含热致液晶高分子的共混体系的粘度与形态结构

综述了含热致液晶高分子的高聚物共混材料粘度与组成的关系,分析了影响共混物形态结构特别是纤维状液晶分散相形成的各种因素。     

非弹性体增韧高分子材料的研究进展

对近些年来热塑性树脂增韧体系、核壳粒子增韧体系、液晶高聚物增韧体系及无机刚性粒子增韧体系等增韧高分子材料的研究进展进行了综述。指出非弹性体增韧拓展了高分子材料增韧改性研究的新领域；纳米粒子增韧开辟了高分子材料的研究新方向。     

非弹性体增韧高分子材料的研究进展

利用非弹性体可以使一些韧性较差的高分子材料达到有效增韧的目的，从热塑性塑料增韧体系、核壳粒子增韧体系、液晶高聚物增韧体系及无机刚性粒子增韧体系等方面分别进行了概述。综述了近年来科研工作者对非弹性体增韧高分子材料的研究进展状况。     

芳香族聚酰胺纤维

芳香族聚酰胺纤维是一种高性能高分子材料，重点介绍了ＰＰＴＡ、ＰＢＡ、Ｔｅｃｈｎｏｌａｒ、Ｘ—５００和Ｘ—７０２等芳香族聚酰胺的合成，以及这些高聚物的液晶纺丝方法与各向同性溶液纺丝方法．     

五种新型高分子液晶研究进展及应用前景

阐述了高分子液晶的形成条件,综述了纤维素液晶、甲壳素液晶、铁电液晶、盘状液晶、卤代液晶等五种新型高分子液晶材料的结构、性能及其应用前景,并对高分子液晶的发展方向进行了展望。     

芳香酯类液晶高分子的研究进展

液晶高分子在结构材料和功能材料方面被称为一类全新的高性能材料，而酯类液晶高分子作为液晶领域发展最为成熟的一个行业，已经取得了巨大的成就，其合成方法与性能研究也日臻完善。本文主要对酯类液晶的合成及其性能进行了归纳和评述，其主要侧重不饱和键、联苯、偶氮、胆甾醇及二茂铁等类型酯类液晶，并将一些具有特殊功能的酯类液晶也进行了简要的介绍，最后得出：酯类液晶的合成方法简单、产率较高且大都具有液晶性。文章最后简要概述了其应用前景。     

热致液晶高分子与热塑性工程塑料合金的研究进展

对热致液晶高分子 /热塑性高聚物 (TL CP/ TP)原位复合材料的物理机械性能、共混加工、形态结构最新研究进展以及如何改善其共混体系相容性进行了论述 ,同时指出该材料在某些特殊用途的高性能工程塑料的应用前景看好。     

液晶高分子及其应用

液晶高分子是一类较新的高分子材料,是一类大规模研究工作起步较晚的液晶材料,但由于其本身无与伦比的优点,以及与信息技术、新材料和生命科学相互促进作用,已成为世纪之交的热点之一。简要介绍了液晶高分子聚合物的类型、特性、主要应用以及液晶高分子设计的前景。     

TLCP/TP共混改性研究进展

综述了热致性液晶高分子（TLCP）／热塑性高聚物㈤合金的研究进展，主要讨论了TL—CP／TP的增强机理、力学性能、流变学特点、共混体系相容性及结晶特点。     

分离膜高分子材料及进展

膜材料是膜分离技术的关键。本文主要介绍了具有重要应用和发展前景的5类高分子膜材料纤维素膜材料、聚酰亚胺膜材料、有机硅膜材料、液晶复合高分子膜材料、高分子金属络合物膜材料。内容涉及结构、性能、改进方法、用途等。     

Study on a series of main-chain liquid–crystalline ionomers containing sulfonate groups

A series of main-chain liquid–crystalline ionomers containing sulfonate groups pendant on the polymer backbone were synthesized by an interfacial condensation reaction of 4,4′-dihydroxy-α,α′-dimethyl benzalazine, a mesogenic monomer, with brilliant yellow (BY), a sulfonate-containing monomer, and a 1/9 mixture of terephthaloyl and sebacoyl dichloride. The structures of the polymers were characterized by IR and UV spectroscopies. DSC and thermogravimetric analysis were used to measure the thermal properties of those polymers, and the mesogenic properties were characterized by a polarized optical microscope, DSC, and wide-angle X-ray diffraction. The ionomers were thermally stable to about 310 °C. They were thermotropic liquid–crystalline polymers (LCPs) with high mesomorphic-phase transition temperatures and exhibited broad nematic mesogenic regions of 160–170 °C, and they were lyotropic LCPs with willowy leaf-shaped textures in sulfuric acid. However, the thermotropic liquid–crystalline properties were somewhat weakened because the concentration of BY was more than 8%. The inherent viscosity in N-methyl-2-pyrrolidone suggested that intramolecular associations of sulfonate groups occurred at low concentration, and intermolecular associations predominated at higher concentration. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2210–2218, 2001     

Phase behavior of blends of poly(ethylene terephthalate) with liquid-crystalline polymers

Poly(ethylene terephthalate) (PET) was melt blended with several liquid-crystalline polymers (LCPs), both with and without Ti(OBu)₄ catalyst. The LCPs, referred to as VA, LC5, LC3, and SBH, respectively, were Vectra-A950, Rodrun LC-5000, Rodrun LC-3000, and a laboratory copolyester of sebacic acid (S), 4,4′-diacetoxybiphenyl (B), and 4-acetoxybenzoic acid (H). Their degree of aromaticity decreases in that order. The phase behavior and the morphology of the blends were studied by differential scanning calorimetry and scanning electron microscopy. All the LCPs retard the dynamic crystallization of PET. The lower the LCPs degree of aromaticity, the more pronounced was the effect. It was not possible to obtain any evidence of ester exchange reactions by the reactive blending of PET with VA. On the contrary, appreciable changes of phase behavior and morphology were observed under comparable conditions for the other blends. With LC5 and LC3, the transesterification process predominantly involved the ET-rich phase of those polymers. Extensive transesterification occurred between PET and SBH, as proven by the gradual formation of a quasi homogeneous material, with lowered temperatures and enthalpies of fusion and crystallization. For blends with more than 25% SBH, homogenization is followed by the segregation of a new, highly aromatic phase.     

Reprocessing of liquid-crystal polymers: Effects on structure and mechanical properties

The effects of reprocessing by successive injection molding cycles on the structure and properties of two thermotropic liquid-crystal polymers (LCPs), namely Rodrun and Vectra, were analyzed. Reprocessing produces a clear decrease in the melt viscosity of both LCPs. This is attributed to molecular weight decreases as a consequence of chemical reactions. The reactions produced chain scission in both LCPs and new products in the case of Vectra. This gave rise to modifications in the crystalline behavior of Vectra that did not take place in the case of Rodrun. All these facts lead to, with the exception of the modulus of elasticity of Rodrun, an overall decrease in properties, more marked in the case of Vectra. © 1995 John Wiley & Sons, Inc.     

Immiscible polymer blend electrorheological fluids: Composition dependence

We investigated the composition dependence of the electrorheological properties of immiscible polymer blends which consist of liquid crystalline polymers (LCPs) and polydimethylsiloxane (DMS). We used two different kinds of LCPs, designated as A and B polymers. We observed that for a fixed ratio of an LCP and DMS (LCP:DMS = 2:1) the electrorheological properties change from type I to type II as the fraction of the A polymer is reduced. Microscopic observations indicate that the change in the electrorheological properties is associated with the structural change; in type I, LCP droplets are dispersed in DMS, while in type II, DMS droplets are dispersed and, furthermore, that the structural change is associated with the miscibility between DMS and the LCPs; the A polymer is partially miscible with DMS, while the B polymer is hardly miscible with DMS. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3673–3680, 2002     

Thermotropic liquid crystalline polymers as protective coatings for aerospace

Liquid crystalline polymers (LCPs) have potential as multifunctional, environmentally friendly coatings for aerospace, overcoming the disadvantages of current materials. Their use, however, has been hindered mainly by their poor adhesion strength. The present work studies novel liquid crystalline thermosetting polymers (LCTs), which can overcome the disadvantages of commercial LCPs for protective coatings in aerospace applications. Phenylethynyl terminated liquid crystalline oligomers based on 4-hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid (HNA) were synthesized and melt-pressed on grit-blasted aluminum to obtain 25 μm and 80 μm thick coatings. The presence of coating defects and curing kinetics were investigated, and the adhesion, mechanical properties and environmental resistance were compared with a commercial LCP reference material (Vectra^®). The LCTs showed highly improved adhesion; moreover, fully cured LCTs are harder and stiffer than commercial LCPs, which are expected to increase their wear and impact resistance. The coatings showed no swelling, peeling, or blistering after 500 h of full immersion in fluids such as jet fuel and turbine oil; furthermore, LCTs resisted 1000 h in corrosive fog (salt-spray) and hot moisture. Exposed samples retained their hardness, modulus, and pull-off strength, evidencing the outstanding chemical resistance of these LCTs. Our findings showed the potential of LCTs as protective and wear resistant coatings, particularly in the aggressive environments of aerospace applications. However, results suggest that exposed coating/substrate interfaces constitute paths for environmental attack. Further research aims at elucidating the possible mechanisms.     

Processing and characterization of blends of fluoroelastomers with semirigid liquid crystal polymers

Fluoroelastomers (FEs) usually have working temperatures above 150°C and a great resistance to aggressive agents such as oils, fuels, aliphatic and aromatic solvents, steam, moderate acid, and basic environments. Liquid crystal polymers (LCPs) can be effective processing aids and reinforcing agents for elastomers. These characteristics are very attractive to lower melt viscosity and to stiffen and strengthen the final product through a simple blending. Among the LCPs, the semirigid LCPs seem the most appealing for blending with flexible thermoplastics (FTs) because their processing temperatures can be arranged to be in the same processing temperature range of FTs and because the presence of flexible segments can improve the compatibility with the flexible matrix. This is very important especially for FEs that are subjected not only to mechanical degradation, but also to thermal degradation. Blends of FEs with two types of semirigid LCPs show easy processability and enhanced mechanical and thermomechanical properties. These improvements were observed both for pure FEs and for filled vulcanized systems. The improvement of the mechanical properties is below that expected on the basis of the additive rule due to the incompatibility between the components; nevertheless, an impressive increase of the elastic modulus, up to 40 times, was noticed by adding 20% of LCP. In vulcanized systems, the tensile strength is also increased, whereas the elongation at break is slightly reduced. The working temperature is also drastically increased both in vulcanized and in unvulcanized systems. © 1996 John Wiley & Sons, Inc.     

低品位菱镁矿与硅石制备镁橄榄石的研究

以低品位菱镁矿与天然硅石为原料制备镁橄榄石材料。研究了低品位菱镁矿轻烧氧化镁粉引入量对制备的镁橄榄石材料中镁橄榄石的晶胞常数、微观结构及常温性能的影响。用X射线衍射（XRD）和扫描电镜（SEM）对试样的相组成和显微结构进行了研究。利用X′ pert plus软件对试样中镁橄榄石相的晶胞常数进行分析。结构与性能分析结果表明：低品位菱镁矿中氧化镁与天然硅石中二氧化硅在高温条件下通过固相反应可以制备出以镁橄榄石为主晶相的镁橄榄石材料。随着低品位菱镁矿轻烧氧化镁粉引入量的增加,镁橄榄石材料中镁橄榄石相的晶胞常数和晶胞体积有增加趋势。同时,随着方镁石相在镁橄榄石材料中的脱溶作用,镁橄榄石材料的体积密度和强度逐渐降低,显气孔率和吸水率逐渐增加。     

Toughening liquid‐crystalline polymers with polyethylenes containing epoxy functionality

To improve toughness, a liquid‐crystalline polymer (LCPs) was blended with polyethylenes containing epoxy functionality in concentrations of 2, 6, and 15 wt %. The blends were prepared with a corotating twin‐screw extruder and were injection‐molded into specimens for mechanical testing. The effect of the amount of the epoxy‐functionalized polyethylenes on the morphology and mechanical and thermal properties was studied. The toughness improved with increasing amount of functionalized polyethylene, and the blend containing 15 wt % epoxy‐functionalized polyethylene had the best toughness properties. Impact strength values up to three times higher than those of the neat LCP were achieved. However, the stiffness of the LCP concurrently decreased substantially. The morphology became much more uniform, and the melting behavior changed. The results show that considerable improvements in the toughness properties of LCPs can be achieved with epoxy‐functionalized polyethylenes. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1886–1891, 2002     

Manufacturing and characterisation of microfibrillar reinforced composites from liquid crystalline polymers and poly(phenylene ether)

Abstract

The purpose of the present study was to investigate the fibrillisation process of liquid crystalline polymers (LCPs) in an amorphous poly(phenylene ether) (PPE) matrix during melt blending and a subsequent drawing operation, as well as to analyse the relationship between morphology and mechanical properties of the fibrillar reinforced LCP/PPE blends. In order to understand the effect of the compatibility between the blend partners, an additional set of LCP/PEE blends, containing different amounts of a compatibiliser, was studied too. The processing steps included: (i) melt extrusion and continuous hot stretching for fibrillisation of the LCP component in the different LCP/PPE blends, and (ii) compression (CM) or injection moulding (IM) of the drawn blends at temperatures below the melting temperature (T_m) of the LCPs. Samples from each processing stage were characterised by means of scanning electron microscopy (SEM), wide and small angle X-ray scattering (WAXS and SAXS), and mechanical testing. SEM and WAXS showed that the as extruded blends were isotropic, but after hot stretching the LCP components became highly oriented, with a high aspect ratio and a diameter of the fibrils between 0·4 and 3 μm. The fibrillated structure of the LCPs in the blends could be preserved after the compression and injection moulding only at temperatures below T_m of the LCPs. Addition of a compatibiliser to the LCP/PPE blend did not remarkably improve the adhesion between the components, as a result of the large difference between the coefficients of thermal expansion of the blend partners, which leads to different shrinkage conditions of the LCP fibrils and the PPE matrix. The flexural modulus (E) of all IM blends increased stepwise with an increase in the weight (wt) fraction of the LCP. At the same time, the highest values for the flexural strength (σ) were obtained for the LCP/PPE blends containing 5 wt-% LCP.     

Molecular orientation of extruded PET/LCP blend films. Part I: Polarized infrared spectroscopy

The polarized infrared (IR) spectroscopy technique was used to evaluate the surface uniaxial molecular orientation of films of poly(ethylene terephthalate) (PET), two thermotropic liquid crystalline polymers (LCPs), Vectra®A950 and Rodrun®LC5000, and their blends obtained by extrusion. The molecular orientation of the LCP and of the crystalline and amorphous PET phases in the draw direction was evaluated along the transverse section of the films and as a function of the blend composition. A compatibilizer agent was used to improve the interfacial adhesion between the PET and LCPs. The results showed that the surface molecular orientation of both LCPs was very high along the draw direction. However, when blended, the orientation of the LCP phase decreased drastically, it was dependent of its content and varied along the transverse section of the extruded films. The maximum orientation was observed in the blend with 5 wt % LCP content and at the position where the shear rate was maxima. The LCP Vectra®A950 showed higher orientation than the Rodrun®LC5000, as a pure material and as blended. For the PET phases, an alignment of the amorphous phase in the draw direction due to the presence of LCP and compatibilizer agent was observed. The crystalline phase of PET, however, showed no significant orientation in the draw direction. The compatibilizer agent proved efficient for both PET/LCP systems. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2241–2248, 2006