biodegradable polymers

BIODEGRADABLE POLYMERS

polymers are widely used in the form of packing material and throw away that bag.The plastic thrown away after use are not biodegradable.this produce a serious waste disposal problem.Scientist these days are carrying on researches to develope plastic which are capable of biodegradability over the period of time

Classifications of polymers

Polymers can be classified in number of ways

1)classification based upon source

polymers can be classified based upon source are

a)Natural polymers:- these are the naturally occurring polymers such as starch cellulose nucleic acids and natural rubber.natural rubber is a polymer of isoprene(2-methyl buta 1,3-diene)
b)Synthetic polymers:- these are man made polymers such as poly vinyl chloride (PVC),Bakelite,nylon,polystyrene etc

2)CLASSIFICATION BASED ON SYNTHESIS

based on the method of synthesis polymers can be classified as follows
a)Addition polymers:-these type polymers are formed by the repeated additions of monomeric unit .the monomers involved are unsaturated compounds and are usually the derivatives of ethene

eg:-polypropylene, PVC,polythene,etc belongs in this type

b)Condensation polymers:-these are formed by a series of condensation reaction between two monomers each monomers having two functional group.during condensation simple molecule like H2O,HCl,NH3 etc are eliminated.The reaction is called condensation polymerisation

eg nylone66

CLASSIFICATION BASED ON INTERMOLECULAR FORCES

based on the inter molecular forces polymers can mainly classified in to 4
a)Elastomers :-the polymers that have elasticity, like rubber are referred to as elastomers.the polymer chain in elastomers are held together by the weakest intermolecular forces.they have ability to be elongated under stress and regain their former shapes when the stress is removed

b)Fibers:-these are thread like polymers which can be woven into fabric.they have high tensile strength and high modulus.this is due to strong inter molecular forces like hydrogen bond.
eg:- cotton,wool,silk,nylon and Dacron etc

c)Thermoplastic:-The inter molecular forces of attraction in the thermoplastics polymers are intermediate between those of elastomers and fibres .As a result thermoplastic polymers when heated became melt and can be molded again in different forms.
eg:- polyethylene polypropylene and polystyrene

d)Thermosetting plastic:- These polymers are prepared from low molecular mass semifluid polymers .thy cannot be reshaped on heating because the polymer chain under go extensive cross linking resulting in the formation of three dimensional network of inter connected polymer chain

eg:- Bakelite,melamine etc