Prediction of crystallinity of spunbond webs

Polymer crystallization is accompanied by a partial macromolecular chain alignment process, which has significant effects on the mechanical, thermal, and optical properties of polymer materials. Particularly, the properties of such widely used nonwoven products as spunbond webs are strongly affected by the degree of crystallinity achieved during their manufacturing. The present work aims at predicting the degree of crystallinity of spunbond webs accounting for thermally-driven and flow-induced crystallization coupled with the dynamics and thermal history of spunbond fibers. In principle, the degree of crystallinity could be in the 0–1 range; however, for semi-crystalline polymers, the degree of crystallinity practically saturates at a lower-than-one value. The degree of crystallinity of 100 spunbond fibers is predicted coupled with the fiber evolution and the final three-dimensional structure of a nonwoven web. The predicted evolution of the degree of crystallinity and its distribution in a three-dimensional spunbond web is discussed in detail. The results reveal that the distribution of the degree of crystallinity over the spunbond web is non-uniform. The effects of nozzle temperature, air-blowing speed, and belt speed on spunbond web characteristics, including the degree of crystallinity, are also investigated in detail.