Influence of the molecular weight on mechanical behavior and associated strain-induced structural evolution of Poly(ethylene 2,5-furandicarboxylate) upon biaxial stretching

Abstract The mechanical behavior of Poly(ethylene 2,5-furandicarboxylate) upon biaxial stretching and the associated strain-induced structural evolution is studied in the light of its molecular weight. Besides it is shown that the increase of molecular weight favors strain-induced crystallization (SIC) and that SIC in PEF occurs when a critical molecular orientation ratio is achieved. The earlier occurrence of SIC in the case of the higher macromolecular weight is explained by the faster macromolecular orientation due to a more robust entanglement network. Regarding the mechanical behavior, it appears that a strain-hardening stage is observed whatever the molecular weight, this stage originates from both macromolecular orientation and formation of crystals upon stretching. Finally, it is shown that biaxial orientation (BO) has a positive effect on both oxygen barrier properties and mechanical properties. Particularly it was highlighted that, while as-cast PEF is brittle, BO PEF films are ductile when a critical biaxial draw ratio is achieved.