SYNTHETIC POLYMERS

The word, polymer, implies that polymers are constructed from pieces (monomers) that can be easily connected into long chains (polymer). When you look at the above shapes, your mind should see that they could easily fit together. Polymer INTRODUCTION

Polymers P olymerization: When carbon molecules combine into long chains. H OW: This happens when a carbon to carbon double bond in a monomer is broken and new single bonds are formed creating a polymer.

Methods for making polymers 1)Addition polymerization 2)condensation polymerization Addition polymerization : monomers react to form a polymer without net loss of atoms Most common form: free radical chain reaction of ethylene n monomersone polymer molecule The processes involved in the synthesis of polymers can be divided into two categories

200 °C 2000 atm O 2 peroxidespolyethylene H2CH2CH2CH2C CH 2 Free-Radical Addition Polymerization of Ethylene

88 MECHANISM – Initiation – Propagation – Termination

1)POLYETHYLENE OR POLYTHENE It is widely used polymer.It is of two types. (a)Low density polythene:- It is formed by heating ethylene to k under a pressure of 1500 atm in the presence of trace of oxygen. (b)High density polythene:- It is formed by heating ethylene to under a pressure of 6-7atm in the presence of Zeigler-Natta catalyst. Monomer unit:- Ethylene SOME IMPORTANT VINYL POLYMER

CHARACTERISTICS:- Low density polythene is chemically inert, tough but flexible and poor electrical conductor. High density polythene is also chemically inert but is tougher & harder than low density polythene. Uses:- It is used for 1)packaging, as insulation for electrical wires. 2)In the manufacture of pipes, squeeze bottles & toys. 3)In the manufacture of containers & house wares.

2)POLYVINYL CHLORIDE (PVC) Monomer unit :- Vinyl chloride Characteristics :- PVC is a hard and horny. It is an electrical insulator and is resistant to fire and chemicals. USES : It is used for making- 1) Rain coats, hand bags, table clothes. 2) Plastic dolls, gramophones records, floor covering. 3) Electrical insulating coating on electrical cables. Vinyl chloride PVC

3) POLYSTYRENE (STYRON) Monomer unit :- Styrene StyrenePOLYSTYRENE (C 6 H 5 CO) 2 O 2 USES :- It is used 1)In making light weight packaging materials. 2)In the manufacture of food containers, egg boxes, etc. 3)In making television cabinets.

Name(s)FormulaMonomerPropertiesUses Polyethylene low density (LDPE ) –(CH 2 -CH 2 ) n – ethylene CH 2 =CH 2 soft, waxy solidfilm wrap, plastic bags Polypropylene (PP) different grades –[CH 2 -CH(CH 3 )] n – propylene CH 2 =CHCH 3 atactic: soft, elastic solid isotactic: hard, strong solid similar to LDPE carpet, upholstery Poly(vinyl chloride) (PVC) –(CH 2 -CHCl) n – vinyl chloride CH 2 =CHCl strong rigid solid pipes, siding, flooring Polystyrene (PS) –[CH 2 -CH(C 6 H 5 )] n – styrene CH 2 =CHC 6 H 5 hard, rigid, clear solid soluble in organic solvents toys, cabinets packaging (foamed) Polyacrylonitrile (PAN, Orlon, Acrilan ) –(CH 2 -CHCN) n – acrylonitrile CH 2 =CHCN high-melting solid soluble in organic solvents rugs, blankets clothing Polytetrafluoroethylene (PTFE, Teflon) –(CF 2 -CF 2 ) n – tetrafluoroet hylene CF 2 =CF 2 resistant, smooth solid non-stick surfaces electrical insulation Poly(methyl methacrylate) (PMMA, Lucite, Plexiglas) –[CH 2 -C(CH 3 )CO 2 CH 3 ] n – methyl methacrylate CH 2 =C(CH 3 )CO 2 CH 3 hard, transparent solid lighting covers, signs skylights Poly(vinyl acetate) (PVAc) –(CH 2 -CHOCOCH 3 ) n – vinyl acetate CH 2 =CHOCOCH 3 soft, sticky solid latex paints, adhesives Some Common Addition Polymers