Thermal degradation of poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) in drying treatment

This study examines the isothermal treatment of poly(3‐hydroxybutyrate) (PHB) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) powders and films. The PHB and PHBV crystallinities were determined using X‐ray diffractometry, and shown to increase with temperature (130–150°C) and then decreased from 55% to 45% at 180°C. The crystal morphology of crystal planes (101) and (111) became sharp at a high temperature. The weight average molecular weight (M_w) of PHB decreased from 1,028,000 to 41,800 g/mol when heated at 180°C for 30 min. The molecular weight of PHB decreased more rapidly than that of PHBV with time. No peak signal was observed in gel permeation chromatography after heating at 150°C because the solubility of PHB changed with crystallinity. The thermal behaviors of PHB and PHBV were analyzed by differential scanning calorimetry and thermogravimetric analysis. The roughness, contact angle, and surface morphology of PHB and PHBV films were also measured to determine the surface properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3659–3667, 2013     

Hydrolysis of poly(hydroxybutyrate‐co‐hydroxyvalerate) nanoparticles

Poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) is a natural polyester known for its biocompatibility and biodegradability. The hydrolysis of PHBV nanoparticles (90–150 nm) and microparticles (33–58 µm) was investigated. Particles were formulated from preformed polymer(s) by miniemulsification/solvent evaporation technique to obtain nanoparticles or by emulsification/solvent evaporation technique to obtain microparticles. The morphology of the nanoparticles was studied by Field Emission Gun‐Scanning Electron Microscopy (FEG‐SEM). The kinetics of PHBV degradation was followed by gel permeation chromatography. After storage of PHBV nanoparticles for 25 days at 37 °C, the M_n and M_w of PHBV was reduced up to 85 and 80%, respectively. PHBV nanoparticles stored at 4 °C presented a much lower molecular weight reduction. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Compatibilization of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)–poly(lactic acid) blends with diisocyanates

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) was blended with poly(lactic acid) (PLA) with various reactive processing agents to decrease its brittleness and enhance its processability. Three diisocyanates, namely, hexamethylene diisocyanate, poly(hexamethylene diisocyanate), and 1,4‐phenylene diisocyanate, were used as compatibilizing agents. The morphology, thermomechanical properties, and rheological behavior were investigated with scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, tensile testing, dynamomechanical thermal analysis in torsion mode (dynamic mechanical analysis), and oscillatory rheometry with a parallel‐plate setup. The presence of the diisocyanates resulted in an enhanced polymer blend compatibility; this led to an improvement in the overall mechanical performance but did not affect the thermal stability of the system. A slight reduction in the PHBV crystallinity was observed with the incorporation of the diisocyanates. The addition of diisocyanates to the PHBV–PLA blend resulted in a notable increase in the final complex viscosity at low frequencies when compared with the same system without compatibilizers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44806.     

The morphology and degradation behavior of electrospun poly(3‐hydroxybutyrate)/Magnetite and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/Magnetite composites

Electrospinning of biodegradable poly(3‐hydroxybutyrate) (PHB)/magnetite and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV)/magnetite composites in 2,2,2‐trifluoroethanol (TFE) and chloroform are investigated to develop nonwoven nanofibrous structure. Ultrafine PHB/magnetite fibers are obtained and the resulting fiber diameters are in the range of 690–710 nm and 8.0–8.4 µm for the polymer dissolved in TFE and chloroform. The surface of PHB composites fiber fabricated in chloroform contains porous structures, which are not observed for the sample of PHB composites fiber dissolved in TFE. The fiber diameters for PHBV5/magnetite composites are in the range of 500–540 nm and 2.3–2.5 µm, depending on the use of TFE and chloroform. The average diameters of PHBV5/magnetite composite fibers are smaller than those of PHB/magnetite composites fiber. All electrospun PHB/magnetite and composite fibers are superparamagnetic. The degradation behaviors of PHB/magnetite and PHBV5/magnetite composite fibers were investigated using Caldimonas manganoxidans. For the fabricated composite fibers, it is found that the degradation rate increased with the increasing loading of magnetite nanoparticles. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41070.     

Mechanical and thermal properties of poly(butylene succinate)/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) biodegradable blends

Biodegradable polymer blends of poly(butylene succinate) (PBS) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) were prepared with different compositions. The mechanical properties of the blends were studied through tensile testing and dynamic mechanical thermal analysis. The dependence of the elastic modulus and strength data on the blend composition was modeled on the basis of the equivalent box model. The fitting parameters indicated complete immiscibility between PBS and PHBV and a moderate adhesion level between them. The immiscibility of the parent phases was also evidenced by scanning electron observation of the prepared blends. The thermal properties of the blends were studied through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The DSC results showed an enhancement of the crystallization behavior of PBS after it was blended with PHBV, whereas the thermal stability of PBS was reduced in the blends, as shown by the TGA thermograms. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42815.     

Development and material properties of poly(lactic acid)/poly(3‐hydroxybutyrate‐co−3‐hydroxyvalerate)‐based nanocrystalline cellulose nanocomposites

This study is focused on the development and analysis of the thermal and structural behavior of nanocrystalline cellulose (NCC)‐based bionanocomposites (BCs). Nanocrystalline cellulose was prepared by controlled acid hydrolysis of oil palm empty fruit bunch fibers. The resulting NCC was surface modified using TEMPO‐mediated oxidation and solvent exchange methods for surface functionalization and also to improve dispersion of fillers. Solvent exchange NCC reinforced polymer blend containing poly(lactic acid)/poly‐(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) was prepared by using solution casting technique at various NCC loading percentages. The addition of NCC resulted in the improvement of structural, thermal, and mechanical properties of BCs as compared to that of the polymer blend. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44328.     

Poly(hydroxybutyrate‐co‐hydroxyvalerate)/titanium dioxide nanocomposites: A degradation study

Nanocomposites, based on a poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) matrix and titanium dioxide (TiO₂) nanoparticles and fabricated with a solvent‐casting technique, were characterized with differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. The content of TiO₂ nanoparticles varied between 0.5 and 10 wt %. Degradation studies, including hydrolytic degradation in a strong base medium (1N NaOH) and degradation under ultraviolet light at 365 nm, were performed. It was confirmed that the inorganic filler had no great influence on thermal properties such as the melting and crystallization temperatures. Improved degradation temperatures were also confirmed with the increase in the filler content. Degradation observations confirmed significant increases in hydrolytic erosion with the filler content increasing in comparison with the degradation of a pure PHBV film. Also, the photocatalytic activity of the inorganic filler TiO₂ in all investigated composites [irradiated at λ = 365 nm and immersed in a liquid medium (H₂O)] was evaluated. The degraded samples were analyzed with Fourier transform infrared spectroscopy, which confirmed their increased crystallinity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of poly(propylene carbonate) on the crystallization and melting behavior of poly(β‐hydroxybutyrate‐co‐β‐hydroxyvalerate)

The crystallization and melting behavior of poly(β‐hydroxybutyrate‐co‐β‐hydroxyvalerate) (PHBV) and a 30/70 (w/w) PHBV/poly(propylene carbonate) (PPC) blend was investigated with differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR). The transesterification reaction between PHBV and PPC was detected in the melt‐blending process. The interaction between the two macromolecules was confirmed by means of FTIR analysis. During the crystallization process from the melt, the crystallization temperature of the PHBV/PPC blend decreased about 8°C, the melting temperature was depressed by 4°C, and the degree of crystallinity of PHBV in the blend decreased about 9.4%; this was calculated through a comparison of the DSC heating traces for the blend and pure PHBV. These results indicated that imperfect crystals of PHBV formed, crystallization was inhibited, and the crystallization ability of PHBV was weakened in the blend. The equilibrium melting temperatures of PHBV and the 30/70 PHBV/PPC blend isothermally crystallized were 187.1 and 179°C, respectively. The isothermal crystallization kinetics were also studied. The fold surface free energy of the developing crystals of PHBV isothermally crystallized from the melt decreased; however, a depression in the relative degree of crystallization, a reduction of the linear growth rate of the spherulites, and decreases in the equilibrium melting temperature and crystallization capability of PHBV were detected with the addition of PPC. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2514–2521, 2004     

Thermal degradation kinetics of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)

The degradation kinetics of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate), a member of the Nodax family of polymers, were investigated using transient constant shear rate and dynamic time sweep rheological tests. The rate of chain scission at several times and temperatures was correlated with viscosity data and verified using molecular weight determination of the degraded samples. The experimental results show that the molecular weight and the viscosity of Nodax decrease with time over the range of temperatures that were studied (155–175°C). The degradation kinetics, which exhibited first‐order behavior, were determined as a function of the flow history and thermal history. An apparent activation energy of 189 ± 5 kJ/mol for thermal degradation was found by modeling variations in the rate with temperature using an Arrhenius law model. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 66–74, 2005     

Compatibility of poly(butadiene‐co‐acrylonitrile) with poly(L‐lactide) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)

Poly(L ‐lactide) (PLLA) and poly(3‐hydrobutyrate‐co‐3‐hydroxyvalerate) (PHBV) were blended with poly(butadiene‐co‐acrylonitrile) (NBR). Both PLLA/NBR and PHBV/NBR blends exhibited higher tensile properties as the content of acrylonitrile unit (AN) of NBR increased from 22 to 50 wt %. However, two separate glass transition temperatures (T_g) appeared in PLLA/NBR blends irrespective of the content of NBR, revealing that PLLA was incompatible with NBR. In contrast, a single T_g, which shifted along with the blend composition, was observed for PHBV/NBR50 blends. Moreover NBR50 suppressed the crystallization of PHBV, indicating that PHBV was compatible with NBR50. Decrease of both elongation modulus and stress at maximum load was less significant and increase of elongation at break was more pronounced in PHBV/NBR50 blends than in PLLA/NBR50 blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3508–3513, 2004     

Preparation and characterization of poly(hydroxybutyrate‐co‐hydroxyvalerate)–organoclay nanocomposites

This study describes the microstructure and thermal and mechanical properties of poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHB/HV)–organoclay nanocomposites prepared by melt intercalation using Cloisite 30B, a monotallow bis‐hydroxyethyl ammonium‐modified montmorillonite clay. X‐ray diffractometry and transmission electron microscopy analyses clearly confirm that an intercalated microstructure is formed and finely distributed in the PHB/HV copolymer matrix because PHB/HV has a strong hydrogen bond interaction with the hydroxyl group in the organic modifier of Cloisite 30B. The nanodispersed organoclay also acts a nucleating agent, increasing the temperature and rate of crystallization of PHB/HV; therefore, the thermal stability and tensile properties of the organoclay‐based nanocomposites are enhanced. These results confirm that the organoclay nanocomposite greatly improves the material properties of PHB/HV. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 525–529, 2003     

Characterization of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) biosynthesized by mixed microbial consortia fed fermented dairy manure

The bioplastic poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), was isolated from a bioreactor using mixed microbial consortia fed volatile fatty acids (VFA), from fermented dairy manure, as the carbon source. The molar fraction of 3‐hydroxyvalerate (3HV) amounted to 0.33 mol mol^?1 for two isolated PHBV samples as determined by GC‐MS and ¹H‐NMR spectroscopy. The chemical, thermal, and mechanical properties were determined. The PHBVs had relatively high M_w (～790,000 g mol^?1). Only a single glass transition temperature (T_g) and melting point (T_m) were observed. Isolated PHBVs exhibited good flexibility and elongation to break as compared with commercial PHBVs with lower HV. The diad and triad sequence distributions of the monomeric units were determined by ¹³C‐NMR spectroscopy and followed Bernoullian statistics suggesting that the PHBVs were random. The PHBV sequence distribution was also characterized by electrospray ionization‐mass spectrometry (ESI‐MSⁿ) after partial alkaline hydrolysis to oligomers showing a random 3HV distribution. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40333.     

Hydrolytic degradation of biobased poly(butylene succinate‐co‐furandicarboxylate) and poly(butylene adipate‐co‐furandicarboxylate) copolyesters under mild conditions

It is indispensable to investigate hydrolytic degradation behavior to develop novel (bio)degradable polyesters. Biobased and biodegradable copolyesters poly(butylene adipate‐co ‐butylene furandicarboxylate) (PBAF) and poly(butylene succinate‐co ‐butylene furandicarboxylate) (PBSF) with BF molar fraction (?_BF) between 40 and 60% were synthesized in this study. The hydrolytic degradation of film samples was conducted in a pH 7.0 PBS buffer solution at 25 °C. Slight mass loss (1–2%) but significant decrease in intrinsic viscosity (35–44%) was observed after 22 weeks. The apparent hydrolytic degradation rate decreased with increasing ?_BF and initial crystallinity. Meanwhile, PBAFs degraded slightly faster than PBSFs with the same composition. The ?_BF and crystallinity increased slowly with degradation time, suggesting the aliphatic moiety and the amorphous region are more susceptible to hydrolysis. And high enough tensile properties were retained after hydrolysis degradation, indicating PBAF and PBSF copolyesters are hydrolytically degradable, with tunable hydrolytic degradation rate and good balance between hydrolytic degradability and durability. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44674.     

Thermogravimetric analysis of poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)

The thermal degradation of poly(3‐hydroxybutyrate) (PHB) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [P(HB‐HV)] was studied using thermogravimetry (TG). In the thermal degradation of PHB, the temperature at the onset of weight loss (T_o) was derived by T_o = 0.97B + 259, where B represents the heating rate (°C/min). The temperature at which the weight loss rate was maximum (T_p) was T_p = 1.07B + 273, and the final temperature (T_f) at which degradation was completed was T_f = 1.10B + 280. The percentage of the weight loss at temperature T_p (C_p) was 69 ± 1% whereas the percentage of the weight loss at temperature T_f (C_f) was 96 ± 1%. In the thermal degradation of P(HB‐HV) (7:3), T_o = 0.98B + 262, T_p = 1.00B + 278, and T_f = 1.12B + 285. The values of C_p and C_f were 62 ± 7 and 93 ± 1%, respectively. The derivative thermogravimetric (DTG) curves of PHB confirmed only one weight loss step change because the polymer mainly consisted of the HB monomer only. The DTG curves of P(HB‐HV), however, suggested multiple weight loss step changes; this was probably due to the different evaporation rates of the two monomers. The incorporation of 10 and 30 mol % of the HV component into the polyester increased the various thermal temperatures (T_o, T_p, andT_f) by 7–12°C (measured at B = 20°C/min). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2237–2244, 2001     

Blends of polylactide and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) with low content of hydroxyvalerate unit: Morphology,structure, and property

The Polylactide (PLA)/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) blends with four different weight ratios were prepared by melt mixing. PLA and PHBV in PLA/PHBV blends were immiscible while the weak interaction between PLA and PHBV existed. The PHBV domains below 2 μm were dispersed in PLA matrix uniformly. The addition of PHBV made the crystallization of PLA easier due to PHBV acting as nucleating agent. PLA spherulites in PLA/PHBV blends presented various banded structures. In addition, the crystallinity of neat PLA was lower than those of PLA/PHBV blends. With the increase of PHBV content in PLA/PHBV blends, the crystallinity of PLA/PHBV blends increased. PHBV could enhance significantly the toughness of PLA. However, with the increase of PHBV content, the yield stress (σ_y), tensile modulus (E), and the yield strain (ε_y) of PLA/PHBV blends decreased gradually. In addition, incorporation of PHBV to PLA caused a transformation from an optical transparent to an opaque system. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42689.     

Biodegradability of and interaction in the packaging of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)–vermiculite bionanocomposites

The aim of this study was to develop poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) bionanocomposites with natural vermiculite (VMT) and modified vermiculite (VMTO), by the melt intercalation technique and to evaluate the thermal behavior, biodegradation, and food–packaging interactions through X‐ray diffraction (XRD). Through XRD, we observed the structure of a microcomposite for the systems with natural clay and possibly an exfoliated structure for the systems with VMTO. We observed from the thermogravimetry and differential scanning calorimetry results that the natural systems showed a small increase in the thermal stability, whereas the organoclay systems had a lower thermal stability. A high biodegradability in the pure polymer and the natural bionanocomposites was evidenced by the Sturm test through the carbon dioxide production and high weight loss of the material. We observed that there was no significant migration of PHBV from the bionanocomposites to the simulants. Under these circumstances, the bionanocomposites with VMT presented better thermal stability and a high biodegradability and were possibly inert when in contact with food. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44700.     

Enhancement of melt elasticity for poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) by addition of weak gel

Rheological properties in a molten state are studied extensively for poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate), PHB‐HV, with a small amount of crosslinked poly(epichlorohydrin), PECH, having low density of crosslink points. It is found that adding 2 wt % of xPECH greatly enhances the melt elasticity of PHB‐HV, one of the serious defects of microbial PHB, whereas it has no effect on the shear viscosity. As a result, viscoelastic nature, and thus processability, of PHB‐HV can be controlled by blending the crosslinked PECH. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of nucleating agents on the crystallization of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)

The effect of nucleating agents on the crystallization behavior of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) was studied. A differential scanning calorimeter was used to monitor the energy of the crystallization process from the melt and melting behavior. During the crystallization process from the melt, nucleating agent led to an increase in crystallization temperature (T_c) of PHBV compared with that for plain PHBV (without nucleating agent). The melting temperature of PHBV changed little with addition of nucleating agent. However, the areas of two melting peaks changed considerably with added nucleating agent. During isothermal crystallization, dependence of the relative degree of crystallization on time was described by the Avrami equation. The addition of nucleating agent caused an increase in the overall crystallization rate of PHBV, but did not influence the mechanism of nucleation and growth of the PHB crystals. The equilibrium melting temperature of PHBV was determined as 187°C. Analysis of kinetic data according to nucleation theories showed that the increase in crystallization rate of PHBV in the composite is due to the decrease in surface energy of the extremity surface. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2145–2152, 2002     

Biobased blends of poly(propylene carbonate) and poly(hydroxybutyrate‐co‐hydroxyvalerate): Fabrication and characterization

Poly(propylene carbonate) (PPC), a CO₂‐based bioplastic and poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) were melt blended followed by injection molding. Fourier transform infrared spectroscopy detected an interaction between the macromolecules from the reduction in the OH peak and a shift in the C?O peak. The onset degradation temperature of the polymer blends was improved by 5% and 19% in comparison to PHBV and PPC, respectively. Blending PPC with PHBV reduced the melting and crystallization temperatures and crystallinity of the latter as observed through differential scanning calorimetry. The amorphous nature of PPC affected the thermal properties of PHBV by hindering the spherulitic growth and diluting the crystalline region. Scanning electron micrographs presented a uniform dispersion and morphology of the blends, which lead to balanced mechanical properties. Incorporating PHBV, a stiff semi‐crystalline polymer improved the dimensional stability of PPC by restricting the motion of its polymer chains. © 2016 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44420.     

Crystallization kinetics of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/clay nanocomposites

The preparation and properties of nanocomposites, consisting of a poly(3‐Hydroxybutyrate‐co‐3‐hydroxyvalerate) and an organophilic clay are described. The effect of organophilic clay on the crystallization behavior of (PHBV) was studied. A differential scanning calorimeter (DSC) was used to monitor the energy of the crystallization process from the melt. During the crystallization process from the melt, the organophilic clay led to an increase in crystallization temperature (T_c) of PHBV compared with that for plain PHBV. During isothermal crystallization, dependence of the relative degree of crystallization on time was described by the Avrami equation. The addition of organophilic clay caused an increase in the overall crystallization rate of PHBV, but did not influence the mechanism of nucleation, and growth of the PHBV crystals and the increase caused by a small quantity of clay is move effective than that large one. The equilibrium melting temperature of PHBV was determined as 186°C. Analysis of kinetic data according to nucleation theories showed that the increase in crystallization rate of PHBV in the composite is due to the decrease in surface energy of the extremity surface. The mechanical test shows that the tensile strength of hybrid increased to 35.6 MPa, which is about 32% higher than that of the original PHBV with the incorporation of 3 wt % clay, and the tensile modulus was also increased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 655–661, 2004