Elastic behaviour of oriented syndiotactic poly(propylene)

Communication: A syndiotactic poly(propylene) film (sPP), quenched from the melt at 0 degreesC, was drawn at room temperature up to a draw ratio of la mbda = 6. The fibre was analysed under tension by X-ray analysis and FTIR s pectroscopy, showing the presence of the oriented crystalline form III desc ribed by Chatani, with the chains in transplanar conformation. Then it was unhooked, undergoing a large shrinkage, and reaching a length corresponding to be a draw ratio of lambda = 3.8. X-ray and FTIR analysis showed that in the relaxed fibre, a conformational transition from the trans-planar to th e helical form occurred. The relaxed fibre was again submitted to increasin g extensions up to lambda = 6, step by step, and the elastic behaviour was analysed through the Mullins' curve and hysteresis cycles. It showed good e lastic properties, which appear to be closely correlated to the conformatio nal transition between helical and trans-planar forms. [GRAPHICS] X-ray fibre pattern of sample A6S (after releasing the tension).