Miscibility and crystallization behavior of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/poly(vinyl acetate) blends

The miscibility and crystallization behavior of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (P(HB‐co‐HV))/poly(vinyl acetate) (PVAc) blends have been investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). It was found that P(HB‐co‐HV)/PVAc blends were miscible in the melt over the whole compositions. Thus the blend exhibited a single glass transition temperature (T_g), which increased with increasing PVAc composition. The spherulitic morphologies of P(HB‐co‐HV)/PVAc blends indicated that the PVAc was predominantly segregated into P(HB‐co‐HV) interlamellar or interfibrillar regions during P(HB‐co‐HV) crystallization because of the volume‐filled spherulites. As to the crystallization kinetics study, it was found that the overall crystallization and crystal growth rates decreased with the addition of PVAc. The kinetics retardation was primarily attributed to the reduction of chain mobility and dilution of P(HB‐co‐HV) upon mixing with higher T_g PVAc. The overall crystallization rate was predominantly governed by the spherulitic growth rate and promoted by the samples treated with the quenched state because of the higher nucleation density. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 980–988, 2006     

Blends of bacterial poly[(R)‐3‐hydroxybutyrate] with oligo[(R,S)‐3‐hydroxybutyrate]‐diol

The miscibility, melting and crystallization behaviour of poly[(R)‐3‐hydroxybutyrate], PHB, and oligo[(R,S)‐3‐hydroxybutyrate]‐diol, oligo‐HB, blends have been investigated by differential scanning calorimetry: thermograms of blends containing up to 60 wt% oligo‐HB showed behaviour characteristic of single‐phase amorphous glasses with a composition dependent glass transition, T_g, and a depression in the equilibrium melting temperature of PHB. The negative value of the interaction parameter, determined from the equilibrium melting depression, confirms miscibility between blend components. In parallel studies, glass transition relaxations of different melt‐crystallized polymer blends containing 0–20 wt% oligo‐HB were dielectrically investigated between ?70 °C and 120 °C in the 100 Hz to 50 kHz range. The results revealed the existence of a single α‐relaxation process for blends, indicating the miscibility between amorphous fractions of PHB and oligo‐HB. © 2002 Society of Chemical Industry     

Preparation and properties of blends from poly(3‐hydroxybutyrate) with poly(vinyl acetate)‐modified starch

This research used the ceric ion to initiate the graft‐polymerization of vinyl acetate (VAc) to a soluble potato starch. Fourier transform infrared spectra confirmed the formation of starch graft copolymer. After 4 h of reaction at 50°C, total monomer conversion, grafting efficiency, and grafting ratio were measured as 91%, 12.5%, and 0.223, respectively. The synthesized PVAc‐modified starch was then blended with poly(3‐hydroxybutyrate) (PHB). Structures, thermal and mechanical properties of the prepared blends were examined. The results showed the PHB and PVAc‐modified starch were miscible in all compositions. In addition, thermal gravimetric analysis revealed that the addition of PVAc‐modified starch increased the thermal stability of the PHB component. Further evidence also showed that the addition of PVAc‐modified starch reduced the extent of decrease in molecular weight of PHB in a melt‐mixer. PHB/PVAc‐modified starch blends exhibit higher toughness than pure PHB because of increased compatibility and the leathery PVAc‐modified starch. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Atactic poly(methyl methacrylate) blended with poly(3‐D(−)hydroxybutyrate): Miscibility and mechanical properties

Atactic poly(methylmethacrylate), aPMMA, was blended with poly(3‐D(−)hydroxybutyrate), PHB, up to a maximum composition of 25% of polyester, at 190°C in a Brabender‐like apparatus. The resulting blends quenched from the melt to room temperature were completely amorphous, and exhibited a single glass transition using DSC and DMTA, indicating miscibility of the components for this time–temperature history. Tensile experiments showed that at room temperature the 10/90 and 20/80 PHB/aPMMA blends exhibited higher values of strain at break, and slight decreases of the modulus and stress at break compared to neat aPMMA. The tensile energy at break was almost twice that of neat aPMMA. Tensile tests were also performed at 80°C, at which point the 25/75 and 20/80 PHB/aPMMA blends are above T_g, while the 10/90 and neat aPMMA are below T_g. The stress–strain curves obtained were functions of the physical state of the amorphous phase, and also depended on the difference between the test temperatures and T_g. In particular, comparing the neat aPMMA and the blends, decreases of the modulus and stress at break and a respectable increase in the strain at break were observed in the latter. Finally, the results were commented considering the thermal degradation of PHB in the melt during the blend preparation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 746–753, 2000     

Development of novel biopolymer blends based on poly(l‐lactic acid), poly((R)‐3‐hydroxybutyrate), and plasticizer

Poly(l ‐lactic acid) (PLLA), a biopolymer that can be derived from renewable resources, is known for its brittleness as a result of slow crystallization rates under supercooling conditions, which is associated with the formation of large spherulites. In addition, the glass transition temperature (T_g) of PLLA is 60°C, such that the polymer chain is immobile at room temperature. These disadvantages make PLLA unsuitable for use in the food packaging sector. In this research, biopolymer blends based on PLLA and poly((R)‐3‐hydroxybutyrate) (PHB), together with tributyl citrate (TBC) as a plasticizer, were developed. TBC was added to increase polymer chain mobility, and to decrease PLLA T_g from 60 to 10°C in blends. Furthermore, the addition of PHB as a nucleating agent to PLLA resulted in an increased proportion of smaller spherulites. Fourier‐transform infrared (FT‐IR) spectroscopy indicated that the carbonyl group and several other characteristic peaks in blends are shifted to lower wavenumber. In addition, polarized optical microscopy experiments confirmed the results of differential scanning calorimetry, FT‐IR, and wide‐angle X‐ray diffraction, showing that PHB enhances the crystallization behavior by acting as a bionucleation. POLYM. ENG. SCI., 54:1394–1402, 2014. © 2013 Society of Plastics Engineers     

Blending and characterizations of microbial poly(3‐hydroxybutyrate) with dendrimers

Blending of microbial polyester poly(3‐hydroxybutyrate) (PHB) with various dendritic polyester oligomers or dendrimers was achieved by solution casting to improve the film forming ability of PHB. Films of the blends were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron micrograph (SEM), and Fourier transform infrared spectroscopy (FTIR). It was revealed that there were mainly two types of interactions in the blending system: the plasticizing or lubricating effect of the low melting spherical dendrimers molecules improved the polymer chain mobility through the suppression of PHB crystallization in the blends; The dendrimers also functioned as crosslinking agents or antiplasticizing agents via weak hydrogen bonding to enhance the overall intermolecular interactions which decrease the chain mobility and thus cause the increase of glass transition temperature (T_g) of PHB. TGA results concluded that incorporating the dendrimers could retard the thermal decomposition of PHB and enhanced its thermal stability accordingly. With the above blend processes, the so‐obtained PHB possessed better film forming ability and even patterned surface structures. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:3782–3790, 2006     

Effect of two different plasticizers on the properties of poly(3‐hydroxybutyrate) binary and ternary blends

Plasticized poly(3‐hydroxybutyrate) (PHB) films were obtained by solvent casting. The effects of two different additives on several properties of PHB have been examined, utilizing tributyrin and poly[di(ethyleneglycol) adipate] (A). Based on changes in the glass transition temperature (T_g) and cold crystallization temperature of host PHB, the two components are miscible with PHB and they can act as plasticizers. Binary and ternary blends were obtained by adding both plasticizers separately or together, respectively. The effect of plasticizer addition on the optical transparency, water vapor permeability, and tensile properties of the films was studied. It was found that the blends remain transparent and water vapor permeability was maintained constant until a 20 wt % of plasticizer content. Plasticizing effect was corroborated and it depended on the plasticizer percentage. Binary blends had an increased plasticity, in concordance with T_g diminution of PHB. Although ternary blends presented T_g diminution, mechanical properties were not improved probaby due to strong interactions between plasticizers. Finally, binary and ternary blends presented enhanced properties, causing an increment on processability. A correct knowledge between the formulation of the film and the role played by each component could allow getting custom films. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46016.     

Preparation of cellulose acetate butyrate and poly(ethylene glycol) copolymer to blend with poly(3‐hydroxybutyrate)

A two‐step procedure was used to synthesize the cellulose acetate butyrate and poly(ethylene glycol) graft copolymer (CAB‐g‐PEG). By choosing the appropriate composition, the crosslinked graft copolymer or not could be obtained. Then, the CAB‐g‐PEG copolymer was blended with poly(3‐hydroxybutyrate) (PHB), to further improve the mechanical properties of PHB. The results indicated that PHB and CAB‐g‐PEG that were not crosslinked were miscible over the entire composition range. As the CAB‐g‐PEG copolymer increased in the PHB/CAB‐g‐PEG blends, the melting temperature of the blends decreased, the crystallization of PHB became more difficult, and the crystallinity of the blend and PHB phase all decreased. The tensile properties and impact strength of the PHB/CAB‐g‐PEG blends were superior to the PHB/CAB blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1471–1478, 2006     

Research on starch‐g‐polyvinyl acetate and epoxy resin‐modified corn starch adhesive

A new corn starch adhesive modified by starch‐g‐polyvinyl acetate (starch‐g‐PVAc) and epoxy resin is described in this study. Starch‐g‐PVAc is used as high cohesive energy component to improve the dry shear strength of the starch adhesive. Although the epoxy resin, which can easily crosslink with the oxidized starch, is used as water‐resistant component to improve the wet shear strength. Because there is no chemical reaction happening between polyvinyl acetate and epoxy resin, both the dry shear strength and the wet shear strength of the corn starch adhesive are notably increased. Considering all the related factors, the optimum of the modification is achieved when the dosage of starch‐g‐PVAc and epoxy resin is 70% of the oxidized starch latex with m(Ep): m(starch‐g‐PVAc) = 1:2. That is, the epoxy resin is 23% in mass fraction and starch‐g‐PVAc 47% in mass fraction. The dry shear strength is 4.50 MPa, and the wet shear strength is 2.51 MPa. The modified corn starch has a broad prospect in the application of plywood industry. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers     

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     

Miscibility and crystallization kinetics of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/ poly(methyl methacrylate) blends

The miscibility and crystallization kinetics of the blends of random poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [P(HB‐co‐HV)] copolymer and poly(methyl methacrylate) (PMMA) were investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). It was found that P(HB‐co‐HV)/PMMA blends were miscible in the melt. Thus the single glass‐transition temperature (T_g) of the blends within the whole composition range suggests that P(HB‐co‐HV) and PMMA were totally miscible for the miscible blends. The equilibrium melting point (T°_m) of P(HB‐co‐HV) in the P(HB‐co‐HV)/PMMA blends decreased with increasing PMMA. The T°_m depression supports the miscibility of the blends. With respect to the results of crystallization kinetics, it was found that both the spherulitic growth rate and the overall crystallization rate decreased with the addition of PMMA. The kinetics retardation was attributed to the decrease in P(HB‐co‐HV) molecular mobility and dilution of P(HB‐co‐HV) concentration resulting from the addition of PMMA, which has a higher T_g. According to secondary nucleation theory, the kinetics of spherulitic crystallization of P(HB‐co‐HV) in the blends was analyzed in the studied temperature range. The crystallizations of P(HB‐co‐HV) in P(HB‐co‐HV)/PMMA blends were assigned to n = 4, regime III growth process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3595–3603, 2004     

Reactive compatibilization of poly(l‐lactide)/poly(butylene succinate) blends through polyester maleation: from materials to properties

The melt blending of poly(l ‐lactide) (PLLA) with biodegradable poly(butylene succinate) (PBS) is considered with a view to fine‐tuning its mechanical properties and its degradability. For this purpose, both maleic‐anhydride‐grafted PLLA (PLLA‐g‐MA) and maleic‐anhydride‐grafted PBS (PBS‐g‐MA) were prepared and used as reactive compatibilizers. The influence of PBS melt viscosity on the morphology and mechanical properties of PLLA/PBS blends was studied. Interestingly, the blending of low viscosity PBS with PLLA allows PLLA to be toughened while the use of high viscosity PBS led to PLLA/PBS blends exhibiting co‐continuous morphology. The nanostructure of the co‐continuous blends may be tuned through the joint action of organo‐modified clays and reactive compatibilizers. The effect of PBS on PLLA degradability was also investigated. The accelerated weathering testing of blends reveals that such combination of biodegradable polymers allows their degradability rate to be tailored. It is found that the addition of 20 wt% PBS to PLLA allows the molar mass loss fraction to be doubled after 425 h of testing. © 2014 Society of Chemical Industry     

High impact poly(lactic acid)/poly(ethylene octene) blends prepared by reactive blending

Poly(ethylene octene) grafted with glycidyl methacrylate (POE‐g‐GMA) was prepared and used to toughen poly (lactic acid) (PLA) via reactive blending. It was found that the notched Izod impact strength of PLA/POE‐g‐GMA blends improved dramatically when the content of elastomer was higher than 10 wt%. Reactive compatibilization between PLA and POE‐g‐GMA were studied by Fourier transform infrared spectroscopy (FTIR) and “Molau test,” the results showed the end carboxyl groups of PLA reacted with the epoxide groups of POE‐g‐GMA during blending. This considerably improved the compatibilization, leading to better wetting of the dispersed phase by the PLA matrix and finer dispersed POE‐g‐GMA particles with narrow distribution. Moreover, the critical interparticle distance (L_c) of the dispersed domains for PLA/POE‐g‐GMA blends system at room temperature was also identified. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Control of biodegradability of poly(3‐hydroxybutyric acid) film with grafting acrylic acid and thermal remolding

Radiation‐induced graft polymerization of acrylic acid (AAc) on poly(3‐hydroxybutyric acid) (PHB) film was carried out and the resulting film was thermally‐remolded. The PHB films grafted with AAc (PHB‐g‐AAc) having a degree of grafting higher than 5% completely lost the enzymatic degradability. The enzymatic degradability of the grafted film was recovered by thermal remolding. The highest enzymatic degradation rate was observed at degree of grafting of 10% after thermal remolding. The PHB‐g‐AAc films and thermally‐remolded PHB‐g‐AAc films were characterized by contact angle and differential scanning calorimetry. The enzymatic degradability of PHB‐g‐AAc films was lost by the grafted AAc, which covered the surface of PHB film. The acceleration of enzymatic degradation in the remolded PHB‐g‐AAc films was mainly caused by decrease of crystallinity of PHB by dispread of grafted AAc during thermal remolding. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3856–3861, 2006     

Effect of the molecular chains grafted on graphene nanosheets on the properties of poly(l‐lactic acid) nanocomposites

We prepared thermally reduced graphene oxide (TRG) grafted with polymethyl methacrylate (PMMA) and polyvinyl acetate (PVAc) (TRG‐g‐PMMA and TRG‐g‐PVAc) by γ‐ray irradiation‐induced graft polymerization and studied their effects on poly(l ‐lactic acid) (PLLA) nanocomposites. PMMA and PVAc chains were proved to be grafted on the TRG surface successfully. TRG‐g‐PMMA and TRG‐g‐PVAc was found to restrict the crystallization behavior of PLLA compared with TRG. Moreover, tensile‐test results showed that TRG‐g‐PMMA and TRG‐g‐PVAc could enhance the elongation at break of PLLA nanocomposites without reducing the tensile strength and modulus compared with TRG, which indicated that the grafting of PMMA and PVAc chains on TRG could improve the toughness of PLLA nanocomposites. POLYM. COMPOS., 38:5–12, 2017. © 2015 Society of Plastics Engineers     

Compatibilizing effect of starch‐grafted‐poly(L‐lactide) on the poly(ε‐caprolactone)/starch composites

The poly(ε‐caprolactone) (PCL)/starch blends were prepared with a coextruder by using the starch grafted PLLA copolymer (St‐g‐PLLA) as compatibilizers. The thermal, mechanical, thermo‐mechanical, and morphological characterizations were performed to show the better performance of these blends compared with the virgin PCL/starch blend without the compatibilizer. Interfacial adhesion between PCL matrix and starch dispersion phases dominated by the compatibilizing effects of the St‐g‐PLLA copolymers was significantly improved. Mechanical and other physical properties were correlated with the compatibilizing effect of the St‐g‐PLLA copolymer. With the addition of starch acted as rigid filler, the Young's modulus of the PCL/starch blends with or without compatibilizer all increased, and the strength and elongation were decreased compared with pure PCL. Whereas when St‐g‐PLLA added into the blend, starch and PCL, the properties of the blends were improved markedly. The 50/50 composite of PCL/starch compatibilized by 10% St‐g‐PLLA gave a tensile strength of 16.6 MPa and Young's modulus of 996 MPa, respectively, vs. 8.0 MPa and 597 MPa, respectively, for the simple 50/50 blend of PCL/starch. At the same time, the storage modulus of compatibilized blends improved to 2940 MPa. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of the compatibility on dielectric performance and breakdown strength of poly(vinylidene fluoride)/low‐density polyethylene blends

Immiscible polymer blends with high dielectric constant (ε) and improved breakdown strength (E_b) performance were obtained by composing poly(vinylidene fluoride) (PVDF) with low‐density polyethylene (LDPE) or the LDPE grafted with maleic anhydride (LDPE‐g‐MAH) through melt‐blending way. The dielectric properties of these blends were emphasized for considering the compatibility effect on the energy storage application. Interface morphology, co‐continuity behavior, and grafted ratio were simultaneously investigated to detect the compatibility enhancement after introducing MAH. Results showed that the MAH positively improved the dielectric properties. Both the measured E_b of PVDF/LDPE and PVDF/LDPE‐g‐MAH blends showed a minimum value at v^PVDF = 50 vol % because of the worst compatibility; meanwhile, higher E_b of PVDF/LDPE‐g‐MAH than that of PVDF/LDPE blend was observed owing to the better compatibility. For considering the effect interface morphology on the dielectric performance, layer‐structure films composing with pure PVDF and LDPE layers were further constructed and studied. It was revealed that the layered structure could be treated as a helpful way to improve ε and E_b for immiscible polymer blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42507.     

Specific interactions in 4‐hydroxybenzoic acid/poly(2‐vinylpyridine)/poly(N‐vinyl‐2‐pyrrolidone) blends

The specific interactions in ternary 4‐hydroxybenzoic acid (HBA)/poly(2‐vinylpyridine) (P2VPy)/poly(N‐vinyl‐2‐pyrrolidone) (PVP) blends were studied by differential scanning calorimetry, Fourier transform infrared (FTIR) spectroscopy, and electron microscopy. FTIR study shows the existence of hydrogen‐bonding interactions between HBA and P2VPy as well as PVP. The addition of a sufficiently large amount of HBA produces a blend showing one glass‐transition temperature (T_g). Microscopic study shows a drastic reduction in domain size in single‐T_g blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 901–907, 2001     

Thermal decomposition behavior of γ‐irradiated poly(vinyl acetate)/poly(methyl methacrylate) miscible blends

Miscible polymer blends based on various ratios of poly(vinyl acetate) (PVAc) and poly(methyl methacrylate) (PMMA) were prepared in film form by the solution casting technique using benzene as a common solvent. The thermal decomposition behavior of these blends and their individual homopolymers before and after γ‐irradiation at various doses (50–250 kGy) was investigated. The thermogravimetric analysis technique was utilized to determine the temperatures at which the maximum value of the rate of reaction (T_max) occurs and the kinetic parameters of the thermal decomposition. The rate of reaction curves of the individual homopolymers or their blends before or after γ‐ irradiation displayed similar trends in which the T_max corresponding to all polymers was found to exist in the same position but with different values. These findings and the visual observations of the blend solutions and the transparency of the films gave support to the complete miscibility of these blends. Three transitions were observed along the reaction rate versus temperature curves; the first was around 100–200°C with no defined T_max, which may arise from the evaporation of the solvent. The second T_max was in the 340–380°C range, which depended on the polymer blend and the γ‐irradiation condition. A third transition was seen in the rate of reaction curves only for pure PVAc and its blends with PMMA with ratios up to 50%, regardless of γ‐ irradiation. We concluded that γ‐irradiation improved the thermal stability of PVAc/PMMA blends, even though the PMMA polymer was degradable by γ irradiation. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1773–1780, 2006     

Synthesis and characterization of biodegradable poly(ester‐urethanes) based on bacterial poly(R‐3‐hydroxybutyrate)

A series of poly(R‐3‐hydroxybutyrate)/poly(ε‐caprolactone)/1,6‐hexamethylene diisocyanate‐segmented poly(ester‐urethanes), having different compositions and different block lengths, were synthesized by one‐step solution polymerization. The molecular weight of poly(R‐3‐hydroxybutyrate)‐diol, PHB‐diol, hard segments was in the range of 2100–4400 and poly(ε‐caprolactone)‐diol, PCL‐diol, soft segments in the range of 1080–5800. The materials obtained were investigated by using differential scanning calorimetry, wide angle X‐ray diffraction and mechanical measurements. All poly(ester‐urethanes) investigated were semicrystalline with T_m varying within 126–148°C. DSC results showed that T_g are shifted to higher temperature with increasing content of PHB hard segments and decreasing molecular weight of PCL soft segments. This indicates partial compatibility of the two phases. In poly(ester‐urethanes) made from PCL soft segments of molecular weight (M_n ≥ 2200), a PCL crystalline phase, in addition to the PHB crystalline phase, was observed. As for the mechanical tensile properties of poly(ester‐urethane) cast films, it was found that the ultimate strength and the elongation at the breakpoint decrease with increasing PHB hard segment content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 703–718, 2002