Phenolic Resin

Phenolic resins are classified into two primary groups—resoles and novolacs—based on the formaldehyde-to-phenol molar ratio and the acidic or alkaline polymerization environment employed during synthesis.

Resoles are thermosetting resin systems that undergo cross-linking and form three-dimensional networks when exposed to heat or cured using acidic or basic catalysts. These resins have a limited storage (shelf) life due to their reactive, self-curing nature.

Novolacs, in contrast, are thermoplastic phenolic resin systems. They do not self-cure and therefore exhibit extended, long-term storage stability. Their curing, when required, is achieved only through the addition of external hardeners (typically hexamethylenetetramine), making them suitable for applications requiring melt processing and controlled curing behavior.