繰り返し温度変化による高強力ナイロン６繊維の構造変化

Abstract

Nylon 6 fibers are used as tire cord in carcass of automobile tire for rubber reinforcement to keep internal pressure. During run state, the internal part of tire is heated up to 100 °C and cooled by stopping, resulting in the same thermal history of Nylon 6 tire cord. It has been reported that crystal phase of Nylon is transformed to other phase under high temperature condition. In room temperature, two reflection peaks assigned to α-phase were observed by wide angle X-ray diffraction measurement for Nylon 6 fiber. On heating, these two peaks became one peak of pseudohexagonal phase at around 70 °C. This transition referred as the Brill transition took place repeatedly by heating and cooling. Also, tensile strength decreased with increasing temperature by heating and increased by cooling. For higher-order structure measured by small angle X-ray scattering, the long period of Nylon 6 lamella was constant on cyclic temperature changes. On the other hand, it was observed that the slope against fiber direction and the size of lamella were irreversibly changed at around 70 °C. It has been reported in former study that the Brill transition was observed at higher temperature region than 150 °C because samples were Nylon 6 pellets and films. Accordingly, the Brill transition temperature changed much lower in high oriented Nylon 6 fiber.