Thermal degradation behaviour of alcoholysis lignin-based polycaprolactones (ALPCL's) with various molar ratios of β-caprolactone
monomer to each hydroxyl group of lignin (CL/OH ratios) was studied by TG-FTIR. The temperature was varied from 20 to 800C.
Thermal degradation temperatures (Td's) of alcoholysis lignin (AL) and ALPCL's were determined using TG curves. Td increased with increasing CL/OH ratio, suggesting that AL becomes thermally stable after the derivatization with PCL chains.
Mass residue (MR) at 500C was also determined using TG curves. MR values decreased with increasing CL/OH ratios. The evolved
gases formed by thermal degradation of ALPCL's at various temperatures were simultaneously analyzed by FTIR. The main peaks
observed for the samples are as follows: wavenumber (assignment): 1160 cm-1 (vC-O-), 1260 cm-1(-C(=O)-O-C-), 1517 and 1617 cm-1 (vC=C), 1770 cm-1 (vC=O), 2345 cm-1 (vCO2), 2945 cm-1 (vC-H) and 3700 cm-1 (vOH). It was found that the peak intensities for C=O, CH, C-O-C, OH peaks, which were observed for evolved gases at 430C,
increased with increasing CL/OH ratios, suggesting that the evolved gases at 430C are mainly formed by thermal degradation
of PCL chains in ALPCL's.