Bakelite: Structure and Uses


Introduction

It is the 21st century and we literally live in the world of plastics. It is hard for us to imagine our life without plastic. The plastic furniture at homes, offices and schools, the electric sockets, plugs, devices, buckets- everything has become an essential part of human life. It was between 1907-1909 that the Belgian chemist Leo Baekeland successfully developed the first commercialized synthetic molding plastic, Bakelite. The two major classifications of plastics are- Thermoplastics and Thermosets. Thermoplastics can be softened by heat and can be molded. E.g., PVC. Thermosets or thermosetting plastics on the other hand become hard and rigid on cooling and retain their shape. Bakelite falls under this category of plastics. This thermosetting plastic created a revolution in the world of product design.

What is Bakelite?

Bakelite, which is also known as a 'material of a thousand uses' is chemically called polyoxybenzyl methylene glycol anhydride. It is a thermosetting phenol-formaldehyde resin formed by the condensation reaction of phenol with formaldehyde. So, we can, in general, say that Bakelite is a condensation polymer or a phenolic resin.

Preparation of Bakelite


Before we move on to the preparation of Bakelite, it is important to know how a polymer is prepared. Polymers are formed by combining 'monomer' or single units using a range of reaction mechanisms.
So, what is the monomer of Bakelite?
Bakelite requires two monomers- phenol and formaldehyde. Different substitutes of phenol and formaldehyde can also be used depending on the application.
The reaction involved is condensation reaction in the presence of either a basic or acidic catalyst. The reaction that takes place is highly exothermic, the loss of water molecule result in the cooling process. Also, the reaction should be conducted under pressure, otherwise the product formed will be brittle and a low density material.

The Bakelite preparation can be demonstrated in the following steps of reactions-

  • I. Combination of phenol and formaldehyde to form ortho and para hydroxy benzyl alcohols.





  • II. Formation of Novalac from ortho hydroxy benzyl alcohol. Water molecule is removed in the process.





  • III. Formation of Bakelite from Novolac.





  • Bakelite Structure


    The structure for the cross-linked polymer, known by the commercial name of Bakelite is given below.



    Structure of Bakelite


    As we now know the Bakelite preparation method as well as its structure, let us now have a look at the properties of Bakelite.

    What are the Desirable Properties of Bakelite?


    It is due to a number of important properties of the first synthetic plastic, Bakelite that it has been aptly named as 'material of a thousand uses'. We see that a number of things like the plastic handle of utensils, telephones, bangles, automobile parts etc., are made of Bakelite. Studying the properties of Bakelite will give us a wider idea as to why it is used for a wide range of applications.

  •  Bakelite is the commercial name for phenol formaldehyde resin.
  •  It is usually brown/amber but can be made in a variety of bright colors.
  •  It is liquefiable and malleable when heated and becomes permanently hard and rigid on cooling. Hence, it is a thermosetting plastic.
  •  It can be easily molded and hence is used in the making of various products.
  •  It shows high resistance towards heat, electricity and chemical action. This is why they are used to make a number of electronic gadgets, switches and automobile parts.
  •  The dielectric constant of Bakelite falls in the range of 4.4 to 5.4

  • Fillers are used to increase the strength and enhance the properties of the Bakelite so that it can be used for various applications. Asbestos, wood flour, cotton flock, cotton pulp, gypsum, mica etc., are a few reinforcing fillers that are added in molding resins like Bakelite. Following are a few properties that are enhanced by the addition of fillers:

  •  Enhanced toughness and strength
  •  Better moldability
  •  Greater thermal, electrical and chemical resistance
  •  Change in color

  • The addition of an inert filler also reduces the cost of molding. Along with fillers, catalysts are used to accelerate the curing process (the process that results in the hardening and toughening of polymers by forming cross-linked polymer chains).

    Bakelite Uses


    Bakelite has emerged out as a huge commercial success and its uses know no boundaries. Based on the above-mentioned properties of the Bakelite, here are some of its uses-

  •  Being a good insulator, it is used in non-conducting parts of radios and other electrical devices like sockets, switches, automobile distribution caps, insulation of wires, brake pads etc.

  •  The ability to be molded makes it a part of the commodities being used in modern life. It is used to make buttons, clocks, washing machine impeller, toys, kitchenware and much more.

  •  Since Bakelite can be made into different colors, Bakelite jewelry was once very much in use. The colorful bangles, earrings and bracelets were widely used. Artificial jewelry made of metals or some other alloys may sometimes result into allergies or skin irritation, but carefully manufactured Bakelite jewelry are cent percent safe to wear which gave it an added advantage in the market.

  • Bakelite was definitely a remarkable invention that paved the way to the 'Age of Plastics'. The use of Bakelite might have been reduced today when compared to the earlier years, but it is still in use. Many cheaper substitutes for Bakelite have been investigated which are replacing its use in the market. We may not realize but we live in a world of polymers, and everything and anything connected to us or our surroundings is chemistry. Bakelite was invented in the early twentieth century but it is an important topic of study even in this 21st century. The properties of Bakelite are studied to get information regarding its commercial usage. The physical, chemical, electrical and thermal properties of Bakelite make it a widely used commercial polymers. It is always fascinating to study about polymers and its chemistry as they offer a wide range of possibilities to be put into our everyday life. Proper understanding of the structure and properties of synthetic polymers like Bakelite is, thus, important in polymer chemistry.