【摘要】 用扭辫分析(TBA)发现在四氟乙烯-全氟烷基乙烯基醚共聚物(PFA)熔体中存在转变T_uPFA从熔点以上T_u以下温度冷却结晶时形成无规晶片,从T_u以上温度冷却时形成球晶;而从转变温度范围冷却时,则形成棒晶或棒晶与其他晶型共存的形态.DSC研究表明,从T_u以下温度冷却结晶时,其速度要比从T_u以上温度冷却时为快,但转变时并无明显的热效应产生.根据上述结果,对PFA熔体中发生的转变性质提出了解释.我们认为,这种转变与分子链从伸展构象转变为卷曲构象有关.更多还原

【Abstract】 A physical transition Tu in the melt of tetraftuoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) can be detected by torsional braid analysis technique. The crystalline morphologies of the melt-crystallized PFA. also show a significant dependence on the melt temperature round about the transition temperature Tu. When PFA is cooled and crystallized from a temperature in the range of Tu to Tm, the randomly arranged lamella will be obtained, when it is cooled from a temperature above Tu, the spherulitic morphology will be formed; and when it is cooled from a temperature within the transition temperature range Tu, the rodlike morphology will be obtained. The isothermal crystallization rate, measured by DSG, also has a distinct change above and below Tu. But differential scanning calorimetry measurement does not show an endothermic peak occurring at transition temperature interval, so the transition is attributed to the change of chain configuration with the increase of temperature.更多还原