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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