Phenolic resins chemistry

Although phenolic resins have been known and widely utilised for over 60 years their detailed chemical structure remains to be established. It is now known that the resins are very complex and that the various structures present will depend on the ratio of phenol to formaldehyde employed, the pH of the reaction mixture and the temperature of the reaction. Phenolic resin chemistry has been discussed in detail elsewhere and will be discussed only briefly here. 

Gardziella, A., Pilato, L.A. and Knop, A., Phenolic Resins Chemistry, Applications,... 

A. Knop and L. A. Pilato, Phenolic Resins — Chemistry, Applications and Performance, Springer-Verlag, Berlin, 1985. 

Megson, N. J. L. Phenolic Resin Chemistry, Academic, New York, 1958, Chap. III. 

Hemingway, R. W. Karchesy, J. J. McGraw G. W. In. Phenolic Resins, Chemistry and Applications Weyerhaeuser Science Symposium 2, Weyerhaeuser Co. Tacoma, Washington. 1981 33-69. 

F. L. Tobiason, in Weyerhaeuser Science Symposium, Vol. 2, Phenolic Resins—Chemistry and Applications, Weyerhaeuser Company, Washington, 1981, pp. 201-212. 

A. GardzieUa, L. A. PUato and A. Knop, Phenolic Resins Chemistry, Applications, Standardization, Safety and Ecology, Chap. 2, Springer-Verlag, Berlin, 2000, pp. 66-72. 

MEOSON, N. I. L., Phenolic Resin Chemistry, Butterworth, London (1958)... 

Knop A, Pilato LA (1985) Phenolic resins chemistry, applications and performance, future directions. Springer, Berlin Heidelberg New York... 

N. J. L. Megson, Phenolic Resins Chemistry, Butterworth, Sevenoaks, UK, 1958. 

W. E. Hillis, in Phenolic Resin Chemistry and Application. Proceedings of Weyerhaeuser Science Symposium, Tacoma, Washington, USA, pp. 171-188 (1980). 

Gardziella, A., Pilato, L.A. and Knop, A., Phenolic Resins Chemistry, Applications, Standardization, Safety and Ecology, 2nd edn. Springer, Berlin, 2000, pp. 66-77. Encyclopedia of Polymer Science and Technology. Interscience, New York, 1969, v. 10. Semon, W.F., History and use of materials which improve aging. In Davis, C.C. and Blake, J.T. (Eds.), The Chemistry and Technology of Rubber, ACS Monograph Series No. 74. Reinhold, New York, 1937. 

The resorcinol-formaldehyde polymer is classified as a phenolic resin. In fact, phenol-formaldehyde condensates are the first synthetic polymers introduced commercially (Bakelite) in the beginning of the twentieth century. Thus, the phenolic resin chemistry, on which there is a vast amotmt of information, can be used to understand the chemistry of the RF aerogel synthesis. In the first step, resorcinol reacts with formaldehyde to form hydro-xymethylated resorcinol in the second step, the hydroxymethyl groups condense with each other to form nanometer-sized clusters, which then crosslink by the same chemistry to produce a gel. The formation of clusters is influenced by typical sol-gel parameters such as the temperature, pH, and concentration of reactants. Though the first RF aerogel is synthesized by the aqueous polycondensation of resorcinol with formaldehyde with the use of sodium carbonate as catalyst [6, 12, 13], now several literature reports exist for aerogels made from phenol and formaldehyde [14—16]. 

The earlier workers established some of the structural features of novolacs " and resoles, but only work published around 1940 provided the knowledge necessary to make significant advances in phenolic resin chemistry. This had to do mostly with the complexity of products which resulted from the reactions of phenolic alcohols. " ... 

---