Impact of high pressure on the progress of polymerization of DGEBA cured with different amine hardeners: dielectric and DSC studies

Abstract

Kinetics and dynamics of the curing of bisphenol-A diglycidyl ether (DGEBA) with various agents i.e. cyclohexylamine, aniline and 2-ethylhexylamine, were investigated by means of Broadband Dielectric Spectroscopy (BDS) over a wide range of thermodynamic conditions. We proposed a novel method of dielectric data analysis to extract information on the progress of the curing reaction. This approach was validated by complementary calorimetry measurements. High pressure studies indicated that compression significantly reduces the time of the reaction. At the same time, a decrease in monomer conversion and the glass transition temperature of the recovered product was observed. This was due to vitrification of the system that occurs in a relatively short time. We found a linear correspondence between the time of the polymerization after which the investigated system undergoes glass transition and the degree of monomer conversion. Additionally, activation volumes for the investigated reactions were determined and found to lie in the range −18 and −38 cm³ mol⁻¹. The calculated values are lower than ΔV estimated for the ring opening reaction provided in the literature. However our data unquestionably showed that this quantity depends strongly on both the chemical structure of the substrates as well as thermodynamic conditions.