MICRO-RAMAN STUDY OF THE TRANSITION FRONT IN UNIAXIALLY STRETCHED SEMICRYSTALLINE POLYMERS

The transition front of the neck between the isotropic and oriented re gion in uniaxially stretched polyvinylidene fluoride (PVDF) and polypr opylene (PP) is analyzed with a high spatial resolution by micro-Raman spectroscopy . The variation of the microstructure, i.e. change in th e degree of crystalline modification in the case of PVDF and in the or ientation of the PP chains in function of the strain rate, is correlat ed with other parameters associated with the drawing response of these polymers and the temperature rise during deformation. The results her e described can be understood through the clear increase of temperatur e that was detected in the neck due to the heat generated by the defor mation work of the drawing process.