Research and Development on Enhanced Degradable Plastics

Three major activities carried out during the report period are those relating to a) development of definitions, standards and test protocols for enhanced biodegradable plastics, b) the testing of selected starch-based plastic films for biodegradation under marine conditions, and c) assessment of two approaches to improved biodegradability in plastic films. Commercial starch- containing plastic films degrade slower at sea than that claimed for soil exposure. Moderate rates of degradation of greater than 9 to 12 months require high levels of starch, thus making it difficult to design a film thick enough for heavy-duty bags, yet retaining moderate biodegradability. Coextrusion of films with the starch (or other degradable material) in the middle layer coated on either side with unfilled plastic material may have improved surface and other properties. These too, however, degrade at rates comparable or slower than the commercial materials. Blends of two plastics, polyethylene and polycaprolactone (PCL) (where the latter is biodegradable in soil), performed well under marine exposure. Films of blends with up to 10 percent of PCL had acceptable physical strength and moderate biodegradability.