Compatibilização de poliestireno com poli(etileno-co-acetato de vinila)

Abstract

In this work, we investigated the possibility of improving the compatibility of poly(ethylene-co-vinyl acetate) (EVA) and polystyrene (PS) blends by introducting zinc sulfonate and sodium sulfonate groups onto PS. The sulfonate groups were introduced with aim of promoting interactions between PS and the acetate groups of EVA. These interactions were examined as a function of the sulfonate content (22, 37, 44 and 66 meq/100g of polymer), metal cation (H+, Na+, Zn2+) and blend composition. The interactions between PS ionomers and EVA in diluted and concentrated xylene-methanol Solutions were investigated by viscosity measurements. FTIR spectroscopy was used to obtain information about the nature of the interactions in the blends as well as about the ionic associations within OS ionomers. The blend morphology was examined by optical microscopy. The termal behavior and the crystalline structure of the blends were analyzed by differential scanning calorimetry (DSC) and x-ray diffraction, respectively. Lightly sulfonated polystyrene (HSPS) was prepared from commercial PS. While the zinc (ZnSPS) and sodium (NaSPS) salts were obtained by neutralizing the HSPS. The blends were prepared by solution cast method. Intermolecular association between ZnSPS and EVA in diluted xylene/methanol solution was evidenced by increase in the reduced viscosity of the blend relative to that of the pure EVA. In concentrated Solutions, suitable interactions were evidenced by pronounced enhancement in the dynamic viscosity of these Solutions, as a function of ZnSPS concentration, relative to that of PS/EVA Solutions. Interactions in the solid State were observed in terms of a shift to lower frequencies in the in-plane stretching vibration of benzenesulfonate groups when the EVA concentration and sulfonation levei increase. Both, glass transition temperature and melting temperature of EVA in ZnSPS/EVA blends were affected by the presence of ZnSPS. The results obtained indicated that EVA solvated the Zn2+ cations decreasing the ionic associations in the blends. Complex formation and iondipoie interactions led to the improvement in the morphology of ZnSPS/EVA and NaSPS/EVA blends as compared with the morphology of the HSPS/EVA and PS/EVA blends.