热塑性聚合物／热致液晶聚合物原位复合材料的制备

介绍了热塑性聚合物 /热致液晶聚合物原位复合材料 (TP/TLCP)的加工。系统阐述了热塑性聚合物 /热致液晶聚合物原位复合材料制备过程中流场、剪切速率、拉伸比、加工温度和冷却速率对材料微纤形成和力学性能的影响。同时 ,将现有的加工方法归结为传统加工方法、新加工方法和其他加工方法三类 ,并详细分析了各种加工方法的优缺点。最后指出 ,今后对热塑性聚合物 /热致液晶聚合物原位复合材料的研究应致力于改善界面相容性、优化加工条件和开发新的加工方法     

热致液晶聚合物／热塑性聚合物原位复合材料研究进展

综述了热致液晶聚合物／热塑性聚合物(TLCP／TP)原位复合材料的最新进展，系统阐述了TLCP／TP体系的微纤形成、流变行为、微观形态和力学性能，并对改善相容性和优化加工条件的研究工作作了具体介绍。     

原位混杂复合材料

新型结构的原位混杂复合材料由纤维、液晶聚合物微纤和热塑性基体树脂组成。它可以用常规的挤出、注射工艺成型,含有直径在两个数量级上的两种增强剂,在结构,加工流变性与力学性能均表现出原位混杂增强形成的优势。同时,叙述了它的制备技术要点。     

PPS/TLCP共混体系结构与流变研究

采用热致液晶聚合物（TLCP）与聚苯硫醚（PPS）熔融共混的方式制备了PPS／TLCP复合材料,研究了PPS／TLCP共混体系的形貌、流变性能以及加工参数对微纤形成的影响。结果表明：TLCP可明显改善体系的加工特性,并能原位生成微纤化复合材料,TLCP对体系黏度有较大影响,在低剪切速率区黏度下降幅度较大,在高剪切速率区,黏度降低幅度小。PPS／TLCP复合材料存在皮芯结构,工艺参数对TLCP微纤的形成起着重要作用,通过提高注塑速度,对TLCP微纤的形成特别有利。     

普通热塑性树脂的原位成纤技术进展

通过与热液晶原位复合材料的对比,系统阐述了具有柔性分子链的普通热塑性树脂就地成纤增强增韧高聚物的国仙外研究进展,着重对近几年来该技术在成纤机理、控制因素以及结构与性能等方面的研究成果作了初步总结。     

原位复合材料

讨论了原位复合材料的流变性能、亚微形态、力学性能和加工工艺之间的相互关系,初步揭示了体系中液晶微纤分散的形成规律,并指出了原位复合材料的发展概况、趋势及应用前景。     

碳纤维增强液晶高聚物复合材料的研究

研究了碳纤维(CF)增强热致性液晶聚合物(TLCP)制备高性能复合材料;探讨了不同纤维含量、不同纤维类型对复合材料力学性能、微观结构的影响;扫描电镜(SEM)结果证实了液晶聚合物在加工过程中自取向,形成了微纤结构,具有自增强作用,使复合材料表现出非常高的力学性能。     

TP／LCP原位复合材料

综述了以PP、PET、PC等几种常见的热塑性高聚物为基体的LCP(液晶共聚酯)原位复合材料,讨论了TP(热塑性高聚物)/LCP的结构与性能以及TP与LCP之间的相容性。     

原位微纤复合材料的研究进展

介绍了原位微纤复合材料制备方法的出现、成纤机制、制备原理以及影响因素;结合当前的研究内容,分析了原位微纤复合材料微观结构和力学性能的调控机制,并探讨了复合材料共混体系粘度比、分散相含量、弹性、相容性以及剪切拉伸速率等因素对复合材料微观结构的影响;综述了原位微纤复合材料的研究现状,并对原位微纤复合材料今后的发展趋势进行了展望。     

黏度比对EVA/PP原位微纤复合材料形态及性能的影响

采用熔融挤出-微纳叠层共挤制备了不同黏度比的乙烯-醋酸乙烯酯共聚物(EVA)/聚丙烯(PP)原位微纤复合材料,通过扫描电子显微镜(SEM)、差示扫描量热仪(DSC)和微机控制电子万能试验机研究了EVA/PP原位微纤复合材料中黏度比对分散相形态的影响,分散相尺寸对复合材料结晶行为、熔融温度以及拉伸强度的影响。结果表明:黏度比增加,分散相PP更易形成大长径比微纤,从而改善分散相与基体相界面相容性,改善复合材料结晶行为,增加结晶度,提高EVA/PP原位微纤复合材料拉伸强度。     

Steady viscosity of a polymer/liquid crystal biphasic system

Steady shear viscosities of blends of poly(butyl acrylate) and cholesteryl oleyl carbonate were studied under a cone and plate fixture. Unique shear behavior was observed for the polymer/low molar mass liquid crystal mixture. The viscosity of the liquid crystal‐rich phase increases with polymer content until a maximum is reached. The height of the viscosity maximum decreases with the magnitude of the shear stress and disappears when the stress reaches 200 Pa. Addition of liquid crystal to the polymer‐rich phase causes a viscosity reduction, and at higher stress levels, the viscosity reduction becomes more effective with the same amount of liquid crystal addition. The viscosity reduction may be related to the fibril morphology of the liquid crystal and the viscosity maximum can be interpreted by the emulsion effect being counteracted by a viscosity reduction effect. A shear‐thickening behavior was observed in the intermediate shear rates for the blends with a volume fraction of poly(butyl acrylate) between 9.4 and 49.8%. This is a novel liquid–liquid system that exhibits a shear thickening behavior. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 25–30, 2004     

Liquid crystal polymer/polyethylene blends for thin film applications

A series of liquid crystal polymer/polyethylene (LCP/PE) blends have been studied to determine the potential of such a system to produce a high modulus film material which retains fabrication and low temperature characteristics of some current PE films. The subject of liquid crystalline polymer blends has been the focus of significant attention for the last decade due to the novel rheological and mechanical properties of this class of polymers. It has been demonstrated that if an LCP blend is processed under elongational flow conditions, the partially ordered LCP meso-phase intermediate allows the development of an oriented fibrillar morphology which is retained upon solidification. In this study, blown films of blends of 5 and 15% LCP in PE have been produced which show an enhancement in modulus over the neat PE matrix. These results are discussed in terms of processing conditions, LCP reinforcement aspect ratio, fibril diameter, and LCP/PE modulus ratio.     

乙烯-醋酸乙烯酯共聚物/高密度聚乙烯的性能研究

讨论了不同高密度聚乙烯(HDPE)含量的乙烯-醋酸乙烯酯共聚物(EVA)/HDPE共混物的流变性能、热性能、相容性,以及共混纤维的可纺性、力学性能。实验结果表明:随着HDPE含量的增加,共混物的流动性变差;共混物的晶区是部分相容的。当共混物中HDPE的百分含量为15%时,共混物的可纺性及共混纤维的力学性能最佳;随着拉伸倍数的增加,共混纤维断裂强度增大、断裂伸长率降低。     

Melt viscosity reduction of polycarbonate with low molar mass liquid crystals

The phase behavior and rheological behavior of low molar mass liquid crystal (LLC) and polycarbonate blends is firstly reported. The results of small angle light scattering (SALS) indicate that the LLC is miscible in the mixture for weight fractions of LLC less than 6%. Mixtures of two different liquid crystals with two different molecular weight of polycarbonate were prepared inside the miscible regime of the blends. Both the complex and steady shear viscosities of the blends were found to be significantly decreased upon addition of small amounts of liquid crystal (1% by weight). At low shear rate, the steady state shear viscosity was similar to the pure polycarbonate, whilst, at higher shear rates, three further regimes of behavior, as has been described for liquid crystals and liquid crystal polymers, were found despite the low concentration of LLC; hence, the rheological properties of the blends can be significantly modified by small concentrations of LLC (as low as 1%). The decrease in melt viscosity of polycarbonate that we observe upon addition of LLC is not due to lubrication effects at the interfaces, as shown by reproducible oscillatory shear flow sweeps. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

热致性液晶共聚酯／聚丙烯共混物

通过熔融共混制备了不同配比的（ＰＨＢ／ＰＥＴ）／ＰＰ共混物，研究表明，共混物的弯曲弹性模量，弯曲强度及拉伸强度均比ＰＰ有所提高，当液晶含量为１５％，ＰＰ－ｇ－ＭＡＨ为２０％时，（ＰＨＢ／ＰＥＴ）（ＰＰ－ｇ－ＭＡＨ）／ＰＰ三元共混物弯曲弹性模量最大，ＰＰ－ｇ－ＭＡＨ作为两相界面相容剂，改善了两相间的亲合性。ＤＳＣ分析表明，共混物中ＰＰ相的结晶温度有较大幅度的提高，（ＰＨＢ／ＰＥＴ）共聚酯起了ＰＰ结晶     

Influence of interactions on the mechanical,morphological and thermal properties of in situ ternary composites based on fluorocarbon elastomer,acrylic elastomer and liquid crystalline polymer blends

The mechanical, morphological and thermal properties of the binary and ternary blends of a fluorocarbon elastomer (FKM), an acrylic elastomer (ACM) and a liquid crystalline polymer (LCP) were investigated. The ternary blends were prepared by varying the amount of the LCP but fixing the ratio of the FKM and ACM. Addition of a third component, a polyacrylic rubber which interacted with the LCP, facilitated the structural development of the LCP phase by acting at the interface. The mechanical properties of the ternary blends were substantially improved because of both the fibril generation and adhesion of rubber particles on the LCP fibrils, which were attributed to the ACM interaction. Morphological investigations suggest that the fine fibrillation of the LCP domains is more apparent in the ternary blends than in the binary blends of FKM and LCP prepared under the same processing conditions. Thermogravimetric analysis (TGA) revealed an improved thermal stability of the FKM in the presence of the LCP for the binary blends, but a lower thermal stability for the ternary blends. Copyright © 2005 Society of Chemical Industry     

Effect of die geometry on the structural development of a thermotropic liquid crystalline polymer in a thermoplastic elastomer matrix

This study investigates deformation of a thermotropic liquid crystalline polymer (TLCP) in different die geometries. Blends of aTLCP with a thermiplastic elastomer of EPDM were made in a twin-screw extruder. Morphological observation of the extruded blends demonstrates the complimentary effect of shear in the die exit on dispersed phase deformation and fibril formation. Shear strain can affect fibril formation for a relatively large dispersed phase in the region close to the die wall. However, the main role of shearing is in breaking up the larger particles and initial polydomain structure. A strong elongational deformation on the blended melt after the die exit is required, and fine microfibrils normally obnserved in in situ composites were not easily formed by shear deformation only in the die.     

Morphology and mechanical properties of fibers from blends of a liquid crystalline polymer and poly(ethylene terephthalate)

The domain morphology and mechanical properties of fibers spun from blends of a thermotropic liquid crystalline polymer, Vectra A-900, and poly(ethylene terephthalate) (PET) have been studied across the entire composition range. The PET phase was removed by etching to reveal fibrillar LCP domains in the blends of all compositions. The 0.5μm fibril appeared to be the basic structural entity of the LCP domains. A primary effect of composition was the change from discontinuous fibrils when the composition was 35 and 60% by weight LCP to continuous fibrils when the composition was 85 and 96% LCP. This transition had major ramifications on the mechanical properties: the modulus increased abruptly between 60 and 85% LCP, and a change in the fracture mode from brittle fracture to a splitting mode was accompanied by an increase in fracture strength. Different models were required to describe the mechanical properties of the discontinuous and continuous fibril morphologies. Analytic models for short aligned fibers of Nielsen, and Kelly and Tyson were applicable when the LCP fibrils were discontinuous, while modulus and strength of blend fibers with continuous LCP fibrils were discribed by the rule of mixtures.     

Hyperstructured polyacetylene

Current progress in the synthesis and properties of conjugated polymers is presented by focusing on recently put forward hyperstructured helical polyacetylene. Interfacial polymerization of acetylene has been carried out in an asymmetric reaction field consisting of chiral nematic liquid crystal (N*‐LC) and Ziegler–Natta catalyst. Since the chiral nematic liquid crystal is composed of nematic liquid crystal and a chiral compound such as axially chiral binaphthyl derivative with R‐ or S‐configuration, the screw directions of the polyacetylene chain and fibril bundle and even the spiral morphology are rigorously controlled by selecting the chirality of the chiral compound. Surprisingly, the screw directions of the fibril and the bundle of fibrils in helical polyacetylene were found to be opposite to that of N*‐LC. It is worthwhile to emphasize that the hierarchical spiral morphology involving the primary to higher order structure is generated in a synthetic polymer such as polyacetylene by using N*‐LC as an asymmetric polymerization solvent. Copyright © 2007 Society of Chemical Industry     

UHMWPE/流动改性剂共混物的结晶形态研究

采用Haake转矩流变仪制备了超高分子量聚乙烯(UHMWPE)与流动改性剂(FM4)的二元共混物,并通过差示扫描量热法和广角X射线衍射图谱对共混物的结晶形态进行了研究。结果表明,在二元共混物中,UHMWPE与FM4之间形成了共结晶,通过计算发现共混物的结晶度随FM4含量的增加而提高;并利用共混物的结晶形态对其力学性能进行了分析。