Epoxy resins based on trimethylolpropane. II. Kinetic and thermodynamic parameters of cure with<i>m</i>‐XDA

Abstract A study of cure of an epoxy resin based on trimethilolpropane (TMP) used as supplied and in purified form and m ‐xylylenediamine ( m ‐XDA), as curing agent has been carried out. Thermodynamic functions such as activation energy, activation entropy, activation enthalpy, and free energy of activation were determinated. From kinetic study we have observed that there are two competitive mechanisms; autocatalyzed and n order, with the values of activation energy ranging between 52.9 and 64.6 kJ/mol. The overall order of reaction is found to be 2.5, and the order of reaction with respect to the hydroxyl group is clearly determined and equal to 1. Gelation study was carried out under two conditions: isothermal and adiabatic. From isothermal study we obtained the values of functionality of the resins (approximately two) and the apparent activation energy of the process. The adiabatic study allowed us the determination of the pot‐life taking into account the theoretical model used, with reasonable theoretical/experimental agreements. The importance of n ‐order path for this kind of resins (with high OH contents) is well demonstrated through kinetic and thermodynamic parameters. The thermodynamic functions showed themselves as very sensitive parameters for the following and evolution of the reaction. © 1995 John Wiley &amp; Sons, Inc.