Question

Give an example of a cross linked synthetic polymer.
(A) Write the compound from which it is prepared.
(B) Give one physical property of cross-linked synthetic polymer.

Answer 1

Hint : We know that cross-link refers to a bond which links one polymer chain to another polymer chain. We can say that cross-linked polymers are those polymers that are obtained when a cross-link bond is formed between the monomeric units.

Complete Step By Step Answer:
As cross-linked polymers create covalent bonds (much stronger than intermolecular forces which attract other polymeric chains), the resultant is a stronger and much more stable material. Bakelite is a thermosetting plastic possessing a permanent shape as well as size which cannot be altered on exposure to heat and pressure without decomposing it. Thermosetting Plastics are prepared via low molecular mass semi-fluid substances. On heating in a mould, these plastics get highly cross-linked leading to the formation of hard infusible and insoluble products. Moreover, thermosetting plastics can tolerate very high temperatures. The polymers link together during the curing process to form a permanent chemical bond. These types of polymers are poor conductors of heat or electricity and hence can be effectively used in electric switches, sockets, frying pan handles, etc. Bakelite is a condensation polymer made from formaldehyde and phenol.
- The compound from which it is prepared is phenol and formaldehyde.
- The physical property of cross-linked synthetic polymers is that they cannot be remolded and reshaped.

Note :
Remember that the cross-linked polymers are polymers in which long polymer chains are cross-linked together to create a three dimensional network. Cross-linked polymers are utilized in making a large number of materials as they are mechanically strong and even resistant to heat, wear or attack by solvents. Examples of these polymers include Bakelite, melamine and formaldehyde resin.