Improving ductility of glassy semicrystalline polymers by pre-deformation*

Having developed some elementary understanding of how glassy polymers gain ductility [1, 2], we have begun to explore molecular mechanics of semicrystalline polymers whose Tg > ambient, to which poly(L-lactic acid) (PLLA), poly(ethylene terephthalate) (PET), and syndiotactic polystyrene (sPS) belong. Our objective is to explain why crystallization can turn a ductile glassy polymer to a brittle material, as is the case for PLLA [3]. Based on PET and s-PS, the present study will show how the ductility of such polymers can be predicted to improve upon introducing predeformation effect that alters the morphology and network structure. In doing so, we are able to further advance our theoretical understanding of factors that influence polymer ductility.

[1] Wang, S.-Q.; Cheng, S.; Lin, P.; Li, X. “A phenomenological molecular model for yielding and brittle-ductile transition of polymer glasses”, J. Chem. Phys. 141 (2014), 094905.
[2] Masoud Razavi, Shiwang Cheng, Da Huang, Shufan Zhang and Shi-Qing Wang, “Crazing and yielding in glassy polymers of high molecular weight, manuscript in preparation for Polymer”.
[3] Masoud Razavi and Shi-Qing Wang, “Why Is Crystalline Poly(lactic acid) Brittle at Room Temperature?”, Macromolecules, 2019, 52, 5429.