Structure and properties of collagen‐konjac glucomannan‐sodium alginate blend films

A new kind of blend film was made by mixing the solutions of collagen, konjac glucommnnan (KGM), and sodium alginate. The structure of the blend film was characterized by FTIR, XRD, atomic absorption spectrophotometer, and SEM, respectively. The effects of weight ratio between the polymers on light transmittance, tensile strength, elongation at break, water permeability, and water absorption of the film were studied. The results showed that there were strong interactions and good compatibility between collagen, KGM, and sodium alginate in the film. The film possesses good mechanical properties. Therefore, it can be applied in biomedicine as a new type of biomaterial. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Compatibilisation of PPE/SAN blends by triblock terpolymers: Correlation between block terpolymer composition, morphology and properties

Immiscible blends of poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and poly(styrene-co-acrylonitrile) (SAN) with a weight composition of 60/40 were compatibilised by polystyrene-block-polybutadiene-block-poly(methyl methacrylate) triblock terpolymers (SBM) using a two-stage melt-processing approach. In order to investigate the influence of the SBM composition on the compatibilisation efficiency, the block lengths of the triblock terpolymers were systematically varied. The resulting morphological features of the blend systems as function of SBM composition and processing parameters are correlated with the resulting thermal and thermo-mechanical properties. In the ideal case, SBM should be located at the interface as PS is miscible with PPE while PMMA is miscible with SAN. The elastomeric middle block as an immiscible component should remain at the interface. This particular morphological arrangement is known as the ‘raspberry morphology’. A detailed TEM analysis of the blend morphologies following initial extrusion-compounding revealed a high compatibilisation efficiency of the SBM types with equal lengths of the end blocks and, furthermore, the desired raspberry morphology was achieved. In contrast, high PS contents in comparison to the other blocks led to a pronounced micelle formation in the PPE phase. Further evaluation of the blend structures following injection-moulding indicated that the morphologies remain relatively stable during this second melt-processing step. A detailed thermal analysis of all blend systems supports the interpretation of the observed morphological features. The fundamental correlation between SBM composition and blend morphology established in this study opens the door for the controlled development of interfacial properties of such compatibilised PPE/SAN blends during melt-processing.     

Effects of compatibilizer type and rubber‐wood sawdust content on the mechanical,morphological, and thermal properties of PVC/LDPE blend

This article aimed to investigate the mechanical, morphological and thermal properties of PVC/LDPE blend with and without the addition of compatibilizers. The effects of LDPE content, compatibilizer type and rubber‐wood sawdust loading on the properties of the blend were evaluated. The experimental results suggested that as the LDPE content was increased the mechanical properties of PVC‐LDPE blend progressively decreased due to poor interfacial adhesion. The continuity and compatibility between PVC and LDPE phases could be improved through three different types of compatibilizers which included chlorinated polyethylene (CPE) poly(methyl‐methacrylate‐co‐butyl acrylate) (PA20) and poly(ethylene‐co‐methacrylate) (Elvaloy). The PA20 was found to be the most suitable compatibilizer for the blend. A radical transfer reaction was proposed in this work to explain the structure and thermal changes of the PVC in PVC‐LDPE blend. The decomposition temperature of PVC in the blend decreased with the loading of the PA20 and the wood sawdust. As the sawdust content was increased the tensile and flexural moduli increased with considerable decreased in the tensile, flexural and impact strength, a slight improvement being achieved if the PA20 was incorporated in the composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 598–606, 2006     

The atactic polystyrene molecular weight effect on the thermal properties and crystal structure of syndiotactic polystyrene/atactic polystyrene blends

This work examined how the molecular weight of atactic polystyrene (aPS) affects the thermal properties and crystal structure of syndiotactic polystyrene (sPS)/aPS blends using differential scanning calorimetry, polarized light microscopy and wide angle X-ray diffraction (WAXD) technique. For comparative purposes, the structure and properties of the parent sPS was also investigated. The experimental results indicated that these blends showed single glass transition temperatures (T_gs), implying the miscibility of these blends in the amorphous state regardless of the aPS molecular weight. The non-isothermal and isothermal melt crystallization of sPS were hindered with the incorporation of aPSs. Moreover, aPS with a lower molecular weight caused a further decrease in the crystallization rate of sPS. Complex melting behavior was observed for parent sPS and its blends as well. The melting temperatures of these blends were lower than those of the parent sPS, and they decreased as the molecular weight of aPS decreased. Compared with the results of the WAXD study, the observed complex melting behavior resulted from the mixed polymorphs (i.e. the α and β forms) along with the melting-recrystallization-remelting of the β form crystals during the heating scans. The degree of melting-recrystallization-remelting phenomenon for each specimen was dependent primarily on how fast the sPS crystals were formed instead of the incorporation of aPSs. Furthermore, the existence of aPS in the blends, especially the lower molecular weight aPS, apparently reduced the possibility of forming the less stable α form in the sPS crystals.     

Ionic elastomer blends of zinc salts of maleated natural rubber and carboxylated nitrile rubber: Effect of grafted maleic anhydride

Zinc neutralized maleated natural rubbers (Zn‐MNR) were prepared by solution grafting and neutralization with zinc acetate in one‐step. It was later used for blending with carboxylated nitrile rubber (XNBR) in the composition of 50/50 parts by weight. The effect of grafted anhydride content (1.2, 1.6, 2.0, and 2.5% wt of NR) on the tensile properties of ionic rubber blends (Zn‐MNR/XNBR) was investigated. The tensile strength of the ionic blends was found to be greater than those of pure rubbers. The modulus, tensile, and tear strength of the blends dramatically increased with increasing levels of grafted anhydride. The ionic rubber blends also possessed superior physical properties compared to those of the corresponding nonionic rubber blends (MNR/XNBR). Dynamic mechanical thermal analysis and scanning electron microscopic studies were performed to verify the process of mixing. Fourier transform infrared spectroscopic studies were carried out to characterize the nature of specific intermolecular interactions between Zn‐MNR and XNBR chain segments. The results indicated that the ion‐ion (Zn⁺ ‐COO^?) interactions between Zn‐MNR and XNBR are formed at the interface, which provides the mean of compatibilization in the ionic rubber blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Sorption/diffusion of aqueous mixtures of 1,4‐dioxane/tetrahydrofuran through blend membranes of poly(vinyl alcohol) and sodium alginate: Their compatibility and pervaporation separation studies

Blend membranes of poly(vinyl alcohol) (PVA) and sodium alginate (NaAlg) were prepared by solution casting and crosslinked with glutaraldehyde (GA). Polymer blend compatibility was studied in water by measuring solution viscosity at 30°C. From the viscosity data, interaction parameters were determined to find the blend compatibility. Thickness of the membranes ranged between 35 and 40 μm. Circular disc‐shaped samples were cut from the thin membranes to perform gravimetric sorption experiments in water + 1,4‐dioxane and water + tetrahydrofuran mixtures at 30°C. Diffusion coefficients were calculated using Fick's equation. Concentration profiles of liquids were computed by solving Fick's equation under suitable boundary conditions. Diffusion coefficients show a dependence on the composition of the blends as well as composition of binary mixtures. A correlation was attempted between concentration profiles and diffusion coefficients of the transporting liquids. Degree of swelling and sorption coefficients were calculated from the gravimetric sorption data. Sorption kinetics was studied using an empirical equation to understand the nature of sorption–diffusion anomalies. Membrane selectivity for water + 1,4‐dioxane and water + tetrahydrofuran mixtures were calculated from the pervaporation experiments. A correlation between sorption and membrane selectivity was attempted. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 178–188, 2005     

异氰酸酯对聚乳酸/热塑性聚氨酯共混物性能的影响

以4,4^′-二苯基甲烷二异氰酸酯（MDI）为反应增容剂，采用熔融共混法制备了不同MDI含量的聚乳酸/热塑性聚氨酯（PLA/TPU）共混物，采用傅里叶变换红外光谱仪（FTIR）、万能试验机、冲击试验机、扫描电子显微镜（SEM）、差示扫描量热仪（DSC）和旋转流变仪对共混物力学性能、微观形态、热性能和流变性能进行了研究。结果表明：MDI可以有效改善共混物的力学性能，当MDI质量分数为1%时，共混物力学性能最佳，缺口冲击强度为40.0kJ/m²，断裂伸长率为214.1%，与未加MDI的共混物相比，分别增加了4.3倍和5.8倍，拉伸强度稍有下降（47.6MPa）；SEM表明，MDI的加入提高了共混物的相容性，加入MDI后，共混物的断面由海-岛结构变为核-壳包覆结构，相界面作用力增强；DSC测试表明，共混物的玻璃化转变温度、冷结晶温度和熔融温度随着MDI含量的增加而升高；流变测试表明，MDI质量分数的增加，共混物呈现更显著的剪切变稀行为，推测共混反应机理为：MDI质量分数的增加，体系内依次发生PLA的扩链、支化和TPU的交联。     

Acceleration or retardation to crystallization if liquid-liquid phase separation occurs: Studies on a polyolefin blend by SAXS/WAXD, DSC and TEM

Blends of statistical copolymers containing ethylene/hexene (PEH) and ethylene/butene (PEB) exhibited the behavior of upper critical solution temperature (UCST). The interplay between the early and intermediate stage liquid-liquid phase separation (LLPS) and crystallization of the PEH/PEB 50/50 blend was studied by time-resolved simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. Samples were treated by two different quench procedures: in single quench, the sample was directly quenched from 160 °C to isothermal crystallization temperature of 114 °C; while in double quench, the sample was firstly quenched to 130 °C for 20 min annealing, where LLPS occurred, and then to 114 °C. It was found that in the early stage of crystallization, the integrated values of Iq² and crystallinity, X_c, in the double quench procedure were consistently higher than those in the single quench procedure, which could be attributed to accelerated nucleation induced by enhanced concentration fluctuations and interfacial tension. In the late stage of crystallization, some morphological parameters were found to crossover and then reverse, which could be explained by retardation of lamellar growth due to phase separation formed during the double quench procedure. This phenomenon was also confirmed by DSC measurements in blends of different compositions at varying isothermal crystallization temperatures. The crystal lamellar thickness determined by SAXS showed a good agreement with TEM observation. Results indicated that the early stage LLPS in the PEH/PEB blend prior to crystallization indeed dictated the resulting lamellar structures, including the average size of lamellar stack and the stack distribution. There seemed to be little variation of lamellar thickness and long period between the two quenching procedures (i.e., single quench versus double quench).     

Blend membranes of chitosan and poly(vinyl alcohol) in pervaporation dehydration of isopropanol and tetrahydrofuran

Blend membranes of a natural polymer, chitosan, with a synthetic polymer, poly(vinyl alcohol) (PVA), were prepared by solution casting and crosslinked with a urea formaldehyde/sulfuric acid (UFS) mixture. Chitosan was used as the base component in the blend system, whereas PVA concentration was varied from 20 to 60 wt %. Blend compatibility was studied by differential scanning calorimetry, and Fourier transform infrared spectroscopy was used to study membrane crosslinking. Membranes were tested for pervaporation dehydration of isopropanol and tetrahydrofuran (THF) at 30°C in close proximity to their azeotropic compositions. Membrane performance was assessed by calculating flux and selectivity. Swelling experiments performed in water + organic mixtures at 30°C were used to explain the pervaporation results. The blend membrane containing 20 wt % PVA when tested for 5 and 10 wt % water–containing THF and isopropanol feeds exhibited selectivity of 4203 and 17,991, respectively. Flux increased with increasing concentration of water in the feed. Selectivity was highest for the 20 wt % PVA‐containing blend membrane. The results of this study are unique in the sense that the crosslinking agent used—the UFS mixture—was novel. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1918–1926, 2007     

Study on the thermoplastic vulcanizate using ultrasonically treated rubber powder

Nowadays, waste EPDM (ethylene propylene diene monomer) increasingly has been causing significant environmental problems with increasing numbers of vehicles. From the perspective of the environment and economics, recycling is the best method to treat waste materials. This study investigated waste EPDM/PP (polypropylene) blends with waste EPDM. Waste EPDM powders were treated ultrasonically, which physically modifies the rubber particles to confer good mechanical properties. Also investigated were the relevance of the mass percentage of the dispersed phase, the influence of the geometry and rotation speeds of the screw used in extrusion, and the melting temperature of PP materials on the morphology and mechanical properties of the blend. The purpose of this study was to develop a valuable thermoplastic elastomer from waste EPDM. This study concentrated on determining the optimum conditions for producing a blend by extrusion, including parameters of screw geometry, screw rotational speed, and operating temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2503–2507, 2003