Adhesives can be classified by raw material source into natural adhesives and synthetic adhesives; by physical state under heat into thermosetting adhesives (liquid at room temperature, solidifying upon heating), thermoplastic adhesives (solid at room temperature, deforming into a fluid state when heated), and hot-melt adhesives (solid, melting when heated and solidifying upon cooling); and by water resistance into water-resistant adhesives (e.g., phenolic resin adhesives), moderately water-resistant adhesives, and non-water-resistant adhesives (e.g., polyvinyl acetate emulsion adhesives).
Natural Adhesives
① Starch-based adhesives. ② Protein-based adhesives: These include animal protein adhesives such as bone glue, hide glue, and fish (bladder) glue; blood glue made from soluble blood protein; casein glue made from milk casein; and plant protein adhesives such as soybean glue and peanut glue. ③ Natural rubber. ④ Inorganic adhesives such as sodium silicate, magnesium oxychloride, and cement.
Synthetic Adhesives
① Thermosetting resins: Including phenolic resin adhesives, resorcinol, epoxy resins, furan resins, and amino resin adhesives (including urea-formaldehyde and melamine-formaldehyde). ② Thermoplastic resins: Including polyvinyl acetate, polyacrylates, polyvinyl alcohol, etc. ③ Synthetic rubbers: Including chloroprene rubber, nitrile rubber, etc.
