The varieties of curing agent have a great influence on the mechanical properties, heat resistance, water resistance, corrosion resistance of the curing agent, such as aromatic polyamines, imidazole, acid anhydride curing agents for epoxy resins. The heat resistance of cured epoxy resins is better than that of aliphatic polyamines and low molecular polyamide curing agents; Aromatic anhydride cured epoxy resins have better water resistance than curing agents of aromatic diamines and aliphatic polyamines; Triethylenetetetramine curing agent has good alkali-resistance, but it is less resistant to acid and formaldehyde solutions. The alicyclic polyamines (such as isophorone diamine) cure epoxy resins have excellent drug resistance. The alkali resistance of acid anhydride curing agent cured epoxy resins is better than its acid resistance. Therefore, the appropriate curing agent should be selected according to different purposes and performance requirements.
Through the compound use of several curing agents, it can achieve complementary results. For example, the use of a low molecular polyamide curing agent with a small amount of resorcinamide curing agent can not only be cured at room temperature but also increase the durability as well as the heat resistance appropriately of the cured substance. The combination of trimellitic anhydride (TMA) and methyl-tetrahydro phthalic anhydride produces a low viscosity eutectic mixture (25°C, 200-250 mPa-s), which is easy to mix with epoxy resin and improves the processability.
The selected curing agents should be non-hazardous to humans and non-polluting to environment. Ethylenediamine should never be used for curing alone.