Wood Adhesive Classification

According to the raw material source of the adhesive

Can be divided into natural adhesives and synthetic adhesives

According to the heated state of the glue

It can be divided into thermosetting adhesives (liquid at room temperature, solidified when heated), thermoplastic adhesives (solid at normal temperature, fluid when heated to deformation) and hot melt adhesives (solid, melted by heating, solidified by cooling)

Press water resistance

Can be divided into water-resistant glue (such as phenolic resin glue), general water-resistant glue (such as blood glue) and non-water-resistant glue (such as vinyl acetate emulsion glue, etc.).

Natural Adhesive

Including: ① Starch. ②Protein glue. Among them, animal protein glue includes bone glue, skin glue, fish (fat) glue, blood glue made of soluble blood protein, and casein glue made of casein in animal milk. Vegetable protein gums include soybean gum and peanut gum. ③Natural rubber. ④Inorganic adhesives. Including sodium silicate, magnesium oxychloride, cement, etc.

Synthetic adhesive

There are: ① Thermosetting resins, including phenolic resin glue, resorcinol, epoxy resin, furan resin and amino resin glue (including urea-formaldehyde, melamine-formaldehyde). ②Thermoplastic resin glue. Including polyvinyl acetate, polyacrylate, alkyd ester, polyvinyl alcohol, etc. ③Synthetic rubber, including neoprene, nitrile rubber, etc.

In addition, there are corresponding new varieties that have been adopted with the development of new wood processing technology, which are described as follows:

Soy gum

It is made from soybean meal crushed into 100-300 mesh soybean meal. Its protein content is 40-50%. Bean protein is a globular protein, and its protein molecule contains polar genes, which are combined into hydrogen bonds within the molecule to make the molecule spiral. When making glue, a small amount of sodium hydroxide solution should be added to break the hydrogen bond, so that the protein molecules will be dispersed in the water with free polarity genes. When the glue layer moisture evaporates, it will reach the glue. Adding water glass can control the viscosity of the glue and prolong the usable time of the glue. Calcium hydroxide is added to make it react with the protein to become an irreversible substance, which can improve the water resistance of the glue. Mixing styrene-butadiene or nitrile emulsion with soybean gum can obtain a water-resistant, viscous, and tough adhesive layer, and shorten the pressing time. Soy gum is mainly used for veneers with a cold-pressed moisture content of 15-20%.

Blood glue

The protein content in animal blood is highest in pig and bovine blood, reaching 17-18%. The serum protein and globulin remaining after the blood is stirred to remove the fibrin during slaughter, spray-dried into powder for sale, or directly used to adjust the glue with fresh blood. Due to different drying conditions, blood meal can be divided into soluble grade (80-95% soluble), partially soluble grade (15-80%) and insoluble grade (below 15%). The latter can only be used as fertilizer. Adding alkali during rubber adjustment can be made into rubber with 10-30% solid content. Blood glue is better in water resistance than bean glue, but the color is darker. It can be used for cold pressing or hot pressing.

Protein glue

It can be modified by adding a crosslinking agent to improve its water resistance. Various protein materials can be used as fillers for synthetic resin glue to improve the toughness of the glue layer.