Environmentally friendly plastic that degrades in seawater

29-Mar-07

A new type of environmentally friendly plastic that degrades in seawater, could free up valuable storage space, making it safe and practical to toss plastic waste overboard, according to scientists at The University of Southern Mississippi (USM). The biodegradable plastics could replace conventional materials used to make stretch wrap for large cargo items, food containers, eating utensils and other plastics used at sea. The biodegradable plastic has not yet been tested in freshwater. This will ease pressure on ships as typically, large volumes of plastic waste generated aboard military, merchant and cruise ships must be stored onboard, often for prolonged periods, until they make port. The new plastic is made of polyurethane that has been modified by the incorporation of PLGA [poly (D,L-lactide-co-glycolide)], a known degradable polymer used in surgical sutures and controlled drug-delivery applications. Through variations in the chemical composition of the plastic, the researchers have achieved a wide range of mechanical properties ranging from soft, rubber-like plastics to hard, rigid structures, depending on their intended use. Depending on the composition of the plastics, these compounds may include water, carbon dioxide, lactic acid, glycolic acid, succinic acid, caproic acid and L-lysine, all of which can be found in nature. The new plastics are capable of degrading in 20 days and result in natural byproducts that are nontoxic, as per findings of a study funded by the Naval Sea Systems Command (NAVSEA). When exposed to seawater, the plastics degrade via hydrolysis into nontoxic products. As the new plastics are denser than saltwater, they have a tendency to sink instead of float, preventing them from washing on shore and polluting beaches. The plastics are not quite ready for commercialization. More studies are needed to optimize the plastics for various environmental conditions they might encounter, including changes in temperature, humidity and seawater composition.