Investigation of the Biodegradability of LDPE/PLA Bioblends: Comparison of Hydrolysis and Soil Burial Tests

Abstract

The present work concerns the preparation and characterization of new biodegradable materials by mixing poly lactic acid (PLA), a biodegradable polymer, with low density polyethylene (LDPE), a current thermoplastic that can be bio-based. For that purpose, LDPE/PLA blends of variable composition (100/0, 80/20, 50/50, 20/80, 0/100) were prepared. They were characterized in terms of physical properties (density, melt flow index), thermal properties (melting temperatures) and mechanical properties (tensile and Shore D hardness). Their morphology was investigated by scanning electron microscopy. Hydrolysis and soil burial tests were conducted to study the biodegradation behavior. The weight loss of the samples with time was followed. The structural changes were investigated by FTIR spectroscopy and microscopic observation. Mechanical analysis showed that the strength at break increased with the level of PLA while the elongation at break decreased strongly due to the non miscibility of the two polymers. The SEM micrograph of blends 20/80, and 80/20 evidenced poor adhesion at the interface between the two polymers. The PLA confers a brittle character to its blends. The highest rates of mass variation were observed for the blend containing 50 and 80 wt% of PLA and were about 72 and 55 wt% after 45 days for the hydrolysis test and 10 and 2.5 wt% after 18 weeks of soil burial.