Mechanical, rheological and anaerobic biodegradation behavior of a Poly(lactic acid) blend containing a Poly(lactic acid)-co-poly(glycolic acid) copolymer

Abstract

The goal of this work is to examine the thermal, rheological, mechanical and thermophilic anaerobic biodegradation performance of PLA blends containing a highly degradable polymer. Here random copolymers consisting of Poly(l-lactic acid) (PLLA) and Poly(glycolic acid) (PGA) structural units (75:25 M ratio) were synthesized at three different molecular weights (Mw = 16, 58 and 113 kg mol−1) and melt blended with a high molecular weight PLA homopolymer. The glass transition temperature (Tg) of poly(lactic acid-co-glycolic acid) (PLGA) was lower than that of PLA and increased with copolymer molecular weight. A single Tg intermediate to that of the two blend constituents was observed suggesting miscibility. Polymer blends showed enhanced methane production at early stages of anaerobic degradation with the rate increasing with increasing PLGA content and decreasing PLGA molecular weight. Blends exhibited a decrease in modulus and tensile strength as compared to pure PLA. Likewise, a decrease in ductility for all but the lowest molecular weight copolymer containing blend was observed. The zero-shear viscosity of polymer blends scaled predictably with PLGA content and exhibited reduced sensitivity to shear-rate. It is envisioned that this strategy could be applied for those applications where recycling is prohibitive such as at universities, hospitals and stadiums where mixed waste streams containing plastics and other waste types, such as food and paper, can be anaerobically co-digested and the resulting biogas used as fuel.