Strain-induced crystallization of poly(ethylene 2,5-furandicarboxylate). Mechanical and crystallographic analysis

Poly(ethylene 2,5-furandicarboxylate), referred to as PEF, was uni-axially stretched for temperatures above glass transition temperature. This bio-based polymer is considered as a serious competitor for the petroleum analogous poly(ethylene terephthalate), named PET. To replace PET in bottle forming, PEF has to be deformed to large strains which are only reachable when it is in its rubbery state. In the present work, the stretching conditions have been chosen by determining precisely the range of temperature and strain rate where PEF exhibits a rubbery-like state. This was feasible through the building of a master curve at a reference temperature. Local strain field measurements allow the description of PEF intrinsic mechanical behaviour. Above a draw ratio of around 6 to 8, the mechanical response presents an impressive strain hardening whereas a well-defined crystalline phase with a high orientation is formed. Diffraction peaks were indexed and compared to previous papers. Only one crystalline phase was observed either under mechanical loading or during static crystallization. Mechanical loading significantly speeds up crystallization.