Condensation Polymerization in Nylon, Terylene, Bakelite and other Methanal Polymers

Condensation polymerization is a process whereby two or more monomers are joined to form a polymer with the elimination of a by-product.

Condensation polymerization can be expressed simply by esterification. Here, organic acid (alkanoic acid) monomer react with alkanol monomer to form an ester dimer with the formation of water as by-product.
RCOOH + HOR^' + H⁺ ↔ RCOOR' + H₂O

Where, RCO of the RCOOH (alkanoic acid) and OR' of the HOR' (alkanol) are the monomeric units; RCOOR', the dimer; and H₂O, the water by-product.

Polyester is formed when the dimer undergoes condensation with more monomers forming an array of ester linkages.

Nylon is the general name for a group of synthetic fibres used in making a wide range of drip-dry and crease-free clothing materials that are resistant to moth and fungal attack. Here, we will be discussing nylon 6.6 as an example of condensation polymer.

Nylon is prepared by the addition of an aqueous solution of hexane- 1,6-diamine to hexanedioc acid in the presence of tetrachloromethane. The monomers for making nylon 6.6 are hexane- 1,6 diamine, H₂N-(CH₂)₆-NH₂, and hexanedioc acid, COOH(CH₂)₄-COOH. The linkage of the monomers invovles a primary condensation reaction where the -NH₂ (amine group) react -COOH (carboxyl group) to form amide linkage group, -CO-NH-.

Apart from the use of nylon in making textile materials, it is also used in other materials in making ropes, fishing nets, strings, e.t.c.

Terylene is a practical example of polyester. Like nylon, it is popular for the use in making synthetic textiles. Terylene is unique in that it is soft and capable of retaining its crease for so long that it is assume that the crease is retained permanently. Small wonder, it is used in making boat sails.

Terylene is made by the condensation polymerization of benzene-1,4-dicarboxylic acid (terephthalic acid) with ethane-1,2-diol in the presence of an acid catalyst.

One thing to note about terylene and nylon, is that water is formed as by-product of the condensation of the monomers to form the respective polymers.

Methanal polymers are made by simple condensation reaction methanal with other monomers such as urea, melamine and phenol. Here, we will be revising the polymers produced from each of the monomers referred to above.

Urea-methanal

Both urea-methanal and phenol-methanal are similar except that they are different by virtue of the ease by which they can be coloured with pigments. Here, urea-methanal is transparent, as such, can easily be coloured with pigments. Urea-methanal is can be prepared as foam and used in making insulators. The use of urea-methanal also extends to making kitchenware and electrical fittings.

Phenol-methanal

Phenol-methanal is commonly known as bakelite. It is a dark-brown polymer often used to make electrical appliances and utensils. Some of the materials made from phenol-methanal include: switches, plugs, telephone casing, sockets, radio housing, and handle for kitchen knives, spoons and other utensils.

Phenol-methanal is a hard plastic formed from the condensation of phenol (hydroxybenzene) and methanal in the presence of acid or alkali catalyst. Here, large amount of water is formed as by-product.

Melamine-methanal

Melamine-methanal is made by the condensation of melamine with methanal. It is used to make heat-resistant and unbreakable cups, plates, bowls, e.t.c.