Processability and Properties of Biodegradable Plastics Made from Agricultural Biopolymers

The use of synthetic and natural biodegradable plastics has been severely limited due to their strong sensitivity to processing conditions such as temperature. The object of our research is to develop novel biodegradable thermoplastic compositions and processing methods for making plastic articles reproducibly from soy protein isolate and corn starch. This paper discusses viable biodegradable soy protein-starch plastic that can be extruded and injection molded into articles of various shapes and sizes. The thermal and mechanical properties of the plastic indicate that it may be useful in many applications where the plastic must biodegrade in an environmentally-benign manner after service. Blending the biodegradable soy protein plastic with novel polyphosphate fillers greatly reduced its water sensitivity, allowing new uses in moist and load-bearing environments where the unfilled biodegradable plastic is not useable.