Mechanical and Thermal Properties of Composites of Epoxy Resin Derived from Kraft Lignin Filled with Cellulose Particles

Abstract

A mixture of ester-carboxylic acid derivatives (KL polyacid, KLP A) was obtained by reaction of an ethylene glycol solution of Kraft lignin (KL) and succinic anhydride in the presence of a catalytic amount of dimethylbenzylamine at 100 °C. Cellulose particles were added to the above mixture with various mixing ratios from 0 to 60 wt%. A prepolymer of lignin-based epoxy resin was prepared by a reaction of the mixture of KLP A and cellulose particles with ethylene glycol diglycidyl ether (EGDGE) at 100 °C. The above mixtures were molded into sheets at 130 °C for 5 hours. The mechanical properties of the samples were investigated by tensile tests using plate type specimens. The elastic modulus and tensile strength were determined by the tensile tests. Thermal properties of composite samples were measured by differential scanning calorimetry (DSC) and thermogravimetry (TG). Glass transition temperatures of samples were determined by DSC. Thermal decomposition temperatures and mass residues were determined by TG. The values of strength and modulus determined by tensile tests were maximum at cellulose content of 60 wt% for composite samples with cellulose particles of 25 mm diameter. Thermal properties such as peak temperatures of thermal decomposition and glass transition temperature determined by TG and DSC were not affected by cellulose contents.