& nbsp; & nbsp; Single component adhesives are much more convenient to use than two-component adhesives, so they are often preferred. However, the preparation technology of single component adhesives is much more difficult, as it requires both reliable performance and long-term storage stability< br />


  & nbsp; & nbsp; For single component epoxy adhesive, its core technology lies in the curing agent used. At present, most single component epoxy adhesives use latent curing agents, which are activated by external forces such as moisture, light, heating, and pressure during use, and undergo curing crosslinking reactions with epoxy groups.
 
  & nbsp; & nbsp; According to the curing method, single component epoxy adhesives can be divided into the following types: room temperature moisture curing type, heat curing type, cationic light curing type, and microcapsule type< br />


  & nbsp; & nbsp; Room temperature moisture curing



  & nbsp; & nbsp; The curing agents used for this type of epoxy adhesive are mostly ketimine compounds. During the curing process, ketimines absorb moisture from the air to produce amines, which then attack the epoxy groups to achieve polymerization reactions< br />


  & nbsp; & nbsp; In order to extend the storage period of the adhesive, ketimines with steric hindrance effect and larger molecular volume on the ketone side are often used, which provide storage stability without reducing the curing speed< br />


  & nbsp; & nbsp; However, the moisture curing method at room temperature is far from meeting the requirements of automated assembly processes for curing speed.
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  & nbsp; & nbsp; Heat curing type



  & nbsp; & nbsp; Generally, it can be divided into medium temperature curing type and high temperature curing type. The former has a curing reaction temperature of 60-140 ℃, while the latter solidifies above 150 ℃< br />




  & nbsp; & nbsp; This type of adhesive uses a heat activated curing agent, which is relatively stable at room temperature and insoluble in epoxy resin. It needs to be heated to obtain external energy before it can melt and decompose and react with epoxy resin< br />


  & nbsp; & nbsp; Common latent curing agents include dicyandiamide, organic hydrazide, organic anhydride, imidazole, boron trifluoride amine complex, etc., which are formulated by adding accelerators and other additives< br />


  & nbsp; & nbsp; Cationic UV curable type



  & nbsp; & nbsp; The curing agent for cationic photopolymerization epoxy adhesive is a cationic photosensitive compound, also known as a photoinitiator. After being irradiated with ultraviolet light, it can absorb light of appropriate wavelength and undergo a photophysical process to a certain excited state. The generated Lewis acid reacts with hydrogen to form a protonic acid, and the resulting positive ion active center can trigger the cationic polymerization reaction of epoxy resin.
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  & nbsp; & nbsp; Common photosensitizers include aromatic diazonium salts, diaryliodonium salts, ferrocene salts, and triarylthionium salts. Compared with free radical curing, they are highly sensitive to light and are not affected by oxygen polymerization. They have low volume shrinkage during curing, good thermal stability, and excellent photo curing promotion. They can continue to react even after removing the light source< br />


  & nbsp; & nbsp; Microcapsule type



  & nbsp; & nbsp; Using certain film-forming materials to encapsulate a component of the adhesive into a capsule, allowing the adhesive to be stored stably. By heating, applying pressure, or chemical treatment to rupture the capsule, the adhesive components inside can be released and cured< br />


  & nbsp; & nbsp; The capsule membrane of microcapsules should not react or be miscible with its components, and should have appropriate thickness and strength to prevent unnecessary damage caused by rupture during transportation< br />


  & nbsp; & nbsp; At present, film-forming agents in microcapsule based single component epoxy adhesives include cellulose, gelatin, polyvinyl alcohol, polyester, polysulfone, etc< br />


  & nbsp; & nbsp; Overall, single component epoxy resin adhesives have the characteristic of easy use, and the development of green and environmentally friendly single component epoxy adhesives is still an inevitable trend for future development.