Improvement of melt viscosity and compatibility of polyglycolic acid (PGA)/polylactic acid (PLA) blend via reactive blending with bifunctional and multifunctional hybrid chain extender

Abstract The low melt viscosity and melt strength of polyglycolic acid (PGA) severely limit its application. In this work, high melt viscosity PGA/PLA blends are prepared by reactive extrusion of bifunctional isocyanate (HDI) and multifunctional epoxy oligomer (ADR) as chain extenders. The use of hybrid chain extender (hCE) containing 2 wt% HDI and 1 wt% ADR results in a long chain branched/cross‐linked structure, thus increasing melt viscosity more effectively than HDI or ADR alone. The complex viscosity, storage modulus and loss modulus of the PGA/PLA/hCE blends are significantly higher than those of the PGA/hCE. The 60PGA/40PLA/hCE has the highest complex viscosity of 72,115 Pa s, which is 69 times of that of PGA/hCE. The modification of hCE significantly improved the mechanical performance of PGA/PLA blend, with the 60PGA/40PLA/hCE having the highest tensile strength and flexural strength. The crystallization temperature and crystallinity of the PGA component in the PGA/PLA/hCE blend are significantly reduced in comparison to that of the PGA/hCE. The PGA/PLA/hCE has the best thermal stability, with the T −5% of 355.3°C, almost 45°C higher than pure PGA. The SEM results show that the adding of hCE decreased the domain size of the PLA dispersed phase in PGA/PLA blend, due to the in situ compatibilization.