Resorcinol-formaldehyde resins, adhesive strength

Nitrile rubber is compatible with phenol-formaldehyde resins, resorcinol-formaldehyde resins, vinyl chloride resins, alkyd resins, coumarone-indene resins, chlorinated rubber, epoxies and other resins, forming compositions which can be cured providing excellent adhesives of high strength, high oil resistance and high resilience. On the other hand, NBR adhesives are compatible with polar adherends such as fibres, textiles, paper and wood. Specific formulations of NBR adhesives can be found in [12]. 

Results of a 2-year paint study indicate acetylated wood is a better painting surface (37) than untreated wood. UV radiation darkens unacetylated wood, but there is no change or a slight bleached effect with acetylated wood (37). In general, acetylation reduces the adhesive strength of wood (48). Adhesive strength is reduced with urea-formaldehyde resins (54, 55) and casein glues (55), but there is very little effect with resorcinol-formaldehyde resins (55). 

Over the years, various types of adhesives have been used in this application. Already in 1926, resins based on urea-formaldehyde were imported in the market by a company named LG. Farben (now BASF) and mark the beginning of structural adhesive technology in timber. Then, the resulting synthetic resin glues based on resorcinol and melamine have proven due to their excellent temperature and humidity resistance in work areas, where the bonded components are exposed to weathering or climatic conditions. The strength of the adhesive joint usually exceeds the inherent strength of the wood. 

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