Biocomposites based on biodegradable polymers

Abstract

The present invention provides a composition for producing a biodegradable biocomposite, the biocomposite comprising poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) or a mixture of PHBV and polybutylene adipate terephthalate (PBAT), hemp residue, and optionally PBAT grafted with one or more compatibilizers selected from maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, acrylic acid, polyacrylic acid, methylene diphenyl diisocyanate, poly(glycidyl methacrylate), copolymers of glycidyl methacrylate, and copolymers of acrylic acid, and / or one or more compatibilizers selected from maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, acrylic acid, polyacrylic acid, methylene diphenyl diisocyanate, poly(glycidyl methacrylate), copolymers of glycidyl methacrylate, and copolymers of acrylic acid.

Description

[Technical Field]

[0001] The present invention relates to the field of biodegradable polymeric materials. In particular, the present invention relates to biocomposites based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and methods for producing the same. [Background technology]

[0002] Plastics have played an important role in the development of human society over the last century. Traditional polymers, such as polyolefins, are primarily used in disposable applications and accumulate in the environment after disposal [Non-Patent Document 1]. The long-term existence of these polymers has polluted our land, water, and air, posing environmental and public health risks, demonstrating that such polymers are unsuitable for applications where plastics are used for a short period of time and then discarded [Non-Patent Documents 2, 3]. While recycling is a reasonable option, contamination of plastic packaging and the degradation of its properties during melt processing make mechanical recycling costly and unfeasible [Non-Patent Document 4].

[0003] Plant- and microbial-derived (i.e., bio-based) polymers are biodegradable because they are susceptible to microbial enzymatic action and hydrolysis [5]. The growing demand for renewable polymers is forcing governments and legislative bodies around the world to develop laws / policies to ban single-use conventional plastics and promote alternative renewable plastics [6].

[0004] Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a biobased, biodegradable thermoplastic derived directly from microorganisms that has shown promising properties to replace single-use plastics for a wide range of applications. In addition to its biodegradability, PHBV has mechanical properties comparable to a wide range of commodity plastics, making it attractive for food packaging and consumer goods applications. However, PHBV is significantly more expensive than conventional plastics, and its brittleness hinders its widespread use.

[0005] The use of natural fillers such as hemp fiber, cellulose nanocrystals, hydroxyapatite, wheat straw fiber, wood and wood flour, coffee grounds, agave fiber, lignin, miscanthus fiber, chitin, soybean hulls, distiller's dried lees and other agricultural residues has been explored by many studies to form polymer-based composites.

[0006] It is well known that the incorporation of natural fillers into renewable polymers can restrict polymer chain mobility, increase melt viscosity, and limit the melt processing of biocomposites.

[0007] Therefore, there is a need for cost-competitive biodegradable materials with desirable mechanical and / or thermomechanical properties and processability that can be prepared from biodegradable polymers and sustainable, low-cost, biodegradable fillers to replace traditional plastics.

[0008] This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should it be construed, that any of the preceding information constitutes prior art against the present invention. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] A. Chamas, H. Moon, J. Zheng, Y. Qiu, T. Tabassum, JH Jang, M. Abu-Omar, SLScott, S. Suh, Degradation Rates of Plastics in the Environment, ACS Sustainable Chemistry & Engineering 8(9)(2020)3494-3511. [Non-patent document 2] AESchwarz, TNLigthart, E. Boukris, T. van Harmelen, Sources, transport, and accumulation of different types of plastic litter in aquatic environments: A review study, Marine Pollution Bulletin 143 (2019) 92-100. [Non-patent document 3] K. Pabortsava, RSLampitt, High concentrations of plastic hidden beneath the surface of the Atlantic Ocean, Nature Communications 11(1)(2020)4073. [Non-patent document 4] JNHahladakis, E. Iacovidou, An overview of the challenges and trade-offs in closing the loop of post-consumer plastic waste (PCPW): Focus on recycling, Journal of Hazardous Materials 380 (2019) 120887. [Non-Patent Document 5] KWMeereboer, M. Misra, AK Mohanty, Review of recent advances in the biodegradability of polyhydroxyalkanoate(PHA) bioplastics and their composites, Green Chemistry 22(17)(2020)5519-5558. [Non-patent document 6] K. Ghosh, BHJones, Roadmap to Biodegradable Plastics-Current State and Research Needs, ACS Sustainable Chemistry & Engineering 9(18)(2021)6170-6187. [Non-Patent Document 7] J.Topping, Investigations on the Theory of the Brownian Movement, Physics Bulletin 7(10)(1956)281-281. [Non-patent document 8] D.Romanzini,A.Lavoratti,HLOrnaghi,SCAmico,AJZattera,Influence of fiber content on the mechanical and dynamic mechanical properties of glass / ramie polymer composites,Materials & Design 47(2013)9-15. Summary of the Invention

[0010] The object of the present invention is to provide a biodegradable biocomposite based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV).

[0011] According to an aspect of the present invention, there is provided a composition for use in making a biodegradable composite material, the composition comprising: a) about 30 to about 99.5 wt. % of a polymer component comprising poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) or a PHBV-polybutylene adipate terephthalate (PBAT) blend; b) about 0.5 to about 60 wt. % of hemp residue; and c) optionally about 0.1 to 50 wt. % of a polyol selected from the group consisting of maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, acrylic acid, and polyacrylic acid. and PBAT grafted with one or more compatibilizers selected from maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, acrylic acid, polyacrylic acid, methylene diphenyl diisocyanate, poly(glycidyl methacrylate), copolymers of glycidyl methacrylate, and copolymers of acrylic acid, and / or one or more compatibilizers selected from maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, acrylic acid, polyacrylic acid, methylene diphenyl diisocyanate, poly(glycidyl methacrylate), copolymers of glycidyl methacrylate, and copolymers of acrylic acid.

[0012] According to an aspect of the present invention, there is provided a biocomposite material comprising a blend, the blend comprising: a) about 30 to about 99.5 wt% of a polymer component comprising poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) or a PHBV-polybutylene adipate terephthalate (PBAT) blend; b) about 0.5 to about 60 wt% of hemp residue; and c) optionally about 0.1 to 50 wt% of a polymer component comprising maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, acrylic acid, polyacrylic acid, methylene diamine acrylate, propylene glycol di ... and / or a blend of PBAT grafted with one or more compatibilizers selected from diphenyl diisocyanate, poly(glycidyl methacrylate), copolymers of glycidyl methacrylate, and copolymers of acrylic acid, and one or more compatibilizers selected from maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, acrylic acid, polyacrylic acid, methylene diphenyl diisocyanate, poly(glycidyl methacrylate), copolymers of glycidyl methacrylate, and copolymers of acrylic acid.

[0013] According to an aspect of the present invention, there is provided a method for preparing the biocomposite material described herein, the method comprising the steps of: a) blending a polymer component with hemp residue and optionally a compatibilizer and / or PBAT grafted with a compatibilizer; and b) heating the blend at a temperature sufficient to melt at least the PHBV and / or PBAT.

[0014] Further features and advantages of the present disclosure will become apparent from the following detailed description when taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 shows tensile test and tensile modulus results for exemplary biocomposites according to embodiments of the present invention. [Figure 2] FIG. 2 shows the elongation at break and tensile resistance of exemplary biocomposites according to embodiments of the present invention. [Figure 3] 3A and 3B show storage modulus and tan δ, respectively, of exemplary PHBV-hemp residue biocomposites versus temperature, according to an embodiment of the present invention. [Figure 4] 4A and 4B show storage modulus and tan δ, respectively, of an exemplary PHBV-PBAT-hemp residue biocomposite versus temperature, according to an embodiment of the present invention. [Figure 5] 5A and 5B show storage modulus and tan δ, respectively, of an exemplary PHBV-PBAT-mPBAT-hemp residue biocomposite versus temperature, according to an embodiment of the present invention. [Figure 6] FIG. 6 illustrates the heat deflection temperatures of exemplary PHBV-hemp residue biocomposites and PHBV-PBAT-hemp residue biocomposites with and without mPBAT according to embodiments of the present invention. [Figure 7]Figures 7A-7C show the rheological properties of PHBV-hemp residue biocomposites according to embodiments of the present invention. Figure 7A shows the storage modulus, Figure 7B shows the loss modulus, and Figure 7C shows the complex viscosity. [Figure 8] Figures 8A-8C show the rheological properties of PHBV-PBAT-hemp residue biocomposites according to embodiments of the present invention. Figure 8A shows the storage modulus, Figure 8B shows the loss modulus, and Figure 8C shows the complex viscosity. [Figure 9] Figures 9A-9C show the rheological properties of PHBV-PBAT-hemp residue biocomposites with mPBAT according to embodiments of the present invention. Figure 9A shows the storage modulus, Figure 9B shows the loss modulus, and Figure 9C shows the complex viscosity. [Figure 10A] FIG. 10A shows the PHBV and water uptake of an exemplary biocomposite according to an embodiment of the present invention over time in days. [Figure 10B] FIG. 10B shows the PHBV and water uptake of exemplary biocomposites according to embodiments of the present invention over time in days. [Figure 10C] FIG. 10C shows the PHBV and water uptake of an exemplary biocomposite according to an embodiment of the present invention over time in days. [Figure 10D] FIG. 10D shows the PHBV and water uptake of exemplary biocomposites according to embodiments of the present invention over time in days. [Figure 11] Figures 11A-D show morphological analysis of exemplary PBAT-hemp residue biocomposites according to embodiments of the present invention. [Figure 12] 12A-D show morphological analysis of exemplary PHBV-PBAT-hemp residue biocomposites according to embodiments of the present invention. [Figure 13] 13A-C show morphological analysis of exemplary PHBV-PBAT-hemp residue biocomposites with mPBAT according to embodiments of the present invention. [Figure 14]FIGS. 14A-C show morphological analyses of exemplary biocomposites of (A) PHBV, (B) (80:20-PHBV:PBAT), and (C) (80:20)-M with 30 wt% hemp residue, according to embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0017] The articles "a" and "an" are used herein to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, "an element" means one element or more than one element.

[0018] As used herein, the term "about" refers to a ±10% variation from the nominal value, and it should be understood that such a variation is always included in any given value provided herein, whether or not it is specifically stated.

[0019] As used herein, the term "hemp residue" (HP) refers to crushed hemp stalk, hemp hurd, and / or fiber that has been ground and / or sliced ​​into micron-sized particles. The residue may be in the form of a powder or dust.

[0020] As used herein, the term "biodegradable" refers to materials that deteriorate or break down when exposed to sunlight or ultraviolet light, water or moisture, microorganisms such as bacteria and fungi, enzymes, or wind erosion.

[0021] As used herein, the term "bio-based" refers to materials made from substances derived from living (or once living) organisms.

[0022] The present invention relates to novel compositions for producing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)-based biodegradable biocomposites and biodegradable biocomposite materials formed from these compositions.

[0023] The biocomposite materials of the present invention can exhibit improved tensile modulus and similar tensile strength and heat deflection compared to the original PHBV, making them promising candidates for consumer goods, rigid packaging applications and additive manufacturing.

[0024] In one aspect, the present invention provides a composition for use in the manufacture of a biodegradable biocomposite material, the composition comprising: a) about 30 to about 99.5 wt. % of a polymer component comprising poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) or a mixture of PHBV and polybutylene adipate terephthalate (PBAT); b) about 0.5 to about 60 wt. % of hemp residue; and c) optionally, about 0.1 to 50 wt. % of a mixture of maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, acrylic acid, polyacrylic acid, methylene diphenyl diisocyanate, PBAT grafted with one or more compatibilizers selected from poly(glycidyl methacrylate), copolymers of glycidyl methacrylate, and copolymers of acrylic acid, and / or one or more compatibilizers selected from maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, acrylic acid, polyacrylic acid, methylene diphenyl diisocyanate, poly(glycidyl methacrylate), copolymers of glycidyl methacrylate, and copolymers of acrylic acid.

[0025] In another aspect, the present invention provides a biodegradable biocomposite material comprising a blend, the blend comprising about 30 to about 99.5 wt. % of a polymer component comprising poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) or a mixture of PHBV and polybutylene adipate terephthalate (PBAT), about 0.5 to about 60 wt. % of hemp residue, and optionally about 0.1 to 50 wt. % of a polymer component selected from the group consisting of maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, acrylic acid, polyacrylic acid, methyl methacrylate, and the like. and / or blends of PBAT grafted with one or more compatibilizers selected from maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, acrylic acid, polyacrylic acid, methylene diphenyl diisocyanate, poly(glycidyl methacrylate), copolymers of glycidyl methacrylate, and copolymers of acrylic acid.

[0026] In some embodiments, the polymer component is poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV).

[0027] In some embodiments, the polymer component is a mixture of PHBV and polybutylene adipate terephthalate (PBAT).

[0028] In some embodiments, the PHBV-PBAT mixture comprises about 10% to about 90% by weight of PHBV and about 90% to about 10% by weight of PBAT, based on the total weight of the blend.

[0029] In some embodiments, the PHBV-PBAT mixture comprises about 50 to about 90 wt % PHBV and about 50 to about 10 wt % PBAT, based on the total weight of the blend.

[0030] In some embodiments, the PHBV-PBAT mixture comprises about 70 to about 90 wt % PHBV and about 30 to about 10 wt % PBAT, based on the total weight of the blend.

[0031] In some embodiments, the composition or composite comprises about 40-90% PHBV component and about 10-60% HP.

[0032] In some embodiments, the compositions and / or biocomposite materials of the present invention comprise one or more compatibilizers selected from maleic anhydride, pyromellitic anhydride, acrylic acid, polyacrylic acid, methylene diphenyl diisocyanate, and copolymers of acrylic acid.

[0033] In some embodiments, the compositions and / or biocomposite materials of the present invention comprise one or more compatibilizers selected from maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, and methylene diphenyl diisocyanate.

[0034] In some embodiments, the compositions and / or biocomposite materials of the present invention comprise PBAT grafted with one or more of maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, and acrylic acid.

[0035] In some embodiments, the compositions and / or biocomposite materials of the present invention comprise about 5% to 20% by weight of PBAT grafted with one or more compatibilizers.

[0036] The hemp residue of the present invention can be prepared by milling and / or crushing hemp stalks to obtain micron-sized particles. In some embodiments, the hemp residue comprises crushed hemp hurd and bast fibers. In some embodiments, the hemp residue consists primarily of hemp cob and residual bast fibers. In some embodiments, the hemp residue consists of hemp hurd. In some embodiments, the residue is in the form of a powder.

[0037] In some embodiments, prior to milling or grinding, the hemp stalk fiber is washed with about 2-10% aqueous sodium hydroxide solution (1 part by weight of stalk per 10 parts by weight of solution) and then dried.

[0038] In some embodiments, the hemp residue comprises particles having a length of about 75 to 150 μm and an average aspect ratio of about 3.5 to 5. In some embodiments, the hemp residue comprises particles having a length of about 1.0 to 2.0 g / cm 3 It has a density of

[0039] In some embodiments, the hemp residue comprises about 60-75% by weight cellulose, 5-15% by weight hemicellulose, and about 10-25% by weight lignin.

[0040] In some embodiments, the hemp residue is processed to remove tetrahydrocannabinol (THC) and cannabidiol (CBD).

[0041] In some embodiments, the compositions and / or biocomposite materials of the present invention comprise about 30 wt% PHBV-PBAT blend, about 60 wt% HP residue, and about 10 wt% PBAT grafted with maleic anhydride.

[0042] In some embodiments, the composition and / or biocomposite material comprises about 1 to about 3 wt. % of a treating agent, such as glycerol monostearate and stearic acid.

[0043] In some embodiments, the composition and / or biocomposite material comprises one or more inorganic fillers (talc, clay, wollastonite, montmorillonite, or alkali or alkaline earth metal carbonates, bicarbonates, oxides, or sulfates).

[0044] In some embodiments, the composition and / or biocomposite material further comprises about 0.5 to about 5% by weight of a colorant, such as a mineral and / or a dye, hi some embodiments, the composition comprises about 1% by weight of a colorant.

[0045] In another aspect, the present invention provides a method for preparing the biodegradable biocomposite material of the present invention, comprising blending a polymer component with hemp residue and optionally one or more compatibilizers and / or PBAT grafted with a compatibilizer as described herein, and heating the blend at a temperature sufficient to melt at least the PHBV and / or PBAT.

[0046] In some embodiments, the method comprises extruding the blend at an extrusion temperature sufficient to melt at least the PHBV and / or PBAT. In some embodiments, the blend is extruded through a screw extruder at a screw speed of about 80 to about 120 rpm and a processing temperature of about 150°C to about 220°C.

[0047] In some embodiments, the polymer component and hemp residue are dried to remove residual moisture prior to processing. Drying can be accomplished in a conventional oven at about 60 to about 100°C, or by common industrial drying methods such as a desiccant wheel dryer or Munters desiccant wheel (overnight at about 40 to 60°C).

[0048] In some embodiments, the produced biocomposite material is air-cooled and pelletized.

[0049] In some embodiments, the compatibilizer-grafted PBAT can be prepared by combining PBAT, one or more compatibilizers, and a free radical initiator to form a reaction mixture, and melt processing the reaction mixture to form the grafted PBAT.

[0050] In some embodiments, the PBAT is first mixed with one or more compatibilizers and heated to a temperature sufficient to melt the at least one compatibilizer, followed by the addition of a free radical initiator prior to melt processing.

[0051] In some embodiments, melt processing is accomplished at a temperature of about 150°C to about 220°C.

[0052] In some embodiments, melt processing comprises melt extrusion, which is carried out by a screw extruder at a screw speed of about 80-120 rpm and a feed rate of about 300-750 g / h.

[0053] In some embodiments, the produced biocomposite is dried to remove unreacted compatibilizer.

[0054] In some embodiments, the biocomposite material of the present invention comprises PBAT grafted with one or more compatibilizers, which are: a) first preparing the grafted PBAT by combining PBAT with one or more compatibilizers and a free radical initiator to form a reaction mixture, and melt processing the reaction mixture to form the grafted PBAT; b) thereafter, mixing the grafted PBAT prepared in step a) with a polymer component, hemp residue and optional fillers, and extruding the mixture at a processing temperature sufficient to melt at least the PHBV and / or PBAT; It can be prepared by

[0055] In one aspect, the present invention provides a biocomposite material produced by the methods described herein.

[0056] In order to gain a better understanding of the invention described herein, the following examples are set forth with reference to the accompanying drawings, which are intended to describe exemplary embodiments of the invention and are not intended to limit the scope of the invention in any manner. [Example]

[0057] Example 1: Preparation of Hemp Powder (HP) To produce HP, the bast fibers were removed from the stem and remaining woody core (also called hurd), and the remaining fibers were processed through a mill to produce a fine powder of hemp hurd and residual fibers as micron-sized particles. The moisture content of the resulting HP was less than 1.5%.

[0058] Example 2: Preparation of MA-grafted PBAT We employed industrially available melt extrusion technology to produce MA-grafted PBAT (mPBAT). First, PBAT pellets were mixed with 5 wt% maleic anhydride (MA) and stored in a hot air oven at 80 °C for approximately 30 min to melt the MA and form a thin crust coating on the PBAT pellets. The mixture was cooled and mixed with 1 wt% dicumyl peroxide (DCP) as a reaction initiator and stirred prior to melt processing. Reactive extrusion was performed using a twin-screw extruder (Process11 Parallel Twin-Screw Extruder, Thermo Fisher Scientific) using a die-to-feed temperature profile of 130 / 135 / 140 / 150 / 150 / 140 / 135 / 130 °C. The screw speed was 60 rpm (length 440 mm and diameter 11 mm, i.e., L / D 40:1), and the feed rate was approximately 500 g / h. The resulting mPBAT was then pelleted, weighed, and dried in a vacuum oven under a reduced pressure of 100 mbar at a temperature of 80° C. for 24 hours. Once the sample was freed of unreacted MA, it was placed in an airtight container until further use.

[0059] Example 3: Preparation of biocomposite materials PHBV biocomposites with HP / mPBAT or PHBV-PBAT biocomposites were prepared by first blending various concentrations of HP and mPBAT (weight percent) shown in Table 1 with PHBV or a mixture of PHBV and PBAT, followed by drying overnight at 80°C in a hot air oven. The blends were extruded in a twin-screw extruder (Process 11 Parallel Twin-Screw Extruder, Thermo Fisher Scientific) at 180°C and a screw speed of 100 rpm. The blends were injection molded using a HAAKE Mini-Jet Pro (Thermo Fisher Scientific, Waltham, MA, USA) at a barrel temperature of 180°C, a mold temperature of 60°C, and a pressure of 700 bar with a 10-second hold. Specimens were further conditioned at room temperature and 50% RH for 48 hours before testing. [Table 1]

[0060] Characterization Tensile tests were performed across all samples using a Mandel-Shimadzu (AGS-X) tensile testing machine (Shimadzu Corporation, Kyoto, Japan) equipped with a 500 N load cell at a crosshead speed of 5 mm / min and a gauge length of 25 mm. Five specimens were tested for each sample, and the average along with the standard deviation was reported according to ASTM D638 type V.

[0061] Dynamic mechanical analysis (DMA) was performed using a dynamic mechanical analyzer (Q800 DMA, TA Instruments). Samples were heated from -80°C to 120°C at a heating ramp rate of 3°C / min. A dual cantilever clamp was used at a frequency of 1 Hz and a strain of 0.2%.

[0062] The heat deflection temperature (HDT) of each blend was estimated using a dynamic mechanical analyzer (Q800 DMA, TA Instruments) with a three-point bending modulus and a heating ramp rate of 2°C / min. As described in the ASTM 648-07 standard, Equation 1 was used to calculate the required force for each sample in this analysis.

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[0063] The rheology of the blends was investigated using a parallel plate viscometer (HAAKE MARS III, Thermo Fisher Scientific) with sample thickness and diameter of 1.55 mm and 20 mm, respectively. A frequency sweep from 0.01 to 100 Hz was performed at 200 °C with a constant strain of 0.1% (in the linear viscoelastic region) and a plate spacing of 1 mm.

[0064] Scanning electron microscopy (SEM) was performed using an Oxford Instruments Quanta FEG250 Environmental SEM (Abingdon, UK) without sputter coating to examine the fracture surface morphology of the blends. Micrographs were taken from freeze-fractured tensile specimens to investigate the interaction of HP and the polymer matrix.

[0065] Water absorption tests were conducted on 0, 10, 30, and 60% HP blends. Five specimens of each sample were weighed and then immersed in 70 mL of distilled water in a glass container at room temperature. The weights of the specimens were recorded after 24 hours and then retested every four days.

[0066] The impact resistance of the fabricated biocomposites was evaluated using an Izod impact tester according to ASTM D256. Tests were performed using a TMI impact tester manufactured by Testing Machines Inc. (Model 43-02), and the average of five specimens was reported along with the standard deviation.

[0067] Mechanical properties of PHBV-based biocomposite materials Figure 1 shows the ultimate tensile strength (UTS) and tensile modulus (TM) of the fabricated biocomposite materials. For PHBV, the UTS increased slightly from 33.2 MPa to 35.3 MPa with the incorporation of 20% hemp residue powder (HP), but decreased to 27 MPa with the incorporation of 60% HP. Interfacial debonding between the PHBV matrix and HP at high concentrations is believed to be the primary cause of premature fracture of specimens after uniaxial tension. Furthermore, the localized accumulation of HP particles due to higher loading rates creates weak areas within the biocomposite that inhibit proper load transfer, reducing the UTS. For the PHBV-PBAT (80:20) matrix, the incorporation of 10% HP showed a slight improvement in UTS from 30.9 to 31.7 MPa, but further increase in HP loading resulted in a decrease to 24.8 MPa. Because PBAT is a relatively soft material, it affects the UTS of the PHBV-PBAT (80:20) biocomposite. Furthermore, its phase separation and insolubility with PHBV also contribute to the decrease in UTS. For PHBV-PBAT blends with 10% maleated PBAT (mPBAT), the incorporation of 50% HP further increased the UTS to 33.1 MPa. The use of 10% mPBAT acts as a compatibilizer between PBAT, PHBV, and HP. Functionalized mPBAT reacts with HP to form HP-grafted PBAT, although partial reaction may also occur with PHBV. The incorporation of mPBAT improved the interfacial adhesion of HP with the polymer matrix and enhanced the compatibility of PBAT with PHBV. The sufficient interfacial interaction of HP with the matrix increased the UTS, which was comparable to that of the original PHBV even after the addition of 50% HP.

[0068] The tensile modulus of PHBV-HP gradually increased from 1,691 MPa to 2,609 MPa with increasing the HP loading to 60%. The increase in tensile modulus demonstrated an improvement in the stiffness of the developed biocomposite, which is a measure of resistance to applied unidirectional deformation. The addition of PBAT and mPBAT to the 60% HP system resulted in a decrease in the tensile modulus to 2,426 MPa and 2,100 MPa, respectively, compared to PHBV-60% HP. This is not surprising, considering that PBAT is a soft and flexible polymer, and its incorporation resulted in a decrease in stiffness. In comparison, the addition of 60% HP with PHBV-PBAT and mPBAT exhibited higher tensile moduli than the original PHBV. Meanwhile, the incorporation of mPBAT contributes to improving the impact resistance of the biocomposite.

[0069] Breaking elongation and Izod impact resistance Figure 2 shows the elongation at break and Izod impact resistance of the developed biocomposites. It is known that the incorporation of a reinforcing agent or filler dramatically reduces the elongation at break, or stretchability, of a biocomposite. The elongation at break of pure PHBV was approximately 3%, which decreased to approximately 1% after the addition of 60% HP. A similar trend was observed for the PHBV-PBAT biocomposite. Meanwhile, a comparable elongation at break (approximately 3%) to PHBV was observed with the incorporation of mPBAT using 30% HP filler. Reactive extrusion of biocomposites with mPBAT provided sufficient tensile strength and relatively high elongation at break with the use of up to 30% HP. The reactive extrusion chemistry worked well at higher HP loadings, as indicated by the acquired impact resistance data. The impact resistance of mPBAT and PHBV-PBAT matrices with 50% HP (23.3 J / m) was comparable to that of pristine PHBV (23.2 J / m). A decrease in HP loading (20%) promoted an increase in impact resistance (25.8 J / m).

[0070] Thermomechanical properties of PHBV biocomposites The dynamic mechanical properties of various composite formulations were evaluated using DMA. The storage moduli of the specimens at -50°C, 0°C, 25°C, and 50°C are shown in Table 2, and the corresponding temperature curves are shown in Figures 3A, 3B, 4A, 4B, 5A, and 5B. As can be seen in Table 3, the incorporation of HP enhanced the storage modulus of all composite combinations. The storage modulus of PHBV at 25°C (4359 MPa) increased by 127.5% to 9916 MPa with the addition of 60% HP, indicating that the materials at 25°C possessed improved elastic behavior after the incorporation of HP. A similar trend was observed for the PHBV-PBAT matrix. Increasing the temperature to 50°C did not have a significant effect on the storage modulus, indicating that the fabricated materials maintained their elastic behavior over a wider temperature range.

[0071] The loss tangent (tanδ) of the biocomposites is also shown in Table 2. For PHBV, the tanδ peak indicated a glass transition that increased from approximately 17 °C to approximately 28 °C with a gradual increase in HP loading to 60%. This decrease can be attributed to the decrease in the amorphous fraction in the biocomposite. The height of the tanδ peak also decreased, indicating chain mobility restriction resulting from the rigid HP particles. In contrast, the PHBV-PBAT matrix exhibited two distinct tanδ peaks at approximately 20 °C and 27 °C, corresponding to the glass transitions of PHBV and PBAT, respectively. The incorporation of HP and mPBAT significantly shifted the tanδ peak to higher temperatures and reduced its height. The incorporation of mPBAT into a highly filled (>30% HP) PHBV-PBAT matrix resulted in a significant suppression of the tanδ peak, indicating improved interfacial interactions in the HP matrix. This was also confirmed by determining the theoretical parameters used to predict the viscoelastic properties of the developed biocomposites. [Table 2]

[0072] Storage modulus of PHBV biocomposite To predict the storage modulus in the presence of HP, the effectiveness factor and reinforcement efficiency factor were employed. Equation 4 proposed by Einstien [J. Topping, Investigations on the Theory of the Brownian Movement, Physics Bulletin 7(10)(1956)281-281.] can be used to evaluate filler reinforcement by calculating the reinforcement efficiency factor (r).

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[0073] The loading level of the filler and its dispersion affect the reinforcement efficiency factor (r), which is E c / E m Against V f The r value can be obtained from a linear plot of the r. Higher r values ​​correspond to less aggregation and more uniform dispersion. The calculated r values ​​for various biocomposites are listed in Table 3. The r values ​​for the PHBV-HP, PHBV-PBAT-HP, and PHBV-PBAT-HP-M biocomposites were 1.47, 1.81, and 1.85, respectively. Higher r values ​​were obtained for composites containing mPBAT, indicating enhanced reinforcement due to the improved dispersing effect of HP in such formulations. Furthermore, the r values ​​were used to theoretically calculate the storage modulus of each biocomposite, and the r values ​​were found to be within the error margin from the experimental values ​​(Table 3).

[0074] Since the storage modulus corresponds to the stored energy within the biocomposite, increasing the temperature affects its value due to the molecular motion and frequency of the polymer chains. The incorporation of HPs increased the storage modulus of each specimen due to the restriction of chain movement by the stiff HPs. The effectiveness of the filler can be evaluated by calculating the reinforcement effectiveness factor (C), which was estimated using Equation 5 [Non-Patent Document 8: D. Romanzini, A. Lavoratti, HL Ornaghi, SC A Mico, AJ Zattera, Influence of fiber content on the mechanical and dynamic mechanical properties of glass / ramie polymer composites, Materials & Design 47 (2013) 9-15].

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[0075] Heat resistance of PHBV biocomposite From the perspective of packaging applications, the heat resistance of biocomposites is an important parameter, especially for packaging and encapsulation of hot beverages and thermal products. This can be quantitatively evaluated by measuring the heat deflection temperature (HDT). Figure 6 shows the heat deflection temperatures (HDT) of the composite formulations. The HDT of the original PHBV was 116 °C, which increased to 170 °C after the addition of 60% HP. The incorporation of HP limits the mobility of the polymer chains even at higher temperatures, allowing for deformation depending on the loading ratio. In contrast, the addition of the softer PBAT reduced the HDT value to approximately 157 °C. This is due to improved overall composite chain behavior and a reduced load-bearing capacity at higher temperatures. It is known that the compatibilizer mPBAT contains lower molecular weight polymer chains, and its use may contribute to a reduction in the HDT. On the other hand, after the addition of 60% HP in PHBV-PBAT in the presence of mPBAT, a HDT higher than 120 °C was shown, which was higher than that of the pristine PHBV. Overall, the heat resistance of the biocomposite is maintained even after the incorporation of a high loading of HP (60%).

[0076] Rheological properties of PHBV biocomposites A parallel plate viscometer was used to characterize the dynamic rheological properties of the developed biocomposites. The corresponding storage modulus, loss modulus, and complex viscosity versus frequency are shown in Figures 7A-7C, 8A-8C, and 9A-9C. It was found that the storage modulus of the composites increased with HP incorporation, suggesting the elastic behavior of the material. A similar trend was observed for the loss modulus of the biocomposite samples. Because melt processing of the material requires a certain viscosity threshold, it is of paramount importance to understand the effect of HP composition on the melt viscosity. Incorporation of 60% HP into the PHBV matrix alone resulted in a complex viscosity of 1.8 MPa s at a frequency of 1 Hz (corresponding to 60 rpm), which increased to 2.6 MPa s due to the higher-order chain entanglement of PBAT molecules. On the other hand, the incorporation of mPBAT into the biocomposite resulted in a decrease in the complex viscosity to 1.02 MPa s, which was mainly attributed to the presence of low molecular weight PBAT chains and wetting of HP, which facilitated chain sliding on its surface and reduced molecular friction forces. Overall, the decrease in complex viscosity of the developed formulation is helpful for smooth melt extrusion processing without reaching the threshold screw torque.

[0077] Water absorption of PHBV biocomposite Most lignocellulosic biofillers are known to be hydrophilic in nature and absorb large amounts of water. It is anticipated that HP, a lignocellulosic material, also possesses high water absorption, which may be inherited by PHBV-PBAT composites. Understanding water absorption behavior and its impact on biocomposites is essential because water absorption directly affects the dimensional stability of the final biocomposite. Plots of water absorption percentage versus time (days) are shown in Figures 10A–10D. In the case of PHBV, a clear increase in water absorption was observed with increasing HP loading. In contrast, biocomposites with a PHBV-PBAT matrix exhibited relatively low water absorption at higher HP loadings. This suggests that the presence of PBAT develops a coating on the hemp flour surface, preventing its absorption. Furthermore, the use of the mPBAT compatibilizer, which forms chemical bonds with the HP particles, prevents water molecules from diffusing and directly accessing the HP particles.

[0078] In terms of water absorption, water molecules can penetrate the surface through various mechanisms, including capillary transport through micropores, diffusion through micropores between polymer chains, and diffusion through the gaps between the biofiller and polymer domains. However, diffusion through the micropores between the biofiller and polymer domains is the most prominent reason for water absorption. Primarily, water molecules can be absorbed directly by the biofiller and through the interface between the biofiller and the matrix through the formation of hydrogen bonds. The use of mPBAT as a compatibilizer develops a coating on the HP, which prevents water molecules from directly accessing the HP. Furthermore, the chemical bond between mPBAT and HP improves the interfacial adhesion between the biofiller and the matrix (as confirmed by SEM microscopy analysis of fractured surfaces), which ultimately significantly reduces the diffusion of water molecules through the interface. Overall, the use of mPBAT as a compatibilizer is not only effective in improving the mechanical properties but is equally important in preventing water absorption in biocomposites, especially at higher loadings.

[0079] As seen in the previous section, the incorporation of mPBAT into PHBV-PBAT HP resulted in a biocomposite with relatively high stiffness and low water absorption. The formulation developed in this study resulted in a biocomposite with similar properties to that of the original PHBV. The reaction of mPBAT with HP and limited reaction with PHBV during reactive extrusion processing leads to an anchoring effect, where the PBAT chains attached to the HP interact with the PHBV-PBAT matrix, increasing the interfacial interaction of the HP with other polymer chains. Morphological images of the fracture surfaces of the original matrix and its biocomposites at 10%, 30%, and 60% HP loading are shown in Figures 11A–11D, 12A–12D, and 13A–13C. Morphological analysis of these polymers and composites suggests proper filler dispersion. Wetting of the HP with the polymer chains is seen in Figures 14A–14C. In the case of the PHBV-30 HP biocomposite, the HP was completely exposed to the outside of the matrix, indicating lower interfacial adhesion. On the other hand, in the case of the (80:20)-M with 30% HP, the filler particles were found to be completely coated by polymer domains, which helped transfer stress to the applied force. This improved interfacial interaction was responsible for stress transfer between the matrix and filler, which resulted in improved mechanical strength and modulus along with impact strength, and reduced water absorption.

[0080] While the present invention has been described with reference to certain specific embodiments, various modifications thereof will become apparent to those skilled in the art without departing from the spirit and scope of the invention. All such modifications as become apparent to those skilled in the art are intended to be included within the scope of the following claims.

Claims

1. 1. A composition for use in the manufacture of a biodegradable biocomposite material, comprising: a) 30% to 99.5% by weight of a polymer component comprising poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) or a blend of PHBV and polybutylene adipate terephthalate (PBAT); b) 0.5% to 60% by weight of hemp residue, comprising crushed hemp stalks in which hemp hurd and / or fiber have been crushed and / or sliced ​​into micron-sized particles; c) optionally 0% or from 0.1% to 50% by weight of at least any of the following: PBAT grafted with one or more compatibilizers selected from the group consisting of copolymers of glycidyl methacrylate, copolymers of acrylic acid, maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, acrylic acid, polyacrylic acid, methylene diphenyl diisocyanate, and poly(glycidyl methacrylate); and one or more compatibilizers selected from the group consisting of copolymers of glycidyl methacrylate, copolymers of acrylic acid, maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, acrylic acid, polyacrylic acid, methylene diphenyl diisocyanate, and poly(glycidyl methacrylate); Including, The total weight percent of all components contained in the composition does not exceed 100 weight percent, The hemp residue composition comprises particles having a length of up to 150 μm and an average aspect ratio of 3.5 to 5.

2. The composition of claim 1, wherein the polymer component is poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV).

3. 10. The composition of claim 1, wherein the polymer component is the mixture of PHBV and polybutylene adipate terephthalate (PBAT).

4. 4. The composition of claim 3, wherein the PHBV-PBAT mixture comprises 10% to 90% by weight of PHBV and 90% to 10% by weight of PBAT, based on the total weight of the mixture.

5. 4. The composition of claim 3, wherein the PHBV-PBAT mixture comprises 50% to 90% by weight of PHBV and 50% to 10% by weight of PBAT, based on the total weight of the mixture.

6. 10. The composition of claim 1, wherein the composition comprises 40% to 90% by weight of a polymer component and 10% to 60% by weight of a hemp residue.

7. The composition of claim 1, wherein the composition comprises 5% to 20% by weight of the PBAT grafted with the one or more compatibilizers.

8. 10. The composition of claim 1, further comprising 1 to 3 wt. % of a treating agent and / or one or more inorganic fillers.

9. 1. A biocomposite material comprising a blend of: a) 30% to 99.5% by weight of a polymer component comprising poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) or a blend of PHBV and polybutylene adipate terephthalate (PBAT); b) 0.5% to 60% by weight of hemp residue, comprising crushed hemp stalks in which hemp hurd and / or fiber have been crushed and / or sliced ​​into micron-sized particles; c) optionally 0% or from 0.1% to 50% by weight of at least any of the following: PBAT grafted with one or more compatibilizers selected from the group consisting of copolymers of glycidyl methacrylate, copolymers of acrylic acid, maleic anhydride, glycidyl methacrylate, pyromellitic anhydride, acrylic acid, polyacrylic acid, methylene diphenyl diisocyanate, and poly(glycidyl methacrylate); and and one or more compatibilizers selected from the group consisting of maleic anhydride, pyromellitic anhydride, acrylic acid, polyacrylic acid, and methylene diphenyl diisocyanate, wherein the mixture is heated and the sum of the weight percents of all components in the biocomposite material does not exceed 100 weight percent; The hemp residue is a biocomposite material comprising particles having a length of up to 150 μm and an average aspect ratio of 3.5 to 5.

10. 10. The biocomposite material of claim 9, wherein the polymer component is poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV).

11. 10. The biocomposite material of claim 9, wherein the polymer component is the mixture of PHBV and polybutylene adipate terephthalate (PBAT).

12. 12. The biocomposite material of claim 11, wherein the PHBV-PBAT mixture comprises 5% to 95% by weight of PHBV and 95% to 5% by weight of PBAT, based on the total weight of the blend.

13. 12. The biocomposite material of claim 11, wherein the PHBV-PBAT mixture comprises 50% to 90% by weight of PHBV and 50% to 10% by weight of PBAT, based on the total weight of the blend.

14. The biocomposite material of claim 9, comprising 40% to 90% by weight of the polymer component and 10% to 60% by weight of hemp residue.

15. The biocomposite material of claim 14, comprising 5% to 20% by weight of said PBAT grafted with said one or more compatibilizers.

16. 10. The biocomposite material of claim 9, further comprising 1-3 wt. % of a treating agent and / or one or more inorganic fillers.

17. 10. A method for preparing the biocomposite material of claim 9, comprising: a) blending said polymer component with said hemp residue and optionally said one or more compatibilizers and / or said PBAT grafted with one or more compatibilizers; b) heating the admixture at a processing temperature of 150°C to 220°C; A method for providing

18. 18. The method of claim 17, wherein the blend is extruded through a screw extruder at a screw speed of 80 to 120 rpm.

19. The biocomposite material comprises PBAT grafted with the compatibilizer, and the method comprises: preparing the compatibilizer-grafted PBAT by combining PBAT, the one or more compatibilizers, and a free radical initiator to form a reaction mixture and melt processing the reaction mixture to form the compatibilizer-grafted PBAT.

20. The method of claim 18, further comprising:

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