Shear-induced interactions in blends of HMMPE containing a small amount of thermotropic copolyester HBA/HQ/SA

Shear-induced interactions between high molecular mass polyethylene (HMMPE) melt and a thermotropic liquid crystalline copolyester, HBA/HQ/SA (TLCP) were investigated using large amplitude oscillatory shear and capillary shear. Polarized optical microscopy (POM) observations show that the mono-domain nematic TLCP droplets embedded inside a HMMPE melt may be readily elongated using large amplitude oscillatory shear. The HMMPE melt adjacent to the elongated TLCP filament was observed to crystallize faster than that in the matrix away from the interface. TEM analysis on the 1 wt% TLCP/HMMPE blend quenched after capillary shear shows that there are strong interfacial interactions between the elongated TLCP filament and the HMMPE matrix. Long range PE lamellae orientational order up to 2 μm away from the TLCP filament surface were observed, with all the lamellae surface normal parallel to the TLCP fiber. Additionally, a strong interfacial compatibility between the TLCP filament and the HMMPE matrix with an interfacial thickness of ∼30 nm has also been observed. The enhanced interfacial compatibility is attributed to the -CH₂- group interactions due to chain alignment in both components at their interface. These results provide a fundamental insight to other TLCP containing thermoplastics where compatibilities may be present due to segmental interactions.     

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。     

加捻对热致液晶聚芳酯初生纤维拉伸性能的影响

热致液晶聚芳酯（TLCP）的特殊化学结构使其具有高强度、高模量、低粘度、易加工等诸多优良特性,且TLCP纤维力学性能对其应用于纺织业具有举足轻重的作用。本论文主要研究加捻对TLCP纤维力学性能的影响,探究其影响机理。研究结果表明：加捻对其力学性能影响很大,TLCP纤维束的强力随着捻度的增加呈先增大后减小趋势。当TLCP纤维束的线密度为52.50 tex,捻度为130Tm时,最大强度为9.14 cN/dtex。未加捻TLCP单纤维的线密度为1.394 tex时,最大强度为11.3cN/dtex。     

TLCP/PPS 原位成纤共混纤维的非等温结晶动力学

 通过熔融纺丝法制备热致性液晶（TLCP）/聚苯硫醚（PPS）原位成纤共混纤维,TLCP微纤的形成将有效增强PPS基体的力学性能,并能优化纺丝工艺。考虑到实际纺丝过程是一个非等温结晶过程,因而首先研究了共混纤维的非等温结晶动力学行为。采用差示扫描量热仪（DSC）,通过非等温结晶方法研究了TLCP微纤对PPS基体结晶行为的影响,并用Jeziorny模型描述了非等温动力学。研究表明,TLCP/PPS原位成纤共混纤维的非等温结晶动力学过程能够使用Jeziorny模型来描述。在共混过程中,TLCP微纤结构起到异向成核的作用,提高结晶速率和结晶温度,降低半结晶时间。此外,采用扫描电镜（SEM）观察了挤出共混物表面形貌及共混纤维的TLCP微纤结构。     

环氧树脂低聚物原位增容PA66/TLCP共混物

用环氧树脂低聚物作界面增容剂,熔融挤出法制备了PA66/TLCP共混物。通过拉伸、弯曲等力学性能测试并结合热失重(TG)分析,结果表明:环氧树脂低聚物增容后的共混物力学性能、热稳定性均有显著提高。共混物断面SEM扫描结果表明,由于环氧树脂低聚物界面增容作用,分散相TLCP在基体PA66中的分散性提高并且相畴尺寸减小。加工流变学测试和红外光谱显示,环氧树脂低聚物与基体树脂PA66和分散相TLCP分子在熔融加工过程中原位发生化学反应,环氧树脂低聚物在共混物界面起到桥的作用。     

马来酸酐接枝三元乙丙共聚物对PA/TLCP共混物摩擦磨损行为的影响

采用MM-2000型摩擦磨损试验机评价了PA/TLCP二元共混物的摩擦学性能;同时考察了马来酸酐接枝三元乙丙共聚物对PA/TLCP二元共混物摩擦学性能的影响.分析测试结果表明:引入马来酸酐接枝三元乙丙共聚物为相容剂能够有效地提高界面增容作用,材料力学性能提高;同时,相容剂的加入,改善TLCP与基体PA66的结合强度,提高了共混物的耐磨性,也有利于转移膜的形成.     

热致性液晶/埃洛石纳米管/尼龙66导热原位混杂复合材料的结构与性能

采用熔融共混方法制备了热致液晶聚合物(TLCP)/埃洛石纳米管(HNTs)/尼龙66(PA66)原位混杂复合材料,研究了其导热性能、力学性能及微观形态。结果表明:在实验范围内,复合材料的导热性能及力学性能均随着HNTs含量的增加而提高,当HNTs质量分数增至40%时,复合材料的导热系数、热变形温度、拉伸强度、弯曲强度及弯曲模量分别提高了134%、144%、15.3%、31.9%、231%;扫描电子显微镜(SEM)显示,TLCP及HNTs均能在基体中均匀分散,并能观察到TCLP所形成的沿纤维轴方向取向的微纤及HNTs所形成的导热网链。     

环氧树脂增韧研究

综述目前环氧树脂增韧的几种最新机理,如分散相的撕裂和塑性拉伸、钝化基体树脂裂纹、裂纹钉铆、逾渗理论及其他几种增韧机理。探讨了橡胶弹性体、热塑性树脂、柔性链段固化剂、刚性纳米粒子、热致液晶(TLCP)、核-壳结构(CSP)、互穿网络(IPN)等增韧环氧树脂的方法及其相应机理,并指明了今后环氧树脂增韧研究发展方向。     

聚丙烯/热致性液晶聚合物原位复合材料的研究进展

聚丙烯是一个通用塑料,为了提高聚丙烯的性能,拓宽其应用领域,人们对聚丙烯进行了改性研究.笔者简述了热致液晶聚合物原位复合改性聚丙烯的研究进展,并讨论热致液晶聚合物对聚丙烯结晶与熔融行为、微观结构、流变性及力学性能的影响,介绍了改进TLCP与PP之间相容性的常用方法.最后对TLCP/PP原位复合材料的发展提出一些看法.     

A phenomenological model for the viscosity reductions in blends of HMMPE containing a small quantity of thermotropic liquid crystalline copolyester HBA/HQ/SA

In this paper, we present a phenomenological model for the viscosity changes in bulk high molecular mass polyethylene (HMMPE) due to the addition of a very small quantity of a main chain longitudinal thermotropic liquid crystalline polymer (TLCP) containing flexible spacers. The chain alignment in the elongated TLCP domains causes chain alignment and disengagement in the neighboring HMMPE melt. In converging capillary flows, this occurs at a certain critical centerline velocity. After the onset of such transition, melt of elongated chain conformations forms from the center core and expands towards the capillary wall with increasing flow rates. The model successfully predicts both the drastic viscosity reduction effects and the critical yield stress in the HMMPE+TLCP blends without any adjustable parameters. Our model is also applicable to other systems that undergo flow-induced phase transitions, e.g. in biphasic liquid crystalline polymer melts.