The epoxy resin curing agent chemically reacts with the epoxy resin to form a network-like three-dimensional polymer, enveloping the composite material in the network. Additives that turn linear resins into tough, bulky solids.
Alkaline
Basic curing agent WTF: including aliphatic diamines and polyamines, aromatic polyamines, other nitrogen-containing compounds and modified fatty amines.
Acidic
Acidic curing agent: including organic acids, acid anhydrides, and boron trifluoride and its complexes.
Addition
Addition type curing agent: This type of curing agent undergoes an addition reaction with the epoxy group to form a part of the chain segment of the cured product, and through a gradual polymerization reaction, the linear molecules are cross-linked into a body-shaped structure molecule. This type of curing agent is also called a melon type curing agent.
Catalytic
Catalytic curing agent: This type of curing agent only initiates the epoxy resin. After opening the epoxy group, it catalyzes the polymerization of the epoxy resin itself into a network structure, forming a homopolymer with ether bonds as the main structure.
Explicit
The obvious curing agent is a commonly used curing agent, which can be divided into addition polymerization type and catalytic type. The so-called addition polymerization type is to open the ring of the epoxy group to carry out the addition polymerization reaction, and the curing agent itself participates in the three-dimensional network structure. If the amount of this type of curing agent is too small, the cured product will be connected with unreacted epoxy groups.
latent type
Latent curing agent refers to that after being mixed with epoxy resin, it is relatively stable for a long time at room temperature (epoxy resin generally requires more than 3 months to have great practical value, and ideally requires more than half a year or more than 1 year), and only needs to be exposed to heat, light, moisture and other conditions to start the curing reaction. This type of curing agent basically uses physical and chemical methods to block the activity of the curing agent. Therefore, these varieties are also classified as latent curing agents in some books, and they can actually be called functional latent curing agents.
Amine curing agent
The curing effect of primary amine and secondary amine on epoxy resin is that the active hydrogen on the nitrogen atom opens the epoxy group to make it cross-linked and cured. Aliphatic polyamines such as ethylenediamine,hexamethylenediamine,diethylenetriamine,triethylenetetramine, diethylaminopropylamine, etc. are highly active and can cross-link and cure epoxy resins at room temperature; while aromatic polyamines are less reactive, such as m-phenylenediamine, which must be cured at 150°C to complete.
Anhydride curing agent
Dibasic acids and their anhydrides such as maleic anhydride and phthalic anhydride can cure epoxy resins, but they must be baked at a higher temperature to cure completely. The acid anhydride first reacts with the hydroxyl group in the epoxy resin to form a monoester, and the carboxyl group in the monoester reacts with the epoxy group to form a diester.
Synthetic resin curing agent
Low molecular weight polyamide resin is an amber viscous resin formed by the reaction of linoleic acid dimer or oleic acid dimer with aliphatic polyamines such as ethylenediamine and diethylenetriamine.