Biorenewable Tough Blends of Polylactide and Acrylated Epoxidized Soybean Oil Compatibilized by a Polylactide Star Polymer

Abstract

Polylactide (PLA), a commercially available thermoplastic derived from plant sugars, finds applications in consumer products, disposable packaging, and textiles, among others. The widespread application of this material is limited by its brittleness, as evidenced by low tensile elongation at break, impact strength, and fracture toughness. Herein, a multifunctional vegetable oil, acrylated epoxidized soybean oil (AESO), was investigated as a biodegradable, renewable additive to improve the toughness of PLA. AESO was found to be a highly reactive oil, providing a dispersed phase with tunable properties in which the acrylate groups underwent cross-linking at the elevated temperatures required for processing the blends. Additionally, the presence of hydroxyl groups on AESO provided two routes for compatibilization of PLA/AESO blends:(1) reactive compatibilization through the transesterification of AESO and PLA and (2) synthesis of a PLA star polymer with an AESO core. The morphological, thermal, and mechanical behaviors of PLA/oil blends were investigated, in which the dispersed oil phase consisted of AESO, soybean oil (SYBO), or a 50/50 mixture of AESO/SYBO. The oil additives were found to toughen the PLA matrix, with significant enhancements in the elongation at break and tensile toughness values, while maintaining the glass transition temperature of neat PLA. In particular, the blend containing PLA, AESO, SYBO, and the PLA star polymer was found to exhibit a uniform oil droplet size distribution with small average droplet size and interparticle distance, resulting in the greatest enhancements of PLA tensile properties with no observable plasticization.

The effect of maleinized linseed oil as biobased plasticizer in poly(lactic acid)‐based formulations

“…T g decreased dramatically from 59.2 °C (neat PLA) to 25.8 °C (25 wt% oligomeric lactic acid). In contrast, Mauck et al reported negligible changes in T g of PLA formulations with acrylated ESBO as a plasticizer …”

Effect of different compatibilizers on environmentally friendly composites from poly(lactic acid) and diatomaceous earth

“…Some research work shows that the addition of naturally derived maleinized oils (MLO, for example) reaches plasticizer saturation in PLA and other polyesters at a relatively low oil concentration. This leads to phase separation, which is visible as rounded shapes and hollows . In addition, a certain decrease in the gap size between the PLA matrix and diatomite particles can be observed.…”

“…The addition of MLO increases the ductility (measured through ϵ b ) of PLA‐DE composites, with a good balance on other mechanical resistance properties ( E t , σ t , HS D ). This good mechanical performance can be due to the reaction of the hydroxyl groups on PLA end‐chains and hydroxyl groups on DE silica with the anhydride groups contained in MLO that lead to several overlapping effects such as chain extension, branching and/or crosslinking . In addition to this phenomenon, MLO can also provide slight plasticization effects on PLA‐DE composites as observed in other polyester composites …”

Bio-based reactive diluents as sustainable replacements for styrene in MAESO resin

“…Thus, MAESO resin possesses more reactive C]C double bonds than that of AESO resin. 20,21 Generally, pure MAESO resin is too viscous to use, and therefore demands approximately 35% of styrene as a reactive diluent before being cured by a free radical polymerization. However, new emission standards for composite manufacturing by the Environmental Protection Agency specically have targeted styrene as a regulated hazardous air pollutant (HAP) and volatile organic compound (VOC).…”