Polylactide (PLA) being a very brittle biopolymer could be toughened by blending with thermoplastic elastomers such as thermoplastic polyurethane elastomer (TPU) and thermoplastic polyester elastomer (TPE); unfortunately, these blends are immiscible forming round domains in the PLA matrix. Therefore, the purpose of this study was to investigate the effects of using maleic anhydride (MA) compatibilization on the toughness and other properties of PLA blended with TPU and TPE. MA grafting on the PLA backbone (PLA-g-MA) was prepared separately by reactive extrusion and added during melt blending of PLA/thermoplastic elastomers. IR spectroscopy revealed that MA graft might interact with the functional groups present in the hard segments of TPU and TPE domains via primary chemical reactions, so that higher level of compatibilization could be obtained. SEM studies indicated that PLA-g-MA compatibilization also decreased the size of elastomeric domains leading to higher level of surface area for more interfacial interactions. Toughness tests revealed that Charpy impact toughness and fracture toughness (K IC and G IC ) of inherently brittle PLA increased enormously when the blends were compatibilized with PLA-g-MA. For instance, G IC fracture toughness of PLA increased as much as 166%. It was also observed that PLA-g-MA compatibilization resulted in no detrimental effects on the other mechanical and thermal properties of PLA blends.

The aim of this study was to investigate influences of three different ethylene copolymers on the toughness and other properties of very brittle biopolymer PLA (polylactide). For this aim, PLA was melt blended by twin-screw extruder with various amounts of ethylene vinyl acetate (EVA), ethylene-methyl-acrylate (EMA) and ethylene-n-butyl acrylate-glycidyl-methacrylate (EBA-GMA). SEM and DSC analyses indicated that these ethylene copolymers were thermodynamically immiscible with phase separation in the form of 1-5 µm sized round domains in the PLA matrix. Rubber toughening mechanisms of EVA, EMA and EBA-GMA were very effective to improve ductility and toughness of PLA significantly. Depending on the type and content of the ethylene copolymers, the highest increases in % elongation at break, Charpy impact toughness and G IC fracture toughness values of PLA were as much as 160, 320 and 158%, respectively. Although there were no detrimental effects of using EVA, EMA and EBA-GMA on the thermal properties of PLA, they resulted in certain level of reductions in stiffness, strength and hardness values.

The purpose of this study was to improve toughness of inherently very brittle polylactide (PLA) without sacrificing strength and thermal properties, so that biopolymer PLA could be used in engineering applications. For this purpose, PLA was blended with various amounts of two different thermoplastic elastomers; TPU (petroleum-based thermoplastic polyurethane) and TPE (bio-based thermoplastic polyester). Melt blending and specimen shaping were achieved by using a twin-screw extruder and injection molder, respectively. SEM analysis indicated that TPU and TPE were immiscible forming fine and uniform round domains in the PLA matrix. It was revealed that rubber-toughening mechanisms of TPU and TPE were very effective. For instance, using only 10 phr of TPU or TPE increased Charpy impact toughness of PLA more than 300 %, while increases in fracture toughness (KIC and GIC) values of PLA were as much as 35 % and 130 %, respectively. Other mechanical tests (tension, flexure, hardness) and thermal analyses (DSC) revealed that there were no significant detrimental effects of using 10 phr TPU or TPE on the engineering performance of PLA.