THE ROLE OF STARCH IN BIODEGRADABLE THERMOPLASTIC MATERIALS

The increasing garbage mountain is more and more recognized as an ecological threat. Space for landfills is limited and additional incineration capacities require high capital investments and pose additional envrironmental problems. In the FRG from total annual 14 million t of household waste, 700,000 t are non‐degradable plastic materials (polyolefines, polystyrene and polyvinylchloride), especially for packaging. Different strategies are being followed to reduce the 5% plastics in household waste: prevention, recycling, chemical valorization, thermic utilization (incineration) and use of degradable polymers. The latter are reviewed in detail: chemical modification of classical polymers into photo‐ and chemo‐degradable materials, physical mixing of 6–20% granular starch with polyethylene or polypropylene, coprocessing of more than 50% disintegrated starch with hydrophilic polymers like polyacrylate or polyvinylalcohol to biodegradable films for agricultural mulch or carrying bags, thermoplastic extruded starch with plasticiser containing more than 90% starch for blister packaging and disposables for fast food and finally biodegradable polyesters like poly‐hydroxybutyric acid (PHB) and polylactic acid, produced by fermentation processes. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim