Polymers chem

COMPOUNDING OF PLASTICS

MATERIALS FOR COMPOUNDING

Resins Plasticizers Extenders/ Fillers Lubricants Catalyst/ Accelerators Stabilizers Coloring Agent

RESINS

Basic binding material 30 – 100% In plastics Two types of plastics

Thermoplastics

Thermoset plastics

PLASTICIZERS

Increase flexibility Enhance Flow properties

E.g vegetable oil, camphor, esters of oleic, phthalic acid

FILLERS/EXTENDERS/REINFORCEMENT

To reduce the cost of finished plastics To improve hardness ,tensile strength ,water resistance,

electrical insulating properties. Enhance mechanical strength

E.g Asbestos-heat & corrosion resistance

Carbon black-tensile strength in natural rubber

Quartz ,mica -hardness

Saw dust ,paper pulp ,wood flour, graphite, cotton fiber, pumice

LUBRICANTS

To impart the flawless glossy finish

Prevent plastic material from sticking

E.g waxes ,oils, soaps , stearates, oleates

CATALYST/ACCELERATORS

Required only for thermosetting resins

Accelerates the polymerization reaction

E.g hydrogen peroxide, benzoyl peroxide, metals like Cu,Pb, ammonia and its salts.

STABILIZERS

Improve the thermal stability during processing

E.g White lead, Lead chromate, lead silicate

COLOURANTS/COLOURING AGENTS OR PIGMENTS

Imparts colour

Provide decorative appeal to the finished plastics

E.g Organic dyestuffs, opaque inorganic pigments

FABRICATION OF PLASTICS

DEFINITION

The process of making various products of plastics is known as fabrication of plastics.

METHODS OF FABRICATION

Compression Moulding Injection MouldTransfer MouldingExtrusion MouldingBlowingThermoforming

COMPRESSION MOULDING

P=100-500 atm

T=100-200ºC

Thermoplastics as well as thermoset resins.

INDUSTRIAL METHOD

EXAMPLES

INJECTION MOULDING PROCESS

PROCESS CONDITIONS

T=90-250ºC For Thermoplastics resin only

http://www.petervaldivia.com/technology/plastics/Injection-molding.php

EXAMPLES

TRANSFER MOULDING

EXAMPLES

EXTRUSION MOULDING

The plastic granules are moved down by the feed screw and heated up.

The molten plastic is forced through the series of dies.

The plastic extrusion is cooled by passing it through a water bath or jets of air.

The extrusion continues until it reaches its predetermined length.

It is then cut off to length and the cycle of operations continues.

EXAMPLES

BLOWING

CONTD..

Bubble casting For thermoplastic materials only

EXAMPLES

THERMO FORMING

3 Dimensional articles

Combination of Extrusion and Compression Moulding.

2 Steps: Heating & Forming

Forming can be achieved by i) Vacuums Thermoforming ii) Pressure Thermoforming iii) Mechanical Thermoforming

VACUUM THERMOFORMING(HTTP://WWW.CUSTOMPARTNET.COM/WU/THERMOFORMING)

PRESSURE THERMOFORMING

MECHANICAL THERMOFORMING

EXAMPLES

CHEMISTRY OF THERMOPLASTICS & THERMOSET PLASTICS

IMPORTANT PLASTICS

Polyethylene Polystyrene Poly Vinyl Chloride Teflon Bakelite Nylon

POLYETHYLENE

][][ 2225015050001000

22

CHCHCHCHn Catm

Polymerization of ethylene

Ethylene Polyethylene

PREPARATION

22/2 CHCHCHCH PdH

OHCHCHOHCHCH CatalystnDehydratio

22223

22233 HCHCHCHCH CatalystationDehydrogen

(i) Hydrogenation Of Acetylene

(ii) Dehydration of ethanol

(iii) Dehydrogenation of ethane

Acetylene Ethylene

Ethanol Ethylene

Ethane Ethylene

TYPES OF PE

LDPE

HDPE

natm

CoxideBenzoylPer

CHCHCHCHn ][][ 221500

25080

22

natmCHCAl

CHCHCHCHn ][][ 2276

120)(

22

352

Obtained at High P Branched Structure Low density 0.91-

0.925 Low M.P(115ºC) Low Crystallinity High Water & gas

permeability Used for making

toys , mugs , carry bags.

Obtained at low P Linear structure High density 0.95-

0.97 High M.P(135ºC) High Crystallinity Low Water & gas

permeability For making milk

bottles ,industrial containers , for domestic water & gas piping.

Low Density PE High Density PE

3/ cmg 3/ cmg

PROPERTIES OF PE

Rigid, waxy, white, translucent, non-polar material

Chemical resistance to strong acids, alkalis and salt solution

Good electrical insulator

Resistant to atmospheric conditions

ENGINEERING APPLICATIONS

POLYSTYRENE

Free radical addition polymerization Initiator is Benzoyl peroxide

Styrene Polystyrene

PREPARATION

+ 2H

PROPERTIES

Transparent & light weight polymers Resistant to moisture Low M.P (90-100ºC) High electrical insulators Good chemical resistant Transmit light through curved section.

APPLICATION

POLY VINYL CHLORIDE (PVC)

Prepared by polymerization of VC Free radical chain polymerization Heated in water Emulsion with catalyst under

pressure.

PREPARATION OF VINYL CHLORIDE

CHClCHHClCHCH tideCatalysMetalChlorC

2

8060

Acetylene Vinyl Chloride

PROPERTIES OF PVC

Colorless & odorless powder Chemically inert & nonflamable High resistance to light, Atmospheric

Oxygen, Acids & Alkalis. Soluble in Chlorate