Structure and deformation behavior of nanocomposites based on LDPE and modified clays

The effects of the type and concentration of a filler on the structure and deformation behavior of nanocomposites based on LDPE and Na + montmorillonite (a natural clay) modified by various substrates were studied by DSC, X-ray diffraction, optical microscopy, and mechanical testing. Upon crystallization of this system from the melt, a part of the polymer crystallizes on the surface of layered silicate particles as heterogeneous nuclei, giving rise to a finely crystallite fraction and a bimodal crystallite size distribution. Layered silicate sheets always arrange parallel to the surface of an isotropic film prepared by melt molding. For the nanocomposites, the Young modulus is higher and strength and elongation at break are lower than the analogous characteristics of the original polymer. The cold drawing of composite films significantly (more than two times) decreases the dimensions of crystallites, although the melting temperature of LDPE in the oriented nanocomposite remains virtually the same as in the starting isotropic film.