Diluent is a compound used to reduce the viscosity of adhesives, give them good penetration, improve process performance, and some can reduce the activity of adhesives, thereby extending their service life. In order to facilitate the application of glue, diluents are often used to dissolve the adhesive and adjust the required viscosity.

Diluents can be divided into two types: non active diluents and active diluents.

① Non active diluents do not contain active groups in their molecules and are mostly inert solvents such as ethanol, acetone, toluene, etc. During the dilution process, it does not participate in the reaction and is only blended into the resin to reduce viscosity. In addition to its dilution effect, it also has an impact on mechanical properties, thermal deformation temperature, medium resistance, and aging damage. The evaporation rate of the solvent should be considered. If the evaporation rate is too fast, the surface of the adhesive layer is prone to film formation, which hinders the escape of solvent inside the adhesive layer. Causing the formation of bubbles in the adhesive layer; If the evaporation rate is too slow, there will be solvent left in the adhesive layer, which will affect the bonding strength. Usually, several solvents with different boiling points are mixed to regulate the evaporation rate. It is commonly used for rubber adhesives, phenolic adhesives, polyester adhesives, and epoxy adhesives.

② Active diluent is a diluent that contains active groups in its molecules. It needs to participate in the reaction during the process of diluting the adhesive, and can also play a toughening role (such as adding glycerol epoxy resin or epichlorohydrin butyl ether to epoxy adhesives).
Active diluents are mostly used in epoxy adhesives, and are less commonly used in other types.
Keyword: Diluent