INFRARED-SPECTROSCOPY MEASUREMENTS OF RESIDUAL-STRESSES IN POLYPROPYLENE FIBERS

Average residual stresses in polypropylene fibers, produced in a full- scale short-spin line, are estimated from the shift of the IR absorpti on peak at 975 cm-1. Linearly polarized incident IR radiation is used to separate between stress components parallel and perpendicular to th e fiber axis. For all the fibers in this study, the axial stress compo nent is larger than the average stress perpendicular to the fiber axis . Axial and perpendicular stresses are correlated with draw ratio and polydispersity index. For narrow molecular weight distributions (M(w)/ M(n) < 4-5), the axial stress increases with increasing draw ratio. Av erage stress perpendicular to the fiber axis decreases with increasing draw ratio for all the molecular weight distributions in this study ( M(w)/M(n) = 3-6). Measurements of residual stresses are consistent wit h other results characterizing molecular structure and mobility. An ex pression for estimating the stored deformation energy is discussed. (C ) 1993 John Wiley & Sons, Inc.