熔体温度对聚四氟乙烯结晶形态的影响

用小角光散射、电子显微镜等方法研究了熔体温度对熔融结晶的PTFE结晶形态的影响。结果表明,当熔体温度超过400℃时,PTFE的结晶形态从棒晶逐步向球晶转化,力学性能也随之变坏。DSC的研究阐明,形态与力学性能的变化是由于大分子的降解,而不是因为熔体中发生了物理转变所致。

INFLUENCE OF THE MELT TEMPERATURE ON THE CRYSTALLINE MORPHOLOGY OF POLYTETRAFLUOROETHYLENE

The influence of the melt temperature on the crystalline morphology of polytetra-fluoroethylene was studied by Small Angle Light Scattering and Electron Microscope techniques. When PTFE was melt-crystallized from temperature below 400℃ under slow cooling rate, the rodlike morphology was obtained; when it was crystallized from temperature above 455℃, the spherulitic morphology was formed. From the intermediate temperature range, the formed sheaflike morphology can be viewed under electron microscope. The DSC study shows that the change of morphology with melt temperature is due to chain scission of macromolecules. The decrease of molecular weight of PTFE with heat-treat temperature was estimated by the measurement of heat of crystallization using Suwa's relation and the deterioration of mechanical property with the increase of heat-treat temperature was also noticed.