Polymers, Applications and Classification.pptx

PAC

1. POLYMERS INTRODUCTION REACTIONS INVOLVED IN POLYMERS’ SYNTHESIS CLASSIFICATION APPLICATIONS

2. INTRODUCTION: Many small molecules are combined together through covalent bonding and form a large molecule called polymer. Reactions Involved in Polymers’ Synthesis: Condensation Polymerization Addition Polymerization

3. Condensation (Step Growth) Monomers contain functional groups which react together e.g. amines, carboxylic acids, alcohols, amides etc. Monomers are of 2 types: A single monomer contains 2 or more same functional groups e.g. nylon 6,6 polymer from adipic acid and 1,6 diaminohexane. A single monomer contains 2 or more different functional groups. Monomers containing 2 functional groups results in linear polymers and monomers containing more than 2 functional groups results in branched or crosslinked polymers. Generally contain fewer atoms in the polymer than in the reactants because of the formation of by products during the polymerization process and the backbone contains non carbon atoms as well.

4. Condensation (Step Growth) In some cases, rearrangment takes place and there is no elimination of by products e.g. polyurethanes from diisocyanate and diol. Lactones and lactams are readily polymerized through a chain wise kinetic process forming polyesters and polyamides and clearly condensation polymers with respect to having non carbon atoms in the backbone but without expulsion of a by product.

5. Addition (Chain Growth) Chain growth polymerization also called addition polymerization. Monomers are unsaturated hydrocarbons or olefins. No elimination takes place. Chain polymerization is characterized by three distinct stages (initiation, propagation and termination). Majorly it proceeds through free radical polymerization. In initiation, radicals are generated thermally or by photolysis and termination can occur either by combination of two radicals with each other or with impurities or by disproportionation. e.g. synthesis of polyvinyl chloride.

6. Classification On the Basis of SOURCES: Natural: Starch, Cellulose, Protein etc. Synthetic: Polyvinyl Chloride, Nylon, Polyurethane etc. On the Basis of COMPOSITION: Homopolymer: All monomers are identical e.g. Polyvinyl Chloride, Polyethylene, Polystyrene etc. Copolymers: Made of two or more than two different monomers e.g. Nylon, Polyurethane etc. On the Basis of STRUCTURE: Linear: Soft and thermoplastic e.g. Nylon, Polyvinyl Chloride etc. Branched: Interparticle forces are in between linear and crosslinked polymers e.g. Glycogen, Amylopectin etc. Crosslinked: Hard and thermosetting e.g. Bakelite.

7. Applications POLYETYLENE is used in food packaging, in making grocery and garbage bags etc. POLYVINYL CHLORIDE is used to make pipes and as wire and cable insulations etc. POLYSTYRENE is used to make styrofoam or disposable plates, dishes, cups, egg cartons, meat trays etc. NYLON is used in textiles, in making carpets and due to good insulating properties it is also used in electronics. POLYURETHANE is used in mattresses, couches and due to it’s thermal and mechanical compatibility it is used in medical devices. BAKELITE is used in making crockery items, automobile parts, electronic devices like microwaves etc.