Phenolic resin glue is a liquid resin which is formed by a polyphenol (phenol, cresol, resorcin, etc.) and an aldehyde (formaldehyde and furfural) in a medium such as an alkaline or an acid to form a certain viscosity, which is also called an initial stage. Phenolic resin or soluble resin. The mucus then continues to polycondense under certain conditions, eventually forming an insoluble, non-melting solid resin, also known as a terminal phenolic resin or an infusible phenolic resin.
The phenolic resin can be made into the following three types of glue:
1. Liquid phenolic resin pre-glue: it is an initial phenolic resin with a certain viscosity. It can be dissolved in an alkaline aqueous solution and alcohol, the former being called a water-soluble phenolic resin and the latter being an alcohol-soluble phenolic resin. Drying can be a solid, and the heating can be a liquid. When the initial phenolic resin is heated or stored for a long period of time and the hardener is added, the polycondensation reaction proceeds, and finally a hard solid which is insoluble and infusible is formed.
2. Powdered phenolic resin glue: it is a powder prepared by drying an initial phenolic resin glue. The powdered rubber has a long storage period and is convenient to transport, but the cost is high, and the solvent is added to adjust the glue when used.
3. Phenolic resin film: an adhesive tape film obtained by dipping or coating an initial phenolic resin on paper and drying. It is also possible to form a wet adhesive film without drying. The dry film has a certain storage period and is convenient to use, but the cost is high.
The initial phenolic resin glue can be heated to cure the resin, and the pH of the resin can be adjusted to cure at room temperature. The former is thermosetting, and the latter is cold-setting phenolic resin.
Phenolic resin adhesive has the advantages of high bonding strength, strong water resistance, good heat resistance, high chemical stability and no attack by bacteria and insects. The disadvantage is that the color is darker and the glue layer is more brittle. Since the phenolic resin has the above characteristics, the adhesive is suitable for the manufacture of various wood-based panels for indoor and outdoor use and various types of wood products having extremely high bonding strength.
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