Fully biodegradable potato starch composites: effect of macro and nano fiber reinforcement on mechanical, thermal and water-sorption characteristics

Nature provides an impressive array of polymers which are generally biodegradable, as biodegradation is part of the natural biogeochemical cycle. Natural polymers, such as starch and cellulose have the potential to replace many current polymers if new material composites can be prepared to rival the performance of exisitng composites. While the conventional composites offer excllent mechanical properties and durability, most commercial polymers are derived from petroleum feed stock. Even though the utilization of petroleum-based composites are non-biodegradable and environmentally undesirable. Environment-friendly "Green" composites, based on potato starch and reinforced with nanocellulose/ramie fabric were prepared by hot compression moulding technique. PCL was coated to reduce water sensitivity. In the absence of reinforcing fillers, residual thermal stress transfer is affected. For reinforced composites, mechanical properties were seen to increase as a result of reinforcement. In composites containing the hydrophilic nanofibres and the hydrophobic PCL, phase inhomogeneity causes lower mechanical properties. Elongation at break increased for multiphase composites due to low interfacial adhesion. The uniformweb-like network of nanofibres decreases water sorption. However, the presence of hydrophilic lignocellulosics increases water sorption. The PCL-containing composites show a low water sensitivity as expected. The nanostructure of the composites were analysed using TEM studies. A detailed investigation on the thermal properties of the thermoplastic potato starch were done by thermogravimetric analysis and flammability studies were done by limiting oxygen index analysis. The starch polymer is almost stable up to 300 degrees C. Also they showed better flame retardant properties.