In today's rapidly developing Internet era, people are paying more and more attention to environmental protection. Among them, epoxy resin curing agents are developing rapidly, and are favored and loved by consumers. How much do you know about the type of material? Is it unclear? Next, follow along to find out below, I hope to help everyone.
The curing agent is an additive that chemically reacts with the epoxy resin to form a net-shaped three-dimensional polymer, encloses the composite material bone material in the net-shaped body, and turns the linear resin into a tough solid body.
1. Explicit type
The obvious curing agent is a commonly used curing agent, and can be divided into addition polymerization type and catalytic type. The so-called addition polymerization type means that the ring of the epoxy group is opened for the addition polymerization reaction, and the curing agent itself participates in the three-dimensional network structure. If this kind of curing agent is added in too small amount, the cured product is connected to the unreacted epoxy group.
Therefore, for this type of curing agent, there is a suitable amount. Catalytic curing agents cationic or anionic to ring-open addition polymerization of epoxy groups. The curing agent does not participate in the network structure, so there is no suitable amount of equivalent reaction; however, increasing the amount will cause curing Speed up.
Epoxy resin curing agent
Among the obvious curing agents, varieties such as dicyandiamide and adipic acid dihydrazide are insoluble in epoxy resins at room temperature, but start to cure after dissolving at high temperatures, so they also show a latent state. Therefore, it can be called a functional latent curing agent.
Acidic curing agents: including organic acids, anhydrides, and boron trifluoride and their complexes.
3. Anhydride curing agent
Dibasic acids and their anhydrides such as maleic anhydride and phthalic anhydride can cure epoxy resins, but they need to 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 and epoxy group in the monoester undergo addition esterification to form a diester.
4. Amine curing agent
The curing effect of the primary and secondary amines on the epoxy resin is that the active hydrogen on the nitrogen atom opens the epoxy group, which makes it cross-linking and curing. Epoxy resin manufacturers said that aliphatic polyamines such as ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, diethylaminopropylamine, etc., are more active and can crosslink and cure epoxy resins at room temperature; and Aromatic polyamines have low activity, such as m-phenylenediamine, which must be cured at 150°C to be complete.
Alkaline curing agent WTF: including aliphatic diamines and polyamines, aromatic polyamines, other nitrogen-containing compounds and modified fatty amines.
6. Additive molding
Additive curing agent: This type of curing agent and epoxy group undergo an addition reaction to form a part of the cured product segment, and through the stepwise polymerization reaction, linear molecules are cross-linked to form structural molecules. This type of curing agent is also called melon-type curing agent. .
Epoxy resin curing agent
Catalytic curing agent: This type of curing agent only initiates epoxy resin. After the epoxy group is opened, the epoxy resin itself is catalyzed to polymerize into a network structure to form a homopolymer with an ether bond as the main structure.
8. Synthetic resin curing agent
The low molecular weight polyamide resin is amber viscous resin produced by the reaction of linoleic acid dimer or tungoleic acid dimer with aliphatic polyamine such as ethylenediamine and diethylenetriamine.
9. Latent curing agent
This curing agent is stable under normal conditions, but when heated to a certain temperature, it shows its activity and cures the epoxy resin. Such as dicyandiamide, mixed with epoxy resin, it is stable at room temperature.
If it is 145-165°C, the epoxy resin can be cured within 30 minutes. Boron trinitride ethylamine complex is stable at room temperature and can cure epoxy resins at temperatures above 100°C.