Synthesis and characterization of maleated poly(3‐hydroxybutyrate)

Graft copolymerization of maleic anhydride (MA) onto poly(3‐hydroxybutyrate) (PHB) was carried out by use of benzoyl peroxide as initiator. The effects of various polymerization conditions on graft degree were investigated, including solvents, monomer and initiator concentrations, reaction temperature, and time. The monomer and initiator concentrations played an important role in graft copolymerization, and graft degree could be controlled in the range from 0.2 to 0.85% by changing the reaction conditions. The crystallization behavior and the thermal stability of PHB and maleated PHB were studied by DSC, WAXD, optical microscopy, and TGA. The results showed that, after grafting MA, the crystallization behavior of PHB was obviously changed. The cold crystallization temperature from the glass state increased, the crystallization temperature from the melted state decreased, and the growth rate of spherulite decreased. With the increase in graft degree, the banding texture of spherulites became more distinct and orderly. Moreover, the thermal stability of maleated PHB was obviously improved, compared with that of pure PHB. Its thermal decomposition temperature was enhanced by about 20°C. In addition, the introduction of the MA group promoted the biodegradability of PHB. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 659–668, 2003     

GRAFT COPOLYMERIZATION OF POLYPROPYLENE COPOLYMER WITH MALEIC ANHYDRIDE: EFFECT OF GRAFTING ON THERMAL,MECHANICAL PROPERTIES,AND PAINTABILITY

Graft copolymerization of polypropylene copolymer (PCP) with maleic anhydride (MA) was studied in melt in Brabender Plasticorder, Twin Screw Extruder by using peroxide initiators, such as benzoyl peroxide (BPO), lauryl peroxide (LPO), luperox-101 (LPU), and dicumyl peroxide (DCP). The variation of MA and initiator concentrations on percent grafting (G), melt flow index (MFI), torque, and gel formation was investigated. Graft copolymers (PgMA and PgMAT) were characterized by FT-IR, DSC, and TGA. Melt flow index increased and torque values decreased with an increase in initiator concentration. The increase in MFI values are in the order: DCP>LUP>BP0>LPO. Maximum chain scission was observed by using DCP and LUP as indicated by their MFI values. The incorporation of MA in PgMA and PgMAT was confirmed by the presence of carbonyl groups at 1712 cm^?1 and a shift in crystallization peak temperature from 113 to 123°C due to nucleating effect of the poly(maleic anhydride). The thermal stability was increased by the presence of PgMA. Addition of PgMAT as an additive to PCP, PCP/PP, and amines improves mechanical properties and paintability. Primary amines are more reactive towards PgMAT compared to tertiary amines.     

Improved thermal stability and mechanical properties of poly(propylene carbonate) by reactive blending with maleic anhydride

To extend the application of a carbon dioxide sourced environmental friendly polymer: poly (propylene carbonate) (PPC), a small amount of maleic anhydride (MA) was melt blended to end‐cap with PPC to improve its thermal stability and mechanical properties. Thermal and mechanical properties of end‐capped PPC were investigated by TGA, GPC, mechanical test, and DMA. TGA and titration results demonstrate that PPC can be easily end‐capped with MA through simple melt blending. TGA results show that the thermal degradation temperature of PPC could be improved by around 140°C by adding MA. GPC measurement indicates that the molecular weight of PPC can be maintained after blending with MA, where pure PPC experiences a dramatic degradation in molecular weight during melt process. More importantly, the tensile strength of PPC after blending with MA was found to be nearly eight times higher than that of pure PPC. It has approached the mechanical properties of polyolefin polymers, indicating the possibility of replacing polyolefin polymers with PPC for low temperature applications. The method described here could be used to extend the applications of PPC and fight against the well known global warming problem. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Structure and properties of polypropylene/clay nanocomposites compatibilized by solid‐phase grafted polypropylene

Polypropylene/organic‐montmorillonite (PP/OMMT) nanocomposites were prepared via a solid‐phase PP graft (TMPP) with a higher grafting level as the compatibilizer. The effects of the compatibilizer on the structure and properties of PP/OMMT nanocomposites were investigated. The structure of the nanocomposites were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that when the weight ratio of TMPP and OMMT is greater than 1:1, the OMMT can be dispersed in PP matrix uniformly at the nanoscale. The mechanical properties of the nanocomposites reached a maximum when the weight ratio of TMPP and OMMT is 1:1, although more uniform dispersion was achieved at a higher content of TMPP. The mechanical properties of the nanocomposites decrease with the content of TMPP. The crystallization behavior, dynamic rheological property, and thermal stability of the nanocomposites were investigated by differential scanning calorimetry (DSC), dynamic rheological analysis, and thermal gravimetric analysis (TGA), respectively. Due to the synergistic effects of TMPP and OMMT on the crystallization of PP, the crystallization peak temperature of the nanocomposites increased remarkably compared with that of the neat PP. TMPP shows β‐phase nucleating ability and OMMT promotes the development of β‐phase crystallite. The nanocomposites show restricted melt flow and enhanced temperature sensitivity compared with the neat PP. The thermal stability of the nanocomposites is obviously improved compared with that of the neat PP. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers.     

Synthesis and thermal characterization of poly(ester-ether urethane)s based on PHB and PCL-PEG-PCL blocks

A series of block poly(ester-ether urethane)s, poly(PHB/PCL-PEG-PCL), based on poly(3-hydroxybutyrate) (PHB-diol), as hard segments, and poly(ε-caprolactone)-b-poly(ethylene glycol)-b-poly(ε-caprolactone), (PCL-PEG-PCL) triblock copolydiol, as soft segments, were prepared using 1,6-hexamethylene diisocyanate (HDI), as non-toxic connecting agent. Polyurethanes block copolymer was synthesized from bacterial PHB and PCL-PEG-PCL blocks. The chemical structure and molecular weights of polymers prepared were characterized by FTIR, ¹H NMR and GPC. The effect of chemical structure on the thermal and mechanical properties was studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile testing. The DSC results revealed that poly(PHB/PCL-PEG-PCL) urethanes are semi-crystalline with two crystallizable PHB and PCL-PEG-PCL blocks. The thermal stability of the urethanes is less than neat PHB. The results of tensile testing showed that the extensibility of PHB is largely enhanced by the incorporation of PCL-PEG-PCL soft segments. Activation energy E _a , as a kinetic parameter of thermal decomposition, was estimated by each of the Ozawa and Kissinger methods. Close values of activation energy were obtained by both methods. The swelling behaviour of the copolymers was also investigated.     

Miscibility,thermal behaviour,morphology and mechanical properties of binary blends of poly[(R)‐3‐hydroxybutyrate] with poly(γ‐benzyl‐L‐glutamate)+

The miscibility, thermal behaviour, morphology and mechanical properties of poly[(R)‐3‐hydroxybutyrate] (PHB) with poly(γ‐benzyl‐L ‐glutamate) (PBLG) are investigated by means of differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and tensile tests. The DSC results show that PHB and PBLG are immiscible in the melt state. Such immiscibility also exists in the amorphous state due to a clear two‐phase separated structure observed by SEM measurements. The blend samples with different thermal history, namely as original and melt samples separately, display differences in thermal behaviour such as the DSC scan profile, the crystallinity and the melting temperature of PHB. The crystallization of PHB both from the molten state and the amorphous state is retarded on addition of the second component. The SEM measurements reveal that a phase inversion occurs between the PHB/PBLG (60/40) and PHB/PBLG (40/60) blends. Except for the PHB/PBLG (40/60) blend, a microphase separated structure is observed for all blend compositions. The mechanical properties vary considerably with blend composition. Compared with pure components, the PHB/PBLG (20/80) blend shows a certain improvement in mechanical properties. © 2001 Society of Chemical Industry     

Melt grafting of vinyltrimethoxysilane and water crosslinking of polypropylene/ethylene-propylene diene terpolymer blends

The melt grafting of vinyltrimethoxysilane (VTMS) onto polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM) blends was studied. The effect of VTMS, EPDM and initiator concentrations on mechanical properties, melt flow index (MFI) and gel content of the modified PP/EPDM samples were investigated. The influence of coagents, i.e. styrene and trimethylolpropane trimethacrylate was also studied. Scanning electron microscopy (SEM) was used to observe the fractured surface of PP/EPDM and the modified PP/EPDM blends. The VTMS grafting reaction was in situ monitored using differential scanning calorimetry (DSC). Moreover, the thermal and crystallization behavior of VTMS-crosslinked PP/EPDM blends were studied by thermogravimetric analysis (TG) and DSC, respectively. It had been found that the thermal stability of VTMS-crosslinked PP/EPDM was improved. DSC measurements showed that the grafting reaction occurs from 170 to 220 °C and the crystallization temperatures increased compared with those of the untreated PP/EPDM.     

几种茂金属线性低密度聚乙烯的结构与性能研究

采用红外光谱(IR)、凝胶渗透色谱(GPC)、差示扫描量热分析(DSC)和热失重分析(TGA)等方法分析了传统线性低密度聚乙烯(LLDPE1和LLDPE2)、茂金属线性低密度聚乙烯(m-LLDPE)和茂金属聚乙烯(m-PE)在结构上、相对分子质量分布上、结晶性能和热稳定性上的差异,并测试了其流动性能和拉伸性能。研究结果表明,m-LLDPE与其它产品相比在结构上存在着差异,其具有不同的几何构型,且相对分子质量分布较窄,而LLDPE与m-LLDPE相比则相对分子质量分布宽,且有拖尾现象;m-LLDPE的结晶性能、拉伸性能及热稳定性与传统的LLDPE相比都极其优越。     

Polypropylene nanocomposite film: A critical evaluation on the effect of nanoclay on the mechanical,thermal, and morphological behavior

Polypropylene (PP)/clay nanocomposites prepared by melt blending technique using different percentages of clay with and without maleic anhydride grafted PP (MA‐PP) were studied. The intercalated and exfoliated structure of nanocomposites was characterized by X‐Ray Diffraction (XRD) and transmission electron microscopy (TEM). Because of the typical intercalated and exfoliated structure, the tensile modulus of the nanocomposites were improved significantly as compared to virgin PP. The viscoelastic behavior of the nanocomposites was studied by dynamical mechanical analysis (DMA) and the results showed that with the addition of treated clay to PP there was substantial improvement in storage modulus increases. The thermal stability and crystallization of the PP nanocomposites as studied by differential scanning calorimeter (DSC) and thermo gravimetric analysis (TGA) were also improved significantly compared to PP. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polyoxymethylene/polyurethane/alumina ternary composites: Structure,mechanical, thermal and dielectric properties

Ternary composites composed of polyoxymethylene (POM), polyurethane (PU), and boehmite alumina were produced by melt blending with and without latex precompounding. Latex precompounding served for the predispersion of the alumina particles. The related masterbatch (MB) was produced by mixing the PU latex with water‐dispersible boehmite alumina. The dispersion of the alumina was studied by transmission and scanning electron microscopy techniques (TEM and SEM, respectively) and discussed. The crystallization of POM was inspected by means of differential scanning calorimetry (DSC) and polarized optical microscopy (DSC and polarized light microscopy, respectively). The mechanical and thermomechanical properties of the composites were determined in uniaxial tensile, dynamic‐mechanical thermal analysis (DMTA), short‐time creep tests (performed at various temperatures), and thermogravimetric analysis (TGA). The melt flow of the composites was characterized in a plate/plate rheometer. In addition, the dielectric response of the nanocomposites was investigated by means of broadband dielectric spectroscopy at an ambient temperature. The composites produced by the MB technique outperformed the direct melt (DM) compounded composites in respect to the thermal and mechanical characteristics. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Crystallization behavior of poly(lactide)/poly(β‐hydroxybutyrate)/talc composites

The morphology and miscibility of commercial poly(lactide) (PLA)/poly(β‐hydroxybutyrate) (PHB, from 5 to 20 wt %) blends prepared by melt extrusion method, were investigated using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) observations. The results show that for all the studied blend contents, PLA/PHB blends are immiscible. The effects of PHB and talc on the nonisothermal cold crystallization kinetics of PLA were examined using a differential scanning calorimetry (DSC) at different heating rates. PHB acted as a nucleating agent on PLA and the addition of talc to the blend yielded further improvement, since significant increase in the enthalpy peak was observed for samples containing 10 wt % PHB and talc (from 0.5 to 5 phr). The crystallization kinetics were then examined using the Avrami–Jeziorny and Liu–Mo approach. The simultaneous presence of PHB and talc induced a decrease of the crystallization half time. The evolution of activation energies determined with Kissinger's equation suggests that blending with PHB and incorporating talc promote nonisothermal cold crystallization of PLA. The synergistic nucleating effect of PHB and talc was also observed on isothermal crystallization of PLA from the melt. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Improvement of physical properties of poly(glycerol sebacate) by copolymerization with polyhydroxybutyrate-diols

The characterizations and physical properties of elastomeric poly(glycerol sebacate) (PGS) copolymerized with different amounts of polyhydroxybutyrate diol (PHB-diol) were analyzed with ¹H-NMR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), mechanical test, biodegradation test, and cytotoxicity analysis. The chemical composition of the PHB-diol prepared and the copolymerization reaction of the PHB-diol in the PGS were confirmed by ¹H-NMR. From ¹H-NMR analysis, the PHB-diol prepared had the molecular weight about 989.6 g/mol and a faster crystallization rate than the PHB according to the DSC measurement. The tensile/compressive strengths of PGS-co-(PHB-diol) increased while the crosslinking densities decreased with the amount of PHB-diol copolymerized. The PGS-co-(PHB-diol) had a slower biodegradation rate but a worse thermal stability than the PGS. Additionally, the biodegradable PGS-co-(PHB-diol) elastomers prepared exhibited no cytotoxicity and could replace PGS used in bio-fields.     

Processability modifications of poly(3‐hydroxybutyrate) by plasticizing,blending, and stabilizing

Poly(3‐hydroxybutyrate) (PHB) was plasticized with dioctyl (o‐)phthalate, dioctyl sebacate, and acetyl tributyl citrate (ATBC). The thermal properties, mechanical properties, and melt flow ability were studied with differential scanning calorimetry, thermogravimetric analysis, a universal material testing machine, and a melt flow indexer. ATBC was revealed to be an efficient plasticizer, reducing the glass‐transition temperature and increasing the thermoplasticization ability of PHB. We also blended poly(3‐hydroxybutyrate‐co‐hydroxyhexanoate) (PHBHHx) and poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) [P(3/4HB)] with PHB, ATBC, and antioxidant 1010 to overcome the brittleness of PHB and improve the melt flow stability of the materials. PHBHHx did little to improve the thermal processing but increased the fluidity of PHB, and P(3/4HB) toned the toughness of PHB. The addition of antioxidant 1010 enhanced the thermal stabilization of PHB. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Maximizing the utility of bio-based diisocyanate and chain extenders in crystalline segmented thermoplastic polyester urethanes: Effect of polymerization protocol

High molecular weight semi crystalline thermoplastic poly(ester urethanes), TPEUs, were prepared from a vegetable oil-based diisocyanate, aliphatic diol chain extenders and poly(ethylene adipate) macro diol using one-shot, pre-polymer and multi-stage polyaddition methods. The optimized polymerization reaction achieved ultra-high molecular weight TPEUs (>2 million as determined by GPC) in a short time, indicating a very high HPMDI – diol reactivity. TPEUs with very well controlled hard segment (HS) and soft segment (SS) blocks were prepared and characterized with DSC, TGA, tensile analysis, and WAXD in order to reveal structure–property relationships. A confinement effect that imparts elastomeric properties to otherwise thermoplastic TPEUs was revealed. The confinement extent was found to vary predictably with structure indicating that one can custom engineer tougher polyurethane elastomers by “tuning” soft segment crystallinity with suitable HS block structure. Generally, the HPMDI-based TPEUs exhibited thermal stability and mechanical properties comparable to entirely petroleum-based TPEUs.     

Physical properties of PP-g-AA prepared by melt extrusion and its effects on mechanical properties of PP

Polypropylene grafting with acrylic acid, PP-g-AA (FPP), was prepared by melt extrusion. The physical properties of FPP and effect of FPP on mechanical properties of polypropylene (PP) were investigated. Experimental results showed that an increase in the grafting rate of FPP resulted in an increase in the crystallization peak temperature, melt peak temperature, and degree of crystallization of PP. Double melting peaks were observed for OPP prepared by adding dicumyl peroxide into PP and FPP with low grafting rate due to the degradation of PP. As the grafting rate was increased, the double melt peaks converted into a single melt peak. It is suggest that FPP with higher grafting rate resulted in enhanced nucleation and crystallization ability of PP. The grafting of AA onto the PP chain improved the thermal stability and mechanical properties of PP materials. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2609–2616, 2001     

Effect of the maleic anhydride content on the structural,thermal, rheological and film properties of the n-butyl methacrylate–maleic anhydride copolymers

Various copolymers of n-butyl methacrylate (nBMA)-maleic anhydride (MA) were synthesized by free radical solution polymerization using xylene as a solvent, with monomer ratio of (nBMA/MA) 80/20, 65/35 and 50/50 wt%. The nBMA/MA copolymers were analyzed by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H NMR), gel permeation chromatography (GPC) differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), rheology, acid value, microhardness and friction resistance. The formation of the nBMA/MA copolymers was proven by FTIR and ¹H NMR. The conversion percentage, glass transition temperature (T_g), thermal stability, hardness and the friction resistance of the nBMA/MA copolymers increased with the MA contents in the copolymers. All copolymers presented a thinning-shear rheological behavior due to the presence of entanglements. All films of the copolymers showed a good chemical resistance to HCl and NaCl solutions, but in the presence of NaOH solutions the films exhibited a blister.     

Effect of montmorillonoite modification and maleic anhydride‐grafted polypropylene on the microstructure and mechanical properties of polypropylene/montmorillonoite nanocomposites

Two types of modified montmorillonite (MMT) were achieved using octadecylamine as the modifying agent by the methods of dry process and wet route. Polypropylene (PP)/MMT nanocomposites were prepared using the melt mixing technique and employing maleic anhydride‐grafted polypropylene (PP‐MA) as the compatibilizer. The modification of montmorillonite was characterized by fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), and scanning electron microscope (SEM). The effect of MMT modification and PP‐MA on the microstructure and properties of PP/MMT nanocomposites was investigated by SEM, differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and polarizing microscopy. The results show that organic montmorillonite modified by wet process (WOMMT) has a large d‐spacing increment; whereas montmorillonite modified by dry process (DOMMT) shows little d‐spacing increment. Furthermore, the mechanical properties of composites incorporating WOMMT are better than that containing DOMMT. As a third component, the addition of PP‐MA benefits the formation of exfoliated structure and the dispersion of MMT in PP matrix, and hence, enhances the physical properties of the nanocomposite. With the presence of PP‐MA, the highly dispersed MMT increases the number of spherulite crystals, enhances the melting enthalpy, improves the thermal stability, and induces the desired tiny crazes more effectively. MMT increases the storage modulus (E′) and glass‐transition temperature (T_g) of PP because of the stiffness of MMT layers, but PP‐MA decreases them owing to its high melt flow index, both of which were in favor of improving the physical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3952–3960, 2013     

Plasticization of poly(3-hydroxybutyrate) with triethyl citrate: Thermal and mechanical properties,morphology, and kinetics of crystallization

Poly(3-hydroxybutyrate) (PHB), is one important biopolymer and a promising alternative to petroleum-based plastics. In this article, formulations of PHB and triethyl citrate (TEC) as plasticizer were prepared by melt extrusion. The effect of TEC on the mechanical, thermal, and morphological properties of PHB was investigated by tensile tests, impact resistance, dynamic-mechanical analysis, differential scanning calorimetry, polarized optical microscopy, and small- and wide-angle X-ray scattering. TEC acted as an efficient plasticizer for PHB, imparting gradual changes in the properties as the mass fraction of TEC increased. A reduction in the elastic modulus, an increase in the intensity of β relaxation indicated a higher capacity of mechanical energy dissipation for the formulations containing higher mass fractions of TEC. TEC reduced its glass transition and melting temperatures, contributing to the increase of the processing window of the temperature and minimizing thermal degradation of PHB. TEC had a strong influence on the kinetics of crystallization, the morphology of the spherulites, and the crystalline structural parameters, such as long period, crystalline lamella, and interlamellar amorphous region thicknesses. Our study clarifies how the morphology of the PHB crystalline phase evolves in the presence of the plasticizer and with the time of crystallization.     

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     

聚苯乙烯/纳米二氧化铈复合材料的制备与表征

通过原位悬浮聚合法制备聚苯乙烯(PS)／纳米二氧化铈(CeO2)复合材料。红外光谱分析表明,复合材料中CeO2粒子的红外吸收存在蓝移现象。采用凝胶渗透色谱仪、差示扫描量热仪、热失重仪和毛细管流变仪等对PS／纳米CeO2复合材料的分子量、玻璃化转变温度、热稳定性及流动性能进行了表征。研究发现,随着纳米CeO2用量的增加,复合材料的分子量呈先升高后降低的趋势,玻璃化转变温度及熔体表现粘度有所升高,热稳定性得到很大提高。