Influences of chemical structures of grafting phenols on thermal properties of lignophenols

Abstract

Thermal properties of 12-different hardwood (Betula maximowicziana) lignophenols (LPs) with 4-alkylphenols, dimethylphenols or naphthols were estimated and evaluated using thermal mechanical analysis (TMA) and thermogravimetry(TGA). Relationships between these thermal properties and chemical structures of grafting phenols determined by FTIR,¹H-NMR and HPLC (SEC) have been investigated. Both glass transition temperatures and thermal stabilities determined by TMA and TGA respectively were different among LPs with 4-alkylphenols, xylenols and naphthols. As length of alkyl chains increased, T_g of LP decreased from 160 ℃ to 120 ℃. Naphthol also increased T_g of LP up to 185 ℃ due to large and planar structures with rich π-interactions. Since xylenols as well as p-cresol showed only small changes in T_g and T_d5. Some dependences of these properties on only grafting phenols were observed. Relationships between free volumes produced by motions and interactions of long alkyl chains and aromatic rings and thermal properties of LP were discussed.