phenolformaldehyd

Phenol-formaldehyde, commonly called phenolic resin, is a class of synthetic thermosetting polymers obtained by condensation of phenol with formaldehyde. Depending on the phenol/formaldehyde ratio and catalysts, PF resins are mainly divided into novolacs and resoles. Novolacs are phenol-rich, require a separate curing agent to crosslink, and are used in adhesives and high-temperature laminates. Resoles are methylolated or otherwise prepolymerized to contain reactive groups and can cure upon heating without an external hardener, forming a rigid network when heated in the presence of acid or base catalysts.

Chemistry and processing: The condensation produces methylene and ether bridges between phenol units. The curing step yields a crosslinked thermoset with high heat resistance and good electrical insulation. PF resins are inherently brittle and have relatively low toughness compared with many thermoplastics.

History and uses: The first commercial PF resin, commonly known as Bakelite, was developed by Leo Baekeland in 1907, marking a milestone in polymer chemistry. PF resins were widely used for electrical insulation, casings, and early laminates, and remain important in high-temperature and flame-retardant applications, particularly in phenolic laminates and molded parts for electrical components.

Properties and safety: PF resins exhibit high thermal stability, flame resistance, and strong chemical resistance, along with excellent electrical insulation. They are thermosetting and form rigid, durable materials. Handling of the monomers (phenol and formaldehyde) requires safety precautions due to toxicity and irritation; cured resins can still release trace formaldehyde under certain conditions, so proper ventilation and safety measures are important.