novolakbased

Novolakbased refers to polymers derived from novolak resins. Novolaks are a class of phenol formaldehyde resins, which are produced by the reaction of phenol with formaldehyde in the presence of an acid catalyst. The ratio of formaldehyde to phenol is typically less than 1:1, resulting in a thermoplastic polymer with unreacted hydroxyl groups along the polymer chain. These unreacted groups are crucial for their subsequent curing process.

Novolakbased materials are thermosetting, meaning they undergo an irreversible chemical change when heated, becoming rigid and infusible. This curing is usually achieved by adding a crosslinking agent, most commonly hexamethylenetetramine (HMTA). Upon heating, HMTA decomposes to form formaldehyde and ammonia, which then react with the phenolic hydroxyl groups and the remaining reactive sites on the novolak chains, creating a highly crosslinked, three-dimensional network structure.

The properties of novolakbased resins can be modified by altering the molar ratio of phenol to formaldehyde, the type of catalyst used, and the molecular weight of the resulting novolak. These resins are known for their good thermal stability, chemical resistance, and mechanical strength. They find widespread applications as binders in friction materials such as brake pads and clutch facings, as well as in adhesives, coatings, and molding compounds. Their ability to form durable and heat-resistant materials makes them valuable in demanding industrial environments.