Polymer | Condensation and addition polymer difference|Epoxy Resin|12th class|Polytechnic F.Y.|MSBTE

#chemistrynotes
Epoxy resins :- Epoxy resins are prepared by condensation of epichlorohydrin with bis -phenol in presence of alkaline catalyst.They are modified by adding external compounds like unsaturated fatty acids or amines and solvents.The solvent evaporates leaving behind a very thin film which posses excellent adhesion property.The reactive epoxide and hydroxyl groups give a three dimensional cross linked structure.
Properties :-
1) They have good electrical resistance
2) They have good adhesive properties
3) Due to presence of very stable ether linkages epoxy resins have high chemical resistance to water acids ,alklies , various solvents and other chemicals.
4) They contain reactive groups as epoxide and hydroxyl which are widely sapaced resultilng in high flexibility , at the same time there are cross links give toughness and heat resistance.
Uses :- 1) It is used as laminating material in electrical equipments.
2) They are used as suface coatings , adhesives like araldite used for bonding glass and metals.
3) Moulds made from epoxy resins are employed for the production of components for automobiles.
4) They are used in air-carft industry.
*Difference between additional and condensation polymerisation :-
Additional polymerisation :- 1) It is the process in which monomers undergo addition repeatedly resulting in formation of long chain polymers without elimination of molecule like H2o, HCl etc.
2) The polymers formed are linked by weak covalent bonds.
3) The polymers are usually soft , weak and less brittle.
4) The polymers formed by this process are known as thermoplastics having smaller molecular weight.
5) Polymers can be reclaimed from wastes.
Condensation polymer :- 1) It is process in which different types of monomers are joined together by condensation forming a large polymer with elimination of molecules such as H2o, HCl etc.
2) The polymer formed are linked by strong covalent bond.
3) The polymers are usually hard, strong and more brittle.
4) The polymers formed by this process are known as thermosetting plastics having higher molecular weight.
5) polymers cannot be reclaimed from wastes.

Homework:-
Q.1) Write the important properties and uses of epoxy-resins.
Q.2) How will prepare epoxy resins.
Multiple choice questions:-
i) ................. polymer is an example of thermosetting polymer.
a) polyethylene b) Teflon c) epoxy-resins d) PVC
ii) ........... is the property of epoxy-resins.
a) Adhesive b) less resistance of chemical c) less resistance of electricity d) None of these
iii) Epoxy-resins is for ........
a) Bonding glass and metallic articles b) Bonding ceramic articles c) Making araldite used in air craft industry d) all of the above
iv) ............. is the condensed polymer.
a) Epoxy resins b) orlon c) PVC d) Teflon
v) Epoxy resins contain ............ Linkage .
a) amide b) ether c) ester d) none of these