A study of the crystallinity index of polypropylene fibres

Abstract

Crystallinity measurements were carried out with the help of X-ray diffraction, differential scanning calorimetry (DSC) and density measurements. The results of this study provide a better understanding of the morphology and complex thermal behaviour of polypropylene fibres. Crystallinity studies show that the crystallinity of PP fibres when measured by X-ray and DSC methods as a function of draw-ratios increases with increasing draw-ratios while the crystallinity of the same samples as derived by density measurements shows an inverse trend. These discrepancies are accounted for by the formation of microvoids within the polypropylene fibres due to drawing. In the DSC scan two endothermic peaks were found to occur in some of the samples. This is explained by the presence of two morphological forms i. e. lamellar and fibrillar morphology in the same sample. The crystallinity values obtained from different methods are correlated with mechanical properties, such as tenacity and elongations.