STARCH-BASED EXTRUDED PLASTIC FILMS AND EVALUATION OF THEIR BIODEGRADABLE PROPERTIES

Plastic formulations containing up to 40% starch were prepared and blo wn into thin films using extrusion methods. Extruded films were evalua ted for their biodegradability by exposing them to a consortium of sta rch degrading bacteria in the laboratory for 45 days and in the 'La Si lla' river located in Monterrey, N.L. Mexico for up to 60 days. Biodeg radability was assessed by measuring changes in weight loss and chemic al composition of the films using Fourier transform infrared (FTIR) sp ectroscopy. While little or no degradation was apparent in control fil ms made up of 100% low density polyethylene (LDPE) or 100% poly-(ethyl ene-co-acrylic acid) (EAA), most of the starch was depleted in starch- containing films exposed in the river. Starch degradation in films exp osed to amylolytic bacteria in the laboratory was relatively slower. A lso, increasing the amount of EAA from 25% to 50% substantially reduce d starch depletion in these films.