Definition - What does Novolacs mean?
These are resins produced by the complete poly-condensation of phenol and aldehydes for industrial uses as a replacement of natural resin such as shellac. They are available in solid and liquid form and is used in binders, articles, paints, molded pieces, laminated plastics and adhesives. They are used as chemically unmodified synthetic resins based on their capability to undergo cross-linking with hexamethylenetetramine.
Corrosionpedia explains Novolacs
Novolacs are formed in acidic conditions where the molar ratio of phenol with formaldehyde should exceed the required quantity. They can be converted into resols through cross-linking by the addition of curing agents. The formation of the resin starts with the electrophilic attack of a carbonyl compound. Hence, there are condensation and substitution reactions present in the controlled manufacturing process of novolacs.
The reactions of monomers and loss of water in the development of this phenol resin lead to a network of polymers with different sizes and structures. Novolacs cannot cure on their own since they are formed from alkylidene bridges and lack functional groups.
The application of novolacs depends on the cross-linking (use of curing agents) or no cross-linking applied in poly-condensation since there is a variance in solubility, hardness, compatibility and stability properties. They are known to provide good strength and chemical resistance at high temperatures. The thermal stability allows them to be used as adhesives, fillers, modifiers and coatings in elevate temperatures.