Crystallization Of PHBV Research Articles

Effect of cellulose derivatives on crystallization and mechanical properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Abstract In this work, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was modified by cellulose derivatives, and the effects of different kinds of cellulose derivatives on the crystallization and mechanical properties of PHBV were investigated. The crystallization and mechanical properties of PHBV/cellulose derivatives composites were measured by means of differential scanning calorimeter, polarizing microscope, and mechanical properties testing instruments. Studies show that cellulose acetate (CA) can promote the crystallization of PHBV, a small amount of CA can significantly increase the crystallization temperature of PHBV. The crystallization rate of PHBV was also accelerated by CA. However, the addition of cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB) decreased the crystallization temperature of PHBV and inhibited the nucleation of PHBV. And the degree of inhibition increased with the increase of CAB and CAP content. CAB and CAP have good compatibility with PHBV, CAB, and CAP can be uniformly dispersed in PHBV. Cellulose derivatives with specific component content can enhance the tensile properties of PHBV without losing the impact strength.

Microcrystalline cellulose grafted hyperbranched polyester with roll comb structure for synergistic toughening and strengthening of microbial PHBV/bio-based polyester elastomer composites

The brittle feature of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is the major challenge that strongly restricts its application at present. Successfully synthesized bio-based engineering polyester elastomers (BEPE) were combined with PHBV to create entirely bio-composites with the intention of toughening PHBV. Herein, the 2,2-Bis(hydroxymethyl)-propionic acid (DMPA) was grafted onto microcrystalline cellulose (MCC) and then further transformed into hyperbranched polyester structure via polycondensation. The modified MCC, named MCHBP, had plenty of terminal hydroxyl groups, which get dispersed between PHBV and BEPE. Besides, a large number of terminal hydroxyl groups of MCHBP can interact with the carbonyl groups of PHBV or BEPE in a wide range of hydrogen bonds, and subsequently increase the adhesion and stress transfer between the PHBV and BEPE. The tensile toughness and the elongation at break of the PHBV/BEPE composites with 0.5phr MCHBP were improved by 559.7 % and 221.8 % in comparison to those of PHBV/BEPE composites. Results also showed that MCHBP can play a heterogeneous nucleation effect on the crystallization of PHBV. Therefore, this research can address the current issue of biopolymers' weak mechanical qualities and may have uses in food packaging.

Biodegradable blends from bacterial biopolyester PHBV and bio-based PBSA: Study of the effect of chain extender on the thermal, mechanical and morphological properties

Being aware of the global problem of plastic pollution, our society is claiming new bioplastics to replace conventional polymers. Balancing their mechanical performance is required to increase their presence in the market. Brittleness of bacterial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was attempted to be decreased by melt blending with flexible starch-based poly(butylene succinate-co-butylene adipate) (PBSA). An epoxy-functionalized chain extender was used to enhance interaction between both immiscible biopolyesters. Mechanical performance, morphology, rheology, and crystallization behavior of injection-molded PHBV-PBSA blends (70–30, 50–50, and 30–70 wt%) were assessed in the presence and absence of the chain extender. Crystallization of PHBV was hindered, which was reflected in the improvement of mechanical properties. When PBSA >50 %, the homogeneity of results increased within the same sample while for PHBV-PBSA 70–30 wt% the elongation was 45 % higher. During the flexural test, it changed from brittle to non-breakable. The additive did not change the type of morphology developed by each blend nor the toughening mechanisms, so impact strength was barely affected. However, it reduced the size of dispersed phase domains due to a viscosity change, improving their processability. The higher the PHBV in the blend, the higher the effect of the chain extender.

Green composites of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) and sugarcane bagasse fibers plasticized with triethyl citrate: Thermal, mechanical and morphological properties

In this work, PHBV composites were prepared by melting extrusion using triethyl citrate (TEC) as a biodegradable plasticizer and sugarcane bagasse fibers (SBF) as reinforcement. The plasticizer TEC played a crucial role in the preparation of the formulations by extrusion, reducing the viscosity of the melt and minimizing the thermomechanical degradation of PHBV. Moreover, TEC was an efficient plasticizer for the composites, reducing the glass transition and melting temperatures of PHBV and making the specimens ductile. The increase in the concentration of TEC led to an enlargement of the interlamellar spacing and larger PHBV spherulites without changing the cell parameters. In contrast, the introduction of the SBF elevated the viscosity of the molten during extrusion, leading to thermomechanical degradation of PHBV. The SBF acted as a nucleation agent for the PHBV crystallization and oriented the growth of the PHBV crystals due to the transcrystallization, which contributed to the matrix-filler adhesion, the increase in the lamellae thickness, and changes in the thermal properties of PHBV. The SBF acted as a reinforcing agent, increasing the tensile properties of the matrix. Therefore, TEC and SBF had antagonistic effects on the properties of the formulations, opening opportunities to tune their properties by varying the composition.

Characterization of a new bio‐based and biodegradable blends of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) and poly(butylene‐co‐succinate‐co‐adipate)

AbstractMelt blending of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) and poly(butylene‐co‐succinate‐co‐adipate) (PBSA) was investigated by means of batch mixing at different weight ratios (100:0, 70:30, 50:50, 30:70, and 0:100). PHBV and PBSA were immiscible. PBSA formed small nodules in PHBV, while PHBV formed large inclusions in PBSA. In 50/50 wt% blends, a co‐continuous structure was obtained. The crystallization rate of PHBV and PBSA increased in the blends, most probably due to mutual nucleation, except at the later stages, where PHBV crystallization rates slowed down inside the nodules and in the co‐continuous structure. The mechanical properties were successfully modeled with the EBM model, including parallel and serial resistances and show that the rigidity of the material can be modulated using PBSA. The elongation at break is however governed by PHBV. The blends featured brittle fracture even if PBSA was the continuous phase. The analysis of the stress at break showed that the fracture could be ascribed to debonding at the interfaces and the fracture behavior of PHBV.

Toughening of Biodegradable Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/Poly(ε-caprolactone) Blends by In Situ Reactive Compatibilization.

Reactive extrusion of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/poly(ε-caprolactone) (PHBV/PCL) blends was performed in the presence of cross-linker 1,3,5-tri-2-propenyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TAIC) and peroxide. The compatibility between the two biodegradable polymers was significantly improved only when TAIC and peroxide work together, as evidenced by the decreased PCL particle size and blurred interfacial gap between the PHBV and PCL. The mechanical, thermal, morphological, and rheological properties of the compatibilized blends were studied and compared to the blends without TAIC and peroxide. At the optimal TAIC content (1 phr), the elongation at break of the compatibilized blends was 380% that of the PHBV/PCL blend without any additives and 700% that of neat PHBV. The improved interfacial compatibility, decreased PCL particle size, and uniform PHBV crystals are all factors that contribute to improving the toughness of the blend. Through Fourier transform infrared (FTIR) and rheological studies, the reaction mechanism is discussed. The study shows that PHBV and PCL are cross-linked by TAIC, resulting in the formation of a PHBV–PCL co-polymer, which improves the compatibility of the blend. The biodegradable polymer blends with high crystallinity and improved toughness prepared in this study are proposed to be used in sustainable packaging or other applications.

Novel biodegradable composites based on PHBV: Effect of nanocellulose incorporation on the non‐isothermal crystallization kinetic and structural parameters

This study presents the non‐isothermal behavior of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) biodegradable films with 1–5 wt% of cellulose nanoparticles (CNs) manufactured by solution casting using N,N‐dimethylformide and chloroform as the solvents. X‐ray diffraction and scanning electron microscopy with field emission gun were performed for CNs in order to determine its morphology and crystalline properties. The effect of non‐isothermal crystallization of PHBV and its nanocomposites was studied using differential scanning calorimetry technique. The incorporation of CNs increases the crystallization rate with up to 3 wt%. Structural parameters were studied using positron annihilation lifetime spectroscopy and small‐angle X‐ray scattering. The free volume does not change upon CNs addition in spite of form less perfect crystals and increase the lamellar thickness. POLYM. COMPOS., 40:3156–3165, 2019. © 2018 Society of Plastics Engineers

Biodegradable multiblock copolymers containing poly[(3-hydroxybutyrate)-co-(3-hydroxyvalerate)], poly(ε-caprolactone), and polyhedral oligomeric silsesquioxane: synthesis, characterization, and tensile property

Biodegradable multiblock copolymers based on poly[(3-hydroxybutyrate)-co-(3-hydroxyvalerate)] (PHBV), poly(e-caprolactone) (PCL), and polyhedral oligomeric silsesquioxane (POSS) were synthesized by one-step copolymerization with 1,6-hexamethylene diisocyanate (HDI) as a coupling agent. The chemical structures, molecular weight, and polydispersity index of the PHBV/PCL/POSS multiblock copolymers were confirmed by 1H NMR, FTIR, and gel permeation chromatography (GPC). XRD analysis illustrated that PHBV and POSS blocks in multiblock copolymers with high content of PHBV and POSS could crystallize to form separate crystalline phases. DSC analysis indicated that the mutual interference of crystallization of PHBV, PCL, and POSS blocks existed. Compared with the crystallinity of PHBV-diol and original PHBV, the crystallinity of PHBV block decreased from 54.8 (original PHBV) and 49.5 (PHBV-diol) to 25.5%. TG measurement revealed that thermal degradation of the multiblock copolymers proceeded by a four-step degradation process and the thermal degradation behavior of PHBV block was similar to that of the original PHBV. The melt processing window of multiblock copolymers was much wider than that of the original PHBV. The results of tensile testing showed that the tensile strength at break of the fibrous membranes of multiblock copolymers increased by 37.5% from 0.8 to 1.1 MPa and the elongation at break reached 307.8%.

The Investigation of the Toughening Mechanism of PHBV/PBAT with a Novel Hyperbranched Ethylenediamine Triazine Polymer Based Modifier: The Formation of the Transition Layer and the Microcrosslinking Structure

A new type of designed hyperbranched ethylenediamine trazine polymer (HBETP) is successfully synthesized and characterized based upon NMR and GPC. The prepared HBETP is used to modify the poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)/poly(butylene adipate-co-terephthalate) (PBAT) blends. The effect of HBETP on the microstructure, mechanical properties and thermal properties of the blends is studied. The results indicate that upon addition of 1.0 wt% of HBETP, the impact strength of the PHBV/PBAT blends is increased by 47.1%; ∆Tg of the blends decreases from 53.2 to 49.9 °C. These results, together with the morphology analysis of the fractured surface of the blends, conclude the formation of the transition layer between PHBV and PBAT. Also, the XRD result shows that the addition of HBETP can limit the growth of the PHBV crystals and causes the decrease of both the crystallinity and the grain crystalline size. The DSC result demonstrates that the addition of HBETP mainly affects the crystallization of the HB-HV binary eutectic region within PHBV. The mechanism of PHBV/PBAT toughening is due to the formation of the strong physical hydrogen bonding and the chemical micro-crosslinking between HBETP and PHBV/PBAT, which is proposed based on XPS characterization.

PHBV-TiO2 mats prepared by electrospinning technique: Physico-chemical properties and cytocompatibility.

One of the most important challenges in tissue engineering research is the development of biomimetic materials. In this present study, we have investigated the effect of the titanium dioxide (TiO2 ) nanoparticles on the properties of electrospun mats of poly (hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), to be used as scaffold. The morphology of electrospun fibers was observed by scanning electron microscopy (SEM). Both pure PHBV and nanocomposites fibers were smooth and uniform. However, there was an increase in fiber diameter with the increase of TiO2 concentration. Thermal properties of PHBV and nanocomposite mats were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC analysis showed that the crystallization temperature for PHBV shifts to higher temperature in the presence of the nanoparticles, indicating that TiO2 nanoparticles change the process of crystallization of PHBV due to heterogeneous nucleation effect. TGA showed that in the presence of the nanoparticles, the curves are shifted to lower temperatures indicating a decreasing in thermal stability of nanocomposites compared to pure PHBV. To produce scaffolds for tissue engineering, it is important to evaluate the biocompatibility of the material. Cytotoxicity assay showed that TiO2 nanoparticles were not cytotoxic for cells at the concentration used to synthesize the mats. The proliferation of cells on the mats was evaluated by the MTT assay. Results showed that the nanocomposite samples increased cell proliferation compared to the pure PHBV. These results indicate that continuous electrospun fibrous scaffolds may be a good substrate for tissue regeneration.

Effect of WS₂ Inorganic Nanotubes on Isothermal Crystallization Behavior and Kinetics of Poly(3-Hydroxybutyrate-co-3-hydroxyvalerate).

Nanocomposites of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and tungsten disulfide inorganic nanotubes (INT-WS2) were prepared by blending in solution, and the effects of INT-WS2 on the isothermal crystallization behavior and kinetics of PHBV were investigated for the first time. The isothermal crystallization process was studied in detail using various techniques, with emphasis on the role of INT-WS2 concentration. Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) showed that, in the nucleation-controlled regime, crystallization rates of PHBV in the nanocomposites are influenced by the INT-WS2 loading. Our results demonstrated that low loadings of INT-WS2 (0.1–1.0 wt %) increased the crystallization rates of PHBV, reducing the fold surface free energy by up to 24%. This is ascribed to the high nucleation efficiency of INT-WS2 on the crystallization of PHBV. These observations facilitate a deeper understanding of the structure-property relationships in PHBV biopolymer nanocomposites and are useful for their practical applications.

Effect of silver contents in cellulose nanocrystal/silver nanohybrids on PHBV crystallization and property improvements

Ternary nanocomposites including cellulose nanocrystals/silver nanohybrids (CNC-Ag) and biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were prepared by using solution casting. The effect of different AgNPs contents in the nanohybrids on crystallization ability and properties of PHBV was comprehensively investigated. Compared to binary PHBV/CNC nanocomposite, the ternary nanocomposites with high AgNPs contents showed larger improvements in the thermal stability, mechanical, barrier, overall migration and antibacterial properties. The property transitions at various AgNPs contents were due to transition of the nanohybrids induced PHBV crystallization ability (from single CNC nucleation to synergistic nucleation of CNC and AgNPs), and increased crystallinity without compromising the amounts of hydrogen bonds. Especially, the PHBV/CNC-Ag-1.7 showed the good barrier property and lower migration levels in food simulants, high antibacterial ratio of 99.9% and biocompatibility to human MG-63 cells, suggesting its potential application in food packaging related materials.

PHBV Crystallization under Injection Molding Conditions: Influence of Packing Pressure and Mold Temperature

PHBV Crystallization under Injection Molding Conditions: Influence of Packing Pressure and Mold Temperature

Crystallization and melting behavior of partially miscible six‐armed poly(l‐lactic acid)/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) blends

ABSTRACTThe crystallization kinetics and spherulitic morphology of six‐armed poly(L‐lactic acid) (6a‐PLLA)/poly(3‐hydroxybutyrate‐co−3‐hydroxyvalerate) (PHBV) crystalline/crystalline partially miscible blends were investigated with differential scanning calorimetry and polarized optical microscopy in this study. Avrami analysis was used to describe the isothermal crystallization process of the neat polymers and their blends. The results suggest that blending had a complex influence on the crystallization rate of the two components during the isothermal crystallization process. Also, the crystallization mechanism of these blends was different from that of the neat polymers. The melting behavior of these blends was also studied after crystallization at various crystallization temperatures. The crystallization of PHBV at 125°C was difficult, so no melting peaks were found. However, it was interesting to find a weak melting peak, which arose from the PHBV component for the 20/80 6a‐PLLA/PHBV blend after crystallization at 125°C, and it is discussed in detail. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42548.

Polymer-Nanoparticle Composites Composed of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and Coated Silver Nanoparticles

The effects of addition of synthesized organic-suspension silver nanoparticles on the crystallization and thermal stability of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were studied by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (XRD), UV-Vis absorption spectroscopy, polarized optical microscopy (POM), and thermal gravimetric analysis (TGA). The TEM images showed the average primary size of the as-synthesized silver nanoparticles, coated with a monolayer of the surfactants consisting of oleic acid and an alkylamine, was about 5 nm with narrow distribution, and that they were uniformly dispersed in n-heptane. PHBV/silver nanocomposites were prepared by melt mixing in an internal mixer and then injection molded into rectangle-shaped specimens by a labscale injection molding device. The coated silver nanoparticles showed a homogenuous dispersion in the PHBV matrix when the content of coated silver nanoparticles was about 1%. Both the DSC and POM data showed the efficient heterogeneous nucleation by the coated silver nanoparticles for facilitating PHBV crystallization. The thermal stability of the PHBV/silver nanocomposites improved with the increase in the content of the coated silver nanoparticles.

Morphology and thermal behavior of poly (3-hydroxybutyrate-co-3-hydroxyvalerate)/poly(butylene adipate-co-terephthalate)/clay nanocomposites

Biopolymers are gaining increasing interest because of decline of mineral oil reserves, increasing waste problem, and increasing consciousness of society for environmental problems. However, competitiveness of biopolymers compared with conventional plastics is still limited due to partly insufficient properties and high prices. This study investigates the influence of blending of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) with poly(butylene adipate-co-terephthalate) (PBAT) as well as the influence of addition of functionalized montmorillonite (OMMT) to the blends on morphology and thermal behavior. Dispersion state and morphology of the nanocomposites are studied by X-ray diffraction as well as scanning electron microscopy. Thermal stability is studied by thermogravimetric analysis and crystallization behavior is studied by differential scanning calorimetry and polarized optical microscopy. With respect to the morphology for the blends it can be seen that the immiscible biopolymers PHBV and PBAT are distributed in interlocking zones. There is a good dispersion and homogeneous distribution of OMMT within the biopolymer blends. The addition of 50% or more PBAT to PHBV as well as the insertion of OMMT enhances thermal stability of PHBV. In the blends, the addition of PBAT retards crystallization of PHBV. The OMMT acts as nucleating agent leading in total to more but less perfect crystals in the blends, and the crystallization slows further due to constraint in the movement of polymer chains. These results contribute to the understanding of the structure–properties relationship of bionanocomposite materials for packaging applications. POLYM. COMPOS., 36:2051–2058, 2015. © 2014 Society of Plastics Engineer

Comparison of covalent and noncovalent interactions of carbon nanotubes on the crystallization behavior and thermal properties of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)

ABSTRACTIn this study, multiwalled carbon nanotubes (MWCNTs) were dispersed into a poly(3‐hydroxybutyrate‐co−3‐hydroxyvalerate) (PHBV) matrix, in which PHBV was either covalently attached to the nanotubes through an esterification reaction between the carboxylic groups of functionalized MWCNTs and the hydroxyl groups of PHBV with toluene diisocyanate as a coupling agent or physically mixed to result in only noncovalent interactions. The structure, crystallization behavior, and thermal properties of the resulting nanocomposites were studied. We found that the crystallization of PHBV grafted onto the MWCNTs (PHBV‐g‐MWCNTs) was markedly hindered and exhibited an exothermic peak caused by cold crystallization, whereas the nonisothermal crystallization of PHBV was enhanced because a heterogeneous nucleation effect appeared in the PHBV/MWCNTs. Moreover, the maximum decomposition temperature of the PHBV‐g‐MWCNTs was improved by about 14.4°C compared with that of the PHBV/MWCNTs and by about 23.7°C compared with that of the original PHBV. Furthermore, the PHBV‐g‐MWCNTs exhibited the wider melt‐processing window than the PHBV/MWCNTs and original PHBV. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4299–4307, 2013

Effects of Size and Specific Surface Area of Boron Nitride Particles on the Crystallization of Bacterial Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)

SummaryThree different grades of Boron Nitride (BN) powder (BN NX1, BN NX5 and BN HCV) having different mean particle size (0.7 to 11 μm) and specific surface area (16 to 40 m2 · g−1) were used as nucleating agents for poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) at a fixed concentration of 2 wt %. Polarized Optical Microscopy (POM) observations, coupled to Differential Scanning Calorimetric (DSC) measurements, allowed to monitor both the isothermal and non‐isothermal crystallization of neat and nucleated PHBVs. It was found that the addition of BN to PHBV modifies the mechanisms of crystallization by starting it at lower supercooling degrees and reducing the half‐crystallization time. This work proved that DSC can replace POM whenever POM does not allow to estimate directly the average linear growth rate of the spherulites during crystallization. The Hoffman‐Lauritzen theory was used to explain the effects of the addition of different grades of BN on PHBV crystallization. As a result, a transition from growth regime III to the growth regime II could be observed for nucleated PHBVs, no matter the grade of BN added. It was evidenced that the coupling between the amorphous and the crystalline phase is modified by the presence of the BN particles. In particular, for a given concentration of nucleating agent, it is the mean size and the specific surface area of BN particles that affect PHBV crystallization.

A study of morphological, thermal, rheological and barrier properties of Poly(3-hydroxybutyrate-Co-3-Hydroxyvalerate)/polylactide blends prepared by melt mixing

The paper aims to study blend properties of biodegradable polymers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polylactide (PLA) prepared by melt mixing. Blend compositions based on PHBV/PLA were investigated according to the following weight ratios, i.e. 100/0, 75/25, 50/50, 25/75 and 0/100 wt%. The study showed through scanning electron microscopy (SEM) that blends of PHBV/PLA are not miscible. This is consistent with differential scanning calorimetry (DSC) data which indicate the presence of two distinct glass transition temperatures (Tg) and melting temperatures (Tm), attributed to the neat polymers, over all the range of blend compositions. Water and oxygen barrier properties of PHBV/PLA blends are significantly improved with increasing the PHBV content in the blend. Further, morphological analyzes indicated that increasing the PHBV content in the polymer blends results in increasing the PLA crystallinity due to the finely dispersed PHBV crystals acting as a filler and a nucleating agent for PLA. On the other hand, the addition of PLA to the blend results in a very impressive increase in the complex viscosity of PHBV. Moreover, the rheological data showed that, excluding the specific behavior of the neat polymers at low frequencies, i.e. less than 0.1 Hz, the complex viscosity of PHBV/PLA blends fits the mixing law well.

Phase Separation-Induced Crystallization of Poly(3-hydroxybutyrate-co-hydroxyvalerate) by Branched Poly(lactic acid)

The nucleation effects of branched poly(lactic acid), having the castor oil core, on the crystallization behavior of the bacterial polyester, poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), were investigated in this study by using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Enhanced crystallization of PHBV was observed in the presence of the branched poly(lactic acid) than in linear poly(lactic acid). Crystallization of the PHBV/branched poly(lactic acid) blend from the melt was completed during the cooling process at 10 °C/min. The crystallization half time (t1/2) of the PHBV/branched poly(lactic acid) blend decreased significantly. By the addition of the branched poly(lactic acid), the spherulite size of PHBV became much smaller than that of neat PHBV.