Characterisation and properties of oriented PVC fibres

Drawn PVC fibres were investigated using birefringence, DSC and TMA techniques, and their tenacity was measured. An increase in fibre draw ratio (DR) for heat set samples produced an increase in tenacity, birefringence and X-ray intensity. The linearity of a tenacity/birefringence plot suggested that tenacity was a good indicator of molecular orientation. An ‘undrawn’ filament was substantially amorphous. Drawing without heat setting produced little three dimensional order, and samples relaxed readily on heating. X-ray results for heat set fibres suggested both an increase in the amount of crystallinity, and in crystallite alignment. After heat setting, a minor DSC endotherm was produced; the onset of this endotherm corresponded to the heat setting temperature, as did the onset of shrinkage measured by TMA. For samples with a DR>1.5, maximum shrinkage measured by TMA corresponded to complete elastic recovery.