Bakelite: Definition, Preparation, and Properties

Bakelite is a polymer that is made up of monomers like phenol and formaldehyde. It is one of the commercially manufactured polymers that we use in everyday life. Bakelite is hard, stable, and chemically resistant. It has numerous applications in everyday life, from being used in a switch to complex machinery and equipment.

Key Terms: Polymers, Exothermic, Elastomers, Monomers, Condensation, Teflon, Synthetic Plastic, Novolac, Polymerisation

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What is Bakelite?

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Bakelite, chemically known as Polyoxybenzylmethylenglycolanhydride, is a thermosetting phenol-formaldehyde resin. It is the first synthetic plastic.

Bakelite Structure

Bakelite is a good example of thermosetting plastics. On cooling, these plastics become hard and rigid and are capable of retaining their shapes.

Also Read: Thermosetting and Thermoplastic Polymer

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How is Bakelite Prepared?

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Bakelite is formed as a result of the condensation reaction between phenol and formaldehyde. Therefore, it is also known as condensation polymer or phenolic resin. The preparation of Bakelite involves several complex stages. It is prepared using two monomers – phenol and formaldehyde. However, on the basis of application, various substitutes of these monomers can also be used to prepare Bakelite. The steps followed for the preparation of Bakelite are as follows:

• Firstly two monomers are combined – phenol and formaldehyde in the presence of an acidic (Hydrochloric Acid and Zinc Chloride) or basic (Ammonia) catalyst. This results in the formation of ortho-hydroxy benzyl and para-hydroxy benzyl alcohols and their derivatives. These products further react to form compounds that are joined to -CH₂ groups by rings. 
• If the formaldehyde to phenol molar ratio is less than one, i.e., phenol is taken in excess, then, acidic catalysts like Hydrochloric Acid (HCl) and Zinc Chloride (ZnCl₂) are used. 
• The condensation product formed is called Novolac. 
• On the other hand, if the formaldehyde to phenol molar ratio is more than one, i.e., formaldehyde is taken in excess, then, basic catalysts like Ammonia (NH₃) are utilized. The condensation product formed, in this case, is called Resolve. 
• When Novolac is repeatedly heated and undergoes cross-linking with another cross-linking agent, commonly hexamethylenetetramine or excess formaldehyde, the polymer, Bakelite – (C₆H₆O-CH₂OH)_n  – is produced. This process is known as polymerization.
• This reaction is highly exothermic in nature and needs to be conducted under pressure so that the product is hard, rigid, and dense.

Backelite Preparation

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Properties of Bakelite

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Some of the important properties of Bakelite are as follows:

• Bakelite is a thermoset or thermosetting plastic. Therefore, when heated, this polymer is malleable and liquefiable. However, when it is cooled, it becomes permanently hard and rigid. 
• It is a non-conductor of electricity, having a dielectric constant of 4.4 to 5.4. 
• It is heat-resistant and therefore, non-flammable. Thus, it functions as a good insulator. 
• Bakelite is also resistant to any kind of chemical action and hence, is non-destructive.
• It can be very easily and quickly molded.
• The moldings of Bakelite are fairly scratch-resistant. 
• Usually, it has a brown or amber color. However, it can be found in a variety of colors. 
• Bakelite has a distinctive sickly-sweet or fishy odor. 

Also Read: Synthetic polymers

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Uses of Bakelite

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Bakelite, commercially known as phenol formaldehyde resin, is widely used in the production of various products. Hence, it is rightly known as ‘material of thousand use’. Some of the important applications of Bakelite are as follows:

• It acts as a good insulator. Therefore, it is widely used in making several electrical devices like sockets, automobile distribution caps, switches, insulation wire, etc. It is also used in making the non-conducting parts of radios and telephones.
• Bakelite can be very easily molded. Thus, it can be used for making a variety of daily-use commodities like clocks, toys (dominoes, chess, poker chips, mah-jong sets), washing machine impellers, buttons, kitchenware, etc.
• Since Bakelite is available in a variety of colors, it is also utilized for making artificial jewelry like bangles, earrings, and bracelets. 
• It is also widely used as adhesives or binding agents and as varnishes or protective coating.
• It is also used in making musical instruments like saxophone, whistle, and electric guitar.

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Previous Year Questions

• Which one of the following is amorphous… [VITEEE 2006]
• Nylon 66 is formed by… [UPSEE 2019]
• In Buna-S, the symbol ′Bu’ stands… [KCET 2013]
• The monomer used in Novolac, a polymer used in paints… [KCET 2017]
• The monomer of polystyrene is… [KEAM]
• Among the following, the branched-chain polymer is… [KCET 2018]
• Cis-1, 4-polyisoprene is called… [KCET 2019]
• The monomers of Buna… [KCET 2008]
• Poly-β-hydroxybutyrate-co-β hydroxyvalerate… [JEE 2019]

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Things to Remember

• Bakelite is a polymer that is made from two monomers – phenol and formaldehyde.
• Bakelite is a thermosetting plastic that becomes hard and rigid upon cooling.
• Bakelite is formed due to a condensation reaction and is, therefore, also known as a condensation polymer.
• Bakelite is resistant to heat, electricity, and chemical action. It can be very easily molded. 
• Bakelite is used as an insulator in electrical devices like sockets, telephones, automobiles, etc. It is also used in making jewelry, toys, adhesives, kitchenware, etc. 

Also Read: