Synthesis, Spectral and Thermal Degradation Kinetics of the Epoxidized Resole Resin Derived from Cardanol

Cardanol-based epoxidized resole resins (ERCF) were synthesized by reacting resole-type phenolic resin (RCF) and epichlorohydrin in a basic medium, at 120oC. Resole-type phenolic resins were synthesized by reacting cardanol and formaldehyde (in molar ratios 1:1.3, 1:1.5, 1:1.7, 1:1.9, 1:2.1) in the presence of sodium hydroxide, as a catalyst, at five different temperatures ranging between 60 and 80oC with an interval of 5oC for a maximum period of 6 h. These prepared samples were cured using 15% polyamide as a curing agent at 120 +/- 2oC for 1 h. The synthesized resins were characterized by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopic analysis. The thermal properties of all these samples were studied by thermogravimetric analysis (TGA) at 10oC min(-1). Decomposition kinetics was studied by various kinetic models for the synthesized compounds. The TG/DTG thermograms showed two-step decomposition behavior in all the samples of ERCF. In the present study, Coast-Redfern, Horowitz-Metzger, and Broido models have been used to calculate the activation energy (E-a) and preexponential factor (A) for different stages. The activation energy calculated from all the three models mentioned above were close to each other for the prepared ERCF.