MORPHOLOGY OF STRAIN-INDUCED CRYSTALLIZATION OF POLYMERS .1.

This review paper points out that interpretations by Flory, Stein, Andrews, Keller, and others from stress changes alone during oriented crystallization have led to widely different proposed chain conformations for the strain-induced crystallites and consequently very different crystallization models that are incompatible with existing stress relaxation, kinetic, or morphological data on strain-induced crystallization (SIC) and/or additional thermally induced crystallization after SIC. The picture that presently emerges from the existing data suggests that the SIC crystallites have (1) T//m much higher than T//m**o for extended chain crystals, (2) near perfect crystalline orientation function, (3) very fast crystallization rates (t// one-half less than 1 s), and (4) fibrillar morphology with limited crystal dimensions along the fibrillar axis. Upon additional thermal treatment (TIC), a morphological fibrillar-to-lamellar transformation can take place in strain-crystallized polymers during stress relaxation.