Mechanical, rheological and anaerobic biodegradation behavior of a Poly(lactic acid) blend containing a Poly(lactic acid)-co-poly(glycolic acid) copolymer Kosar Samadi, Michelle Francisco, Swati Hegde 1 , Carlos A. Diaz, Thomas A. Trabold, Elizabeth M. Dell, Christopher L. Lewis * Rochester Institute of Technology, 78 Lomb Memorial Drive, Rochester, NY,14623, USA article info Article history: Received 8 May 2019 Received in revised form 4 October 2019 Accepted 22 October 2019 Available online 31 October 2019 Keywords: Poly(lactic acid) Poly(lactic acid-co-glycolic acid) Blend Anaerobic degradation Mechanical Rheology Packaging 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 co- polymers 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 (M w ¼ 16, 58 and 113 kgmol 1 ) and melt blended with a high molecular weight PLA homopolymer. The glass transition temperature (T g ) of pol- y(lactic acid-co-glycolic acid) (PLGA) was lower than that of PLA and increased with copolymer molecular weight. A single T g intermediate to that of the two blend constituents was observed suggesting misci- bility. 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 sensi- tivity 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. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction The omnipresence of synthetic polymers in daily life can be attributed to their many advantages over competing materials including their low cost, low density, their ability to be tailored through the use of additives and low temperature conversion into useful objects. However, traditional plastics present a unique so- cietal challenge in that their high usage coupled with their inability to biodegrade results in the rapid accumulation of waste. While recycling efforts aim to reduce this problem, remarkably only about 8% of the 31 million tons of plastics produced a year are recycled [1]. One reason for this poor recycling record is that almost half of the plastics used are aimed at disposable, single-use applications, such as packaging and disposable consumer items [2]. If plastics contain other organic materials as contaminants, they generally go to a landfill or incinerator as the current recycling infrastructure doesn't support extensive sorting and contaminant removal [3,4]. Recently, biodegradable plastics have become available, thus offering alter- native end-of-life scenarios to recycling such as compositing or anaerobic digestion (AD). However, the degradation rates of these materials are often too slow thus limiting their widespread adoption. AD is used as a means of converting dairy manure on large farms and is being promoted for co-digestion of other waste types such as food waste [5]. Food waste or other common organic waste streams, such as paper and yard debris, biodegrade relatively quickly (<30 days) [6]. In contrast, most biodegradable polymers exhibit much longer degradation times even under aggressive conditions (Fig. 1). For example, polylactic acid (PLA), arguably the * Corresponding author. E-mail address: cllmet@rit.edu (C.L. Lewis). 1 Present Address: The Water Center, University of Pennsylvania, 412 McNeil Building 3718 Locust Walk, Philadelphia, PA 19104, USA. Contents lists available at ScienceDirect Polymer Degradation and Stability journal homepage: www.elsevier.com/locate/polydegstab https://doi.org/10.1016/j.polymdegradstab.2019.109018 0141-3910/© 2019 Elsevier Ltd. All rights reserved. Polymer Degradation and Stability 170 (2019) 109018