Morphological evolution of thermotropic liquid crystalline copolyester and its effects on rheological, thermal and flame-retarding behaviors of polycarbonate
2014
Shen, Jiabin | Chen, Baoshu | Zhu, Jiaming | Guo, Shaoyun | Wang, Yuzhong
Polycarbonate (PC)/phosphorus-containing thermotropic liquid crystalline copolyester (PHDDT) composites were prepared through a novel multistage stretching extrusion. The morphology of the PHDDT phase was controlled by combining an assembly of force-assembling elements (FAEs) with an extruder. SEM observation revealed that morphological evolution of PHDDT from platelets to microfibrils occurred by applying different number of FAEs. The dynamic rheological and thermogravimetric results showed that the increased interfacial area between PHDDT and PC led to a drastic reduction of the complex viscosity and a lower temperature of the maximum loss. Accompanied with the elongation of the PHDDT along flowing direction, the storage modulus and glass transition temperature of the composite were enhanced. However, compared with the system dispersed with the platelet-like phase, the micro-fibrillation of the flame-retarding PHDDT resulted in the decrease of the temperature of the heat release rate curve starting to rise up and the value of the limiting oxygen index. The confined space formed between the platelet-like PHDDT phase was considered to effectively retard the combustion of the whole material.
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