Morphological and mechanical behavior of chemically treated jute‐PHBV bio‐nanocomposites reinforced with silane grafted halloysite nanotubes

In this study, at first, thin films of poly(3‐hydroxybutyrate‐co?3‐hydroxyvalerate) (PHBV) nanocomposites were prepared by adding 1–3 wt % grafted halloysite nanotubes (G‐HNTs). Jute‐PHBV bio‐nanocomposites were then fabricated using these films and chemically treated jute fibers in a compression mold machine. The effect of treatment and modification on jute fiber and halloysite nanotubes (HNTs), and the change in their morphology was investigated using Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), scanning and transmission electron microscopy (SEM, TEM). Flexural and thermomechanical properties were determined using a three‐point bend test and dynamic mechanical analysis (DMA). The results showed separation of fiber bundles with rough fiber surfaces, and grafting of silane coupling agents on fibers and HNTs after the chemical treatment. As a result, a strong bonding was established between the PHBV, G‐HNTs and jute fibers that lead to significant improvements in flexural and thermomechanical properties of jute‐PHBV bio‐nanocomposites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43994.     

Poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)]/layered double hydroxide nanocomposites

BACKGROUND: The thermomechanical performance of poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] (PHBV) is associated with its crystallization. Enhanced nucleation using a stearate‐functionalized synthetic layered double hydroxide (LDH) presents a potential solution. RESULTS: PHBV crystallization varied with concentration of LDH. At lower LDH concentration, thermal history‐induced cold crystallization was present. The extent of this order–disorder transition decreased with increasing LDH concentration and was completely eliminated at 7 wt% LDH. PHBV did not have a melt recrystallization peak but the introduction of LDH resulted in an increasingly pronounced melt recrystallization with increasing LDH concentration. Polarized optical microscopy coupled with differential scanning calorimetry and wide angle X‐ray diffraction (WAXD) analysis indicated increased lamella thickness in the nanocomposites compared to pure PHBV. WAXD and transmission electron microscopy showed that the nanocomposites had an intercalated but aggregated dispersion. CONCLUSION: The concentration of nanofiller provides unique effects in PHBV. Mechanical performance was found to scale with composition as determined using dynamic mechanical analysis and tensile testing. Copyright © 2008 Society of Chemical Industry     

Mechanical and electrical multifunctional poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)—multiwall carbon nanotube nanocomposites

In this work, nanocomposites of poly(hydroxybutyrate‐co‐hydroxyvalerate) PHBV and multiwalled carbon nanotubes (MWNT) were prepared by melt blending. Mechanical, thermal, morphological, and electrical properties of the prepared PHBV/MWNT nanocomposites were investigated. Differential scanning calorimetry (DSC) and X‐ray diffraction (XRD) results showed MWNT effectively enhanced the crystallization and nucleation of PHBV. Dynamic thermo‐mechanical and static uniaxial mechanical tensile and compressive properties were increased by the addition of MWNT. MWNT observed in the nanocomposites using transmission electron microscopy (TEM) showed dimensions similar to separated nanotubes inferring a good dispersion. The presence of nanotubes in close vicinity with each other formed an interconnecting network that led to the formation of electrically conductive nanocomposites. The electrical resistance of the nanocomposites was reduced with the addition of MWNT. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Crystallization and mechanical behavior of covalent functionalized carbon nanotube/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) nanocomposites

To improve the dispersity of multi‐walled carbon nanotubes (MWCNTs) in poly(3‐hydroxybutyrate‐co?3‐hydroxyvalerate) (PHBV) matrix, MWCNTs functionalized with carboxyl groups, hydroxyl groups, and atactic poly (3‐hydroxybutyrate) (ataPHB) through acid oxidation, esterification reaction, and “grafting from” method, respectively, were used to fabricate nanofiller/PHBV nanocomposites. The crystallization behavior, dispersion of MWCNTs before and after functionalization in PHBV matrices, and mechanical properties of a series of nanocomposites were investigated. The differential scanning calorimetry, wide‐angle X‐ray diffraction, and polarized optical microscope results suggested that the four types of MWCNTs acted as effective heterogeneous nucleation agents, inducing an increase in the crystallization rate, crystallinity, and crystallite size. Scanning electron microscope observations demonstrated that functionalized MWCNTs showed improved dispersion comparing with MWCNTs, suggesting an enhanced interfacial interaction between PHBV and functionalized MWCNTs. Consequently, the mechanical properties of the functionalized MWCNTs/PHBV nanocomposites have been improved as evident from dynamic mechanical and static tensile tests. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42136.     

Microcellular poly(hydroxybutyrate‐co‐hydroxyvalerate)‐hyperbranched polymer–nanoclay nanocomposites

The effects of incorporating hyperbranched polymers (HBPs) and different nanoclays [Cloisite® 30B and halloysite nanotubes (HNT)] on the mechanical, morphological, and thermal properties of solid and microcellular poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) were investigated. According to the X‐ray diffraction (XRD) and transmission electron microscopy (TEM) analyses, Cloisite 30B exhibited a combination of exfoliation and heterogeneous intercalation structure for both solid and microcellular PHBV–12% HBP–2% Cloisite 30B nanocomposites. TEM images indicated that HNTs were uniformly dispersed throughout the PHBV matrix. The addition of 2% nanoclays improved the thermal stability of the resulting nanocomposites. The addition of HBP+poly(maleic anhydride‐alt‐1‐octadecene) (PA), Cloisite 30B, and HNT reduced the average cell size and increased the cell density of the microcellular components. The addition of (HBP+PA), Cloisite 30B, and HNT also increased the degree of crystallinity for both solid and microcellular components in comparison with neat PHBV. Also, with the addition of 12% (HBP+PA), the area under the tan‐δ curve, specific toughness, and strain‐at‐break of the PHBV–HBP nanocomposite increased significantly for both solid and microcellular specimens, whereas the storage modulus, specific Young's modulus, and specific tensile strength decreased. The addition of 2% nanoclays into the PHBV–HBP nanocomposites improved the storage modulus, specific Young's modulus, and specific tensile strength of the PHBV–HBP–nanoclay‐based nanocomposites, but they were still lower than those of the neat PHBV. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

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     

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

In 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     

Thermal properties of blends of poly(hydroxybutyrate‐co‐hydroxyvalerate) and poly(styrene‐co‐acrylonitrile)

Thermal properties of blends of poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) and poly(styrene‐co‐acrylonitrile) (SAN) prepared by solution casting were investigated by differential scanning calorimetry. In the study of PHBV‐SAN blends by differential scanning calorimetry, glass transition temperature and melting point of PHBV in the PHBV‐SAN blends were almost unchanged compared with those of the pure PHBV. This result indicates that the blends of PHBV and SAN are immiscible. However, crystallization temperature of the PHBV in the blends decreased approximately 9–15°. From the results of the Avrami analysis of PHBV in the PHBV‐SAN blends, crystallization rate constant of PHBV in the PHBV‐SAN blends decreased compared with that of the pure PHBV. From the above results, it is suggested that the nucleation of PHBV in the blends is suppressed by the addition of SAN. From the measured crystallization half time and degree of supercooling, interfacial free energy for the formation of heterogeneous nuclei of PHBV in the PHBV‐SAN blends was calculated and found to be 2360 (mN/m)³ for the pure PHBV and 2920–3120 (mN/m)³ for the blends. The values of interfacial free energy indicate that heterogeneity of PHBV in the PHBV‐SAN blends is deactivated by the SAN. This result is consistent with the results of crystallization temperature and crystallization rate constant of PHBV in the PHBV‐SAN blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 673–679, 2000     

Fabrication of honeycomb‐structured porous films from poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) via the breath figures method

Formation of porous films from poly(3‐hydroxybutyrate) (PHB) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) using the breath figures (BF) method was investigated by evaporating solutions in chloroform in humid air and examining film structure using optical and scanning electron microscopy (SEM). BF films were successfully fabricated from PHB (M_w = 486,000 g/mol) and displayed hexagonal arrays of pores, which varied in diameter (D = 7–2 μm) with solution concentrations (0.5–2.00%). SEM of fractured films also showed subsurface closed nano‐pores (D = 500–700 nm). BF films cast from PHBV (5% HV) formed arrays with smaller pores and apparent surface defects. Differential scanning calorimetry showed that porous PHB and PHBV films produced using the BF method were more crystalline than nonporous solvent cast films of PHB and PHBV. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Effect of carbon nanotubes on the biodegradability of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) nanocomposites

In this work, the effect of carbon nanotubes (CNT) on the biodegradability of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanocomposites with 1 and 2% (w/w) of CNT has been evaluated by biodegradation assays in aqueous medium containing microorganisms extracted from garden soil. After biodegradation process, samples of PHBV and PHBV/CNT were compared regarding magnitude of degradation by visual macroscopic analysis, by measurement of percentage of weight loss and by scanning electron microscopy (SEM). The samples were further characterized regarding roughness and hydrophilicity by contact angle measurement. The final residue resultant from biodegradation of PHBV/CNT was analyzed in a FEI Inspect F50 field emission scanning electron microscope (FESEM) in order to verify the presence of CNT. Our results indicated that CNT did not compromise the biodegradability of PHBV matrix although the biodegradation rate has decreased with the increase of CNT content as shown by the weight loss measurements. SEM analysis of PHBV/CNT nanocomposites after biodegradation process showed increased amount of CNT exposed at the matrix surface suggesting the possibility of CNT recovering after the biodegradation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48020.     

Biopolymer nanocomposites based on poly(hydroxybutyrate‐co‐hydroxyvalerate) reinforced by a non‐ionic organoclay

In this study, a nanocomposite based on a biodegradable polymer poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) reinforced by triethylene glycol mono‐n‐decyl ether (C₁₀E₃) non‐ionic organoclay (C₁₀E₃‐Mt) was prepared. The morphology and the thermal and mechanical properties of PHBV/C₁₀E₃‐Mt were compared with those of PHBV nanocomposites prepared using commercial organically modified montmorillonite Cloisite^® 30B (OMt) and raw montmorillonite (Mt). Nanocomposites with 3 wt% nanoparticles were obtained by melt processing. The high level of dispersion with improved interfacial interactions between OMt and polymer led to an increase in the thermal stability and modulus of PHBV. However, this nanocomposite presented a lower strain before fracture, typical of brittle behavior. The transmission electron microscopy and wide angle X‐ray diffraction results revealed a significant increase in the interlayer spacing of clay for the PHBV/C₁₀E₃‐Mt nanocomposite, which was favored by the wide expansion of the platelets of the starting non‐ionic organoclay. This characteristic of C₁₀E₃‐Mt, together with its hydrophobic behavior, allowed its easy incorporation in the PHBV matrix, thus improving the processing and maintaining a high modulus with increased material toughness. © 2014 Society of Chemical Industry     

Thermal analysis of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) irradiated under vacuum

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) was irradiated by ⁶⁰Co γ‐rays (doses of 50, 100 and 200 kGy) under vacuum. The thermal analysis of control and irradiated PHBV, under vacuum was carried out by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The tensile properties of control and irradiated PHBV were examined by using an Instron tensile testing machine. In the thermal degradation of control and irradiated PHBV, a one‐step weight loss was observed. The derivative thermogravimetric curves of control and irradiated PHBV confirmed only one weight‐loss step change. The onset degradation temperature (T_o) and the temperature of maximum weight‐loss rate (T_p) of control and irradiated PHBV were in line with the heating rate (°C min^?1). T_o and T_P of PHBV decreased with increasing radiation dose at the same heating rate. The DSC results showed that ⁶⁰Co γ‐radiation significantly affected the thermal properties of PHBV. With increasing radiation dose, the melting temperature (T_m) of PHBV shifted to a lower value, due to the decrease in crystal size. The tensile strength and fracture strain of the irradiated PHBV decreased, hence indicating an increased brittleness. Copyright © 2004 Society of Chemical Industry     

Preparation and physical properties of functionalized graphene/waterborne polyurethane UV‐curing composites by click chemistry

Functionalized graphene nanoplatelets (f‐GNS) were modified with (3‐mercaptopropyl)trimethoxysilane (MPTMS) to enhance their compatibility with the polyurethane coating matrix. The results of Fourier transform infrared spectroscopy, AFM, Raman and XRD showed that the MPTMS was successfully attached onto the surface of the graphene nanoplatelets. Functionalized graphene/waterborne polyurethane acrylate (f‐GNS/WPUA) nanocomposites were fabricated by UV‐curing technology. The SEM and TEM images indicated that f‐GNS could be well dispersed in the polymer matrix and improved the interfacial adhesion. With the incorporation of 1 wt% f‐GNS, the thermal decomposition temperature of the composites was increased by 25 °C. Meanwhile, the conductivity, hydrophobicity and tensile strength were increased. When the load was further increased, the performance of the composites showed varying degrees of reduction. However, the dielectric loss tangent (tan δ) could be maintained at 0.08 or less and the electromagnetic shielding factor of the composites reached from 5 to 36 dB, showing a good electromagnetic shielding effect at a high content (2.5 wt% f‐GNS). It was considered that f‐GNS could disperse in the waterborne polyurethane well and crosslink with the polyurethane. © 2016 Society of Chemical Industry     

Photografting polymerization of polyacrylamide on PHBV films (I)

Photografting polymerization of polyacrylamide (PAM) onto poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) films using benzophenone as photoinitiator was studied. The morphology and structure of the grafted PHBV film were characterized by Fourier transformed infrared spectroscopy (FTIR) with attenuated total reflectance (ATR) and scanning electron microscope (SEM) with energy dispersive X‐ray spectrometer (EDX). The grafting percentage and grafting efficiency of the grafted PHBV film went up with the increase of acrylamide concentration and irradiation time. It was observed that photografting polymerization of PAM was not only limited to the film surface, but also in situ occurred inside the film to form the pore microstructure. Sheep bone marrow stromal cell studies showed that MSCs cells attachment efficiency on the grafted PHBV films increased and cells grew well. These results demonstrated the potentiality of PAM‐photografting PHBV in medical applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104, 4088–4095, 2007     

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     

Synthesis of highly conductive PPy/graphene nanosheets/NiO composite using ultrasonic technique

Highly conductive polypyrrole/graphene nanosheets/NiO (PPy/GNS/NiO) composites are fabricated via ultrasound technique using p‐toluenesulfonic acid as a dopant and FeCl₃ as an oxidant. The effects of the GNS and NiO loading on the electrical conductivity are investigated. The maximum conductivity of PPy/GNS/NiO composites about 24.39 S/cm found with 3 wt% GNS and 48.7 wt% NiO at room temperature. The results showed that the high‐aspect‐ratio structure of GNS played an important role in forming a conducting network in PPy matrix. The microstructures of PPy/GNS/NiO are evidenced by the scanning electron microscope and transmission electron microscope examinations. The cyclic voltammetry curves can be seen that the PPy/GNS/NiO composites also have good electrochemical performance, and it can be used as a supercapacitor electrode material. POLYM. COMPOS., 34:997–1002, 2013. © 2013 Society of Plastics Engineers     

Antimicrobial nanocomposites and electrospun coatings based on poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) and copper oxide nanoparticles for active packaging and coating applications

Active biodegradable poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) melt mixed nanocomposites and bilayer structures containing copper oxide (CuO) nanoparticles were developed and characterized. The bilayer structures consisted of a bottom layer of compression molded PHBV3 (3% mol valerate) coated with an active electrospun fibers mat made with CuO nanoparticles and PHBV18 (18% valerate) derived from microbial mixed cultures and cheese whey. The results showed that the water vapor permeability increased with the CuO addition while the oxygen barrier properties were slightly enhanced by the addition of 0.05 wt % CuO nanoparticles to nanocomposite films but a negligible effect was registered for the bilayer structures. However, the mechanical properties were modified by the addition of CuO nanoparticles. Interestingly, by incorporating highly dispersed and distributed CuO nanoparticles in a coating by electrospinning, a lower metal oxide loading was required to exhibit significant bactericidal and virucidal performance against the food‐borne pathogens Salmonella enterica, Listeria monocytogenes, and murine norovirus. The biodisintegration tests of the samples under composting conditions showed that even the 0.05% CuO‐coated structures biodegraded within 35 days. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45673.     

Morphology and thermal degradation studies of melt‐mixed PLA/PHBV biodegradable polymer blend nanocomposites with TiO2 as filler

The morphology and thermal stability of melt‐mixed poly(lactic acid) (PLA)/poly(hydroxybutyrate‐co‐valerate) (PHBV) blends and nanocomposites with small amounts of TiO₂ nanoparticles were investigated. PLA/PHBV at 50/50 w/w formed a co‐continuous structure, and most of the TiO₂ nanoparticles were well dispersed in the PLA phase and on the interface between PLA and PHBV, with a small number of large agglomerates in the PHBV phase. Thermogravimetric analysis (TGA) and TGA–Fourier‐transform infrared spectroscopy was used to study the thermal stability and degradation behavior of the two polymers, their blends, and nanocomposites. The thermal stability of PHBV was improved through blending with PLA, whereas that of the PLA was reduced through blending with PHBV, and the presence of TiO₂ nanoparticles seemingly improved the thermal stability of both polymers in the blend. However, the degradation kinetics results revealed that the nanoparticles could catalyze the degradation process and/or retard the volatilization of the degradation products, depending on their localization and their interaction with the polymer in question. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42138.     

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     

Crystallization and melting behavior of blends comprising poly(3‐hydroxy butyrate‐co‐3‐hydroxy valerate) and poly(ethylene oxide)

Blends of poly(3‐hydroxy butyrate‐co‐3‐hydroxy valerate) (PHBV) and poly(ethylene oxide) (PEO) were prepared by casting from chloroform solutions. Crystallization kinetics and melting behavior of blends have been studied by differential scanning calorimetry and optical polarizing microscopy. Experimental results reveal that the constituents are miscible in the amorphous state. They form separated crystal structures in the solid state. Crystallization behavior of the blends was studied under isothermal and nonisothermal conditions. Owing to the large difference in melting temperatures, the constituents crystallize consecutively in blends; however, the process is affected by the respective second component. PHBV crystallizes from the amorphous mixture of the constituents, at temperatures where the PEO remains in the molten state. PEO, on the other hand, is surrounded during its crystallization process by crystalline PHBV regions. The degree of crystallinity in the blends stays constant for PHBV and decreases slightly for PEO, with ascending PHBV content. The rate of crystallization of PHBV decreases in blends as compared to the neat polymer. The opposite behavior is observed for PEO. Nonisothermal crystallization is discussed in terms of a quasi‐isothermal approach. Qualitatively, the results show the same tendencies as under isothermal conditions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2776–2783, 2006