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Abstract
Partial esters of cycloaliphatic epoxy resins C1 and C2, containing glycidyl and epoxy cyclohexane groups, respectively, as their reactive units were synthesized using a 1:0.4 stoichiometric ratio of resin and methacrylic acid in the presence of triphenylphosphine. The reaction was performed as a function of temperature to determine various kinetic and thermodynamic parameters of the reaction. The prepared esters of C1 and C2, designated as C1P and C2P, respectively, were characterized for their structure by FT-IR spectroscopy. The degree of esterification and epoxy content in partial esters were determined by their epoxide equivalent weight. The curing behaviour of the CERs and their esters was studied using DSC. Dynamic DSC scans of cycloaliphatic epoxy resins mixed with nadic methyl anhydride (NMA)/methyl tetrahydrophthalic anhydride (MTHPA) showed that curing of C1 starts earlier than that of C2. DSC thermograms for the curing of C1P and C2P with benzoyl peroxide (BPO) and NMA/MTHPA showed two distinct exothermic peak positions, T p and T p′, due to the curing of esterified fraction and epoxy groups, respectively. The hydroxyl groups formed during partial esterification were found to catalyse the epoxy–anhydride reaction.
