UNIT-5

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

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. 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

6.  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

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

8. Thermosetting Plastics
 Thermosetting - Plastics which are hardened by
heat effecting non reversible chemical change .
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

9. 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

10. 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

11. 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

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

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

14. THERMOPLASTICS – INDUSTRIAL APPLICATION
2) BLOW MOULDING

15. THERMOPLASTICS – INDUSTRIAL APPLICATION
3) ROTATIONAL MOULDING

16. THERMOPLASTICS – INDUSTRIAL APPLICATION
4) FILM BLOWING

17. THERMOPLASTICS – INDUSTRIAL APPLICATION
5) SHEET MAKING
*Calendering process is used for sheet making.
*A calender is a series of hard pressure rollers used to form or
smooth a sheet of material such as paper or plastic film.
*thickness of the sheet is controlled by combination of squeezing
and altering the speed of rolls.

18. THERMOPLASTICS – INDUSTRIAL APPLICATION
6) EXTRUSION PROCESS

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

22. THERMOSETS
1) COMPRESSION MOULDING

23. THERMOSETS
2) TRANSFER MOULDING

24. BONDING OF THERMOPLASTICS
Laminations:
• It is done by the applications of heat and pressure. It
consist of layers such as paper, cellulose, glass fiber etc.
• thermoplastics are bonded by the process of lamination.
• the pressure applied is 7MPa and temperature about 150
C

25. The methods of joining plastics
and composites:
 Mechanical fastening
Uses of additional parts such as metallic screws,
bolts, washers, rivets.
 Adhesive and solvent bonding
Adhesive is placed between parts to be bonded
where it serves as the material that joins the parts and
transmits the load through the joint.
 Welding or fusion bonding.

26. YoucaN

27. Friction bonding or friction
welding
 Friction welding of PVC tubes and pipes is well
developed. Prior to welding process, the ends of the
tubes are sized by heating the tube ends oil to 100 C for
3 to 4 minutes and then tube are clamped in gauge for
3 minutes followed by water cooling to room
temperature.

28. Ultrasonic welding
 Process in which mechanical vibrations of high
frequency are used. The frequency range from 15 to 20
kHz.
 Transducer which converts high frequency energy
supplied by ultrasonic oscillator into vibrations.
 It is possible to weld acetyl, nylon nd high density
polyethylene, PVC