-based polymer comprises impact modified propylene-based copolymer.

[0072] In embodiments, the propylene-based polymer may comprise post consumer recycle polypropylene.

[0073] The crosslinkable polymer composition and the resulting crosslinked composition may comprise a minimum amount of propylene-based polymer (e.g., greater than or equal to 70 wt%) to ensure the crosslinked composition has desirable mechanical properties, heat stability, and chemical resistance. The amount of propylene-based polymer may be limited (e.g., less than or equal to 99 wt%) to ensure that enough bifunctional disulfide crosslinker, coagent, or other components are present to achieve desirable properties. Accordingly, the crosslinkable polymer composition and the resulting crosslinked composition may comprise from 70 wt% to 99 wt% of the propylene-based polymer. In embodiments, the amount of propylene-based polymer in the crosslinkable polymer composition and the resulting crosslinked composition may be greater than or equal to 70 wt%, greater than or equal to 75 wt%, greater than or equal to 80 wt%, greater than or equal to 85 wt%, or even greater than or equal to 90 wt%. In embodiments, the amount of propylene-based polymer in the crosslinkable polymer composition and the resulting crosslinked composition may be less than or equal to 99 wt%, less than or equal to 98.5 wt%, less than or equal to 97 wt%, less than or equal to 95 wt%, less than or equal to 93 wt%, or even less than or equal to 91 wt%. In embodiments, the amount of propylene-based polymer in the crosslinkable polymer composition and the resulting crosslinked composition may be from 70 wt% to 99 wt%, from 70 wt% to 98.5 wt%, from 70 wt% to 97 wt%, from 70 wt% to 95 wt%, from 70 wt% to 93 wt%, from 70 wt% to 91 wt%, from 75 wt% to 99 wt%, from 75 wt% to 98.5 wt%, from 75 wt% to 97 wt%, from 75 wt% to 95 wt%, from 75 wt% to 93 wt%, from 75 wt% to 91 wt%, from 80 wt% to 99 wt%, from 80 wt% to 98.5 wt%, from 80 wt% to 97 wt%, from 80 wt% to 95 wt%, from 80 wt% to 93 wt%, from 80 wt% to 91 wt%, from 85 wt% to 99 wt%, from 85 wt% to 98.5 wt%, from 85 wt% to 97 wt%, from 85 wt% to 95 wt%, from 85 wt% to 93 wt%, from 85 wt% to 91 wt%, from 90 wt% to 99 wt%, from 90 wt% to 98.5 wt%, from 90 wt% to 97 wt%, from 90 wt% to 95 wt%, from 90 wt% to 93 wt%, or even from 90 wt% to 91 wt%, or any and all sub-ranges formed from any of these endpoints.

[0074] Bifunctional Disulfide Crosslinker

[0075] As described in further detail below, bifunctional disulfide crosslinker ensures crosslinking with reduced chain scission, thereby causing the crosslinked material to have desirable properties, such as a lower intrinsic viscosity at TOG 6.5 (Mw(abs)), a highercomplex viscosity at 0.1 rad / s, and lower tan 8 at 0.1 rad / s as compared to a similar composition lacking a bifunctional disulfide crosslinker.

[0076] In embodiments, the crosslinkable polymer composition and the resulting crosslinked composition may include a bifunctional disulfide crosslinker, bifunctional disulfide has Structure 1 shown below:STRUCTURE 1

[0077] As mentioned hereinabove, conventional processes, such as radical processes, to crosslink propylene-based polymers made lead to difficulties, such as chain scission that occurs in the presence of radicals. Crosslinking of propylene-based polymers may be established by increasing the grafting yield while reducing chain scission if tertiary radicals propagate to and are stabilized by a vinyl crosslinker prior to chain scission. As shown in Structure 1, bifunctional disulfide includes a phenyl ring adjacent to the vinyl group, which may increase reactivity toward a tertiary carbon radical by stronger stabilization energy via resonance, thereby preventing chain scission.

[0078] In embodiments, each R is independently selected from the group comprising: methyl, phenyl, aryl, heteroaryl, and hydrogen.

[0079] In embodiments, the bifunctional disulfide may include bis(4- phenacryloyloxyphenyl) disulfide (BPST) comprising Structure 2:

[0080] Compared to BPST, which bears a styrene-like substructure for resonance stabilization, as described herein, bis(4-methacryloyloxyphenyl) disulfide (BPMA) has less resonance stabilization and, therefore, has lower reactivity toward a tertiary radical. As such, a coagent may be added to help improve reactive toward a tertiary radical, thereby preventingchain scission. In embodiments, the bifunctional disulfide may include BPMA comprisingStructure 3 :STRUCTURE 3

[0081] The crosslinkable polymer composition and the resulting crosslinked composition may comprise a minimum amount of bifunctional disulfide crosslinker (e.g., greater than or equal to 1 wt%) to ensure crosslinking with reduced chain scission. The amount of bifunctional disulfide crosslinker may be limited (e.g., less than or equal to 20 wt%) to prevent undesirable aggregation or homopolymerization of the crosslinker rather than crosslinking, which may lead to undesirable properties. Accordingly, in embodiments, the crosslinkable polymer composition and the resulting crosslinked composition may comprise from 0.25 wt% to 20 wt% of the bifunctional disulfide crosslinker. In embodiments, the amount of the bifunctional disulfide crosslinker in the crosslinkable polymer composition and the resulting crosslinked composition may be greater than or equal to 0.25 wt%, greater than or equal to 1.5 wt%, greater than or equal to 2 wt%, greater than or equal to 2.5 wt%, greater than or equal to 3 wt%, or even greater than or equal to 3.5 wt%. In embodiments, the amount of the bifunctional disulfide crosslinker in the crosslinkable polymer composition and the resulting crosslinked composition may be less than or equal to 20 wt%, less than or equal to 15 wt%, less than or equal to 10 wt%, less than or equal to 9 wt%, less than or equal to 8 wt%, less than or equal to 7 wt%, less than or equal to 6 wt%, less than or equal to 5 wt%, or even less than or equal to 4 wt%. In embodiments, the amount of the bifunctional disulfide crosslinker in the crosslinkable polymer composition and the resulting crosslinked composition may be from 0.25 wt% to 1 wt%, from 1 wt% to 20 wt%, from 1 wt% to 15 wt%, from 1 wt% to 10 wt%, from 1 wt% to 9 wt%, from 1 wt% to 8 wt%, from 1 wt% to 7 wt%, from 1 wt% to 6 wt%, from 1 wt% to 5 wt%, from 1 wt% to 4 wt%, from 1.5 wt% to 20 wt%, from 1.5 wt% to 15 wt%, from 1.5 wt% to 10 wt%, from 1.5 wt% to 9 wt%, from 1.5 wt% to 8 wt%, from 1.5 wt% to 7 wt%, from 1.5 wt% to 6 wt%, from 1.5 wt% to 5 wt%, from 1.5 wt% to 4 wt%, from 2 wt% to 20 wt%, from 2 wt% to 15 wt%, from 2 wt% to 10 wt%,from 2 wt% to 9 wt%, from 2 wt% to 8 wt%, from 2 wt% to 7 wt%, from 2 wt% to 6 wt%, from 2 wt% to 5 wt%, from 2 wt% to 4 wt%, from 2.5 wt% to 20 wt%, from 2.5 wt% to 15 wt%, from 2.5 wt% to 10 wt%, from 2.5 wt% to 9 wt%, from 2.5 wt% to 8 wt%, from 2.5 wt% to 7 wt%, from 2.5 wt% to 6 wt%, from 2.5 wt% to 5 wt%, from 2.5 wt% to 4 wt%, from 3 wt% to 20 wt%, from 3 wt% to 15 wt%, from 3 wt% to 10 wt%, from 3 wt% to 9 wt%, from 3 wt% to 8 wt%, from 3 wt% to 7 wt%, from 3 wt% to 6 wt%, from 3 wt% to 5 wt%, from 3 wt% to 4 wt%, from 3.5 wt% to 20 wt%, from 3.5 wt% to 15 wt%, from 3.5 wt% to 10 wt%, from 3.5 wt% to 9 wt%, from 3.5 wt% to 8 wt%, from 3.5 wt% to 7 wt%, from 3.5 wt% to 6 wt%, from 3.5 wt% to 5 wt%, from 3.5 wt% to 4 wt%, or any and all sub-ranges formed from any of these endpoints.

[0082] Coagent

[0083] As described herein, in embodiments, the bifunctional disulfide crosslinker, such as BPMA, may have relatively low resonance stabilization and a relatively low reactivity toward a tertiary radical. As such, a coagent may be added to help improve reactivity toward a tertiary radical, thereby preventing chain scission.

[0084] In embodiments, the coagent may comprise styrene; divinyl benzene; 1,1,1- trimethylolpropane trimethacrylate; pentaerythrityl tetramethacrylate (PETM); trimethylolpropanetiacrylate (TMPTA); pentaerythritol tetraacrylate (PETA); pentaerythritol tetrallyl ether; diallyl maleate; triallyl cyanurate; diallyl itaconate; triallylisocyanurate (TAIC); 4-vinylnapthalene; or a combination thereof. In embodiments, the coagent may comprise styrene, pentaerythritol tetraacrylate (PETA), or a combination thereof.

[0085] Coagents, like styrene and divinyl benzene, may be included to propagate tertiary radicals and provide resonance stabilization to prevent chain scission. Coagents, like 1,1,1- trimethylolpropane trimethacrylate; PETM; TMPTA; PETA; pentaerythritol tetrallyl ether; diallyl maleate; triallyl cyanurate; diallyl itaconate; and TAIC, may be included to increase crosslink density by establishing permanent crosslinks alongside dynamic crosslinks provided by bifunctional disulfide and other coagents, like styrene and divinyl benzene. In embodiments, the coagent includes styrene; divinyl benzene, 1,1,1 -trimethylolpropane trimethacrylate; pentaerithrityl tetramethacrylate (PETM); trimethylolpropanetiacrylate (TMPTA); pentaerythritol tetraacrylate (PETA); pentaerythritol tetrallyl ether; diallylmaleate; triallyl cyanurate; diallyl itaconate; triallylisocyanurate (TAIC); or a combination thereof.

[0086] The crosslinkable polymer composition and the resulting crosslinked composition may comprise a minimum amount of coagent (e.g., greater than or equal to 0.5 wt%) to prevent chain scission and / or increase crosslink density. The amount of the coagent may be limited (e.g., less than or equal to 15 wt%) to ensure a sufficient amount of propylene-based polymer is present to achieve desired results. Accordingly, in embodiments, the crosslinkable polymer composition and the resulting crosslinked composition may comprise from 0.1 wt% to 15 wt% of the coagent. In embodiments, the amount of the coagent in the crosslinkable polymer composition and the resulting crosslinked composition may be greater than or equal to 0.5 wt%, greater than or equal to 1 wt%, greater than or equal to 2 wt%, greater than or equal to 3 wt%, greater than or equal to 4 wt%, or even greater than or equal to 5 wt%. In embodiments, the amount of the coagent in the crosslinkable polymer composition and the resulting crosslinked composition may be less than or equal to 15 wt%, less than or equal to 10 wt%, less than or equal to 9 wt%, less than or equal to 8 wt%, less than or equal to 7 wt%, or even less than or equal to 6 wt%. In embodiments, the amount of the coagent in the crosslinkable polymer composition and the resulting crosslinked composition may be from 0.5 wt% to 15 wt%, from 0.5 wt% to 10 wt%, from 0.5 wt% to 9 wt%, from 0.5 wt% to 8 wt%, from 0.5 wt% to 7 wt%, from 0.5 wt% to 6 wt%, from 1 wt% to 15 wt%, from 1 wt% to 10 wt%, from 1 wt% to 9 wt%, from 1 wt% to 8 wt%, from 1 wt% to 7 wt%, from 1 wt% to 6 wt%, from 2 wt% to 15 wt%, from 2 wt% to 10 wt%, from 2 wt% to 9 wt%, from 2 wt% to 8 wt%, from 2 wt% to 7 wt%, from 2 wt% to 6 wt%, from 3 wt% to 15 wt%, from 3 wt% to 10 wt%, from 3 wt% to 9 wt%, from 3 wt% to 8 wt%, from 3 wt% to 7 wt%, from 3 wt% to 6 wt%, from 4 wt% to 15 wt%, from 4 wt% to 10 wt%, from 4 wt% to 9 wt%, from 4 wt% to 8 wt%, from 4 wt% to 7 wt%, from 4 wt% to 6 wt%, from 5 wt% to 15 wt%, from 5 wt% to 10 wt%, from 5 wt% to 9 wt%, from 5 wt% to 8 wt%, from 5 wt% to 7 wt%, or even from 5 wt% to 6 wt%, or any and all sub-ranges formed from any of these endpoints.

[0087] Free Radical Initiator

[0088] Free radical initiator enables crosslinking of the crosslinkable polymer composition, thereby forming the crosslinked composition. The free radical initiator decomposes whereby forming free radicals and the reaction of primary radicals with polymer composition.

[0089] In embodiments, the free radical initiator may comprise an organic peroxide. Nonlimiting examples of suitable organic peroxide include bis( 1,1 -dimethylethyl) peroxide; bis( 1,1 -dimethylpropyl) peroxide; 2,5-dimethyl-2,5-bis(l,l-dimethylethylperoxy) hexane; 2, 5 -dimethy 1-2, 5 -bis( 1,1 -dimethylethylperoxy) hexyne; 4,4-bis(l,l- dimethylethylperoxy) valeric acid; butyl ester; l,l-bis(l,l-dimethylethylperoxy)-3,3,5- trimethylcyclohexane; benzoyl peroxide; tert-butyl peroxybenzoate; di-tert-amyl peroxide (“DTAP”), bis(a-t-butyl-peroxyisopropyl) benzene (“BIBP”); isopropylcymyl t-butyl peroxide; t-butylcumylperoxide; di-t-butyl peroxide; 2,5-bis(t-butylperoxy)-2,5- dimethylhexane; 2,5-bis(tbutylperoxy)-2,5-dimethylhexyne-3,l,l-bis(t-butylperoxy)-3,3,5- trimethylcyclohexane; isopropylcumyl cumylperoxide; butyl 4,4-di(tert-butylperoxy) valerate; di(isopropylcumyl) peroxide; dicumyl peroxide, and combinations thereof. In embodiments, the free radical initiator may comprise dicumyl peroxide.

[0090] The crosslinkable polymer composition may comprise a minimum amount of free radical initiator (e.g., greater than or equal to 0.5 wt%) to initiate crosslinking of the crosslinkable polymer composition. The amount of the free radical initiator may be limited (e.g., less than or equal to 10 wt%) to prevent formation of permanent crosslinks incapable of dynamic chemistry. Accordingly, in embodiments, the crosslinkable polymer composition may comprise from 0.5 wt% to 10 wt% free radical initiator. In embodiments, the amount of the free radical initiator in the crosslinkable polymer composition may be greater than or equal to 0.5 wt%, greater than or equal to 1 wt%, greater than or equal to 2 wt%, or even greater than or equal to 3 wt. In embodiments, the amount of the free radical initiator in the crosslinkable polymer composition may be less than or equal to 10 wt%, less than or equal to 8 wt%, less than or equal to 6 wt%, or even less than or equal to 4 wt%. In embodiments, the amount of the free radical initiator in the crosslinkable polymer composition may be from 0.5 wt% to 10 wt%, from 0.5 wt% to 8 wt%, from 0.5 wt% to 6 wt%, from 0.5 wt% to 4 wt%, from 1 wt% to 10 wt%, from 1 wt% to 8 wt%, from 1 wt% to 6 wt%, from 1 wt% to 4 wt%, from 2 wt% to 10 wt%, from 2 wt% to 8 wt%, from 2 wt% to 6 wt%, from 2 wt% to 4 wt%, from 3 wt% to 10 wt%, from 3 wt% to 8 wt%, from 0.5 wt% to 6 wt%, or even from 3 wt% to 4 wt%, or any and all sub-ranges formed from any of these endpoints.

[0091] Blend Component

[0092] In embodiments, the crosslinkable polymer composition and / or the crosslinked composition includes a blend component. Nonlimiting examples of suitable blend componentinclude ethylene vinyl acetate (EVA), polyolefins (e.g., polypropylene other than the propylene-based polymer crosslinked with a crosslinker and polyethylene), polymers (e.g., polystyrene, ABS, SBS and the like) and combinations thereof. Non-limiting examples of suitable polyolefins include polyethylene; polypropylene; polybutylene (e.g., polybutene- 1); polypentene- 1; polyhexene- 1; polyoctene- 1; polydecene- 1; poly-3-methylbutene-l; poly-4- methylpentene-1; poly isoprene; poly butadiene; poly- 1,5 -hexadiene; interpolymers derived from olefins; interpolymers derived from olefins and other polymers such as polyvinyl chloride, polystyrene, and polyurethane; and combinations thereof.

[0093] In an embodiment, the polyolefin is a homopolymer such as polyethylene, polypropylene, poly butylene, polypentene- 1, poly-3 -methylbutene- 1, poly-4-methylpentene- 1, poly isoprene, poly butadiene, poly- 1,5 -hexadiene, polyhexene-1, poly octene- 1 and poly decene- 1.

[0094] Nonlimiting example of suitable polypropylene as a blend component (other than the propylene-based polymer that is crosslinked with a crosslinker) include low density polypropylene (LDPP), high density polypropylene (HDPP), high-melt strength polypropylene (HMS-PP) and combination thereof. Nonlimiting examples of polyethylene include ultra low density polyethylene (ULDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), high molecular weight high density polyethylene (HMW-HDPE), ultra high molecular weight polyethylene (UHMW-PE) and combinations thereof. In an embodiment, the blend component is a high-melt strength polypropylene (HMS-PP), a low density polyethylene (LDPE) or a combination thereof.

[0095] Additives

[0096] The crosslinkable composition and / or the crosslinked composition may contain one or more optional additives. Nonlimiting examples of suitable additives include grafting initiators, crosslinking catalysts, blowing agent, blowing agent activators (e.g., zinc oxide, zinc stearate and the like), coagents (e.g., triallyl cyanurate), plasticizers, processing oils, processing aids, carbon black, colorants or pigments, stability control agents, nucleating agents, fillers, antioxidants, acid scavengers, ultraviolet (UV) stabilizers, flame retardants, lubricants, processing aids, extrusion aids, and combinations thereof. When present, the total amount of additive can be from greater than 0% to 80%, or from 0.001% to 70%, or from0.01% to 60 %, or from 0.1 % to 50 %, or from 0.1 % to 40%, or from 0.1% to 20%, or from 0.1 % to 10 %, or from 0.1% to 5% of the total weight of the composition.

[0097] In embodiments, the crosslinkable composition and / or the crosslinked composition includes an antioxidant. Non-limiting examples of suitable antioxidants include aromatic or hindered amines such as alkyl diphenylamines, phenyl-a-naphthylamine, alkyl or aralkyl substituted phenyl-a-naphthylamine, alkylated p-phenylene diamines, tetramethyldiaminodiphenylamine and the like; phenols such as 2,6-di-t-butyl-4-methylphenol; 1,3,5- trimethyl-2,4,6-tris(3',5,-di-t-butyl-4,-hydroxybenzyl)benzene; tetrakis[(methylene(3,5 -di-t- butyl-4-hydroxyhydrocinnamate)]methane (e.g., IRGANOX™ 1010, from Ciba Geigy, NewYork); acryloyl modified phenols; octadecyl-3,5- di-t-butyl-4-hydroxycinnamate (e.g., IRGANOX 1076, commercially available from Ciba Geigy); phosphites and phosphonites; hydroxylamines; benzofuranone derivatives; and combinations thereof. When used, the amount of the antioxidant in the composition can be from greater than 0 to 5%, or from 0.0001 to 2.5%, or from 0.001 to 1%, or from 0.001 to 0.5% of the total weight of the composition.

[0098] In embodiments, the crosslinkable composition and / or the crosslinked composition includes a UV stabilizer. Non-limiting examples of suitable UV stabilizers include benzophenones, benzotriazoles, aryl esters, oxanilides, acrylic esters, formamidines, carbon black, hindered amines, nickel quenchers, hindered amines, phenolic antioxidants, metallic salts, zinc compounds and combinations thereof. When used, the amount of the UV stabilizer can be from greater than 0 to 5%, or from 0.01 % to 3 %, or from 0.1 % to 2 %, or from 0.1% to 1% of the total weight of the composition.

[0099] In embodiments, the crosslinkable composition and / or the crosslinked composition includes a colorant or a pigment. Non-limiting examples of suitable colorants or pigments include inorganic pigments such as metal oxides such as iron oxide, zinc oxide, and titanium dioxide, mixed metal oxides, carbon black, organic pigments such as anthraquinones, anthanthrones, azo and monoazo compounds, arylamides, benzimidazolones, BONA lakes, diketopyrrolo-pyrroles, dioxazines, disazo compounds, diarylide compounds, flavanthrones, indanthrones, isoindolinones, isoindolines, metal complexes, monoazo salts, naphthols, b- naphthols, naphthol AS, naphthol lakes, perylenes, perinones, phthalocyanines, pyranthrones, quinacridones, and quinophthalones, and combinations thereof. When used, the amount of the colorant or pigment in the composition can be from greater than 0 to 10%, or from 0.1% to 5 %, or from 0.25% to 2% of the total weight of the composition.

[0100] In embodiments, the crosslinkable composition and / or the crosslinked composition includes a filler. Nonlimiting examples of suitable fillers include talc, calcium carbonate, chalk, calcium sulfate, clay, kaolin, silica, glass, fumed silica, mica, wollastonite, feldspar, aluminum silicate, calcium silicate, alumina, hydrated alumina such as alumina trihydrate, glass microsphere, ceramic microsphere, thermoplastic microsphere, barite, wood flour, glass fibers, carbon fibers, marble dust, cement dust, magnesium oxide, magnesium hydroxide, antimony oxide, zinc oxide, barium sulfate, titanium dioxide, titanates and combinations thereof.

[0101] In embodiments, the filler is barium sulfate, talc, calcium carbonate, silica, glass, glass fiber, alumina, titanium dioxide, or a mixture thereof. In a further embodiment, the filler is talc, calcium carbonate, barium sulfate, glass fiber or a mixture thereof. When used, the amount of the filler in the composition can be from greater than 0 to 80%, or from 0.1 to 60%, or from 0.5 to 40%, or from 1 to 30%, or from 10 to 40% of the total weight of the composition.

[0102] In embodiments, the crosslinkable composition and / or the crosslinked composition includes a lubricant. Nonlimiting examples of suitable lubricants include fatty alcohols and their dicarboxylic acid esters, fatty acid esters of short chain alcohols, fatty acids, fatty acid amides, metal soaps, oligomeric fatty acid esters, fatty acid esters of long-chain alcohols, montan waxes, polyethylene waxes, polypropylene waxes, natural and synthetic paraffin waxes, fluoropolymers and combinations thereof. When used, the amount of the lubricant in the composition can be from greater than 0% to 5%, or from 0.1 to 4%, or from 0.1% to 3% of the total weight of the composition.

[0103] In embodiments, the crosslinkable composition and / or the crosslinked composition includes an antistatic agent. Non-limiting examples of suitable antistatic agents include conductive fillers (e.g., carbon black, metal particles and other conductive particles), fatty acid esters (e.g., glycerol monostearate), ethoxylated alkylamines, diethanolamides, ethoxylated alcohols, alkylsulfonates, alkylphosphates, quaternary ammonium salts, alkylbetaines and combinations thereof. Where used, the amount of the antistatic agent in the composition can be from greater than 0 % to 5 %, or from 0.01 to 3 %, or from 0.1 to 2 % of the total weight of the composition.

[0104] In embodiments, the crosslinkable composition and / or the crosslinked composition includes a blowing agent. A "blowing agent" is a substance that is capable of producing a cellular structure in the composition via a foaming process. The blowing agent is used for foaming the crosslinked composition. Nonlimiting examples of suitable blowing agent include an inorganic physical blowing agent, such as air, argon, nitrogen, carbon dioxide, argon, helium, oxygen, and neon, and an organic physical blowing agent, such as an aliphatic hydrocarbon, e.g., propane, n- butane, isobutane, n-pentane, isopentane, and n-hexane, an alicyclic hydrocarbon, e.g., cyclohexane and cyclopentane, a halogenated hydrocarbon, e.g., chlorofluoromethane, trifluoromethane, 1,1 -difluoro ethane, 1,1,1,2-tetrafluoroethane, methyl chloride, ethyl chloride, and methylene chloride, and a dialkyl ether, e.g., dimethyl ether, diethyl ether, and methyl ethyl ether.

[0105] Non-limiting examples of suitable organic blowing agents include aliphatic hydrocarbons having 1-6 carbon atoms, aliphatic alcohols having 1-3 carbon atoms, and fully and partially halogenated aliphatic hydrocarbons having 1-4 carbon atoms. Non-limiting examples of suitable aliphatic hydrocarbons include methane, ethane, propane, n-butane, isobutane, n- pentane, isopentane, neopentane, and the like. Non-limiting examples of suitable aliphatic alcohols include methanol, ethanol, n-propanol, and isopropanol. Nonlimiting examples of suitable fully and partially halogenated aliphatic hydrocarbons include fluorocarbons, chlorocarbons, and chlorofluorocarbons. Non-limiting examples of suitable fluorocarbons include methyl fluoride, perfluoromethane, ethyl fluoride, 1,1 -difluoroethane (HFC152a), 1,1,1- trifluoroethane (HFC-143a), 1,1,1,2-tetrafluoroethane (HFC-134a), pentafluoroethane, difluoromethane, perfluoroethane, 2,2-difluoropropane, 1,1,1- trifluoropropane, perfluoropropane, dichloropropane, difluoropropane, perfluorobutane, perfluorocyclobutane. Non-limiting examples of suitable partially halogenated chlorocarbons and chlorofluorocarbons include methyl chloride, methylene chloride, ethyl chloride, 1,1,1- trichloroethane, 1,1-dichloro- 1 -fluoroethane (HCFC-141b), l-chloro-l,ldifluoroethane (HCFC-142b), l,l-dichloro-2,2,2- trifluoro ethane (HCFC-123) and l-chloro-1,2,2,2- tetrafluoroethane(HCFC-124). Non-limiting examples of suitable fully halogenated chlorofluorocarbons include trichloromonofluoromethane (OPOI 1}, dichlorodifluoromethane (CFO-12}, trichlorotrifluoroethane (CFO-113), 1,1,1- trifluoro ethane, pentafluoroethane, dichlorotetrafluoroethane (CFO-114), chloroheptafluoropropane, and dichlorohexafluoropropane. Non-limiting examples of suitable chemical blowing agents include azodicarbonamide, azodiisobutyro-nitrile, benezenesulfonhydrazide, 4,4-oxybenzene sulfonyl-semicarbazide, p- toluene sulfonyl semi-carbazide, barium azodicarboxylate, N,N'- dimethyl-N,N'- dinitrosoterephthalamide, and trihydrazino triazine.

[0106] Crosslinked Composition

[0107] The crosslinkable polymer compositions as described herein, including a propylene- based polymer and bifunctional disulfide crosslinker, may be melt blended at a temperature from 100 °C to 250 °C, from 120 °C to 200 °C, from 120 °C to 180 °C, or from 120 °C to 160 °C to trigger a crosslinking reaction and form the crosslinked composition.

[0108] In embodiments, the propylene-based polymer of the crosslinked composition may form a polymer backbone. The crosslinked composition may include disulfide linkages formed from the BPST or BPMA by way of the crosslinking reaction, the disulfide linkages formed from BPST shown in Structure 4 below and the disulfide linkage formed from BPMA shown in Structure 5 below.

[0109] The term (and structure) “Pm” in Structures 4 and 5 above refers to the chain of polymerized propylene (and optional comonomer(s)) for the propylene-based polymer.

[0110] In embodiments, the crosslinked composition includes the linkages of Structure 5.

[0111] The term (and structure) “Pm” in Structures 4 and 5 above refers to the chain of polymerized propylene (and optional comonomer(s)) for the propylene-based polymer.

[0112] As described herein, the crosslinked composition may comprise desirable properties, such as lower intrinsic viscosity at LOG 6.5 (Mw(abs)), a higher complex viscosity at 0.1 rad / s, and a lower tan 8 at 0.1 rad / s as compared to a similar composition lacking a bifunctional disulfide crosslinker, which may be indicative of improved melt strength.

[0113] In embodiments, the crosslinkable composition may comprise a complex viscosity at 0.1 rad / s of from 100 to 10,000 Pa*s. For example, the crosslinkable composition may comprise a complex viscosity at 0.1 rad / s of from 100 Pa*s to 75,000 Pa*s, from 200 Pa*s to 50,000 Pa*s, from 500 Pa*s to 20,000 Pa*s, from 100 Pa*s to 5,000 Pa*s; or any and all subranges formed from any of these endpoints.

[0114] In embodiments, the crosslinkable composition may comprise a complex viscosity at 1 rad / s of from 100 to 3,000 Pa*s. For example, the crosslinkable composition may comprise a complex viscosity at 1 rad / s of from 100 Pa*s to 2,500 Pa*s, from 200 Pa*s to 2,000 Pa*s, from 500 Pa*s to 1,500 Pa*s, from 100 Pa*s to 1,500 Pa*s; or any and all subranges formed from any of these endpoints.

[0115] In embodiments, the crosslinkable composition may comprise a complex viscosity at 10 rad / s of from 10 to 1000 Pa*s. For example, the crosslinkable composition may comprise a complex viscosity at 10 rad / s of from 10 Pa*s to 900 Pa*s, from 15 Pa*s to 750 Pa*s, from 20 Pa*s to 500 Pa*s, from 50 Pa*s to 250 Pa*s; or any and all sub-ranges formed from any of these endpoints.

[0116] In embodiments, the crosslinkable composition may comprise a complex viscosity at 100 rad / s of from 10 to 1000 Pa*s. For example, the crosslinkable composition may comprise a complex viscosity at 100 rad / s of from 10 Pa*s to 900 Pa*s, from 15 Pa*s to 750 Pa*s, from 20 Pa*s to 500 Pa*s, from 50 Pa*s to 250 Pa*s; or any and all sub-ranges formed from any of these endpoints.

[0117] In embodiments, the crosslinked composition may comprise a weight-average molecular weight (Mw) of from 75,000 to 1,000,000 g / mol. For example, the crosslinkable composition may comprise an Mwof from 75,000 g / mol to 800,000 g / mol; from 90,000 g / mol to 700,000 g / mol; from 100,000 g / mol to 500,000 g / mol; from 150,000 g / mol to 300,000 g / mol; from 200,000 g / mol to 250,000 g / mol; or any and all sub-ranges formed from any of these endpoints.

[0118] Higher molecular weights indicate increased levels of crosslinking and branching. In embodiments, the crosslinked composition may comprise a number-average molecular weight (Mn) of 15,000 g / mol or greater. For example, the crosslinkable composition may comprise an Mn of from 15,000 g / mol to 500,000 g / mol; from 15,000 g / mol to 400,000 g / mol; from 20,000 g / mol to 300,000 g / mol; from 30,000 to 250,000 g / mol; from 50,000 g / mol to 200,000 g / mol; from 100,000 g / mol to 150,000 g / mol; or any and all sub-ranges formed from any of these endpoints.

[0119] Increased Polydispersity Index (PDI) is indicative of increased branching and crosslinking. In embodiments, the crosslinked composition may comprise a Polydispersity Index (PDI, Mw / Mn) of 4 or greater. For example, the crosslinkable composition may have an Mw / Mn of from 4 to 8; from 5 to 7; from 4 to 6; from 5.5 to 7; or any and all sub-ranges formed from any of these endpoints.

[0120] A lower tan 8 (or tan delta) indicates increased damping, indicating that a material is more elastic than viscous. In general, higher viscosity correlates with increased branching and crosslinking. In embodiments, the crosslinkable composition may comprise a tan 8 at 0.1 rad / s of from 0.5 to 30. For example, the crosslinkable composition may comprise a tan 8 at 0.1 rad / s of from 0.5 to 25; from 1 to 20; from 2 to 15; from 5 to 10; or any and all sub-ranges formed from any of these endpoints.

[0121] In embodiments, the crosslinkable composition may comprise a tan 8 at 1 rad / s of from 0.5 to 15. For example, the crosslinkable composition may comprise a tan 8 at 1 rad / s of from 0.5 to 12; from 1 to 10; from 2 to 8; from 3 to 5; or any and all sub-ranges formed from any of these endpoints. In embodiments, the crosslinkable composition may comprise a tan 8 at 10 rad / s of from 0.5 to 6. For example, the crosslinkable composition may comprise a tan 8 at 10 rad / s of from 0.5 to 5; from 0.7 to 4; from 1 to 3; from 2 to 4; or any and all subranges formed from any of these endpoints. In embodiments, the crosslinkable composition may comprise a tan 8 at 100 rad / s of from 0.5 to 3. For example, the crosslinkable composition may comprise a tan 8 at 100 rad / s of from 0.5 to 2.8; from 0.6 to 2.5; from 0.8 to 2; from 1 to 2; or any and all sub-ranges formed from any of these endpoints.

[0122] Elongational viscosity versus Hencky Strain is indicative of a material’s resistance to stretching and elongating. This property often correlates with the melt strength property ofpolymers. A higher Elongational viscosity indicates a higher melt strength, and a lower Elongational viscosity indicates a lower melt strength.

[0123] In embodiments, at a temperature of 230 °C, the crosslinkable composition may comprise an Elongational viscosity of from 1,500 Pa.s to 15,000 Pa.s at a Hencky Strain of 1, an Elongational viscosity of from 1,500 Pa.s to 50,000 Pa.s at a Hencky strain of 2, an Elongational viscosity of from 2,000 Pa.s to 150,000 Pa.s at a Hencky strain of 3, and an Elongational viscosity of from 2,000 Pa.s to 300,000 Pa.s at a Hencky strain of 4.

[0124] In embodiments, at a temperature of 190 °C, the crosslinkable composition may comprise an Elongational viscosity of from 4,000 Pa.s to 15,000 Pa.s at a Hencky Strain of 1, an Elongational viscosity of from 10,000 Pa.s to 50,000 Pa.s at a Hencky strain of 2, an Elongational viscosity of from 15,000 Pa.s to 150,000 Pa.s at a Hencky strain of 3, and an Elongational viscosity of from 1,000 Pa.s to 300,000 Pa.s at a Hencky strain of 4.

[0125] In embodiments, the crosslinkable composition may comprise an intrinsic viscosity at LOG 6.5 (Mw(abs)) from 0.4 dL / g to 0.85 dL / g. For example, the crosslinkable composition may comprise intrinsic viscosity at LOG 6.5 (Mw(abs)) of from 0.4 dL / g to 0.5 dL / g, from 0.5 dL / g to 0.6 dL / g, from 0.6 dL / g to 0.7 dL / g, from 0.7 dL / g to 0.8 dL / g, from 0.55 dL / g to 0.65 dL / g, from 0.65 dL / g to 0.75 dL / g, from 0.75 dL / g to 0.85 dL / g, or any and all subranges formed from any of these endpoints.

[0126] A higher gel content indicates a greater degree of crosslinking in a polymer. In embodiments, the crosslinkable composition may comprise a gel content in accordance with ASTM D2765 of from 0.2% to 15%. For example, the crosslinkable composition may comprise a gel content of from 0.2% to 12%; of from 0.5% to 10%; from 1% to 7%; from 2% to 6%; from 3% to 5%; or any and all sub-ranges formed from any of these endpoints.

[0127] A lower % mass recovery from Gel Permeation Chromatography analysis indicates a higher level of crosslinking in the polymer. In embodiments, the crosslinked composition may comprise a mass recovery of 99% or lower. For example, the crosslinked composition may comprise a mass recovery of from 90% to 99%, from 91% to 98%, from 92% to 97%, from 93% to 96%, from 96% to 99%, or any and all sub-ranges formed from any of these endpoints.

[0128] In embodiments, the crosslinked composition may comprise a z-average molecular weight (Mz) of from 200,000 to 1,000,000 g / mol. For example, the crosslinkable compositionmay comprise an Mzof from 200,000 g / mol to 800,000 g / mol; from 300,000 g / mol to 700,000 g / mol; from 400,000 g / mol to 500,000 g / mol; from 150,000 g / mol to 300,000 g / mol; from 200,000 g / mol to 250,000 g / mol; or any and all sub-ranges formed from any of these endpoints.

[0129] In embodiments, the crosslinked composition may comprise apeak molecular weight (Mp) of from 50,000 to 1,000,000 g / mol. For example, the crosslinkable composition may comprise an Mpof from 50,000 g / mol to 800,000 g / mol; from 75,000 g / mol to 700,000 g / mol; from 100,000 g / mol to 500,000 g / mol; from 150,000 g / mol to 300,000 g / mol; from 200,000 g / mol to 250,000 g / mol; or any and all sub-ranges formed from any of these endpoints.

[0130] Reprocessability and / or Recyclability

[0131] In some embodiments, the crosslinkable composition and / or the crosslinked composition may be reprocessable and / or recyclable. The dynamic crosslinker bifunctional disulfide enables a cyclic “reprocessing” for fabrication of new polymeric articles or molds. The aromatic disulfide bonds of bifunctional disulfide crosslinker are mostly associative in nature and, thus, crosslinked compositions containing them retain their crosslinked nature at the reprocessing temperature. More specifically, when the crosslinked propylene-based polymer composition is heated to the reprocessing temperature, a relatively small amount of the disulfide linkages break, or otherwise cleave, into sulfur radicals. The sulfur radicals interchange with still-existing disulfide linkages to simultaneously “swap in” the radical to become a new partner and eject one of the old partners as a new radical. The new radical can then interact with other linkages for further bond exchange, enabling reprocessing. This may be referred to as a “[2+1] radical mediated mechanism.”

[0132] The cleaving and interchange that occurs at the reprocessing temperature enables the previously-crosslinked propylene-based polymer composition to flow at the reprocessing temperature, forming a reprocessable propylene-based composition. Heating to the reprocessing temperature enables link interchange and polymer chain flow, allowing the propylene-based composition to be reshaped readily. At the reprocessing temperature, the reprocessable propylene-based polymer composition is flowable, enabling shaping and / or fabrication of the now flowable re-processable propylene composition (with bifunctional disulfide) into a new pre-form or article. Upon cooling to below the reprocessing temperature, the disulfide linkages essentially become static, the network is re-established, and the re-crosslinked propylene-based polymer (with bifunctional disulfide) becomes a recrosslinked propylene-based polymer composition in the shape of a newly-fabricated article. Below the reprocessing temperature, the network disulfide linkages are stable, and the recrosslinked propylene-based polymer composition exhibits the high viscosity and resistance to mechanical deformation indicative of a crosslinked network. This cycle of crosslink / reprocess / re-crosslink, and fabrication into a new article can be repeated.

[0133] Bounded by no particular theory, the number of “reprocessing” cycles that are possible with the present crosslinked propylene-based composition (before competitive thermal and oxidative permanent crosslinking occurs and prevents further reprocessing), can be determined by calculating the ratio of the melt viscosity of the crosslinked propylene- based polymer composition before and after a reprocessing cycle. For the crosslinked propylene-based polymer composition to be re-processable, the ratio of the complex melt viscosity after reprocessing to the complex melt viscosity before reprocessing is from 0.5 to 5, or from 0.7 to 3 or from 0.9 to 2 or from 0.95 to 1.2.

[0134] Other metrics for monitoring the number of “reprocessing” cycles that are possible with the bifunctional disulfide crosslinkers before competitive oxidative permanent crosslinking occurs include visual observation. Formed film that is mechanically deformed is heated to the reprocessing temperature and is visually inspected to determine whether the mechanically deformed film heals to form a stable film.

[0135] In embodiments, a process may comprise heating a first article to a reprocessing temperature; forming, at the reprocessing temperature, the first article into a re-processable propylene-based polymer composition; shaping, at the reprocessing temperature, the reprocessable propylene-based composition into a re-processed pre-form; cooling the reprocessed pre-form to below the reprocessing temperature; and forming a second article, the second article comprising a re-crosslinked composition. The second article may be different from the first article.

[0136] In embodiments, the reprocessing temperature may be from 100 °C to 250 °C, thereby breaking disulfide linkages of the crosslinked composition and forming the reprocessable propylene-based polymer composition. In embodiments, the reprocessing temperature may be from 100 °C to 250 °C, from 100 °C to 225 °C, from 100 °C to 200 °C, from 100 °C to 175 °C, from 130 °C to 250 °C, from 130 °C to 225 °C, from 130 °C to 200°C, from 130 °C to 175 °C, from 160 °C to 250 °C, from 160 °C to 225 °C, from 160 °C to 200 °C, from 160 °C to 175 °C, from 190 °C to 250 °C, from 190 °C to 225 °C, or even from 190 °C to 200 °C, from 100 °C to 175 °C, or any and all sub-ranges formed from any of these endpoints.

[0137] In embodiments, the shaping step is a procedure selected from the group comprising injection molding, extrusion molding, thermoforming, slushmolding, over molding, insert molding, blow molding, cast molding, tentering, compression molding, and combinations thereof.

[0138] Nonlimiting examples of suitable articles (first article and second article) for the present crosslinked / re-crosslinked propylene-based polymer (with bifunctional disulfide or BPST) composition include elastic film; elastic fiber; soft touch good, such as tooth brush handles and appliance handles; gaskets and profiles; adhesives (including hot melt adhesives and pressure sensitive adhesives); footwear (including shoe soles and shoe liners); auto interior parts and profiles; foam articles (both open cell foam and closed cell foam); impact modifiers for other thermoplastic polymers such as high density polyethylene, isotactic polypropylene, or other olefin polymers; coated fabrics; hoses; tubing; weather stripping; cap liners; flooring; and combinations thereof.

[0139] TEST METHODS

[0140] Gel Permeation Chromatography (GPC)

[0141] The chromatographic system consisted of a Polymer Char GPC-IR (Valencia, Spain) high temperature GPC chromatograph, equipped with an internal IR5 infrared detector (IR5). The autosampler oven compartment was set at 160 °C, and the column compartment was set at 150° Celsius. The columns were one Agilent PEgel MIXED 7.5 x 50 mm, 20 pm linear mixed-bed guard column and four Agilent PLgel MIXED-A 7.5 x 300 mm, 20 pm linear mixed-bed columns. The chromatographic solvent was 1,2,4-trichlorobenzene, which contained 300 ppm of butylated hydroxytoluene (BHT) and was nitrogen sparged. The injection volume used was 200 microliters, and the flow rate was 1.0 milliliters / minute.

[0142] Calibration of the GPC column set was performed using Agilent EasiCal Polystyrene standards (EasiCal PS-1 and EasiCal PS-2). Each EasiCal system consisted of two different spatulas supporting a mixture of 5 polymer standards (approximately 5 mg) to obtain 20 molecular weights points ranging from approximately 580 to 6,570,000 g / mole. Individualspatulas were added to septa-capped vials, sealed, and loaded into the Polymer Char autosampler. Polymer Char Instrument Control Software was utilized to add 8 mL of solvent to each vial and the standards were dissolved for 15 minutes at 160 °C under high-speed shaking prior to injection to the chromatography system. A third order polynomial was used to fit the nominal polystyrene standard peak molecular weights to obtain molecular weight equivalent calibration points at each chromatographic slice. The polystyrene standard peak molecular weights were converted to polyethylene molecular weights using Equation 1 (as described in Williams and Ward, J. Polym. Sci., Polym. Let., 6, 621 (1968)).:where M is the molecular weight, A has a value of 0.41 and B is equal to 1.0.

[0143] The total plate count of the GPC column set was performed with decane (3% v / v in 1,2,4-trichlorobenzene (TCB) introduced via micropump). The plate count for the chromatographic system should be greater than 18,000 for the 4 Agilent “Mixed A” 30 cm 20-micron linear mixed-bed columns.

[0144] Samples were prepared in a semi-automatic manner with the Polymer Char Instrument Control Software, wherein the samples were weight-targeted at 2 mg / ml, and the solvent was added to a septa-capped sealed vial via the Polymer Char high temperature autosampler. The samples were dissolved for two hours at 160° Celsius under high-speed shaking.

[0145] The calculations of Mn(GPC), MW(GPC), and MZ(GPC) were based on GPC results using the internal IR5 detector (measurement channel) of the Polymer Char GPC-IR chromatograph according to Equations 2-4. Using Polymer Char GPCOne™ software, the baseline- subtracted IR chromatogram at each equally-spaced data collection point (i) was converted to the polyethylene equivalent molecular weight, obtained from the narrow standard calibration curve, for the equivalent chromatographic data point (i). Equations 2-4 are as follows:

[0146] In order to monitor the deviations over time, a flowrate marker (3% v / v decane in solvent) was introduced into each sample via a micropump controlled with the Polymer Char GPC-IR system. This flowrate marker (FM) was used to linearly correct the pump flowrate (Flowrate(nominaij) for each sample by RV alignment of the respective decane peak within the sample (RV(FM sample)) to that of the decane peak within the narrow standards calibration (RV(FM calibrated)). Any changes in the time of the decane marker peak were then assumed to be related to a linear-shift in flowrate (Flowrate(effective)) for the entire run. After calibrating the system based on a flow marker peak, the effective flowrate (with respect to the narrow standards calibration) is calculated as Equation 5. Processing of the flow marker peak was done via the Polymer Char GPCOne™ Software. Acceptable flowrate correction is such that the effective flowrate should be within + / -0.7% of the nominal flowrate.

[0147] Flowrate(effective) = Ffowrate(nominal) * (RV(FM Calibrated) / RV(FM Sample)) (EQ 5)

[0148] GPC recovery was determined in a way consistent with that used within PolymerChar GPCOne Software using the total signal areas of a sample eluted by the GPC method via IR5 broad filter detector measurement channel and adjusted using a mass constant as determined with a vendor recommended polyethylene homopolymer standard. Mass recovery is calculated by the expression M-REC = 100 x [ (initial analyte - filtered analyte) / initial analyte ] using the analyte mass values obtained in the PolymerChar SoGPC test. It is understood that polymers with internal crosslinking form insoluble gels that are quantifiably detectable by low mass recovery analysis.

[0149] For the determination of the viscometer and light scattering detector offsets from the IR5 detector, the Systematic Approach for the determination of multi-detector offsets is done in a manner consistent with that published by Balke, Mourey, et. al. (Mourey and Balke, Chromatography Polym. Chpt 12, (1992)) (Balke, Thitiratsakul, Lew, Cheung, Mourey, Chromatography Polym. Chpt 13, (1992)), optimizing triple detector fog (Mwand IV) results from a linear homopolymer polyethylene standard (3.5 > Mw / Mn> 2.2) with a molecular weight in the range of 115,000 to 125,000 g / mol to the narrow standard column calibration results from the narrow standards calibration curve using PolymerChar GPCOne™ Software.

[0150] The absolute molecular weight data was obtained in a manner consistent with that published by Zimm (Zimm, B.H., J. Chem. Phys., 16, 1099 (1948)) and Kratochvil (Kratochvil, P., Classical Light Scattering from Polymer Solutions, Elsevier, Oxford, NY (1987)) using PolymerChar GPCOne™ software. The overall injected concentration, used in the determination of the molecular weight, was obtained from the mass detector area and the mass detector constant, derived from a suitable linear polyethylene homopolymer, or one of the polyethylene standards of known weight-average molecular weight. The calculated molecular weights (using GPCOne™) were obtained using a light scattering constant, derived from one or more of the polyethylene standards mentioned below, and a refractive index concentration coefficient, dn / dc, of -0.104. Generally, the mass detector response (IR5) and the light scattering constant (determined using GPCOne™) should be determined from a linear standard with a molecular weight in excess of about 50,000 g / mole. The viscometer calibration (determined using GPCOne™) can be accomplished using the methods described by the manufacturer, or, alternatively, by using the published values of suitable linear standards, such as Standard Reference Materials (SRM) 1475a (available from National Institute of Standards and Technology (NIST)). A viscometer constant (obtained using GPCOne™) is calculated which relates specific viscosity area (DV) and injected mass for the calibration standard to its intrinsic viscosity. The chromatographic concentrations are assumed low enough to eliminate addressing 2nd viral coefficient effects (concentration effects on molecular weight).

[0151] The absolute weight average molecular weight (Mw(abs)) is obtained (using GPCOne™) from the Area of the Light Scattering (LS) integrated chromatogram (factored by the light scattering constant) divided by the mass recovered from the mass constant and the mass detector (IR5) area. The molecular weight and intrinsic viscosity responses are linearly extrapolated at chromatographic ends where signal to noise becomes low (using GPCOne™). Other respective moments, Mn(abs) and Mz(abs) are be calculated according to Equations 6-8 as follows :Mz(Abs) — — -. -(EQ 8)TX - Absolute i )

[0152] Dynamic Mechanical Spectroscopy Frequency Sweep

[0153] All DMS frequency tests were conducted on an ARES-G2 Rheometer of which is manufactured by TA Instruments. Data analyses were conducted using the TA Instruments TRIOS software.

[0154] Prior to testing, test samples were placed into a 1.5-inch diameter chase having a thickness of 2 mm and compression molded in a hydraulic press for 10 minutes at a temperature of 190 °C and a pressure of 150 bar. After cooling to ambient temperature at a rate of 10 °C / min, the samples were extracted for rheological testing.

[0155] The DMS frequency sweep was conducted using 25 mm parallel plates at frequencies ranging from 0.1 rad / s to 100 rad / s. The test gap separating the plates was 1.8 mm and a strain satisfying linear viscoelastic conditions was utilized. Each test was conducted under nitrogen atmosphere and isothermal conditions at 230 °C. To initiate the DMS test, the Rheometer oven was first allowed to equilibrate at 230 °C for at least 30 minutes before loading the sample into the test geometry. The sample was then equilibrated in the oven, with the door closed, for 1 minute. The test gap was set to 1.8 mm, and the sample was allotted 5 minutes to relax the resulting normal force. Afterwards, the oven was quickly opened, and the sample was trimmed so that no bulge was present. The DMS measurement was initiated after reclosing the oven.

[0156] Mass recovery was determined in a way consistent with that used within PolymerChar GPCOne Software using the total signal areas of a sample eluted by the GPC method via IR5 broad filter detector measurement channel and adjusted using a mass constant as determined with a vendor recommended polyethylene homopolymer standard. Mass recovery is calculated as Equation 9:Mass recovery = 100 x [ initial analyte — filtered analyte) I initial analyte] (EQ 9)

[0157] using the analyte mass values obtained in the PolymerChar SoGPC test. It is understood that polymers with internal crosslinking form insoluble gels that are quantifiably detectable by low mass recovery analysis.

[0158] Gel %

[0159] Resin specimens were prepared by cutting them into small resin pieces. A piece of 120-mesh stainless steel cloth measuring approximately 80 by 40-mm (3 in. by 1.5 in.) was folded in half to form a square measuring approximately 40 mm (1.5 in.). Two parallel edges of the square were folded along respective parallel open edges of the square to form an unsealed pouch having folded edges. The folded edges were stapled to form an open pouch that was weighed (Wl). The small cut resin pieces were inserted into the open pouch, until the combined weight of sample and pouch (W2) reached approximately 0.3 grams. The open edge of the open pouch was folded over to form a top fold. The top fold was stapled to form a cage. The cage and the specimen were weighed (W3).

[0160] The cage and specimen were suspended in xylene in excess, 40 g of antioxidant (2,2’- methylene-6-tertiary butyl phenol), and boiling chips. The xylene was boiled for 12 hours at 138 °C to 141 °C under a fume hood. The cage and specimen were removed from the xylene and placed immediately into a 150 °C vacuum oven and left to dry in the vacuum oven at 28 mmHg vacuum for 12 hours. The cage and specimen were removed from the vacuum oven and placed in a dessicator for one hour. The cage and specimen (W4) were weighed after drying.

[0161] The solvent extraction % and % gel content were calculated as follows (Equations 10-11): 100 (EQ 10)7% Gel Content = 100 — (Solvent Extraction %) (EQ 11)Wl = weight of the open pouch;W2 = weight of the specimen and open pouchW3 = weight of the specimen and cageW4 = weight of the specimen and cage after extraction and drying.

[0162] The average of two specimens was reported as the percent gel content.

[0163] Elongational Viscosity

[0164] Elongational viscosity measurements were made using an ARES rheometer (TA instruments) with an ARES-EVF attachment. Compression molded samples having a length of 18 mm, a width of 10 mm, and a thickness of between 0.3 mm and 1 mm were measured. The samples were mounted between the clamps of the drums and the samples were stabilized at temperature of 230 °C for about three minutes. The experiment was performed at a strain rate of 1 s'1and 230 °C on the samples having thicknesses of between 0.3 mm and 1 mm, during which force was measured by the ARES rheometer. The elongational viscosity was determined by Equations 12-14:Extensional stress = - - (f rce) -(surf ace area normal to the direction of def ormation)(Extensional stress)Elonqation Viscosity Ne = — - — (EQ 13) ' Elongation rate)

[0165] The test was repeated at a temperature of 190 °C. Results were reported in Elongational Viscosity (Pa.s) versus Hencky Strain.

[0166] EXAMPLES

[0167] By way of example, and not limitation, some embodiments of the present disclosure will now be described in detail by the following examples.

[0168] Materials

[0169] Materials used in Comparative Compositions Cl and C2 and Inventive Compositions 11-14 and are provided in Table 1 below.

[0170] Table 1

[0171] Synthesis of BPST

[0172] To synthesize BPST, 2-phenylacryloyl chloride (5.00 g, 30.0 mmol) was dissolved in 150 mF dichloromethane (DCM) and was stirred at 0 °C in an ice bath. Bis(4- hydroxyphenyl) disulfide (2.5 g, 10 mmol, supplied by Ambeed, Inc.) and 4- dimethylaminopyridine (DMAP) (20 mg, 0.08 mmol, supplied by Sigma-Aldrich) were added to the mixture, resulting in a milky yellowish solution. Triethylamine (supplied by Sigma- Aldrich) was added dropwise. The solution developed purple hue upon addition and gradually turned back to be milky yellowish. Triethylamine was continually added until the solution was no longer purple. 10% more triethylamine was added dropwise to ensure completion. In total, about 5 mL (36 mmol) triethylamine was added. The mixture returned to room temperature and stirred overnight for 18 hours. 500 mL of 0.1 M K2CO3 solution (supplied by Sigma-Aldrich) was poured into the mixture and stirred for 1 hour. 500 mL DCM was then added, and the aqueous phase was removed by a separation funnel. The organic phase was further extracted with DI water twice and dried over magnesium sulfate. Then DCM was then removed by a rotary evaporator. The crude product was purified twice by first dissolving in 15 mL DCM at 40 °C and then recrystallized at room temperature for 5 hours and dried in a vacuum oven at 80 °C for 24 hours to yield BPST.

[0173] Preparation of crosslinked compositions

[0174] Samples were prepared in ventilated Haake enclosure under a dinitrogen inert atmosphere. At 180 °C, D115A was melted and mixed at 10 RPM in a Haake mixer. Aftermelting the DI 15 A, BPST and dicumyl peroxide (DCP) were sequentially added to the melted DI 15A to form a mixture. The mixture was melt mixed for ten minutes in the Haake mixer. Table 2 shows the composition (in wt%) of Comparative Examples Cl and C2 and Inventive Examples 11-14 and the properties thereof. Table 2 also shows the GPC, DMS, and gel results for the Inventive and Comparative Examples. Table 3 shows the Elongation Viscosity results for the Inventive and Comparative Examples.

[0175] Table 2

[0176] As shown in Table 2, Inventive Compositions II- 14, crosslinked compositions including BPST, exhibited a higher complex viscosity at 0.1 rad / s as compared to Comparative Composition Cl, a composition lacking BPST. Comparative Composition C2,containing neither BPST or DCP, exhibited higher viscosity than Comparative Cl, a crosslinked composition lacking BPST.

[0177] As shown in Table 2, Inventive Compositions 11-14, crosslinked compositions including BPST, exhibited a lower tan 8 at 0.1 rad / s as compared to Comparative Composition Cl, a composition lacking BPST.

[0178] As exemplified by Table 2, crosslinkable polymer compositions including a bifunctional disulfide crosslinker may be used to produce a crosslinked composition that exhibits desirable properties (e.g., a higher complex viscosity at 0.1 rad / s, a lower tan 8 at 0.1 rad / s as compared to a similar composition lacking a bifunctional disulfide crosslinker).

[0179] Referring now still to Table 2 and also to the Figure, a Mark-Houwink plot is shown. The left-hand y-axis (dWf / (dEogM (Absolute by FS))) is normalized molecular weight distribution MWD, in which Wf is weight fraction and M is molecular weight; the x-axis (FogM (Absolute by FS)) normalized molecular weight M; and the right-hand y-axis (hog IV (Absolute)) is intrinsic viscosity. In the Figure, the SEC plot is by normalized MWD vs. normalized MW (left-hand y vs. x). The Mark-Houwink plot is depicted by normalized intrinsic viscosity vs. normalized MW (right-hand y vs. x).

[0180] As shown in the Figure and also in Table 2, each of Inventive Compositions 11-14, crosslinked compositions including BPST, exhibited a lower intrinsic viscosity at FOG 6.5 (Mw(abs)) as compared to Comparative Compositions Cl and C2, compositions lacking BPST.

[0181] Referring still to the Figure and also to Table 2, each of the Inventive Compositions 11-14, crosslinked compositions including BPST, exhibited lower mass recovery % as compared to Comparative Compositions Cl and C2, compositions lacking BPST. This indicates that Inventive Compositions 11-14 underwent crosslinking and / or branching that caused their respective molecular weights to increase.

[0182] Referring still to the Figure, a Mark-Houwink plot representing linear polyethylene (PE) 100 is shown, for comparison. In the Figure, the Mark-Houwink plot 105 for Comparative Composition C2 (homopolymer) and the plot 130 for the Comparative Composition Cl (DCP only) each show a substantially linear relationship between their respective molecular weights and intrinsic viscosities in solution, similar to linear polyethylene (PE) 100, indicating that these Comparative Compositions Cl and C2, each of which did not include BPST, did not appear to undergo crosslinking or branching. The result,lack of crosslinking or lowering of polymer molecular weight due to chain scission, is expected when using conventional peroxide crosslinkers with polypropylene compounds.

[0183] In contrast, each of the Mark-Houwink plots 110, 115, 120, 125 for the Inventive Compositions 11-14 deviated from the linear Mark-Houwink plots 105,130 of the Comparative Compositions Cl and C2 (105, 130). The greater the deviation of the Mark- Houwink plot 110, 115, 120, and 125 of Inventive Compositions 11-14 from the plots 105, 130 for the comparative examples, the greater the branching or crosslinking of the Inventive Compositions 11-14.

[0184] As exemplified by the Figure and by Table 2, crosslinkable polymer compositions including a bifunctional disulfide crosslinker may be used to produce a crosslinked composition that exhibits desirable properties such a lower intrinsic viscosity at FOG 6.5(Mw(abs)) as compared to a similar composition lacking a bifunctional disulfide crosslinker.

[0185] Table 3*Elongational Viscosity was tested at a strain rate of 1 s’1. The average density of the samples prior to the test was 0.90 g / cm3, and the melt density of the samples was 0.78 g / cm3.

[0186] As shown in Table 3, at a Hencky Strain of 3, each of the Inventive Compositions exhibited a higher Elongational Viscosity than Comparative Compositions Cl and C2, compositions without BPST. This suggests that the Inventive Compositions 11-14 may have a higher melt strength than Comparative Compositions Cl and C2 under certain conditions.

[0187] As exemplified by Table 3, crosslinkable polymer compositions including a bifunctional disulfide crosslinker may be used to form crosslinked compositions having desirable properties, such as increased Elongation viscosity, as compared to compositions lacking bifunctional disulfide crosslinker.

[0188] As exemplified by the Figure and by Tables 2-3, crosslinkable polymer compositions including a bifunctional disulfide crosslinker may be used to form crosslinked compositions having desirable properties (e.g., a lower intrinsic viscosity at EOG 6.5 (Mw(abs)), a higher complex viscosity at 0.1 rad / s, a lower tan 8 at 0.1 rad / s as compared to a similar composition lacking a bifunctional disulfide crosslinker). These properties, especially in combination, may be suggestive of increased melt strength.

[0189] While particular embodiments of the present disclosure have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the disclosure. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this disclosure.

Claims

CLAIMS1. A crosslinkable polymer composition comprising: a propylene-based polymer; a free radical initiator; and a bifunctional disulfide crosslinker, wherein the crosslinker comprises Structure 1 :STRUCTURE 1;wherein each R is independently selected from the group comprising: methyl, phenyl, aryl, heteroaryl, and hydrogen.

2. The crosslinkable polymer composition of claim 1, wherein the propylene-based polymer is selected from the group comprising polypropylene homopolymer, polypropylene- based elastomer, polypropylene-based block copolymer, propylene-based impact copolymer, and combinations thereof.

3. The crosslinkable polymer composition of any one of the preceding claims, wherein the propylene-based polymer comprises a propylene / ethylene copolymer, a propylene / a- olefin copolymer, or combinations thereof.

4. The crosslinkable polymer composition of claim 3, wherein the a-olefin comprises 1- butene, 1 -hexene, 1 -octene, or combinations thereof.

5. The crosslinkable polymer composition of any one of the preceding claims, wherein the free radical initiator comprises an organic peroxide.

6. The crosslinkable polymer composition of any one of the preceding claims, wherein the bifunctional disulfide crosslinker comprises bis(4-phenacryloyloxyphenyl) disulfide (BPST).

7. The crosslinkable polymer composition of any one of claims 1-5, wherein the bifunctional disulfide crosslinker comprises bis(4-methacryloyloxyphenyl) disulfide (BPMA).

8. The crosslinkable polymer composition of any one of the preceding claims, wherein the crosslinkable polymer composition comprises: from 70 wt% to 99 wt% of the propylene-based polymer; from 0.5 wt% to 10 wt% of the free radical initiator; and from 0.25 wt% to 20 wt% of the bifunctional disulfide crosslinker.

9. The crosslinkable polymer composition of any one of the preceding claims, wherein the crosslinkable polymer composition further comprises: from 0.1% to 15 wt% of a coagent.

10. The crosslinkable polymer composition of claim 9, wherein the coagent comprises styrene; divinyl benzene, 1,1,1 -trimethylolpropane trimethacrylate; pentaerithrityl tetramethacrylate (PETM); trimethylolpropanetiacrylate (TMPTA); pentaerythritol tetraacrylate (PETA); pentaerythritol tetrallyl ether; diallyl maleate; triallyl cyanurate; diallyl itaconate; triallylisocyanurate (TAIC); 4-vinylnapthalene, or a combination thereof.

11. A crosslinked composition comprising: a propylene based polymer; and a bifunctional disulfide crosslinker, wherein the crosslinker comprises Structure 1 :wherein each R is independently selected from the group comprising: methyl, phenyl, aryl, heteroaryl, and hydrogen.

12. The crosslinked composition of claim 11, wherein the crosslinked composition comprises:from 70 wt% to 99 wt% of the propylene-based polymer; and from 0.25 wt% to 20 wt% of the bifunctional disulfide crosslinker.

13. The crosslinked composition of claim 11 or claim 12, wherein the propylene-based polymer is selected from the group comprising polypropylene homopolymer, polypropylene- based elastomer, polypropylene-based block copolymer, propylene-based impact copolymer, and combinations thereof.

14. The crosslinked composition of any one of claims 11-13, wherein the bifunctional disulfide crosslinker comprises bis(4-phenacryloyloxyphenyl) disulfide (BPST) or bis(4- methacryloyloxyphenyl) disulfide (BPMA).

15. The crosslinked composition of any one of claims 11-14, wherein the crosslinked composition comprises at least one of a lower intrinsic viscosity at TOG 6.5 (Mw(abs)), a higher complex viscosity at 0.1 rad / s, or a lower tan 8 at 0.1 rad / s, as compared to a composition lacking the bifunctional disulfide crosslinker.

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