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用差示扫描量热仪与扭辨分析检出了四氟乙烯-六氟丙烯共聚物熔体中的转变。为了阐明转变的性质,用毛细管流变仪和微型平板粘度计研究了其熔体粘度的温度依赖性。发现,当温度上升到转变温度附近,熔体粘度先升高,然后下降,其粘度行为与热致型小分子液晶相似。但用偏光显微镜观察FEP共聚物熔体,未发现双折射现象。根据实验结果对转变的机制提出了解释。
The transition in the melt of the tetrafluoroethylene-hexafluoropropylene copolymer was detected by differential scanning calorimetry and twist analysis. To clarify the nature of the transition, the temperature dependence of melt viscosity was investigated using a capillary rheometer and a mini-plate viscometer. It is found that when the temperature rises to near the transition temperature, the viscosity of the melt first increases and then decreases, and its viscosity behavior resembles that of a thermally induced small molecule liquid crystal. However, observation of the FEP copolymer melt with a polarizing microscope revealed no birefringence. Based on the experimental results, the mechanism of transformation is proposed.