氯化聚丙撑碳酸酯增容聚丙撑碳酸酯/秸秆粉复合材料的制备及性能

聚丙撑碳酸酯(PPC)是一种新型热塑性生物降解材料,但其热性能及力学性能较差,应用受到限制。以秸秆粉这种农作物副产品作为增强体改性PPC,既可以提高PPC的力学性能同时又可开发利用秸秆资源。氯化聚丙撑碳酸酯(CPPC)是聚丙撑碳酸酯(PPC)经过氯化得到的,对天然纤维表面具有良好的浸润性和粘结性。本文以CPPC为增容剂,通过熔融共混法制备了PPC/秸秆粉复合材料。采用扫描电子显微镜(SEM)、拉伸实验、动态力学性能测试(DMA)及转矩流变仪对复合材料的结构及性能进行了表征,重点考察了CPPC的添加量对复合材料力学和流变性能的影响。结果表明,当CPPC质量分数为1.8%时,可使添加质量分数为30%秸秆粉的PPC复合材料拉伸强度提高38%,模量提高30%。同时,CPPC的引入使复合材料的粘度下降,改善了PPC/秸秆粉复合材料的加工性能。因此,作为增容剂的CPPC为制备高性能PPC/天然纤维复合材料提供了新的解决办法。     

Thermal behavior and intermolecular interactions in blends of poly(3‐hydroxybutyrate) and maleated poly(3‐hydroxybutyrate) with chitosan

The thermal behavior and intermolecular interactions of blends of poly(3‐hydroxybutyrate) (PHB) and maleated PHB with chitosan were studied with differential scanning calorimetry, Fourier transform infrared (FTIR), wide‐angle X‐ray diffraction (WAXD), and X‐ray photoelectron spectroscopy (XPS). The differences in the two blend systems with respect to their thermal behavior and intermolecular interactions were investigated. The melting temperatures, melting enthalpies, and crystallinities of the two blend systems gradually decreased as the chitosan content in the blends increased. Compared with that of the PHB component with the same composition, the crystallization of the maleated PHB component was more intensively suppressed by the chitosan component in the blends because of the rigid chitosan molecular chains and the intermolecular hydrogen bonds between the components. FTIR, WAXD, and XPS showed that the intermolecular hydrogen bonds in the blends were caused by the carbonyls of PHB or maleated PHB and chitosan aminos, and their existence depended on the compositions of the blends. The introduction of maleic anhydride groups onto PHB chains promoted intermolecular interactions between the maleated PHB and chitosan components. In addition, the intermolecular interactions disturbed the original crystal structures of the PHB, maleated PHB, and chitosan components; this was further proven by WAXD results. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 35–47, 2005     

Compatibility and thermal properties of poly(3‐hydroxybutyrate)/poly(glycidyl methacrylate) blends

Poly(3‐hydroxybutyrate) (PHB)/poly(glycidyl methacrylate) (PGMA) blends were prepared by a solution‐precipitation procedure. The compatibility and thermal decomposition behavior of the PHB/PGMA blends was studied with differential scanning calorimetry, thermogravimetric analysis, and differential thermal analysis (DTA). The blends were immiscible in the as‐blended state, but for the blends with PGMA contents of 50 wt % or more, the compatibility was dramatically changed after 1 min of annealing at 200 °C. In addition, PHB/PGMA blends showed higher thermal stability, as measured by maximum decomposition temperatures and residual weight during thermal degradation. This was probably due to crosslinking reactions of the epoxide groups in the PGMA component with the carboxyl chain ends of PHB fragments during the degradation process, and the occurrence of such reactions can be assigned to the exothermic peaks in the DTA thermograms. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 351–358, 2002     

Electrospun fiber mats of poly(3‐hydroxybutyrate), poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate), and their blends

Electrospinning of poly(3‐hydroxybutyrate) (PHB), poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), and their blends was first carried out in chloroform at 50 °C on a stationary collector. The average diameter of the as‐spun fiber from PHB and PHBV solutions decreased with increasing collection distance and increased with increasing solution concentration and applied electrical potential. In all of the spinning conditions investigated, the average diameter of the as‐spun pure fibers ranged between 1.6 and 8.8 μm. Electrospinning of PHB, PHBV, and their blends was carried out further at a fixed solution concentration of 14% w/v on a homemade rotating cylindrical collector. Well‐aligned, cross‐sectionally round fibers without beads were obtained. The average diameter of the as‐spun pure and blend fibers ranged between 2.3 and 4.0 μm. The as‐spun fiber mats appeared to be more hydrophobic than the corresponding films and much improvement in the tensile strength and the elongation at break was observed for the blend fiber mats over those of the pure fiber ones. Lastly, indirect cytotoxicity evaluation of the as‐spun pure and blend fiber mats with mouse fibroblasts (L929) indicated that these mats posed no threat to the cells. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2923–2933, 2006     

Compatibilizing effect of a graft copolymer on bacterial poly(3‐hydroxybutyrate)/poly(methyl methacrylate) blends

Blends of isotactic (natural) poly(3‐hydroxybutyrate) (PHB) and poly(methyl methacrylate) (PMMA) are partially miscible, and PHB in excess of 20 wt % segregates as a partially crystalline pure phase. Copolymers containing atactic PHB chains grafted onto a PMMA backbone are used to compatibilize phase‐separated PHB/PMMA blends. Two poly(methyl methacrylate‐g‐hydroxybutyrate) [P(MMA‐g‐HB)] copolymers with different grafting densities and the same length of the grafted chain have been investigated. The copolymer with higher grafting density, containing 67 mol % hydroxybutyrate units, has a beneficial effect on the mechanical properties of PHB/PMMA blends with 30–50% PHB content, which show a remarkable increase in ductility. The main effect of copolymer addition is the inhibition of PHB crystallization. No compatibilizing effect on PHB/PMMA blends with PHB contents higher than 50% is observed with various amounts of P(MMA‐g‐HB) copolymer. In these blends, the graft copolymer is not able to prevent PHB crystallization, and the ternary PHB/PMMA/P(MMA‐g‐HB) blends remain crystalline and brittle. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1390–1399, 2002     

Influence of multiple processing on selected properties of poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate)

The effect of multiple (up to 10 times) injection molding of processed poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P(3,4HB)) on its phase transition temperatures, degree of crystallinity, degradation temperature, mass flow rate, mechanical properties, dynamic mechanical properties, and Charpy's impact strength is presented. The studies have shown that the multiple injection lowers the degree of crystallinity and the thermal stability of P(3,4HB). The mass flow rate values increased with increasing the injection number. It was found that the multiple injections had no substantial effect on the tensile strength up to 10 injection cycles and the tensile strength at break, tensile strain at tensile strength, and tensile strain at break up to 6 injection cycles. The maximum value of storage modulus at 30 °C and impact strength were recorded for sample after 4 cycles of injection, while the values of storage modulus at 120 °C increased with increase of the injection cycles. Copyright © 2015 John Wiley & Sons, Ltd.     

Antibacterial poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) fibrous membranes containing quaternary ammonium salts

In this study, antimicrobial membranes based on biodegradable material poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) [P(3HB‐4HB)] and quaternary ammonium salts (QASs) by two methods have been performed. Three QASs with varied alkyl chain lengths have been synthesized successfully and characterized by ¹H nuclear magnetic resonance and Fourier transform infrared. The synthesized QASs were blended with P(3HB‐4HB) and electrospun into composite fibrous membranes or casted into conventional membranes. Electrospun fibrous membranes with large surface areas are a superior type of antimicrobial biomaterials, and they exhibit preferable properties than solution casting membranes. Specifically, electrospun fibrous membranes are tougher and can inactivate both Gram‐positive Staphylococcus aureus and Gram‐negative Escherichia coli O157:H7 in a contact time of 30 min, whereas the solution casting membranes cannot. The length of alkyl chain in the quaternary ammonium groups on the modified P(3HB‐4HB) membranes is able to influence the antimicrobial activity. This type of antimicrobial material may have potential applications in biomaterial field. Copyright © 2016 John Wiley & Sons, Ltd.     

Impact of cellulose nanocrystal aspect ratio on crystallization and reinforcement of poly(butylene adipate‐co‐terephthalate)

Cellulose nanocrystals (CNCs) are appealing nanomaterials for the reinforcement of polymeric materials. It is now well established that high mechanical properties are obtained when preparing the nanocomposite by casting/evaporation methods and using CNC contents above the percolation threshold. This phenomenon results from the formation of a stiff CNC network within the matrix meaning that the properties of the matrix play only a limited role on the mechanical properties of the material when the matrix is in the rubbery state. In subpercolation concentration or when using a different processing technique, the level of understanding is less clear, mainly when the CNC‐induced crystallization of the matrix interferes with the reinforcing mechanism. In this study, we used CNCs with different aspect ratios to prepare nanocomposites by extrusion with polybutyrate adipate terephthalate as matrix. The impact of CNC on the crystallinity of the matrix and mechanical properties of the nanocomposite has been investigated. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2284–2297     

Effect of poly(vinyl alcohol) fine particles as a novel biodegradable nucleating agent on the crystallization of poly(3‐hydroxybutyrate)

The effect of poly(vinyl alcohol)(PVA) fine particles as the nucleating agent on the crystallization behavior of bacterial poly(3‐hydroxybutyrate)(PHB) was studied using differential scanning calorimetry measurements and polarized light microscope observation. The results were compared with the effect of PVA conventionally blended with PHB. The PVA fine particles were found to be able to greatly enhance the crystallization of PHB, while the conventionally blended PVA extremely retarded the crystallization of PHB. The nucleating effect of PVA fine particles is almost comparable to that of the talc powder. Considering the biodegradability and biocompatibility of PVA, the usage of PVA particle as a nucleating agent provides marked benefits over the currently employed nonbiodegradable nucleating agents, such as talc and boron nitride. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44:1813–1820, 2006     

Effect of aging on fractional crystallization of poly(ethylene oxide) component in poly(ethylene oxide)/poly(3‐hydroxybutyrate) blends

The effect of aging on the fractional crystallization of the poly(ethylene oxide) (PEO) component in the PEO/poly(3‐hydroxybutyrate) (PHB) blend has been investigated. The partial miscibility of the PEO/PHB blends with high PEO molecular weight (M_v = 2.0 × 10⁵ g/mol) was confirmed by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis. The fractional crystallization behavior of the PEO component in the PEO/PHB blends with low PEO content (not more than 30 wt% of PEO), before and after aging under vacuum at 25 °C for 6 months, were compared by DSC, fourier transform infrared microscopic spectroscopy, small angle X‐ray diffraction, and scanning electron microscopy. It was confirmed that nearly all the PEO components remain trapped within interlamellar regions of PHB for the PEO/PHB blends before aging. Under this condition, the crystallization of PEO is basically induced by much less active heterogeneities or homogeneous nucleation at high supercoolings. While, after the same PEO/PHB samples were stored at 25 °C in vacuum for 6 months, a part of the PEO component was expelled from the interlamellar region of PHB. Under this condition, the expelled PEO forms many separate domains with bigger size and crystallizes at low supercoolings by active heterogeneous nucleation, whereas the crystallization of PEO in the interlamellar region is still mainly induced by less active heterogeneities or homogeneous nucleation at extreme supercoolings. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2665–2676, 2005     

Poly[(R)‐3‐hydroxybutyrate)]/poly(styrene) blends compatibilized with the relevant block copolymer

A novel triblock copolymer PS–PHB–PS based on the microbial polyester Poly[(R)‐3‐hydroxybutyrate)] (PHB) and poly(styrene) (PS) was prepared to be used as compatibilizer for the corresponding PHB/PS blends. It was prepared in a three‐step procedure consisting of (i) transesterification reaction between ethylene glycol and a high‐molecular‐weight PHB, (ii) synthesis of bromo‐terminated PHB macroinitiator, and (iii) atom transfer radical polymerization polymerization of styrene initiated by the PHB‐based macroinitiator. Fourier transform infrared, gel permeation chromatography, ¹H‐, and ¹³C‐NMR spectroscopies were used to determine the molecular structure and/or end‐group functionalities at each step of the procedure. Although thermogravimetric analysis showed that the block copolymer underwent a stepwise thermal degradation and had better thermal stability than their respective homopolymers, differential scanning calorimetry displayed that the PHB block in the copolymer could not crystallize, and thus generating a total amorphous structure. Atomic force microscopy images indicated that the block copolymer was phase segregated in a well‐defined morphological structure with nanodomain size of ～40 nm. Contact angle measurements proved that the wettability properties of the block copolymer were in between those of the PHB and PS homopolymers. Blends analyzed for their morphology and thermal properties showed good miscibility and had well‐defined morphological features. Polymer blends exhibited lower crystallinity and decreased stiffness which was proportional to the amount of compatibilizer content in the blends. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Thermal memory of poly(3‐hydroxybutyrate) using temperature‐modulated differential scanning calorimetry

The influence of thermal history on morphology, melting, and crystallization behavior of bacterial poly(3‐hydroxybutyrate) (PHB) has been investigated using temperature‐modulated DSC (TMDSC), wide‐angle X‐ray diffraction (WAXRD) and polarized optical microscopy (POM). Various thermal histories were imparted by crystallization with continuous and different modulated cooling programs that involved isoscan and cool–heat segments. The subsequent melting behavior revealed that PHB experienced secondary crystallization during heating and the extent of secondary crystallization varied with the cooling treatment. PHB crystallized under slow, continuous, and moderate cooling rates were found to exhibit double melting behavior due to melting of TMDSC scan‐induced secondary crystals. PHB underwent considerable secondary crystallization/annealing that took place under modulated cooling conditions. The overall melting behavior was interpreted in terms of recrystallization and/or annealing of crystals. Interestingly, the PHB analyzed by temperature modulation programs showed a broad exotherm before the melting peak in the nonreversing heat capacity curve and a multiple melting reversing curve, verifying that the melting–recrystallization and remelting process was operative. WAXRD and POM studies supported the correlations from DSC and TMDSC results. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 70–78, 2006     

Isothermal crystallization kinetics of poly(3‐hydroxybutyrate)/layered double hydroxide nanocomposites

Poly(3‐hydroxybutyrate) (PHB)/layered double hydroxides (LDHs) nanocomposites were prepared by mixing PHB and poly(ethylene glycol) phosphonates (PEOPAs)‐modified LDH (PMLDH) in chloroform solution. Both X‐ray diffraction data and TEM micrographs of PHB/PMLDH nanocomposites indicate that the PMLDHs are randomly dispersed and exfoliated into the PHB matrix. In this study, the effect of PMLDH on the isothermal crystallization behavior of PHB was investigated using a differential scanning calorimeter (DSC) and polarized optical microscopy. Isothermal crystallization results of PHB/PMLDH nanocomposites show that the addition of 2 wt % PMLDH into PHB induced more heterogeneous nucleation in the crystallization significantly increasing the crystallization rate and reducing their activation energy. By adding more PMLDH into the PHB probably causes more steric hindrance of the diffusion of PHB, reducing the transportation ability of polymer chains during crystallization, thus increasing the activation energy. The correlation among crystallization kinetics, melting behavior and crystalline structure of PHB/PMLDH nanocomposites can also be discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3337–3347, 2006     

Blends of poly(3‐hydroxybutyrate)/4,4′‐thiodiphenol and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/ 4,4′‐thiodiphenol: Specific interaction and properties

The specific interaction between poly(3‐hydroxybutyrate) [P(3HB)] and 4,4′‐thiodiphenol (TDP) and between poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) and TDP was investigated by Fourier transform infrared (FTIR) spectroscopy. Interassociated hydrogen bonds were found between the polyester chains and the TDP molecules in the binary blends. The fractions of associated carbonyl groups, F_b 's, in the blends first increased and then decreased as the TDP content increased. The thermal and dynamic mechanical properties of P(3HB)–TDP and PHBV–TDP blends were investigated by differential scanning calorimetry and dynamic mechanical thermal analysis, respectively. Thermal analysis revealed that the P(3HB)–TDP blends possessed eutectic phase behavior. Furthermore, it was found that the thermal and dynamic mechanical properties of P(3HB) and PHBV were greatly modified through blending with TDP. Environmental degradability in river water was evaluated by a biochemical oxygen demand tester, and it was clarified that TDP lowered the degradation rate of P(3HB). The results suggest that TDP is effective in modifying the physical properties as well as the biodegradability of polyesters. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2891–2900, 2000     

Nonisothermal crystallization and melting behavior of poly(β‐hydroxybutyrate)–Poly(vinyl‐acetate) blends

Nonisothermal crystallization and melting behavior of poly(β‐hydroxybutyrate) (PHB)–poly(vinyl acetate) (PVAc) blends from the melt were investigated by differential scanning calorimetry using various cooling rates. The results show that crystallization of PHB from the melt in the PHB–PVAc blends depends greatly upon cooling rates and blend compositions. For a given composition, the crystallization process begins at higher temperatures when slower scanning rates are used. At a given cooling rate, the presence of PVAc reduces the overall PHB crystallization rate. The Avrami analysis modified by Jeziorny and a new method were used to describe the nonisothermal crystallization process of PHB–PVAc blends very well. The double‐melting phenomenon is found to be caused by crystallization during heating in DSC. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 443–450, 1999     

Thermal degradation kinetics of biodegradable poly(3‐hydroxybutyrate)/layered double hydroxide nanocomposites

The thermal degradation behaviors of biodegradable poly(3‐hydroxybutyrate) (PHB) and PHB/poly(ethylene glycol) phosphonates (PEOPAs)‐modified layered double hydroxide (PMLDH) nanocomposites have been investigated using thermogravimetric analysis. Effects of PMLDH contents on the isothermal degradation kinetics of PHB were explored. These experimental results show that the degradation kinetics of PHB/PMLDH nanocomposites is the chain‐scission process of cyclic β‐elimination reaction with the following autocatalytic reactions, which is very similar to that of pure PHB matrix. Further calculated data based on the autocatalytic model can fit very well with the experimental data. The E_a value of PHB/PMLDH nanocomposites is increased as the content of PMLDH increases. This can be attributed to the incorporation of more PMLDH loading to PHB induced a decrease in the degradation rate and an increase in the residual weight for PHB/PMLDH nanocomposites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1207–1213, 2008     

Crystallization and morphology of poly(vinylidene fluoride)/poly(3‐hydroxybutyrate) blends. II. Morphology and crystallization kinetics by time resolved X‐ray scattering

The development of the morphology in poly(vinylidene fluoride)/poly(3‐hydroxybutyrate) (PVDF/PHB) blends upon isothermal and anisothermal crystallization is investigated by time‐resolved small‐ and wide‐angle X‐ray scattering. The components are completely miscible in the melt but crystallize separately; they crystallize stepwise at different temperatures or sequentially with isothermal or anisothermal conditions, respectively. The PVDF crystallizes undisturbed whereas PHB crystallizes in a confined space that is determined by the existing supermolecular structure of the PVDF. The investigations reveal that composition inhomogeneities may initially develop in the remaining melt or in the amorphous phases of the PVDF upon crystallization of that component. The subsequent crystallization of the PHB depends on these heterogeneities and the supermolecular structure of PVDF (dendritically or globularly spherulitic). PHB may form separate spherulites that start to grow from the melt, or it may develop “interlocking spherulites” that start to grow from inside a PVDF spherulite. Occasionally, a large number of PVDF spherulites may be incorporated into PHB interlocking spherulites. The separate PHB spherulites may intrude into the PVDF spherulites upon further growth, which results in “interpenetrating spherulites.” Interlocking and interpenetrating are realized by the growth of separate lamellar stacks (“fibrils”) of the blend components. There is no interlamellar growth. The growth direction of the PHB fibrils follows that of the existing PVDF fibrils. Depending on the distribution of the PHB molecules on the interlamellar and interfibrillar PVDF regions, the lamellar arrangement of the PVDF may contract or expand upon PHB crystallization and the adjacent fibrils of the two components are linked or clearly separated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 974–985, 2004     

Tuning the localization of finely dispersed cellulose nanocrystal in poly (lactic acid)/bio‐polyamide11 blends

A versatile approach to control the localization of cellulose nanocrystal (CNC) in PLA/PA11 blends is presented. A PEO/CNC mixture with a high level of CNC dispersion is prepared through a combination of high pressure homogenization and freeze‐drying. The prepared PEO/CNC mixture is then incorporated into the PLA/PA11 blends using two different strategies. Typically for CNC/PLA/PA11, the CNCs selectively localize in PA11. However, PEO‐coated CNC particles segregate into PLA irrespective of whether the PEO/CNC mixture is premixed with PLA or PA11. It is suggested that a strong interaction between PEO and CNC particles combined with the PLA/PEO miscibility facilitates the localization of PEO‐coated CNC in the PLA. The localization of PEO‐coated CNC in the PLA has no effect on the morphology of the PLA‐5PEO/PA11 with matrix/dispersed phase form. However, 2 wt % PEO‐coated CNC in the co‐continuous (PLA‐5PEO)/PA11 50/50 vol % blend diminishes the phase thickness from 11 ± 1 to 4 ± 1.5 μm. This is attributed to a retarded relaxation of the PLA phase. This work outlines a strategy to control the CNC localization into a given polymeric phase in a binary polymer–polymer mixture. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 576–587