Diluent is a compound that is used to reduce the viscos […]
Diluent is a compound that is used to reduce the viscosity of the adhesive , allow the adhesive to have good penetration, improve process performance, and reduce the activity of the adhesive, thereby extending the life of the adhesive. In order to facilitate the glue application, a diluent is generally used to dissolve the binder and adjust the required viscosity. The diluent can be divided into two kinds of inactive diluent and reactive diluent.
(1) Inactive diluent This diluent contains no active groups in the molecule, most of which are inert solvents such as ethanol, acetone, toluene, etc. (2) It does not participate in the reaction during the dilution process, it is only blended in the resin and To reduce the viscosity of the purpose. In addition to the dilution effect, it has an effect on the mechanical properties, heat distortion temperature, resistance to media and aging damage. The volatilization rate of the solvent should be taken into consideration. If the volatilization rate is too fast, the surface of the adhesive layer will tend to form a film and hinder the escape of the solvent inside the adhesive layer. Causes air bubbles to form in the adhesive layer; if the volatilization rate is too slow, the solvent is left in the adhesive layer, which may affect the bonding strength. Usually, several different boiling point solvents are mixed to adjust the volatilization rate. It is mostly used for rubber adhesives, phenolic adhesives, polyester adhesives and epoxy adhesives.
(2) Reactive diluent A reactive diluent is a diluent containing active groups in the molecule. It participates in the reaction while diluting the adhesive, and it also has a toughening effect (such as adding glycerol epoxy resin or propylene oxide butyl ether to the epoxy type adhesive to increase the toughening effect).
Reactive diluents are mostly used in epoxy adhesives, and other types are less used.