Chain reorientation in ß-PVDF films upon transverse mechanical deformation studied by SEM and dielectric relaxation

• Autor(a) principal: Barbosa, R.
• Data de Publicação: 2003
• Outros Autores: Mendes, J. A., Sencadas, Vítor João Gomes Silva, Mano, J. F., Lanceros-Méndez, S.
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/1822/3521
• topic: PVDF; SEM; Dielectric relaxation; Mechanical deformation; Science & Technology

Chain reorientation may be induced in polyvinylidene fluoride (PVDF) in its ß-phase by applying a deformation perpendicular to the pre-oriented polymeric chains. This reorientation begins right after the yielding point and seems to be completed when the stress-strain curve stabilizes. We have studied the chain reorientation mechanism by scanning electron microscopy (SEM) and dielectric relaxation methods and we have analyzed its influence in the alpha- and ß-relaxations of the polymer. SEM images confirm the existence of a reorientation upon transversal deformation. The decrease of crystallinity with increasing reorientation and the dependence of the dielectric permittivity upon deformation indicate that a model of stress-induced melting followed by an incomplete recrystallization properly describes the reorientation mechanism.