EVOH/clay nanocomposites produced by melt processing

Ethylene-vinyl alcohol copolymer (EVOH)/clay nanocomposites were prepared v ia a dynamic melt-intercalation process. The phase morphology and the cryst allization behavior of the nanocomposites were investigated, using DSC, DMT A, XRD and SEM. It was found that the treated clay content and dynamic proc essing time affect the viscosity of the EVOH/clay mixtures: higher clay con tents and longer mixing times result in higher torque/viscosity levels. Thi s is due to the increased interaction of the molten polar matrix (EVOH) wit h the treated organosilicate surface. Under the dynamic high shearing force s, the polymer penetrates the clay agglomerates/aggregates, intercalates wi thin the organoclay galleries, and finally causes delamination. Thermal ana lysis of the EVOH/clay nanocomposites showed that the melting temperature, crystallization temperature and heat of fusion of the EVOH matrix, sharply decrease with increasing both, the clay content and processing time. The in tercalation level was characterized by X-ray diffraction (XRD), which verif ied an increased gallery height. The DMTA spectra showed that longer proces sing times resulted in higher damping (E" intensity) levels of the EVOH/cla y composites, indicating higher fractions of the EVOH amorphous phase. Howe ver, no T-g changes were seen in spite of the high polymer/treated clay int eraction levels, which may be attributed to a plasticizing effect of the lo w molecular weight organic cations.