Thermal stability of lignin in ground pulp (GP) and the effect of lignin modification on GP’s thermal stability: TGA experiments with dimeric lignin model compounds and milled wood lignins

Abstract

Abstract For ground pulp (GP) utilization in wood fiber composites as reinforced material, its thermal behavior is relevant. The contribution of lignin to thermal performance of GP from Pinus densiflora was the focus of the present study. Dimeric lignin model compounds and isolated milled wood lignins (MWLs) from three sources were submitted for thermogravimetric analysis (TGA). The temperatures leading to 1% weight loss (T per 1% WL) for the material were determined. The thermal stability of β-O-4 models was the lowest. Among the MWLs, the abaca MWL with its high β-O-4 content was the least thermostable. An acetylated nonphenolic β-O-4 lignin model compound showed that acetylation improves the thermal stability of this type of dimeric models. The acetylation of benzylic OH groups in β-O-4 linkages is especially relevant for the thermal resistance, which was also shown based on pre-acetylated benzylic OH groups in the GP before the total acetylation.