Dispersion of Wood Microfibers in a Matrix of Thermoplastic Starch and Starch–Polylactic Acid Blend

Abstract

The successful dispersion of cellulose fibers of submicrometer diameter in polymers has been restricted to solution-cast films so far. In this work, the dispersion of microfibers in biopolymers was investigated by melt-mixing using conventional processing equipment. Thermoplastic starch and a blend of starch and polylactic acid (PLA) were used as matrix materials. A suspension of cellulose microfibers less than 1 μm in diameter was prepared in water. This microfiber suspension was poured into molten thermoplastic starch to obtain fiber loadings up to 2%. The composites were compression molded into thin films roughly 0.25 mm thick. there was a 10% increase in tensile strength and a 50% increase in stiffness with each percentage increase in microfiber loading in the starch polymer. Similar improvement in tensile properties was also noted for a polymer system prepared by blending starch and PLA. Laser confocal microscopy images were analyzed to quantify microfiber dispersion at different composite processing parameters. This was the first work where successful dispersion of cellulose fibers of submicrometer was achieved in a composite prepared solely by the melt-mixing process.