Effect of fine structure on fatigue resistance property of poly(ethylene terephthalate) tire cord fibers

Abstract

Seven experimental poly(ethylene terephthalate) (PET) fibers were spun and then drawn under different processing conditions (i.e., spinning speed and draw ratio) in such a way that the fibers possessed different long periods but retained the same crystal structure. Wide angle X‐ray diffraction, small angle X‐ray scattering, loss modulus, initial modulus, and taut tie molecules measurements were used to characterize the fine structure and the physical property of the fibers. The influence of the fine structure on the extensional fatigue behavior of the PET fibers was studied by subjecting them to 120–180 rpm at a repeated extension at 104–106 cycles. In order to detect the molecular motion of PET with the extensional fatigue, we carried out differential scanning calorimetry, X‐ray diffraction, density, and thermoluminescence (TL) experiments. The high temperature TL (above room temperature) intensity decreased with a 104 cycle extension but increased with a 105 cycle extension. The extent of change in the TL intensity was found to be a function of the long period and loss modulus. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 90–100, 2000