EC/CA共混物的相容性和热稳定性

EC/CA共混物的相容性和热稳定性;乙基纤维素;醋酸纤维素;溶液共混;相容性     

聚醚酰亚胺/酚酞型聚醚醚酮共混体系相容性的稀溶液粘度法研究

<正> 近年来,有关高性能树脂聚酰亚胺共混物的研究日益引起人们的关注。已经发现许多种分子结构不同的聚酰亚胺之间,聚酰亚胺与聚苯并咪唑,或聚醚醚酮能形成完全相容的共混体系,从而扩大了高性能树脂聚酰亚胺的应用范围。 酚酞型聚醚醚酮(PEK-C)是由我所研究开发出的一种新型的聚醚醚酮类高性能树脂,它具有良好的可溶性,优异的机械强度和加工流动性,已广泛应用于结构材料及复合材料的制备。为进一步扩大该树脂的应用范围,本实验室在PEK-C共混物的研究做了大量的工作。本工作研究了聚醚酰亚胺(PEI)/PEK-C共混体系的相容性。PEI和PEK-C的分子结构如下:     

天然橡胶/聚乙烯共混体相容性的研究

本工作首先对橡胶/聚乙烯共混体系的相容性进行了计算,推测聚乙烯的非晶部分和橡胶间有一定的互容性,提出了橡胶和聚乙烯相互作用模型。然后用动态力学方法、有效网链密度测定、密度测定和广角X-射线衍射方法对天然橡胶分别未交联和交联的天然橡胶(NR)/低密度聚乙烯(LDPE)共混体系的相容性进行了验证。实验结果表明,LDPE非晶部分和NR之间存在一定的相互渗透。     

聚乙烯醇/聚乙烯基吡咯烷酮共混体系相容性研究

用DSC、FTIR、SAXS和测定Flory-Huggins相互作用参数等方法对聚乙二醇(PVA1)/聚乙烯基吡咯烷酮(PVP)共混体系的研究。结果表明,该体系具有完全互容的性质。共混物只有一个玻璃化转变温度。用DMSO作溶剂浇铸的膜光学透明。PVA1的长周期和片晶厚度均随PVP含量增加而增大,但后者增大的幅度比前者小得多,表明PVP和PVA1的非晶部分形成均相并夹入到球晶内部。共混物中PVP羰基吸收峰和PVA1的羟基吸收峰与相应均聚物相比,在红外光谱图中皆向低频方向迁移,迁移波数随第二组分含量的增加而增大。表明二者间有氢键生成。用平衡熔点计算的Flory-Huggins相互作用参数为-0.88。     

改性淀粉/聚乳酸共混体系增容方法的研究

研究了聚乳酸和改性淀粉共混挤出前的固相酯化反应对共混体系的增容作用。比较挤出样条经二氯甲烷抽提后剩余物的固体13C-NMR光谱谱图,发现未经酯化反应时剩余物为淀粉,经酯化反应后剩余物的固体13C-NMR光谱谱图在20ppm和170ppm处出现聚乳酸特征的碳吸收峰,说明剩余物中含有聚乳酸和淀粉的接枝物。由共混物中聚乳酸的端羧基含量的测定结果也能说明酯化反应后共混物剩余物中含有聚乳酸和淀粉的接枝物。考察了生成的接枝物对共混体系相容性的影响,扫描电镜分析结果表明,经过预处理酯化反应后共混物相容性得到了提高。挤出样条取向拉伸后进行力学性能测试,发现酯化反应明显提高了力学性能。该方法可以通过设计共混挤出过程实现改变共混物相容性的目的,具有广阔的前景和很强的应用价值。     

聚丙烯/聚乙烯醇缩丁醛共混相容性研究

聚乙烯醇缩丁醛(PVB)分子结构上含有大量羟基,可用于改进聚丙烯的非极性。本文采用不同结构的聚乙烯醇缩丁醛(B-98、B-76、B-72)与抗冲聚丙烯(ICPP)按5/95进行共混,并测试了共混物的相结构(SEM)、结晶过程(POM)、热性能(DSC)和力学性能。SEM测试结果表明,PVB和ICPP表现出一定的相容性,其中B-98相容性最好;DSC和POM测试结果表明,PVB对ICPP的结晶有抑制作用;力学测试结果表明,B-98改性ICPP后的综合力学性能效果优于B-76和B-72。B-98和聚丙烯较好的相容性主要和其较小的分子量有关。     

PVC/PBD-b-PMMA共混体系相容性的研究

采用ＤＭＡ和ＴＥＭ系统研究了聚丁二烯－聚甲基丙烯酸甲酯的嵌段共聚物（ＰＢＤ－ｂ－ＰＭＭＡ）与聚氯乙烯（ＰＶＣ）共混体系的相容性问题。结果表明：ＰＶＣ／ＰＢＤ－ｂ－ＰＭＭＡ共混体系具有部分相溶性。相容的程度与共混体系的组成、组分聚合物的分子量以及共聚物中ＰＢＤ和ＰＭＭＡ嵌段的比例密切相关。     

PBT／PET共混体系非晶区的相容性

利用ＰＢＴ、ＰＥＴ的特性参数，通过不同组份比ＰＢＴ／ＰＥＴ共混体系的混合自由能△Ｇｍ，从理论上预测其相容性。在一定的条件下△Ｇｍ＜０，ＰＢＴ、ＰＥＴ可以相容。对不同组份比共混体系的玻璃化转变过程从分子链段运动的角度进行分析。     

PC／PBT共混体系的研究：（Ⅱ）PC,PBT熔融共混时的相容性

采用ＤＳＣ测定了一系列ＰＣ／ＰＢＴ熔融共混物的Ｔｇ，结果显示ＰＣ、ＰＢＴ是部分相容的两相体系，ＰＣ、ＰＢＴ之间的酯交换反应有利于相容性的提高。通过对ＰＣ、ＰＢＴ两相中各组分表观质量分数的计算，发现ＰＣ溶于ＰＢＴ的能力要比ＰＢＴ溶于ＰＣ的能力大。通过对ＰＣ、ＰＢＴ相互作用参数χ１２的计算，发现在所研究的范围内（ＰＣ含量为３０～７０％）ＰＣ、ＰＢＴ之间的相互作用参数χ１２略大于其临界相互作用参数（χ１２）ｃ，表明ＰＣ、ＰＢＴ在熔融共混时会发生相分离，亦即形成部分相容的两相体系     

聚联苯酰亚胺/聚硫醚酰亚胺共混体系的相容性

<正> 聚酰亚胺是一种性能极其优异的高性能树脂,它在许多高技术领域有着极其重要的应用价值。在80年代以前,人们工作的重点是合成出一系列分子结构不同的聚酰亚胺,研究分子结构与性能间的关系,开发聚酰亚胺新品种。自80年代后期,有关高性能树脂聚酰亚胺共混物的研究日益引起人们的关注,其中有关不同分子结构的聚酰亚胺/聚酰亚胺共     

Structure and blood compatibility of highly oriented poly(lactic acid)/thermoplastic polyurethane blends produced by solid hot stretching

Highly oriented poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blends were fabricated through solid hot stretching technology in an effort to improve the mechanical properties and blood biocompatibility of PLA as blood‐contacting medical devices. It was found that the tensile strength and modulus of the blends can be improved dramatically by stretching. With the increase of draw ratio, the cold crystallization peak became smaller, and the glass transition and the melting peak moved to high temperature, while the crystallinity increased, and the grain size of PLA decreased, indicating of the stress‐induced crystallization during drawing. The oriented blends exhibited structures with longitudinal striations which indicate the presence of micro‐fibers. TPU phase was finely and homogeneously dispersed in the PLA, and after drawing, TPU domains were elongated to ellipsoid. The introduction of TPU and orientation could enhance the blood compatibility of PLA by prolonging kinetic clotting time, and decreasing hemolysis ratio and platelet activation. Copyright © 2013 John Wiley & Sons, Ltd.     

Structure,properties and interfacial interactions in poly(lactic acid)/polyurethane blends prepared by reactive processing

Polyurethane elastomers are promising candidates for the impact modification of PLA producing blends for example for biomedicine. Poly(lactic acid) (PLA)/polyurethane elastomer (PU) blends were prepared by reactive processing and physical blending as comparison. The blends were characterized by a number of techniques including microscopy (scanning electron microscopy, SEM, and atomic force microscopy, AFM), rotational viscometry, thermal (dynamic mechanical analysis, DMA), and mechanical (tensile) measurements. The analysis and comparison of the structure and properties of physical and reactor blends proved the successful coupling of the phases. Coupling resulted in more advantageous structure and superior mechanical properties compared to those of physical blends as confirmed by morphology, macroscopic properties and the quantitative estimation of interfacial interactions. Structural studies and the composition dependence of properties indicated the formation of a submicron, phase-in-phase structure which positively influenced properties at large PU contents. The results strongly support that reactive processing is a convenient, cost-effective and environmentally friendly technique to obtain blends with superior properties.     

Thermal properties of poly(vinyl chloride)/polyurethane blends

Blends of poly(vinyl chloride) and a polyurethane elastomer were investigated by DSC and tensile testing. Up to 30 wt% single glass transition was found. It was concluded that the polyurethane forms partly a true blend and is partly disperged in the continuous blend phase.     

Compatible and tearing properties of poly(lactic acid)/poly(ethylene glutaric‐co‐terephthalate) copolyester blends

Fourier transform infrared and nuclear magnetic resonance results suggest that the carboxylic acid groups of poly(lactic acid) (PLA) molecules react with the hydroxyl groups of FePol (FP) molecules during the melt‐blending of PLA_xFP_y specimens. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) experiments of PLA and PLA/FP specimens suggest that only small amounts of poor PLA and/or FP crystals are present in their corresponding melt crystallized specimens. In fact, the percentage crystallinity, peak melting temperature, and onset re‐crystallization temperature values of PLA/FP specimens reduce gradually as their FP contents increase. However, the glass transition temperatures of PLA molecules found by DSC and DMA reduce to a minimum value as the FP contents of PLA_xFP_y specimens reach 6 wt %. Further DMA and morphological analysis of PLA/FP specimens reveal that FP molecules are compatible with PLA molecules at FP contents equal to or less than 6 wt %, as no distinguished phase‐separated FP droplets and tan δ transitions were found on fracture surfaces and tan δ curves of PLA/FP specimens, respectively. In contrast to PLA, the FP specimen exhibits highly deformable and tearing properties. After blending proper amounts of FP in PLA, the inherent brittle deformation and poor tearing behavior of PLA were successfully improved. Possible reasons accounting for these interesting crystallization, compatible and tearing properties of PLA/FP specimens are proposed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 913–920, 2010     

Enhancing toughness of poly (lactic acid)/Thermoplastic polyurethane blends via increasing interface compatibility by polyurethane elastomer prepolymer and its toughening mechanism

Due to the environmental pollution caused by the petroleum-based polymer, poly (lactic acid) (PLA), a biodegradable and biocompatible polymer that obtained from natural and renewable sources, has attracted widespread attention. However, the brittleness of PLA greatly limits its application. In this study, the super toughened PLA-based blends were obtained by compatibilizing the PLA/thermoplastic polyurethane (TPU) blends with the polyurethane elastomer prepolymer (PUEP) as an active compatibilizer. The mechanical properties, thermal properties and corresponding toughening mechanism of PLA/TPU/PUEP system were studied by tensile test, instrumented impact test, dynamic mechanical analysis (DMA), scanning electronic microscope (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). All the results demonstrate that the isocyanate (−NCO) group in PUEP is successfully reacted with the –OH groups at both sides of the PLA and the obtained polyurethane (PU)~PLA copolymer (PU ~ cõ PLA) significantly improves the interfacial compatibility of PLA/TPU blends. The gradually refined dispersed phase size and fuzzy phase interface as displayed in SEM images suggest a good interfacial compatibilization in the PLA/TPU/PUEP blends, probably due to the isocyanate reaction between PLA and PUEP. And the interfacial reaction and compatibilization among the components led to the formation of super toughened PLA/TPU/PUEP blends. And the instrumented impact results indicate that most of the impact toughness is provided by the crack propagation rather than the crack initiation during the entire fracture process.     

聚氨酯对聚乳酸溶液流变性能的影响

采用高级旋转流变仪研究了1,4-二氧六环/左旋聚乳酸/聚氨酯(DO/PLLA/PU)共混溶液的流变性能,探讨了PU的加入对共混溶液的流动曲线、非牛顿指数及表观粘流活化能的影响.结果表明,在实验条件下,共混溶液为剪切变稀非牛顿流体,PU含量的增加使得共混溶液的表观粘度增大;共混溶液的非牛顿指数的研究表明,随着PU含量的增加,非牛顿指数呈现下降趋势,随着温度的升高,同一组成的共混溶液非牛顿指数也呈现下降趋势,说明共混溶液的粘度随着PU含量的增加以及温度的升高,对剪切速率的依赖性依然很强.粘流活化能的研究结果表明,在较高剪切速率下,PU的加入使得共混溶液对温度的敏感性下降.     

Morphology and properties of biodegradable poly (lactic acid)/poly (butylene adipate-co-terephthalate) blends with different viscosity ratio

Phase morphology exerts a tremendous influence on the properties of polymer blends. The development of the blend morphology depends not only on the intrinsic structure of the component polymers but also on extrinsic factors such as viscosity ratio, shearing force and temperature in the melt processing. In this study, various poly (butylene adipate-co-terephthalate) (PBAT) materials with different melt viscosity were prepared, and then poly (lactic acid) (PLA)/PBAT blends with different viscosity ratio were prepared in a counter-rotating twin-screw extruder under constant processing conditions. The influence of viscosity ratio on the morphology, mechanical, thermal and rheological properties of PLA/PBAT (70/30 w/w) blends was investigated. The experimental results showed that the morphology and properties of PLA/PBAT blends strongly depended on the viscosity ratio. Finer size PBAT phase were observed for viscosity ratio less than 1 (λ < 1) compared to samples with λ > 1. It was found that the interfacial tensions of PLA and PBAT were significantly different when the viscosity ratio was changed, the lowest interfacial tensions (0.12 mN/m) was obtained when the viscosity was 0.77. Additionally, the maximal tensile strength in PLA/PBAT blends were obtained when the viscosity ratio was 0.44, while the maximal impact properties were obtained when the viscosity ratio was 1.95.     

Crystallization,thermal behavior,and compatibility of poly(ethylene oxide)/poly(propylene oxide) blends

Isothermal and nonisothermal crystallization kinetics of different poly(ethylene oxide)/poly(propylene oxide) blends were investigated by means of differential scanning calorimetry (DSC). Glass transition temperature of quenched samples have also been reported. Phase morphologies and poly(ethylene oxide) spherulite growth rates were analyzed by polarizing light transmission microscopy. Results show morphological changes along with regime transitions of poly(ethylene oxide) crystal growth. Kinetic analyses of the data suggest that, although the blend behaves as a noncompatible, phase-separated system, there exists a certain degree of interaction between polymer chains. © 1996 John Wiley & Sons, Inc.