Additive-Enhanced PAX Polyesters for Industrial Processing and Increased Longevity

Biobased and degradable polyesters with high material performance are essential for short-term applications like packaging. However, enhancing degradability often leads to challenges such as instability during high-shear melt processing and premature degradation. Previously, we introduced a novel class of degradable polyesters, poly(alkylene xylosediglyoxylates) (PAX), which combine strength, ductility, thermal stability, and low gas permeability. However, PAX’s hydrophilicity and limited hydrolysis resistance cause significant degradation during air-exposed high-shear extrusion and short product lifetimes in warm water. In this study, we scaled up the synthesis of a key PAX polyester and addressed these challenges using extrusion-based additive engineering with a food-grade molecular weight chain extender (styrene-acrylate-glycidyl methacrylate copolymer) and an antihydrolysis agent (bis(2,6-diisopropylphenyl)carbodiimide). Adding 0.5 wt % of the chain extender improved molecular weight retention, thermomechanical properties, extrusion melt-strength, and processability. Additionally, the antihydrolysis agent doubled the material’s resistance to water-induced degradation. These strategies enable the production of PAX resin under industrial conditions, retaining the virgin material’s properties while extending and tuning its lifetime in water. This work demonstrates how additives can enhance the performance of new degradable polymers.