COMPATIBILIZATION OF POLY(VINYLIDENE FLUORIDE) NYLON-6 BLENDS BY CARBOXYLIC-ACID FUNCTIONALIZATION AND METAL-SALTS FORMATION .2. MECHANISM AND EFFECTS ON PHYSICAL-PROPERTIES

A study was made of the mechanism for the compatibilization of blends of PVDF and Nylon 6, induced first by grafting the chains of the two p olymers with methacrylic acid and, subsequently, by the formation of z inc salts. The physical properties and rheological behaviour of the bl ends were examined in order to elucidate the mechanism. It was found t hat for blends containing minor amounts of PVDF effective compatibiliz ation was achieved only when either grafted Nylon 6 was blended with p ristine PVDF, or zinc acetyl acetonate was added to blends of grafted PVDF and pristine Nylon 6. This second effect was attributed to the in terfacial sharing of zinc cations between the carboxylate anions in th e PVDF phase and the amide groups of the Nylon component. At high conc entrations of grafted PVDF compatibilization was observed even in simp le mixtures with Nylon 6, owing to the greater propensity of interfaci al amidation reactions during mixing. As in the previous case compatib ilization of the blends was enhanced by the addition of zinc acetyl ac etonate. The type of improvements in mechanical properties, resulting from compatibilization induced by the addition of ZnAcAc, however, was found to depend on the nature of the component forming the main phase . A large increase in tensile strength was observed in blends with PVD F as the main component, while a higher ductility was achieved when th e polyamide formed the main phase. Dynamic mechanical property measure ments have revealed that an appreciable level of molecular miscibiliza tion takes place within the amorphous domains of the blend, which is m ore easily discerned for blends in which the Nylon component forms the main phase. No evidence for the formation of ionomeric clusters for e ither components or the corresponding blends could be found for acid g rafted systems neutralized by the addition of ZnAcAc. (C) 1997 Elsevie r Science Ltd.