Curing of epoxy resins by bio-based phenalkamines vs low-molecular-weight amines: study by DSC

In this study, curing of BPA-based epoxy resins Araldite®GY-2600 and Araldite®GY-240 by low-molecular-weight amines EDA, TETA and Jeffamine D-230, and bio-based phenalkamines Cardolite®NX-6019, Cardolite®Lite-2002 and Cardolite®GX-6004 was studied by differential scanning calorimetry (DSC) and rheology measurements. DSC provided quantitative information on the overall reaction kinetics (the enthalpy of curing reaction, ΔHR; cure degree, α; curing reaction rate, dα/dt) and the glass transition temperature (Tg) of the cured product. It was demonstrated that the DSC curing of epoxy resins by phenalkamines started at lower temperature, and the curing rates were slightly lower compared to those cured by low-molecular-weight amine hardeners. The enthalpy of the curing by phenalkamines was lower, especially in the case of more viscous epoxy resin GY-2600. Tg of the cured epoxy resins varied from 50 to 98°C and was slightly lower when cured with cardanol-based phenalkamines. The results demonstrate that curing of epoxy resins by bio-based phenalkamines proceeds in a similar temperature interval like using low-molecular-weight amines as hardeners but with less exothermic effect, which could be an advantage.