热致液晶聚合物共混改性聚酰胺的研究进展

综述了近几年来热致性液晶聚合物(TLCP)与聚酰胺(PA)共混改性的研究进展,以及TLCP的加入对PA的熔融和结晶行为、粘度、形态结构以及力学性能方面的影响,并阐述了增容技术在共混改性中的重要性。     

尼龙6共混改性研究进展

系统介绍了国内外用聚乙烯、聚丙烯、PVDF、PAR、PET、PVOH、ABS、PC、PPO、SAN、弹性体、TLCP等改性尼龙 6的系列方法、研究成果及其性能 ,并提出了反应挤出共混改性和无机纳米材料改性尼龙 6的设想     

环氧树脂共混改性及其发展趋势

综述了环氧树脂共混改性的主要方法及最新进展,对环氧树脂互穿网络聚合物(IPN)和热致液晶聚合物(TLCP)改性环氧树脂的前景进行了分析。     

热致液晶共聚酯——聚磷酸酯原位复合体系的性能

液晶共聚酯60PHB/PET(TLCP)与聚碳酸酯(PC)共混可制备原位复合材料,两者1:1的共聚物(TLCP-b-PC)可作其共混体系的相容剂。本文对该原位复合体系的流变性能、力学性能、纺丝性能和微观形态作了讨论。结果表明:该体系为切力变稀流体;PC:TLCP:TLCP-b-PC组成为79:19:2时,综合力学性能最优;不同原位复合体系最佳纺丝温度各不相同;相容剂对提高界面粘合力起了良好的作用。     

TLCP/GF混杂增强聚醚砜酮复合材料的研究

用热致性液晶聚合物(TLCP)和玻璃纤维(GF)对二氮杂萘酮联苯结构聚醚砜酮(PPESK)进行混杂增强改性,用双螺杆挤出机通过熔融共混的方式制备了改性PPESK复合材料。研究了PPESK/TLCP、PPESK/TLCP/GF复合材料的加工性能和力学性能,并对复合材料的拉伸断面形貌进行观察。结果表明,随着TLCP用量的增加,熔体的粘度逐渐降低,加工流动性得到改善;TLCP/GF的混杂增强使PPESK复合材料的拉伸强度得到一定提高,冲击强度有所降低;TLCP用量小于10份时,TLCP以球状粒子或棒状形式存在,当TLCP用量为20份时,TLCP在材料中形成直径为亚微米数量级的高长径比微纤。     

高流动性聚酰胺6、聚碳酸酯复合材料

通过熔融共混的方法制备出一类含有玻璃纤维(GF)或玻璃微珠(GB)和热致液晶聚合物(TLCP)的聚酰胺6(PA6)、聚碳酸酯(PC)增强／填充塑料。毛细管流变测试表明，TLCP作为一种加工助剂，少量加入即可有效降低基体树脂(PA6、PC)的熔体表观黏度。而对于含有短纤维或刚性颗粒填料的三元混杂复合材料，在5％～55％(质量含量，下同)较宽的填料含量范围内，三元混杂复合材料的熔体表观黏度在一定的剪切速率范围内低于或接近于任一纯树脂或任一二元共混物的熔体表观黏度，说明这类增强／填充塑料具有优异的加工流动性。     

回收PET与PC熔融共混改性研究

以回收的聚对苯二甲酸乙二酯(R-PET)瓶片为主要原材料,以聚碳酸酯(PC)为改性材料,通过加入酯交换催化剂单丁基氧化锡(MBTO)和反应性增韧剂乙烯-丙烯酸丁酯-甲基丙烯酸缩水甘油酯(PTW),采用双螺杆挤出机熔融共混的方法制备了R-PET/PC共混改性材料。研究了MBTO和PTW对共混改性材料力学性能、特性黏度的影响,并观察了其冲击断面形貌。结果表明,酯交换催化剂MBTO可以催化R-PET与PC的酯交换反应,改善R-PET与PC间的相容性和R-PET/PC共混改性材料的力学性能,提高其特性黏度;PTW可以有效提高R-PET/PC共混改性材料的冲击强度和特性黏度;同时加入MBTO与PTW时,能够提高R-PET/PC共混改性材料韧性和特性黏度。SEM观察表明,只加入PTW的R-PET/PC共混改性材料的相容性最好,同时加入MBTO和PTW的R-PET/PC共混改性材料的相容性比未加PTW的好。     

温差共混法制备聚丙烯／热致液晶原位增强复合材料

采用温差共混法制备了聚丙烯／热致液晶（PP／TLCP）原位增强复合材料，研究了其共混物微观形貌以及力学性能。SEM分析表明，TLCP在体系中的成纤效果受到其含量的影响，当TLCP含量达到30％时，体系的表层和芯层均形成取向良好的TLCP纤维。力学性能分析表明，当TLCP含量低于20％时，PP／TLCP共混物的拉伸强度和拉伸模量均随着TLCP含量的增加而提高，断裂伸长率则有所下降。     

汽车用ABS/PC共混物改性研究进展

综述了近年来汽车用丙烯腈-丁二烯-苯乙烯共聚物/聚碳酸酯(ABS/PC)共混物改性的研究进展,通过对ABS/PC共混物的改性,提高了ABS/PC共混物的阻燃性、导电性及力学性能。分析讨论了汽车对各种改性材料的需求,并对汽车用ANN/PC共混物改性的发展方向做出了展望。     

热致液晶聚合物的研究进展

热致液晶聚合物(TLCP)在电子电器、汽车、航天航空等领域有着广泛的应用。本文介绍了TLCP的主要合成方法与工艺及其成型加工技术,同时对近年来通过分子结构设计、聚合工艺及合金化、填充和增强等共混改性方法实现高性能化、功能化的新产品及其最新应用进行了综述。     

Inhibited transesterification and enhanced fibrillation of TLCP by nano-SiO2 in polycarbonate matrix

Hybrid composites composed of a thermotropic liquid crystalline polymer (TLCP), nano-SiO₂ and polycarbonate (PC) were prepared by melt blending in a twin-screw extruder. Infrared spectroscopy analysis indicated that the transesterification between PC and TLCP molecules during melt blending was significantly reduced in TLCP/PC blends filled with nano-SiO₂, compared to the unfilled TLCP/PC one. Scanning electron microscopy (SEM) observation showed that better compatibility and finer TLCP dispersion were reached in the unfilled blend, which made the fibrillation of TLCP difficult in capillary flow even at high shear rate. In contrast to this, well-developed TLCP fibrils were formed by capillary flow in nano-SiO₂ filled TLCP/PC blends. By increasing the nano-SiO₂ concentration and shear rate, the fibrillation of TLCP was significantly enhanced. Thermodynamically the interfacial tension between these components and dynamically the viscosity ratio of TLCP to PC were used to investigate the mechanism of nano-SiO₂ in inhibiting the transesterification and enhancing the fibrillation of TLCP droplets in these hybrid composites.     

热致液晶高分子与尼龙共混改性进展

综述了近几年来热致液晶聚合物（ＴＬＣＰ）与尼龙（ＰＡ）共混改性的新进展，简要介绍了ＴＬＣＰ的加入对ＰＡ的熔融和结晶行为、粘度、形态结构以及力学性能等的影响，并阐述了增容技术在共混改性中的重要性以及影响ＴＬＣＰ成纤的主要因素。     

UHMPET/TLCP/PVDF共混体系的研究

采用原位复合法对Veclra A-950热致液晶聚合物（TLCP）、聚偏氟乙烯（PVDF）与超高摩尔质量聚酯（UHMPET）进行共混改性，以改善UHMPET的加工流动性。对其流变性能、热性能以及共混形态进行了探讨。研究了不同混合方法和不同TLCP与PVDF用量对UHMPET各种性能的影响。结果表明，当采用HAAKE流变仪进行混合时，TLCP在UHMPET中呈珠状，二者之间的界面比较模糊，说明两者之间存在相互作用；而采用挤出拉丝时，TLCP在UHMPET中形成明显的微纤状；PVDF在UHMPET基体中无论是采用HAAKE流变仪进行混合还是挤出拉丝，基本上都呈珠状，而且与UHMPET之间存在着明显的界面，在DSC曲线上表现出特有的转变峰，说明两者的相容不好。TLCP和PVDF对改善UHMPET的加工流动性都有贡献。     

Study of the Processing and Mechanical Properties of In Situ Composite Materials of Thermoplastics with Thermotropic Liquid Crystalline Polymers

By blending thermoplastics (TPs)—polycarbonate (PC) and polyethersulfone (PES)—with thermotropic liquid crystalline polymers (TLCPs)—KU9221 and KU9231—and then extruding the blends to form fibers, the in situ reinforcing characteristics were studied. The injection experiment of blends was compared with the extrusion experiment. According to the experimental results, in situ reinforcing characteristics of these processes were analyzed theoretically. These researches have come to some important conclusions. TLCP domains can be transformed to form fibers that are oriented in the direction of flow during processing; these TLCP microfibers result in improved mechanical properties of the TP/TLCP blends. The extruding flow is more effective in orienting TLCP domains and results in better in situ reinforcement than that of injection molding, and the extruded fibers have better mechanical properties. The mechanical properties of the blend fibers are improved greatly with increasing tensile ratio of melt drawing and the content of TLCPs.     

A comparative study of thermotropic LCP and organoclay as fillers in high molecular mass polyethylene with different blending sequences

The influences of thermotropic liquid crystalline copolyester (TLCP) on viscosity reduction in high molecular mass polyethylene (HMMPE) filled with organoclay were investigated by controlling the blending sequence. The interactions between organoclay and TLCP in HMMPE create different morphologies and influence rheological properties of the clay/TLCP/HMMPE blends. When the organoclay was blended with TLCP first, large amounts of organoclay formed partially intercalated structures in TLCP, with phase separation occurring at the temperature when TLCP was in the nematic phase, corresponding an antagonistic effect which weakens viscosity reduction ability of TLCP for HMMPE. However, with first blending of TLCP with HMMPE and then adding organoclay into the blend, most of the organoclay enriched on TLCP surfaces in the blend. Such interaction prevents TLCP droplets from coalescing at high shear stresses, enlarging the processing window. A phenomenological model, originally for HMMPE/TLCP systems, was successfully adopted to predict the flow behaviors of clay/HMMPE/TLCP blends. POLYM. ENG. SCI., 50:1679–1688, 2010. © 2010 Society of Plastics Engineers     

Reinforcement of mechanical properties of a poly(ethylene terephthalate) and polycarbonate blend by the addition of thermotropic liquid crystalline polymer

Mechanical properties of the ternary blends of poly(ethylene terephthalate) (PET), polycarbonate (PC), and thermotropic liquid crystalline (TCLP, Vectra A950) were investigated. The ternary blends were prepared by varying the amount TLCP but fixing the ration of PET and PC. The fiber fallen freely through the capillary die had the highest initial modulus (1.46 GPa)/tensile strength (73 MPa) when 10% of TLCP was added. Above this TLCP content, however initial modulus and tensile strength decreased. The scanning electron microscope (SEM) micrographs of the TLCP phase which was extracted by dissolving PET/PC matrix from the blend showed the fine fibrils formed at 5 and 10% of TLCP, while the aggregated TLCP phases at 20 and 30% of TLCP. It was suggested that the decrease of the mechanical properties of the resulting blend was caused by the aggregation of TLCP phase above 10% of TLCP. A high draw ratio gave a rise to the formation of highly oriented fibrils of TLCP phase in the PET/PC matrix and the improvement of mechanical properties of the ternary blend.     

Morphology evolution of a thermotropic liquid‐crystalline polymer in a polyamide 6,6 matrix regulated by graphene

A two‐step process, thermotropic liquid‐crystalline polymer (TLCP) premixing with reduced graphene oxide (RGO) followed by blending with polyamide 6,6 (PA66), was used to prepare ternary TLCP/RGO/PA66 blends. The rheological behaviors, morphology, and mechanical properties of the blends were investigated. The results show that RGO migrated from the TLCP phase to the interface between the TLCP and PA66 phase during melt blending; this was due to a similar affinity of the RGO nanosheets to both component polymers. The dimensions of the dispersive TLCP domains were markedly reduced with the mounting RGO content; this revealed a good compatibilization effect of RGO on the immiscible polymers. The hierarchical structures of the TLCP fibrils were found in both the unfilled TLCP/PA66 blends and TLCP/RGO/PA66 blends. This supposedly resulted from the extensional and torsional action of unstable capillary flow. With the addition of RGO, the viscosities of the blends decreased further, and the fibrillation of TLCP and the mechanical performance of TLCP composites were both enhanced. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43735.