Cure kinetic study of epoxidized hemp oil cured with a multiple catalytic system

Abstract

The cure kinetics of two epoxidized hemp oil (EHO) based bioresins were studied and compared under both dynamic and isothermal conditions using differential scanning calorimetry (DSC). Neat triethylenetetramine (TETA) for the first system and a combination of isophorone diamine (IPD) and TETA for the second system were used as the hardeners for the two EHO-based bioresins. Lower total heats of reaction and an approximate 10% decrease in activation energies were observed for the IPD/TETA system. Maximum conversions of the TETA/IPD system were consistently higher than those of the TETA system throughout the entire temperature range suggesting enhanced curing characteristics. Kissinger and Ozawa–Flynn–Wall models were used to determine activation energies from dynamic DSC data. Both bioresin systems were found to display autocatalytic behavior with the TETA/IPD system showing high nth order influence. Kamal's autocatalytic isothermal model, modified to account for diffusion postvitrification was found to satisfactorily describe the cure behavior of both bioresin systems. Overall, the addition of IPD was found to increase the curing rate of the EHO bioresin systems.