Structure and mechanical properties in drawn poly(L-lactide)/clay hybrid films

Films composed of poly(L-lactide) (PLLA)/organophilic montmorillonite hybrids (PLACHs) have been prepared via a melt-compounding process, which is followed by uniaxial drawing at 90 degrees C in air. In addition, an enhancement of the mechanical properties of these drawn PLACH films, which is expected to differ depending on the drawn ratios, is also estimated by dynamic viscoelastic measurements. Three different organoclay concentrations in the hybrid of 3, 5, and 9 wt% were investigated. The structural parameters for the PLLA crystallites in the drawn films, such as the c-axis orientation function (f(PLLA)) and crystallite size, were measured by X-ray diffraction, and their drawn ratio (lambda) and clay concentration dependence were examined from a textural viewpoint. Another orientation function (f(clay)) of the organoclay particles was obtained by transmission electron microscopy (TEM). The values of f(PLLA) and crystallinity for PLLA sharply increased with lambda for lambda < 3, although f(clay) was unchanged during the initial stage of elongation. In the high-lambda region (>5), the organoclay particles in the PLACHs started orienting themselves parallel to the draw direction. Copyright (C) 2008 John Wiley & Sons, Ltd.