MANUFACTURING OF PLASTIC COMPONENTS

1. MANUFACTURING OF PLASTIC COMPONENTS
Types of plastics - Characteristics of the forming and shaping processes –
Moulding of Thermoplastics – Working principles and typical applications
of - Injection moulding – Plunger and screw machines – Compression
moulding, Transfer moulding – Typical industrial applications –
Introduction to Blow moulding – Rotational moulding – Film blowing –
Extrusion - Thermoforming, - Bonding of Thermoplastics.

2. ORGANIC MATERIALS
 Natural – Wood, Coal, Petroleum &
Natural Rubber
 Synthetic – Plastics, Synthetic rubber,
Ceramics & Glass
 Organic material - Polymers

3. Polymers
 Poly means ‘Many’ & ‘Mers’ means ‘Parts’
 Polymer built of several repeating
units(Monomer)
 Monomer – small molecules
 Polymer is made up of thousands of
monomers jointed together to form large
molecule.
 Plastics – Organic polymer
 The Main raw material for making plastic is
resin.
 Resin – acrylic resin, polyethylene resin

4. Polymerization process
 A Polymer is made up of linking thousands
of monomer and thus obtaining large
molecule is called Polymerization process
 Additives – Plasticizers (liquid form) –
Water, Organic solvents & resins
 Catalyst – Promote faster & complete
Polymerization
 Dyes – Impart desired colour
 Initiators – Initiate the reaction (H2O2)
Hydrogen peroxide

5.  Addition polymerization:
 Similar monomers of large numbers are added
chemically one by one
 These monomers form a long chain molecule.
 Polyethylene is produced by addition polymerization,
 Condensation polymerization :
 Two or more unlike monomers are linked and there is a
repetitive elimination of smaller molecules to form a by-
product. During this process, by-product such as water or
ammonic is formed.

6. Plastics
 Can be moulded into required shape
with the help of pressure or heat or
both heat and pressure
 Resin – liquid form of plastics, also raw
material for making plastics
 Types of resin: acrylic resin,
Polyethylene resin & amino resin –
Produced by polymerization process
 Catalysts, Binders & Lubricants added
with resin to form plastics

7.  Modifiers – To improve the mechanical
properties of plastics
 Lubricants – To reduce friction during processing ,
Avoid sticking to mould walls(Oils, Soaps and
waxes)
 Solvents – Dissolve fillers or Plasticizers & Allow
the processing in fluid state(Alcohol)
 Fillers – Mica, Cloth fiber
 Elastomers – To enhance the elastic properties

8. Properties of Plastics
 Elongation
 Heat resistance
 High rigidity
 Surface hardness
 High viscosity
 Density
 Chemical resistance

9. Thermosetting Plastics
 Thermosetting - Plastics which are hardened by
heat effecting non reversible chemical change .
 Plastics do not soften on reheating and cannot be
reworked.
 Molecules are formed by condensation
polymerization process.
 All the molecules have three dimensional
network and very strong binding force between
molecules
 Bakelite, Polyester resin, Epoxy resin(Araldite),
Silicones, Urea formaldehyde(Amino resin) &
Alkyds

10.  Phenol formal dehyde: Reaction of phenol with
formaldehyde.
 Produced dark colour and it has high strength, stability
and rigidity.
 Uses: plugs, knobs, pulleys, bottle caps, tooling and
forming die.
 Polyster resin: Low moisture, good electrical resistance
and variety of colours.
 It is used in paper mat, TV parts and car bodies.
 Main drawback is polyster is high cost.
 Epoxy resin: most popular variety of epoxy resins is
Araldite. Good chemical and electrical resistance.
 Mostly available in the form of liquid.
 Good resistance to wear and impact.

11. Thermo Plastics
 Have separate long and large size molecule arranged
side by side
 When thermoplastics are heated it becomes very soft
and rehardens on cooling
 During heating the linear bonding links between
molecules are breakup and separated. Relinking takes
place on cooling and retains their hardness.
 Cellulose nitrate – pen bodies, Table tennis balls, Frames
 Ethyl cellulose – Jigs, Fixtures, hose nozzles
 Cellulose acetate - Radio cabinets, steering wheels,
Insulating tapes

12. Synthetic resins
 Polyethylene – Fabrics, tray, pipes, tubing chemical
containers & corrosion resistant coatings
 Polystyrene - Battery boxes, radio parts, toys
 Vinyles(PVC) – Tarpaulin, Water roofing, raincoats, tubes
 Polytetra fluroethylene (Teflon)- Gaskets, Greaseless
bearing, Electrical insulators, Chemical containers
 Polyamide(Nylon) – Gears, wire insulation, combs,
Bearings and couplings

13. S.
No
Thermoplastics Thermosetting plastics
1 Softened by heating Cannot be softened by
heating
2 Structure is made of linear
chain molecule
Structure is made of cross-
linked molecule
3 Produced by addition
polymerization process
Produced by condensation
polymerization process
4 Can be reproduced by
heating and cooling
Cannot be reproduced
5 When the temp increases
the plasticity also
increases
Plasticity is stable at high
temperature
6 Softer and less strong Harder and strong
7 Scrap can be reused Scrap can not be reused

14. INJECTION MOULDING
1) RAM OR PLUNGER TYPE INJECTION MOULDING

15. THERMOPLASTICS - INJECTION MOULDING
2) SCREW TYPE INJECTION MOULDING

16. THERMOPLASTICS – INDUSTRIAL APPLICATION
2) BLOW MOULDING

17. THERMOPLASTICS – INDUSTRIAL APPLICATION
3) ROTATIONAL MOULDING

18. THERMOPLASTICS – INDUSTRIAL APPLICATION
4) FILM BLOWING

19. THERMOPLASTICS – INDUSTRIAL APPLICATION
5) SHEET MAKING

20. THERMOPLASTICS – INDUSTRIAL APPLICATION
6) EXTRUSION PROCESS

21. THERMOPLASTICS – INDUSTRIAL APPLICATION
7) VACUUM FORMING PROCESS ( THERMO FORMING)

22. THERMOSETS
1) COMPRESSION MOULDING

23. THERMOSETS
2) TRANSFER MOULDING

24. BONDING OF THERMOPLASTICS