Mechanical Properties of Ultra-Quenched Polytetrafluoroethylene Cast Film

Structures and mechanical properties of the ultra-quenched polytetrafluoroethylene cast film (UQ-PTFE), which was prepared by being rapidly immersed into the ethanol/methanol mixed gel (-160°C) cooled in liquid nitrogen after the sintering at 400°C for 60min, being compared with those of the slowly cooled PTFE cast film (SC-PTFE). The degree of crystallinity of UQ-PTFE was about 30%, which increased with decreasing the cooling rate to be 80% finally for the slowly cooled sample. The distinct morphological characteristics or the band structure was not observed in the UQ-PTFE, which was highly transparent. The breaking elongation of SC-PTFE decreased as temperature reduced from 50 to 0°C, while high tensile strength and high breaking elongation of UQ-PTFE were retained even at 0°C. The transitional phenomena in the crystalline region was also examined using thermomechanical analysis and dynamical viscoelasticy measurement, being associated with the molecular mobility.