Studies on degradability of high density polyethylene HDPE polylactide PLA blends

Abstract

Polyethylene (PE) is predominantly used for consumer packaging in the form of trash bags and other short-term flexible packaging and disposable products because they are economical and convenient. But, due to non-biodegradable nature, they cause hazardous environmental pollution and become carcinogenic for human beings, marine bodies and other living species. Hence, the major challenges and opportunities exist in developing biodegradable polyethylene blends having similar mechanical and processing properties as that of the conventional PE. The objectives of this research work were set to develop biodegradable and oxo-biodegradable blends of high-density polyethylene (HDPE) by compounding poly(lactic acid) (PLA) in varying amounts and/or pro-oxidant with/without compatibilizer maleic anhydride grafted high density polyethylene (MA-g-HDPE), to investigate the effect of blend composition on the performance properties and degradability and to study degradation kinetics of the polymer blends. The selection of HDPE was made due to its large use in current commercial packaging. PLA is a well known biodegradable polyester polymer having good mechanical properties, fair processability and superior recyclability; hence, emerging as a viable substitute for synthetic, semi-crystalline non-biodegradable polymers. MA-g-HDPE was selected as compatibilizer due to the intrinsic immiscibility between HDPE and PLA. Thin films from HDPE/PLA blends were produced through melt-compounding followed by hot-pressing. Initially, the ratios of HDPE/PLA blends were taken as 100/0, 95/5, 90/10, 85/15, 80/20, 75/25, and 70/30 and after recognizing 80/20 blend with optimum combination of mechanical (tensile) properties and PLA content, it was further compatibilized with 2, 4, 6, and 8 parts per hundred of resin (phr) of MA-g-HDPE. Amongst compatibilized HDPE/PLA (80/20) blends, 4 phr quantity of MA-g-HDPE blends had the finest relevant mechanical properties.