SACCHARIDE-AND LIGNIN-BASED POLYCAPROLACTONES AND POLYURETHANES

Abstract

Saccharide- and lignin-based polycaprolactones were synthesized from glucose-, fructose, sucrose, alcoholysis lignin (AL) and Kraft lignin (KL) by the polymerization of -caprolactone (CL) which was initiated by the OH group of saccharides and lignins. The CL/OH (mol/mol) ratios of the saccharide-based PCL's were changed from 1 to 5 and those for lignin-based PCL's were changed from 2 to 25. PU sheets were prepared from the above PCL derivatives by the reaction with diphenylmethane diisocyanate (MDI). Thermal properties of the prepared saccharide- and lignin-based PCL's and PU sheets were studied by differential scanning calorimetry (DSC), thermogravimetry (TG) and TG-Fourier transform infrared spectroscopy (FTIR). Glass transition temperatures (Tg's), cold-crystallization temperatures (T∞'s) and melting temperatures (Tm's) of saccharide- and lignin-based PCL's and PU's were determined by DSC, and phase diagrams were obtained. Tg's decreased with increasing CL/OH ratio, suggesting that PCL chains act as a soft segment in the amorphous region of PU molecules. Two thermal degradation temperatures (Td's) were observed in TG curves of PU's from saccharide- and lignin-based PCL's with low CL/OH ratios. TG-FTIR analysis of PU's from lignin-based PCL's suggested that compounds having C-O-C, C=O and C-H groups are mainly produced by thermal degradation of PCL chains in lignin-based PCL's and PU's.