. Polymers The term Polymer is derived from the Greek word ‘polumeres’ meaning “having many parts”. The constitution of a polymer is described in terms of its structural units called monomers. Polymers consists of large number of monomer units derived from simple molecules.
For example: PVC(Poly Vinyl Chloride). is a polymer which is obtained from the monomer vinyl chloride. Polymers can be classified based on the source of availability, structure, molecular forces and the mode of synthesis. The following chart explain different classification of polymers.
XII U15 Chemistry in XII U15 Chemistry in - - - - Polymers Source Structure Molecular foces Mode of synthesis Natural polymers polymers polymers polymers (obtained from plants/ animals). E.g. Cellulose, Silk Synthetic polymers (man made from chemicals) E.g. polythene, PVC, etc., Semisynthetic polymers (natural polymers-modified by chemical treatment) E.g.
viscose rayon, cellulose diacetate Linear (long continuous chain) E.g. HDPE, PVC. Branched (one main chain with small chains as branches) E.g. polypropylene, LDPE.
Cross linked (linking of chain polymers) E.g. bakelite, melamine, formaldehyde Elastomers (soft and stretchy) E.g. neoprene, buna-S, buna-N Fibers-Polymer chains forms fibers by hydrogen bonding (high tensile strength) E.g.Nylon- , , Terylene Thermoplastic E.g.polythene, PVC, polystrene Thermo setting Do not be come soft on heating set to an infusible mass upon heating. E.g.
bakelite, melamine, formaldehyde Addition polymers. monomers without the elimination of byproduct. E.g. polyethylene, PVC, teflon.
Condensation Polymer formed by the condensation of two or more monomers with the elimination of simple molecules like H O, NH , etc., E.g. Nylon- , polyester. They become soft on heating and hard on cooling. they can be remolded but Formed by polymerisation of any .
. Classification of Polymers: XII U15 Chemistry in XII U15 Chemistry in - - - - . . Types of polymerisation The process of forming a very large, high molecular mass polymer from small structural units i.e., monomer is called polymerisation.
Polymerisation occurs in the following two ways i. Addition polymerisation or chain growth polymerisation ii. Condensation polymerisation or step growth polymerisation Addition polymerisation Many alkenes undergo polymerisation under suitable