Classes Of Polymer..Base on Intermolecular Force...

Classes Of Polymer..Base on Intermolecular Force...

(i) Elastomers: Elastomers, the elastic polymers, have weak van der Waals type of intermolecular forces which permit the polymer to be stretched. A few crosslinks between the chains help the stretched polymer to retract to its original position on removal of applied force. E.g.: Vulcanized rubber, neoprene.

(ii) Fibres: The fibres possess high tensile strength which is a property to have resistance to breaking under tension. This character due to the strong intermolecular forces like hydrogen bonding and strong dipole-dipole forces. Due to the strong inter molecular forces the fibres are crystalline in nature. E.g.: polyamides, polyesters.

(iii) Thermoplastic polymers: These polymers possess moderately strong intermolecular forces that are intermediate between elastomers and fibres. There is no cross linking between the chains. Therefore, thermoplastic polymers are capable of repeated softening on heating and hardening on cooling. E.g.: polythene, polystyrene.

(iv) Thermosetting poly degNylon- e setting polymers are prepared from semi-fluid substances. They undergo extensive cross linking when heated in moulds and become hard and infusible. Once hardened, cannot be softened by heating and therefore cannot be remoulded. E.g.: bakelite. urea formaldehyde resin.

Ans. Bio degradable Polymers: Polymers that can be broken into small segments by enzyme catalysed reactions are called biodegradable polymers. The required enzymes are produced by micro-organisms. Since carbon-carbon bonds of chain-growth polymers are inert to enzyme- catalysed reactions, these polymers are non biodegradable . To overcome this, certain bonds in the chain are to be inserted so that it can be made biodegradable. One such method to make a polymer biodegradable is to insert hydrolysable ester group into the polymer. Aliphatic polyesters are biodegradable polymers and many of them are important commercial biomaterials. For example, poly B-hydroxybutyrate-CO- ẞ-hydroxy valerate (PHBV), Nylon-2-nylon-6, Dextron etc.