Fenolit d.d.

Phenol - Formaldehyde (PF) resins

Phenolic resins (polymers) are obtained by the reaction of phenols with aldehydes (monomers). Phenol and formaldehyde are by far the most important components in commercial phenolic resin production.

The reaction of formaldehyde with phenol can lead to either a heat reactive resole or a stable novolak and is dependent upon the mode of catalysis and molar ratio of formaldehyde to phenol.

Resoles are usually made from phenol-formaldehyde mixtures in which there is a molar excess of the aldehyde. Phenol and formaldehyde are allowed to react to a certain condensation degree where PF resins are still liquid and/or soluble. Base catalysts (caustic, amine) are used for the polycondensation reaction. The curing of resoles is achieved by heating and/or with addition of catalysts.

Novolaks are normally prepared with a slight molar excess of phenol. The molecular weight of the polymer is determined by the molar ratio of the monomers where formaldehyde is completely consumed during the polycondensation reaction. Cross-linking (curing) of novolaks can be done by adding more formaldehyde and/or formaldehyde donors such as hexamethylenetetramine (HEXA).

Most common applications of PF-resins can be found in wood materials, insulating materials (inorganic fibers), molding compounds, laminates as well as foundry, refractory, abrasives specialty applications and many others.