EVOH/clay nanocomposites produced by dynamic melt mixing

Abstract

AbstractEthylene‐vinyl alcohol copolymer (EVOH)/clay nanocomposites were prepared via a dynamic melt‐intercalation process using a Brabender Plastograph or extruder. The phase morphology and the crystallization behavior of the nanocomposites were investigated, using differential scanning calorimetry (DSC), X‐ray diffraction (XRD), and transmission electron microscopy (TEM). Mechanical properties were determined using an Instron machine. It was found that the viscosity of EVOH/clay mixtures increases with processing time. Thermal analysis of the EVOH/clay nanocomposites showed that the melting temperature, crystallization temperature, and heat of fusion of the EVOH matrix sharply decrease when clay is added. XRD verified an increased gallery height for the clay in the composites. Maleic anhydride–grafted ethylene vinyl acetate (EVA‐g‐MA) or maleic anhydride–grafted linear low‐density polyethylene (LLDPE‐g‐MA) were added as compatibilizers of EVOH with clay, in various concentrations (1, 5 and 10 wt%). Significantly higher viscosity levels were obtained for the compatibilized systems as the torque dramatically increased when processed in the Brabender machine. Enhanced intercalation within the galleries was obtained. EVOH crystallinity decreased with increasing compatibilizer content, until at a certain content no crystallization took place. EVOH/clay composites were also processed in an extruder, showing improved mechanical properties for as low as 1 wt% clay. The strong EVOH/clay interactions are responsible for the unique behavior of their nanocomposites. Polym. Eng. Sci. 44:1019–1026, 2004. © 2004 Society of Plastics Engineers.