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 polymers with methacrylic acid and, subsequently, by the formation of zinc salts. The physical properties and rheological behaviour of the blends were examined in order to elucidate the mechanism. It was found that for blends containing minor amounts of PVDF effective compatibilization was achieved only when either grafted Nylon 6 was blended with pristine PVDF, or zinc acetyl acetonate was added to blends of grafted PVDF and pristine Nylon 6. This second effect was attributed to the interfacial sharing of zinc cations between the carboxylate anions in the PVDF phase and the amide groups of the Nylon component. At high concentrations of grafted PVDF compatibilization was observed even in simple mixtures with Nylon 6, owing to the greater propensity of interfacial amidation reactions during mixing. As in the previous case compatibilization of the blends was enhanced by the addition of zinc acetyl acetonate. 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 PVDF as the main component, while a higher ductility was achieved when the polyamide formed the main phase. Dynamic mechanical property measurements have revealed that an appreciable level of molecular miscibilization takes place within the amorphous domains of the blend, which is more easily discerned for blends in which the Nylon component forms the main phase. No evidence for the formation of ionomeric clusters for either components or the corresponding blends could be found for acid grafted systems neutralized by the addition of ZnAcAc. (C) 1997 Elsevier Science Ltd.