There are about 300 kinds of curing agents for epoxy resins, and there are more than 40 kinds of commonly used curing agents. As an important anti-corrosion coating, epoxy resin coatings mostly use room temperature and low temperature curing agents. Commonly used are polyamides, amines and amine adducts, and isocyanuric acid curing agents.
Polyamide curing agent is a commonly used type of epoxy resin coating curing agent, which is formed by polycondensation of dimers of unsaturated fatty acids in vegetable oil and polyamines. Polyamide cured epoxy resin coating has good bonding strength to metal and non-metal, good construction performance, less toxic to human body, and the coating can be used for a long time after preparation (6,-.,.,8h), The water resistance of the coating film is good, but the chemical resistance is slightly worse than that of the polyamine curing agent. When preparing the coating, an induction period of 30 minutes (at room temperature) is required.
Polyamine curing agents include aliphatic amines, aromatic amines, alicyclic amines and tertiary amines, as well as amine adduct curing agents.
Aliphatic amines such as ethylenediamine, diethylenetriamine, triethyleneamine and tetraethylenepentamine, etc. These curing agents can be cured at room temperature, but they are more toxic, especially the LD 50 of ethylenediamine It is 620mg/kg, and the vapor pressure is as high as 1466.5Pa. After contact and inhalation, construction workers will cause skin allergies, dizziness, chest tightness and other nervous system and liver diseases. In severe cases, it will cause acute poisoning and even death. The use of such curing agents should be strictly controlled.
Aromatic amine curing agents mainly include m-phenylenediamine, m-xylylenediamine, etc. The cured products with benzene ring structure have good temperature resistance and corrosion resistance, and are mainly used in heating curing process or as raw materials for curing of modified amines.
Alicyclic amines, that is, cycloaliphatic polyamines, such as isophorone diamine, 4,4'-diaminodicyclohexyl methane, etc., are suitable for high solid and solvent-free coatings, and the coating film has light color after curing , good gloss, good chemical resistance, no need for construction induction curing period, but the toughness of the coating film is poor. When curing, heating or adding accelerators is required to cure at room temperature.
Tertiary amines mainly include triethylamine, triethanolamine, N,N-dimethylaniline, N,N-dimethylbenzylamine and 2,4,6-tris(dimethylaminomethyl)phenol COMP). The molecular structure does not contain active H atoms, and it is a catalytic curing agent, so it is mainly used as an accelerator for epoxy curing agents to accelerate curing.
Aliphatic amine and aromatic amine curing agents are toxic and prone to whitening, and the use of amine epoxy resin adduct curing agents can effectively improve their performance. Commonly used amine adduct curing agents include ethylenediamine-epoxy adducts, Mannich base curing agents, etc.
The amine adduct curing agent phenol aminoalcohol curing agent based on cashew nut shell oil is developed and produced by Cardolite in the United States. After the aromatic compound of the aliphatic side chain is combined with the amine, it has better properties than the simple reaction product of phenol and amine. Excellent flexibility, but also curing in low temperature and humid environment. These curing agents are suitable for high solids and solvent-free heavy duty coatings.
Polymer epoxy resin base and polyisoneonate can be cross-linked and cured at room temperature and low temperature. Polyisoneonate cured epoxy resin coating, the paint film has excellent water resistance, solvent resistance, chemical resistance and flexibility.