What is the purpose of a post-cure in epoxy resins?

• A. To shorten cure time
• B. To reduce resin viscosity
• C. To increase crosslink density, improve thermal stability and high-temperature properties
• D. To reduce crosslink density

Answer: (C)

Post-curing epoxy resins is about driving additional crosslinking by heating the already cured material. This extra heat lets remaining reactive groups find partners and form more bonds, increasing the crosslink density of the network. A higher crosslink density boosts thermal stability and raises the glass transition temperature, so the material performs better at elevated temperatures. It also tends to improve solvent/chemical resistance and mechanical properties like stiffness and hardness. This step isn’t primarily aimed at shortening the cure time, altering viscosity as the main goal, or reducing crosslink density.