Effect of the temperature on the structure and mechanical properties of poly(ethylene terephthalate) fibres and yarns

The load-elongation diagrams were obtained for PETP yarns and monofilaments at different deformation temperatures, demonstrating the dependence of the sigma(epsilon) curves on the testing temperature and the thermomechanical history of the samples. The dependences of the basic sn ain characteristics determined from the sigma(epsilon) curves on the temperatures can be used to predict the change in the mechanical properties of PETP yarns and fibres at high temperatures. In addition to the fundamental relaxation transition, the sigma(epsilon) curves can be used to find a new transition in the 180 degrees C region which controls the behavior of PETP yarns and fibres above the transition temperature. The thermomechanical tests and structural studies of the fibres at different temperatures allow correlating the transition found with crystallites and assigning it to an alpha(e) transition based on the characteristic set of properties.