Effect of clay on mechanical and gas barrier properties of blown film LDPE/Clay nanocomposites

Low density polyethylene (LDPE)/clay nanocomposites, which can be used in packaging industries, were prepared by melt-mix organoclay with polymer matrix (LDPE) and compatibilizer, polyethylene grafted maleic anhydride (PEMA). The pristine clay was first modified with alkylammonium salt surfactant, before melt-mixed in twin screw extruder attached to blown-film set. D-spacing of clay and thermal behavior of nanocomposites were characterized by Wide-Angle X-ray Diffraction (WAXD) and differential scanning calorimetry (DSC), respectively. WAXD pattern confirmed the increase in PEMA contents exhibited better dispersion of clay in nanocomposites. Moreover, DSC was reported the increased PEMA contents caused the decrease in degree of crystallinity. Mechanical properties of blown film specimens were tested in two directions of tensile tests: in transverse tests (TD tests) and in machine direction tests (MD tests). Tensile modulus and tensile strength at yield were improved when clay contents increased because of the reinforcing behavior of clay on both TD and MD tests. Tensile modulus of 7 wt % of clay in nanocomposite was 1.00% increasing from neat LDPE in TD tests and 17% increasing in MD tests. However, elongation at yield decreased when increased in clay loading. Oxygen permeability tests of LDPE/clay nanocomposites also decreased by 24% as the clay content increased to 7 wt %. (c) 2007 Wiley Periodicals, Inc.