Effect of pressure on the α2-relaxation of single crystal mats of polyethylene

Publisher Website
Google Scholar
Abstract
Sound velocity of longitudinal ultrasonic waves at 4.64 MHz in a polyethylene single crystal mat was measured as a function of temperature under constant hydrostatic pressure. The velocity vs temperature curves at 1, 1000, and 3100 atm showed dispersion of the sound velocity at 96, 120, and 149°C, respectively. These dispersions correspond to the α2-relaxation which has been identified as being associated with the crystalline phase of polyethylene. The relaxation strength has a tendency to increase with increasing pressure, which is similar to the relationship between the relaxation strength and the lamellar thickness of crystals established for single crystal mats by dynamic measurements at audio frequencies. The pressure coefficient of the relaxation temperature T(α2) at 1 atm was semiempirically evaluated using the thermodynamical properties of polyethylene crystals and was found to be in reasonable agreement with the experimental value.

This publication has 8 references indexed in Scilit: