Applications of Phenolic Resins

The resin content in abrasive and friction lining materials is about 10%, whereas binder content is much less (approximately 2%) in foundry materials. For friction lining applications (e.g., automobile braking operation), the surface temperature of the lining may increase up to 800 °C for a short time due to tremendous friction. Phenolic resins are most suitable for such applications because of their high thermal stability. 

Because of their high aromatic content, phenolic resins absorb a lot of heat for their degradation. This is why they are used as an ablative material in re-entry vehicles. When a space vehicle re-enters the earth s atmosphere, due to tremendous friction with air, a lot of heat is generated. Phenolic resins can absorb the heat at the cost of its degradation, and stops the vehicle from deteriorating as a result of the extremely high temperature. 

Phenolic resins exhibit excellent dimensional stability with a constant use temperature range of 180-200 °C, excellent resistance to chemicals, moisture, and heat and favorable behaviour against fire and smoke. The predominant consideration in the use of phenolic resins as a matrix resin in fibre-reinforced composites is fire behaviour. Phenolic-based composites perform better under fire conditions compared with epoxy- or vinyl ester-based composites. This is due to their delayed ignitability coupled with low heat release, low smoke evolution with little or no toxic gas emission, and capability to provide significant strength retention (70%) 

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W. Knop and A. Scheib, Chemistry and Applications of Phenolic Resins-Polymer Properties and Applications, Springer-Verlag, Berlin (1979). 

A. Knop and W. Scheib, Chemistry and Application of Phenolic Resins, Springer-Verlag, New York, 1979. 

Knop, A. Scheib, W. "Chemistry and Applications of Phenolic Resins" Springer-Verlag New York, 1979. 

Knop W, Scheib A (1979) Chemistry and applications of phenolic resins-polymer properties... 

III. CHEMISTRY AND TECHNOLOGY OF APPLICATION OF PHENOLIC RESIN ADHESIVES FOR WOOD... 

Some resoles contain latent acid catalysts, which on heating generate moderately strong acids. Examples inclnde aryl phosphites such as diphenyl hydrogen phosphite and ammonium sulfate (48,49). The use of latent acid catalysis broadens the range of applications of phenolic resins to include areas such as liquid composite molding and pultrusion. Also resoles, which can contain so-called free formaldehyde, can be formulated with formaldehyde scavengers in form of amines such as melamine. 

The main engineering applications of phenolic resins are laminates, foundry and friction materials. In the electrical laminating field, phenolic resins are used to impregnate kraft paper for the production of insulation boards, printed circuits and transformer bushings. The resin used in this case is usually based on cresol or a substituted phenol and used in a water/alcohol solution. The properties obtained would be a function of the reinforcement and the characteristics of resin used, eg high or low molecular weight. 

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