Preparation of Surface-Modified Silica Particles from Rice Husk Ash and Its Composites with Degradable Polylactic Acid

A method for preparation of silica particles from rice husk ash (RHA) is developed for use as fillers in an enhancement of gas permeability of polylactic acid (PLA) resin. Silica particles are produced in a one-step process by employing PLA-grafted-chitosan copolymer (PCT) as a polymeric surfactant. Particles with an average size of ca. 30 micron, which are smaller than those obtained from a conventional method, are obtained. The major advantage of this technique is its ease of operation, in which mechanical grinding is not required. The resulting particles are then used in preparation of PLA/silica composites by varying the silica contents from 0-2.0 wt %. The PCT copolymer is present as a coating layer on the particles surface, which promotes compatibility with the PLA matrix. Gas permeability (water vapor, carbon dioxide, and oxygen) and mechanical properties of the composite films are examined. Enhancements in gas permeability and selectivity are achieved, with slight drops in mechanical properties. The materials have high potential for use as degradable packaging films with tunable gas permeability.