(The) study on preparation and characterization of maleated polyethylene/silicate nanocomposites

Abstract

Polymer nanocomposites are a class of hybrid materials composed of organic polymer matrix in which inorganic particles with nano scale dimension are imbedded. We synthesized various polyethylene-layered silicate nanocomposites by melt intercalation. Morphology of these polyethylene-layered silicate nanocomposites were characterized and related to the mechanical properties. Maleic anhydride grafted polyethylene (maleated polyethylene) /silicate nanocomposites were prepared by simple melt intercalation. The exfoliation and intercalation behaviors depended on the hydrophilicity of polyethylene grafted with maleic anhydride and the chain length of organic modifier in the silicate. When the number of methylene groups in alkylamine (organic modifier) was larger than 16 the exfoliated nanocomposite was obtained. And the maleic anhydride grafting level was higher than about 0.1wt% for the exfoliated nanocomposite with the silicate modified with dimethyl dihydrogenated tallow ammonium ion or octadecylammonium ion. The pure LLDPE showed only the intercalation, which did not depend on the initial spacing between silicate layers. Maleated polyethylene/silicate nanocomposite with different aspect ratio of silicate and maleated polyethylene/$SiO_2$ composite were prepared by melt intercalation. Layered silicates (montmorillonite, laponite) were exfoliated in maleated polyethylene (PEMA) matrix while $SiO_2$ was not well dispersed in matrix. The nanocomposite with high aspect ratio silicate (montmorillonite, 20A) showed the faster decrease in terminal slope of storage modulus and the steeper increase in complex viscosity than those with low aspect ratio silicate (laponite) and $SiO_2$. Addition of montmorillonite increased the crystallization and the melting temperature of PEMA but again decreased their temperature above 3 volume% by increased viscosity. The nanocomposite with montmorillonite (PEMA/20A) showed the higher yield strength and secant modulus than the nanocomposit...