Toughening Poly(lactic acid) with Thermoplastic Elastomers Modified by Thiol-ene Click Chemistry

Due primarily to the inherent brittleness of poly(lactic acid) (PLA), numerous studies have sought to improve the mechanical properties (e.g., fracture toughness) of PLA for a wide range of contemporary applications. In this study, we report a facile method by which to prepare esterified poly[styrene-b-(ethylene-alt-propylene)-b-styrene] (eSEPS) as a toughening agent for PLA through the use of thiol-ene click chemistry. The effects of adding 1 to 30 wt % eSEPS on the thermomechanical properties and morphological characteristics of PLA/eSEPS blends have been systematically investigated. Since eSEPS copolymers are more thermodynamically compatible with PLA than their parent partially hydrogenated SIS copolymer, we find a measurable reduction in the thermal properties of PLA from thermal calorimetry and enhanced dispersion of eSEPS within the PLA matrix according to electron microscopy. Considerable boosts in mechanical properties such as toughness (similar to 60 MJ/m(3)) and elongation at break (similar to 470%) are about 16x and 24x higher, respectively, than those of neat PLA. An optimum level of eSEPS incorporated in the PLA matrix between 1 and 5 wt % plays an essential role in achieving maximum property improvements.