Self adhesion of semi-crystalline polymers between their glass transition temperature and their melting temperature
Adhésion des polymères semi-cristallins entre leur température de transition vitreuse et leur température de fusion
Résumé
We studied the self adhesion of semicrystalline polymers with variable degrees of crystallinity by performing fracture studies of interfaces formed between their glass transition temperature, Tg, and their melting temperature, Tm, in order to elucidate the role of crystallinity. We used a series of copolymers of polybutylene(terephthalate-co-isophthalate). For pre-crystallized samples, when the temperature of contact (Tcontact) was decreased below Tm, the fracture toughness, Gc decreased with Tcontact to vanish at a temperature corresponding to the onset of the fusion process. For quenched samples obtained in the amorphous state and put in contact before rising the temperature to Tcontact, Gc was very low for temperatures of contact well above Tg. The very thin crystalline layer observed in TEM was held responsible of this weak adhesion. The essential role played by surfaces and interfaces in nucleating crystallinity was shown to be an important factor affecting self-adhesion below Tm.
Nous avons étudié l'auto-adhésion de polymères semi-cristallins de taux de cristallinité variable, par un test de fracture des interfaces formées entre leur température de fusion, Tf, et leur température de transition vitreuse, Tg, dans le but de définir le rôle de la cristallinité sur l'adhésion. Nous avons utilisé des copolymères de polybutylène(téréphthalate-co-isophthalate). Pour les polymères pré-cristallisés, l'énergie de fracture, Gc, diminue fortement avec la température de contact (pour Tcontact