Compatibility confirmation and refinement of thermal and mechanical properties of poly (lactic acid)/poly (ethylene-co-glycidyl methacrylate) blend reinforced by hexagonal boron nitride

Abstract

The formation of PLA/PEGM graft copolymers during the melt blending of poly (lactic acid) (PLA) and poly (ethylene-co-glycidyl methacrylate) (PEGM) act as an interface between two polymer matrices was illustrated by the epoxide ring-opening mechanism. There are two coupling reaction mechanisms of glycidyl methacrylate (GM) unit of PEGM with the terminal groups of PLA. The analysis of FTIR and 1H NMR spectra elucidates the chemical reaction of GM unit of PEGM with carboxylic and hydroxyl terminal groups of PLA. FTIR analysis also confirms that the carboxylic terminal groups of PLA are more likely to react with GM group of PEGM. Hence, PLA grade having carboxyl terminal groups is more compatible with PEGM as compared to the PLA grade having hydroxyl and ester terminal groups. The hexagonal boron nitride(HBN) is incorporated with various labels such that 1phr, 5phr and 10phr to prepare PLA/PEGM/HBN blend-composites. The blend-composite with low HBN content i.e. 1phr shows better mechanical and thermal properties than neat PLA, PLA/PEGM blend and other blend-composites. This is attributed to the formation of covalent bond between polymer chains and HBN crystal layers and also due to the intermolecular interaction between the hydrogen atoms of polymer chains with the nitrogen atoms of HBN, which is confirmed by the FTIR and 1H NMR studies. TG/DTG, SEM, XRD analysis and the improvement in the mechanical and thermal properties of the prepared blend also asserts the interfacial compatibility between PLA and PEGM in the blend and chemical interaction of HBN particles with polymer matrix.