polymers in simple
Post on 19-Oct-2014
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POLYMER
WHAT IS POLYMER? POLYMER IS A MARCOMOLECULE WHICH
ARE JOINED TOGTHER BY SMALL MOLECULE.
EXAMPLE: POLYETHYLENE HEAT n CH2=CH2 (CH-CH2)
ETHYLENE CATALYST POLYETYLENE
CHARACTERISTICS OF POLYMER
LOW DENSITY
GOOD MOULDABILITY
GOOD CORROSION RESISTANCE
POOR TENSILE STRENGTH
LOW MECHANICAL PROPERTIES
POOR TEMPERATURE RESISTANCE
CLASSIFICATION OF POLYMER
POLYMERS ARE MAINLY CLASSIFIED INTO TWO TYPES
NATURAL POLYMER SYNTHETIC POLYMER
NATURAL POLYMER
NATURAL POLYMER ARE THE POLYMER EXIST AS NATURAL RESOURCE
SUCH AS CELLOUSE WHICH IS THE MAIN CONSITUTENT OF WOOD AND PAPER.
EXAMPLES:CELLOUSE AMINO ACIDS etc..,
SYNTHETIC POLYMER
POLYMER MADE BY ARTIFICIALLY USING CHEMICAL ARE CALLED AS SYNTHETIC POLYMERS.
EXAMPLE:BAKELITE NEOPRENE NYLON
POLYVINYL CHOLRIDE POLYSTYRENE
NYLON 6-6
IT IS OTBTAINED BY POLYMERIZATION OF HEXAMETHYLENE DIAMINE AND ADIPIC ACID.
PROPERTIES
NYLON 6:6 IS LESS SOFT AND STIFF MATERIAL.
THEY BEHAVE AS PLASTIC AS WELL AS FIBER.
THAY HAVE GOOD MECHANICAL STRENGTH.
HIGH ABRASION RESISTANCE.
USES
USED IN FIBERS IN MAKING SCOKS,DRESSES etc.,
USED IN MOULDING PURPOSE FOR MAKING GEAR.
USED FOR MAKING FILAMENTS IN TOOTH BRUSHES.
EPOXY RESIN
IT IS PREPARED BY CONDENSING EPICHLOROHYDRIN WITH BISPHENOL.
PROPERTIES
HIGHLY CHEMICAL RESISTANCE TO WATER,ACIDICS,ALKALIS AND OTHER CHEMICALS.
THEY ARE FLEXIBLE AND TOUGH. POSSES VERY GOOD HEAT RESISTANCE. POSSES EXCELLENT ADHESION
QUALITY.
USES
EPOXY RESIN ARE USED AS SURFACE COATINGS AND ADHESIVE.
USED AS LAMINATING MATERIAL IN ELECTRICAL EQUIPMENTS.
USED FOR THE PRODUCTION OF COMPONENTS FOR AIRCRAFTS AND AUOTMOBLIES.
MECHANISM OF ADDITION POLYMERIZATION
IT CAN BE EXPLAINED BY THE TWO FOLLOWING METHODS
FREE RADICAL
MECHANISM IONIC RADICAL
MECHANISM
FREE RADICAL
IT OCCURS IN THREE STEPS INITIATION PROPAGATION TERMINATION
INTIATION PRODUCTION OF FREE RADICAL BY
HOMOLYTIC DISSOCIATION. I 2R0
INTIATOR FREE RADICAL
ADDITION OF FREE RADICAL TO THE FIRST MONOMER.
PROPAGATION GROWTH OF CHAIN INTIATING
SPECIES
TERMINATION COUPLING INVOLVES COUPLING OF FREE RADICAL
ONE CHAIN END TO ANOTHER.
DISPROPORTIONATION INVOLVES TRANSFER OF HYDROGEN
ATOM OF ONE RADICAL CENTRE TO ANOTHER,FORMING SATURATED AND UNSATURATED MOLECULE.
IONIC MECHANISN
IT IS INITIATED BY A POSITIVE ION AND NEGATIVE ION.
CATIONIC
POLYMERIZATION ANIONIC POLYMERIZATION
CATIONIC POLYMERISATION
IT TAKES PLACE WHEN ELECTRON DONATING GROUPS LIKE PRESENT IN MONOMER.
THESE GROUPS STABILISE THE CABONIUM ION FORMATION.
STYRENEINTIATOR USED TO INTIATE THE REACTION
ARELEWIS ACIDS()
INTIATOR
PROPAGATION IT INOLVES THE GROWTH OF CHAIN
INITIATING SPECIES.
TERMINATION IT INVOLVES THE REMOVAL OF
CATALYST BY THE ADDITION OF PROTON
ANIONIC POLYMERIZATION
IT TAKE PLACE WHEN ELECTRON WITHDRAWING
GROUP LIKE ()PRESENT IN MONOMER.
THESE GROUP STABILISE CARBANION FORMATION.
ACRYLONITRILEINITIATOR USED TO INITIATE THE
REACTION ARE LEWIS BASES LIKE()
INTIATIONIT INVOLVES THE FORMATION OF CHAININITIATING SPECIES.
PROPAGATION IT INVOLVES THE GROWTH OF CHAIN
INTIATING SPECIES.
TERMINATION IT OCCURS BY ADDING AMMONIA.
Presented by dhayanidhi.e gokul.s amarnath.aMUTHAYAMMAL ENGINEERING COLLEGE RASIPURAM NAMAKKAL