EN
Better quality
Better QualityBetter service
Better Quality
The Largest Manufacturer of MTHPA Products in China.

Acid Anhydride Curing Agent Guide

The curing reaction mechanism of anhydrides can be divided into two forms according to the presence or absence of accelerators.

1. In the absence of accelerants, the hydroxyl group in epoxy resin reacts with anhydride first, and the anhydride is turned on, then the addition polymerization is carried out. The order is as follows:

  • Hydroxyl reacts with anhydride to form ester bond and carboxylic acid.
  • Carboxylic acid is added to epoxy group to form hydroxyl group.
  • The hydroxyl groups formed continue to react with other anhydrides.

The reaction proceeds repeatedly to form bulk polymers. In addition, in this system, due to the acidic state, the reaction parallel to the above reaction is the reaction of other epoxy groups with hydroxyl groups, resulting in the formation of ether bonds. From the above mechanism, it can be seen that there are two kinds of structures in the cured product: ether bond and ester bond, and the reaction rate is controlled by the concentration of epoxy group and hydroxyl group.

2. In the presence of accelerants, the acid anhydride curing reaction is promoted by Lewis base. Accelerators (usually tertiary amines) initiate an attack on anhydride. The main reactions are as follows:

  • accelerator attacked anhydride to form carboxylate anion.
  • carboxylate anion reacts with epoxy group to form oxygen anion.
  • oxygen anion reacts with other anhydrides to form carboxylate anion again.

In this way, acid anhydride reacts with epoxy group, and additive polymerization is carried out step by step. In the presence of promoter Lewis base, all the bonds formed are ester bonds, and no ether bond was found as in the absence of promoter.

In the presence of accelerants, the curing rate of epoxy resin is also controlled by the concentration of hydroxyl groups in the acceptor system. Therefore, the addition of accelerators is very effective for liquid epoxy resin, and the curing reaction can be completed at the temperature of the 120~150℃. But for solid epoxy resin, we should pay attention to the problem of very short application period. In the absence of accelerants, theoretically, an epoxy group should be used for an anhydride, but in fact, only 80%-90% of the theoretical chemical quantity is enough. In the presence of accelerants, the amount of anhydride used is the chemical theoretical quantity.
Related News
  • Methyl Tetrahydrophthalic Anhydride Use

    Methyl Tetrahydrophthalic Anhydride Use

    June 5, 2019It is used for curing agent of epoxy resin, solvent-free paint, laminate, epoxy adhesive, etc. Epoxy resin curing agent has excellent properties such as long-term storage at room temperature, low free...view
  • Methyl Tetrahydrophthalic Anhydride Definition

    Methyl Tetrahydrophthalic Anhydride Definition

    June 5, 2019Methyl tetrahydrophthalic anhydride is a chemical substance. It has two isomers, namely 4-methyl tetrahydrophthalic anhydride and 3-methyl tetrahydrophthalic anhydride, with melting points of 65 and 6...view
  • Acid Anhydride Curing Agent Definition

    Acid Anhydride Curing Agent Definition

    June 5, 2019Curing agent refers to a kind of substance which can transform soluble and meltable linear structure polymer compound into insoluble body structure. The acid anhydride curing agent is an important kin...view
  • Cured Epoxy Melting Point

    Cured Epoxy Melting Point

    June 5, 2019Epoxy resin is not pure, such as bisphenol A epoxy resin is composed of homologous compounds with different degree of polymerization, so it has no clear melting point, only a melting temperature range...view
  • Acid Anhydride Curing Agent Composition

    Acid Anhydride Curing Agent Composition

    June 5, 2019First, Phthalic acid (PA)Phthalic anhydride is a traditional curing agent, which is still used in a large amount up to now, which is mainly used in the casting of electrical appliances. Phthalic anhyd...view
  • Ethyl Tetrahydrophthalic Anhydride Benefits

    Ethyl Tetrahydrophthalic Anhydride Benefits

    June 5, 2019High purity and light color: epoxy resin products with various colors required can be directly prepared or modulated.Low Viscosity: Casting, filling, impregnation process is good. When casting, a larg...view


Contact Us