Novolaks (sometimes: novolacs) are low molecular weightpolymers derived fromphenols andformaldehyde. They are related toBakelite, which is more highly crosslinked. The term comes from Swedish "lack" for lacquer and Latin "novo" for new, since these materials were envisioned to replace natural lacquers such ascopal resin.
Typically novolaks are prepared by the condensation of phenol or a mixture of p- and m-cresol with formaldehyde (as formalin). The reaction is acid catalyzed.Oxalic acid is often used because it can be subsequently removed bythermal decomposition. Novolaks have adegree of polymerization of approximately 20-40. The branching density, determined by the processing conditions, m- vs p-cresol ratio, as well as CH2O/cresol ratio is typically around 15%.[1]
Novolaks are especially important inmicroelectronics where they are used asphotoresist materials.[2][3] They are also used astackifiers in rubber.