What Is Bakelite?
Bakelite is the most produced thermosetting resin and the first man-made synthetic resin.
Other names include phenol resin and phenol-formaldehyde resin.
Bakelite was first discovered in 1872 by Bayer of Germany in a reaction between phenol and formaldehyde. It was later industrialized by Leo Baekeland in 1907 and spread throughout the world.
Uses of Bakelite
Bakelite is used in a variety of applications due to its high resistance to heat, acids, and oils.
1. Molding Materials
Molding materials are most commonly used for electrical equipment parts and are mainly used for daily commodities, automotive parts, and communication equipment parts.
2. Laminated Products
The majority of applications for laminated products are for printed circuits used in home appliances and electronic devices.
3. Shell Mold
Shell mold is a metal casting process, which is mainly used for casting automotive parts. The raw material for the mold used in this process is a mixture of silica sand and Bakelite called resin sand.
4. Wood-Processing Adhesives
Wood-processing adhesives are often used in the manufacture of plywood, hardboard, and particleboard.
Paints made with Bakelite can withstand harsh environments because they are chemical-resistant and rust-resistant. In addition, when used as a binder for sand molds for 3D printers, it can print with more precise dimensions by making the sand molds stronger.
Characteristics of Bakelite
Plastics can be divided into thermoplastics and thermosetting resins, with Bakelite falling into the latter category. Thermosetting resins are formed by the reaction curing of liquid raw materials upon heating.
Once molded, they do not return to a liquid state when reheated, making it possible to create highly heat-resistant molded products.
Since the late 2000s, Bakelite has consistently ranked first among thermosetting resins in terms of domestic production volume.
The advantages of Bakelite include electrical insulation, heat resistance, flame resistance, adhesiveness, chemical resistance, acid resistance, and thermal insulation. In particular, its high heat resistance is its greatest feature, so many products are manufactured applying this performance.
On the other hand, as a disadvantage, it is weak against alkali and has low impact resistance.
Other Information on Bakelite
How Bakelite Is Produced
Bakelite is produced by polymerizing phenol and formaldehyde. Depending on the catalyst used, two types of Bakelite precursors are synthesized: novolac and resol.
From these precursors, Bakelite is made by adding a cross-linking agent to further the reaction.
1. Novolac
A mixture of phenol and formaldehyde is reacted at or above the boiling point for 1.5~3 hours using hydrochloric acid or oxalic acid as an acid catalyst. This leads to repeated addition and condensation reactions, resulting in linear polymers in which phenols are joined by CH2 groups.
After the reaction, water and unreacted phenol are removed, the product is removed from the reaction tank, cooled and solidified, and crushed to obtain Novolac. By reacting this with hexamethylenetetramine, a curing agent, the molecules of the Novolac are cross-linked to form thermosetting insoluble and insoluble Bakelite.
2. Resol
Resol is reacted at 80-100°C for 1.5-3 hours using an alkali catalyst and with an excess of formaldehyde over phenol. This produces a mixture of monomethylolphenol, dimethylolphenol, and trimethylolphenol, which condense to form resol.
Further reaction under heat and pressure results in cross-linking of the dimethylphenol and trimethylphenol portions to form thermosetting insoluble and insoluble Bakelite. The reaction of the resol with an alkali catalyst, phenol, and formaldehyde resols generally takes place during the processing of Bakelite molded products.