Wood Adhesives Classifications
Adhesive Systems’ Custom Wood Adhesive Products
Wood adhesives are substances capable of binding wood to itself or other materials (or substrates). Historically, many different substances have been used for bonding wood, but these adhesives were all made of natural materials until the late 1940s. Synthetic wood adhesives were introduced just after World War II, and have surpassed natural glues for wood binding in modern times.
Natural and Synthetic Wood Adhesives
Each specific wood adhesive can be placed into one of two distinct categories – natural and synthetic. Natural wood adhesives include animal, vegetable, casein, soybean and blood glues. Synthetic wood adhesives include glues derived from petroleum, gas, coal and other synthetic resins.
Synthetic wood glues, also known as resins, are manmade polymers that resemble natural resins, but are created to meet specific woodworking needs. They are waterproof wood glues that have superior moisture resistance and create very strong bonds.
Epoxy wood glue can be placed into one of two classifications:
Thermosetting Wood Adhesives –
- Include urea-formaldehyde, phenol, resorcinol, melamine and epoxy. Urea is the most popular wood adhesive, as it provides moderate moisture resistance and can cure in minutes at high temperatures. Phenol and resorcinol glues are expensive but versatile, and provide extremely durable bonds. Melamine glue is rarely used alone, but must be combined with urea to increase moisture resistance. Epoxy is the most expensive thermosetting wood adhesive, and is typically impractical for large scale woodworking projects.
- Include polyvinyl acetates and thermal hot melts. Polyvinyl acetate adhesives are the common white glues used in the woodworking industry. Sometimes referred to as simply “wood glue,” polyvinyl has poor heat and moisture resistance, but is the easiest of the synthetic adhesives to use. Thermal hot melt adhesives are solid glues which must be heated and applied as drops or beads, and form a bond as the glue cools. The main advantages of thermal wood adhesives are their ease of handling and fast curing times.
Thermoplastic Wood Adhesives –
Because of the importance of adhesives for wood, it is expected that improvements in wood adhesive systems will continue. Future areas for the improvement of wood adhesives will concentrate on increased durability, faster curing, and curing in the presence of higher moisture contents within the wood materials being bonded.