Curing kinetics and mechanical properties of epoxy based coatings: The influence of added solvent

Commercial coatings based on epoxy and amine hardener and organic solvent were prepared to investigate the effect of organic solvent on coating properties, their mechanical property and curing kinetics were discussed in terms of different solvent content. The curing degree was characterized by FT-IR, the mechanical properties were studied by tensile and adhesion tests, the non-isothermal curing kinetics and glass transition temperature of epoxy coating were also investigated by differential scanning calorimetry (DSC). The results indicated that the presence of solvent could lower the curing degree thus affecting the cross-linked structure, the tensile strength and modulus of elasticity, while the flexibility was highly improved by adding more solvent into the system. Different adhesive failure modes were observed with the increasing amount of solvent in comparison with that of pure epoxy, it transformed from cohesive to adhesive failure. Furthermore the two parameter autocatalytic kinetic model Sestak- Berggren (m,n) was introduced to describe the curing process and it shows a good agreement with the experimental rates. The results also demonstrated that activation energy of curing reaction increased with rising conversion which revealed that curing process was considered to be diffusion controlled.