Different curing agents have different curing temperature and cured products are diverse in heat resistance. Generally speaking, the curing agent with high curing temperature can produce excellent heat-resistant cured materials. For addition polymerized curing agents, the curing temperature and heat resistance are increased in the following order: aliphatic polyamines < alicyclic polyamines < aromatic polyamines ≈ phenolic < anhydride.
Most of the heat resistance of addition polymerized curing agents is equal to that of aromatic polyamines. The high temperature resistance of curing agent of anionic polymerization type (tertiary amine and imidazole compound) and cationic polymerization type (BF3 complex) are basically the same. The main reason is that although the initial reactive mechanism in producing the curing agents are different, the final formation will always be ether bond network structure.
The curing reaction is a chemical reaction, which is greatly affected by the curing temperature. When the temperature increases, the reaction speed will accelerate and the gel time will shorten. The logarithm of gel time declines linearly with higher curing temperature. However, if the curing temperature is too high, the performance of the curing agents will decrease. Thus there is an upper limit of the curing temperature. A suitable curing temperature should be chosen which can balances the curing speed and the performance of the curing agents.
According to the curing temperature, curing agents can be divided into four categories: the low-temperature curing agent whose curing temperature is below room temperature; the room-temperature curing agent whose curing temperature is between room temperature and 50℃; the medium-temperature curing agent whose curing temperature is 50-100 ℃; the high-temperature curing agent whose curing temperature is above 100℃. There are few kinds of low-temperature curing agent: polyarylcohol type, polyisocyanate type and so on. T-31 modified amine and YH-82 modified amine developed and produced domestically can be cured below 0℃. There are many kinds of room-temperature curing agent: aliphatic polyamines, alicyclic polyamines, low molecular polyamides and modified aromatic amines. Some aliphatic polyamines, tertiary amines, imidazoles and boron trifluoride complexes belong to moderate-temperature curing agent. Aromatic polyamines, anhydrides, first-order phenolic resin, amino resin, dicyandiamide and hydrazide are high-temperature curing agents.