Abstract: Hydroxypropyl distarch phosphate/polyhydroxyalkanoate (PHA) composite films were prepared by extrusion blowing using maleic anhydride (MAH) as a compatibilizer. MAH was added at 1%, 3% or 5% into the starch/PHA system by two different methods, viz., blending starch and PHA with MAH directly by extrusion (method 1) or blending PHA modified with MAH under dry conditions with starch by extrusion (method 2). The aim was to explore the effects of modification methods and MAH content on the properties of composite films were explored. The results showed that when PHA content was 12%, the films prepared by direct addition of 1% MAH exhibited higher tensile strength and light transmittance, as well as better moisture barrier property, heat stability and compatibility with a flat, smooth and uniform microstructure, while those prepared by method 2 with 5% MAH had higher elongation at break and a flat and smooth surface. The films prepared with 24% PHA and 3% MAH by the first method exhibited higher tensile strength, moisture barrier property and heat stability with a smooth and uniform microstructure. The films prepared by the second method with 24% PHA and 3% MAH had better mechanical properties, while films with higher light transmittance were obtained with 5% MAH when other conditions were kept the same. Fourier transform infrared spectroscopy suggested that addition of MAH could enhance the intermolecular interaction. These results suggested that the films prepared by direct addition of 1% MAH exhibited better properties when PHA content was 12%, whereas those prepared by direct addition 3% MAH showed better properties when PHA content was 24%.

Key words: maleic anhydride, modification method, extrusion blowing, starch/polyhydroxyalkanoate composite films, properties