What is Bakelite and How Is It Formed?

Bakelite is a type of phenolic resin. Phenolic resin (PF) is an industrial plastic product that was first produced in the United States in 1910. The primary raw materials for producing phenolic resin are phenol and aldehyde, commonly phenol and formaldehyde. These compounds undergo a condensation reaction under the catalysis of acids or bases to polymerize. There are two industrial production methods: dry and wet.

Under the influence of different catalysts, phenol and aldehyde can form two types of phenolic resins: thermoplastic phenolic resin and thermosetting phenolic resin. The former requires only the addition of a curing agent and heating to solidify into a block structure, while the latter only needs heating without a curing agent to solidify into a block structure.

Both thermoplastic and thermosetting phenolic resins can only be used through a curing process that forms a cross-linked network. This curing process continues the shape polycondensation and formation of the final product shape. This process differs from the melting and solidification of general thermoplastics. Both the physical and chemical processes are irreversible.

Phenolic resin can be injection-molded in a manner similar to thermoplastics. Injection-molding grade phenolic resins require good flow properties, low injection pressure for molding, high thermal rigidity, rapid hardening, smooth surface finish of the plastic parts, easy demoulding, and non-contamination of the mold. However, injection molding also has its disadvantages, such as limitations on the type of fillers in the melt, unsuitability for forming plastic parts with many inserts, and the inability to recycle large amounts of sprues and channels after solidification, which must be discarded.

In summary, thermoplastic phenolic resin can be produced using standard injection molding machines but requires strict process control. Thermosetting phenolic resin must be produced using specialized phenolic resin injection molding machines, and the molds also employ special design structures.