Dynamic DSC curing kinetics and thermogravimetric study of epoxy resin of 9,9′-bis(4-hydroxyphenyl)anthrone-10

Abstract

Dynamic DSC curing kinetics of epoxy resin of 9,9′-bis(4-hydroxyphenyl) anthrone-10 (EAN) was carried out at 5, 10, 15 and 20 °C min−1 heating rates in nitrogen atmosphere using 4,4′-diaminodiphenylsulfone (DDS), 4,4′-diaminodiphenylmethane (DDM) and tetrahydrophthalicanhydride (THPA) hardeners. Peak exotherms shifted toward higher temperature range with increasing heating rate. DSC data were analyzed by Ozawa, Kissinger and Flynn–Wall–Ozawa methods to derive activation energy (E a) and frequency factor (A). Observed trend in E a and A is EAN-DDS > EAN > EAN-THPA > EAN-DDM. For EAN-amine systems, both E a and A decreased with increasing conversion and for EAN-THPA they increased up to 30% conversion and then decreased slowly with increasing conversion. Friedman plots showed autocatalytic nature of the EAN-hardener systems. Autocatalytic nature is due to dehydration of secondary alcohol groups with simultaneous formation of allylic double bonds. EAN-THPA showed 1.34 and 0.34, respectively, for n and m orders of kinetics. The validity of kinetic model was performed by simulation analysis using obtained kinetic constants for EAN-THPA. Experimental and calculated curves are in agreement between α = 0.2–0.6. Thermogravimetric study at 10 °C min−1 heating rate in nitrogen atmosphere revealed that cured resins (310–337 °C) are more thermally stable than thermally cured EAN (279 °C) and followed either one- or two-step degradation kinetics.