Introduction to classification of epoxy resin curing agents

The realization of the excellent properties of epoxy resin depends on the curing agent. As an indispensable component of the epoxy system, the curing agent determines the structure and physical and chemical properties of the cured product to a large extent. Therefore, this article will give a classification introduction to epoxy resin curing agents.

Epoxy resin curing agents are generally divided into two categories: alkaline curing agents and acidic curing agents. Among them, alkaline curing agents mainly include Lewis bases such as primary amines, secondary amines, amides and other nitrogen-containing compounds that can cross-link with epoxy resin; acidic curing agents include organic anhydrides, organic acids, thiols, boron -Lewis acids such as amine complexes and phenolic compounds.

In the research and application of epoxy resin curing agents, the most widely used are amine curing agents, among which aromatic amine curing agents, alicyclic amine curing agents, and aliphatic amine curing agents are the main ones.

Fatty amine curing agents mainly include ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, etc. This type of curing agent can fully cure and cross-link with epoxy resin at room temperature or lower temperature, and the cured product has good corrosion resistance, water resistance, mechanical strength and bonding performance. However, most fatty amine curing agents are low molecular weight linear molecules. They have high vapor pressure, strong irritation, and high toxicity. Their proportions are strict and they require high operators. These shortcomings limit their application. In order to improve the obvious shortcomings of fatty amine curing agents, researchers used low molecular weight primary fatty amines as raw materials and obtained amine adducts through certain chemical modifications. This improved the smell of primary fatty amines and reduced the ratio requirements, thus Greatly broadens its application scope.

Therefore, in order to improve the performance of curing agents, modification of curing agents is an inevitable development trend. Commonly used modification methods are as follows: phenolic modification, addition modification with epoxy compounds, reaction modification with carbonyl and carboxyl compounds, condensation modification with thiourea, amine self-condensation reaction modification, boron trifluoride complexation Modification, addition modification of chlorosulfonated polyethylene, modification by physical methods, etc. The modified curing agent has been greatly improved in terms of compatibility, reactivity, toxicity and irritation, greatly broadening its application scope.

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