Anhydride curing agent is a kind of reactive epoxy resin curing agents. Compared to polyamide, anhydride curing agent has many advantages.
In the operation, it is low volatile, low toxicity and little irritation to the skin. The combination of epoxy resin is large, and the viscosity is low after mixing with epoxy resin. It can be modified by adding some additives to reduce the cost. That can be used long term and easy to operate.
From curing properties, the curing reaction is slow and the shrinkage rate is low. Anhydride curing agent also has some advantages, such as high thermal deformation temperature, excellent heat resistance, good mechanical and electrical properties.
However, the curing temperature of the anhydride curing agent is high. The curing period is long and not easy to modify. During storage, it is easy to absorb water and form free acid. That can cause bad effects (slow curing speed and degradation of curing properties). The deficiency of anhydride curing agent is that the alkali resistance and solvent resistance of curing products are inferior.
The curing reaction mechanism is shown below:
Acid anhydride curing agent is widely used. Chain enyl succinic anhydride and trimellitic anhydride are good prospects.
The chain enyl succinic anhydride is a liquid acid anhydride. It greatly enhances the flexibility of the resin and reduces brittleness because of its long linear alkenyl side chain.
It is suitable for curing, epoxy resin impregnating and coating of epoxy resin for casting or laminating.
Epoxy resin curing substance of trimellitic anhydride has excellent heat resistance, electronic, mechanical properties and the drug resistance. It also can significantly improve the brittleness of epoxy resin curing agent. The trimellitic anhydride has been used for heat-resistant insulation laminate board, insulating paint from heat-resistant cable and powder coating.
Phthalic anhydride has a high solid melting point. The use of technology is not ideal. In that case, a series of modified products were developed. Such as low eutectic mixtures with various anhydride, partial benzene dicarboxylic acid acetic ester and partial benzene dicarboxylic acid propionic acid ester, etc.
In addition, the comprehensive properties of tung oil anhydride. The application is limited due to the poor heat resistance.
The modification of 3 (2-hydroxyethyl) isocyanurate was used to improve the heat resistance of the solidified material obviously, and the use value was better.
These are some characteristics and applications of the curing agent of anhydride.
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