High melt viscosity, low yellowing, strengthened and toughened biodegradable polyglycolic acid via chain extension of aliphatic diisocyanate and epoxy oligomer

Abstract

Poly(glycolic acid) (PGA) is a biodegradable plastic with excellent degradation rate, barrier properties, and heat resistance. However, its low melt viscosity and narrow processing temperature severely limit its application. To overcome these drawbacks, the aromatic diisocyanates TDI and MDI, aliphatic diisocyanate HDI, and multifunctional epoxy oligomer ADR were used as the chain extender to modify PGA. The PGA/HDI shows a faster chain extension reaction rate and significantly less yellowing than PGA/TDI or PGA/MDI. The combined use of HDI and ADR to modify PGA can produce long chain branched/crosslinked structures, resulting in a significant increase in melt viscosity, with complex viscosity two orders of magnitude higher than that of pure PGA and minimal yellowing. The T-5% of PGA/HDI/ADR is 45 °C higher than that of pure PGA, and its crystallization temperature, crystallization rate and melting temperature are significantly decreased, suggesting that it has a wider processing temperature window. Moreover, the tensile and flexural strength of PGA/HDI/ADR are 113.8 MPa and 216.8 MPa, respectively, an increase of 25% and 26% over pure PGA, while the elongation at break and impact strength increase to 9.5% and 11.6 KJ/m2, respectively, 42% and 176% higher than pure PGA.