Remarks on the deformation of semicrystalline polymers: double yielding, crystal relaxation, and beyond

Improvement of the mechanical properties of existing semicrystalline polymers (SCPs) or synthesis of new SCPs with enhanced mechanical performance requires a molecular-level understanding of the deformation in these polymers. In this respect, we design experiments to provide better insights into the deformation of SCPs. Apparent decoupling of yielding of amorphous and crystalline phases will be shown for the first time [1], as a generic behavior of deformation of SCPs. We will show that crystal mobility (α_c relaxation) is not the only criteria to have an ultra-drawable SCP. This will be supported by a counter-example of PLLA, uncommon rate dependency of drawability in this polymer, and ultra-deformability of SCPs in compression. It will be indicated that crystal relaxation not only controls the later stages of deformation but can also affect small strain behavior of SCPs e.g., yield stress. Discussions will be continued with the classification of SCPs based on drawability and a simple estimation for the chain pullout force from a single crystal.

 

 

 

1.           Razavi, M., and S.Q. Wang, Double Yielding in Deformation of Semicrystalline Polymers. Macromolecular Chemistry and Physics, 2020. 221(19): p. 2000151.