Effect of stretch ratio on the induced crystallinity and mechanical properties of biaxially stretched PET
Hillary Onyebuchi Onyishi, Chukwumaobi K. Oluah
Abstract
Semi-crystalline polymers are observed to change their mechanical properties upon processing due to the changes in the crystallinity of the polymer. This paper investigates the changes in the crystallinity and mechanical properties of biaxially stretched polyethylene terephthalate, PET, for different stretch ratios (or strains). Each stretched PET sample was heated to 100°C in a biaxial stretching machine before being stretched to the desired stretch ratio. The same strain rate of 2/s was used for the stretching and mode of deformation was simultaneous on either side. Differential Scanning Calorimetry (DSC) was used to investigate the variation of induced crystallinity with stretch ratio. Tensile tests were used to determine the variation of the processing stretch ratios with mechanical properties. The results show that the higher the stretch ratio, the higher the amount of induced crystallinity in the PET sample. Also, the higher the stretch ratio, the better the mechanical properties.