Mechanism and Kinetics of Curing of Diglycidyl Ether of Bisphenol A (DGEBA) Resin by Chitosan

Crosslinking behavior of Diglycidyl Ether of Bisphenol A (DGEBA) resins cured by chitosan was isothermally studied by Fourier Transform Infrared (FTIR) Spectroscopy for various molar ratios of chitosan at different temperatures. Results indicated that oxirane undergoes nucleophilic attack by the primary amine groups in chitosan to form crosslinked structure. Epoxy fractional conversion (alpha) was calculated by following the change in area of oxirane peak at 914 cm(-1). Value of a and reaction rate (d alpha/dt) increased with increase in curing temperature and chitosan concentration. The maximum epoxy fractional conversion of 70% was obtained for 1: 4 molar ratio (Epoxy: Chitosan) at 200 degrees C. A four parameter kinetic model with two rate constants was employed to simulate the experimental data. Overall reaction order and activation energy for all compositions were in the range of 2.5-3 and 25-50 kJ mol(-1), respectively. Results indicated that cure reaction is autocatalytic and does not follow simple nth order cure kinetics. Thermogravimetric analysis (TGA) performed on chitosan cured DGEBA films and compared against neat epoxy and neat chitosan films. Results showed that the degradation of chitosan crosslinked epoxy network occurred in the temperature range of 450-508 degrees C. POLYM. (C) 2016 Society of Plastics Engineers