Evaluating the Curing Kinetics of Coal-Based Phenolic Resin Composites Using Calorimetric and Spectroscopic Analyses

Abstract

Phenolic-coal composites are a potential class of thermosetting composites that could offer enhanced thermal stability due to the similarity in the aromatic macromolecular structures of the filler and polymer. Evaluating the curing kinetics of the composite can provide insight into the dynamics of bond formation in this composite during heat curing. In this work, the curing kinetics of phenolic resin and coal mixes were evaluated using differential scanning calorimetry (DSC) and characterized using Fourier transform infrared spectroscopy (FTIR) to evaluate the interaction between the coal filler and the polymer network and correlate the coal structure and composite processing. The two ranks of coal studied were sub-bituminous coal (Powder River Basin) and bituminous coal (Itmann) at filler weight percentages of 10 and 40% weight content, respectively. Isoconversional analyses indicated that the 60% phenolic-PRB mix had the highest activation energy: 142 ± 8 kJ/mol, while the 60% phenolic-Itmann mix yielded the lowest range of activation energy values: 85 ± 5 kJ/mol. In comparison, the pure phenolic resin has activation energies in the range 128–135 kJ/mol. The difference in curing activation energy and postcured vibrational spectroscopy between the composite systems could be attributed to the more reactive functional end groups present in the PRB coal. The higher level of interaction observed in the sub-bituminous coal and phenolic mix confirms enhanced polymeric behavior. These overall results suggest possible varied end properties of cured phenolic resins tailored for different applications based on the choice of coal ranks as fillers.