Correlation crystallinity and physical properties of heat-treated cellulose triacetate fibres

Abstract

Previous measurements of crystallinity in fibres of cellulose triacetate have been qualitative or semi-quantitative; in this work quantitative measurements of relative crystallinity have been made on cellulose triacetate yarn heat treated in the range 20–300°C following the x-ray diffraction method of correlation crystallinity index. The onset of crystallization is clearly marked by a transition in the crystallinity index at 172°C, and beyond this annealing temperature tenacity and crystallinity are inversely correlated. Orientation also improves with annealing temperature with a less well defined transition around 120–180°C. Initial Young's modulus increases with temperature whilst other physical properties have optimum values in the range 180–220°C. Cutting and grinding are found to have an adverse effect on the correlation crystallinity index which is in fact a measure of lattice perfection.