Effects of NCO/OH ratios and polyols during polymerization of water-based polyurethanes on polyurethane modified polylactide fabrics

Polylactides (PLAs) are a type of environmental friendly material. PLA fabrics feature excellent performance in terms of texture, comfort, curling effect, crystallinity, and transparency. However, because of its aliphatic polyester structure, PLA is relatively fragile as compared with the commercially available products like PET or Nylon. This study adopted water-based polyurethane (PU) to modify the surface of PLA fabrics, thereby enhancing the fabrics’ mechanical properties. Various polyols such as polytetrahydrofuran (PTMG), polycaprolactone diol (PCL), and polycarbonates diol (PC) were used and various NCO/OH molar ratios were designed in this study. As the PLA fabric was processed by dipping in various PU dispersions, it was found that the breaking strength of the fabric was increased, while its elongation at breakage decreased. Particularly, the breaking strength of the fabric modified by PUD50PC containing 50 weight percent of PC and two other polyols was the most prominent showing an 80 % increase in strength. Furthermore, the abrasion resistance of the PUD50PC-modified PLA fabric showed a roughly 6 times increase as compared to the plain PLA fabric. SEM images also reveal that after processing with water-based PU, the PLA fibers are bonded tightly with the water-based PU molecules to increase the breaking strength of the PLA fabrics.