TG-FTIR studies on lignin-based polycaprolactones

Thermal degradation behaviour of alcoholysis lignin-based polycaprolactones (ALPCL's) with various molar ratios of c-caprolactone monomer to each hydroxyl group of lignin (CL/OH ratios) was studied by TG-FTIR. The temperature was varied from 20 to 800degreesC. Thermal degradation temperatures (T-d's) of alcoholysis lignin (AL) and ALPCL's were determined using TG curves. T-d increased with increasing CL/OH ratio, suggesting that AL becomes thermally stable after the derivatization with PCL chains. Mass residue (MR) at 500degreesC 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) (vCO(2)), 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 430degreesC, increased with increasing CL/OH ratios, suggesting that the evolved gases at 430degreesC are mainly formed by thermal degradation of PCL chains in ALPCL's.