Production Technology

1. PLASTIC MOULDING PROCESSES

2. PLASTICS : -
 Plastic is a material consisting of any of a wide
range of synthetic or semi-synthetic organic that are
malleable and can be moulded into solid objects of
diverseshapes.
 Plastics are typically organic polymers of high
molecular mass, but they often contain other
substances.
 They are usually synthetic, most
commonly derived from
petrochemicals.

3. TYPES OF PLASTIC : -
1. THERMOSETTING PLASTIC: -
The molecules of thermosetting plastics areheavily
cross-linked. They form a rigidmolecular
structure.
Although they soften when heated the first time,
which allows them to be shaped they become
permanently stiff and solid and cannot be
reshaped.
 Ex. Polyester resin and ureaformaldehyde
Cross-linked molecules
Contd.

4. 2. THERMOPLASTIC: -
 Thermoplastics can be heated and reshaped
becauseof the ways in which the molecules are
joined together.
 The molecules of thermoplastics are in linesor
long chains with very fewentanglements.
 When heat is applied the molecules moveapart,
which increases the distance between them,
causing them to become untangled. This allows
them to becomesoftwhen heated so that theycan
be bent into all sortsof shapes.
 Ex. Polyvinyl chlorides(PVC), Nylons, etc.
Contd.
individual monomer molecule

5. PROCESSING OF PLASTICS: -
1. Compression moulding
2. Transfer moulding
3. Injection moulding
4.Extrusion moulding
5. Blow moulding
6.Calendaring
7. Thermoforming
8.Rotational moulding
9.Laminating

6. 1. COMPRESSION MOULDING : -
Compression moulding is the forming process.
Compression moulding process is followed by two step first
one preheating and pressurizing.
Measured charge of compound placed between halves of
splitmold
Pressure is applied so that compound flows to fill mold
cavity
 Compression moulding is generally used for
thermosettingplastic.
 Example:- urea formaldehyde and phenolformaldehyde.

7. PROCESS DESCRIPTION

8. PARAMETERS : -
Thequantityof charge ( moulding material ) put into the mould.
 Pressure of the moulding process:-
Range of pressure ( 13.8-20.7 mpa).
Mould temperature:-
Temperaturerange ( 149⁰C- 191⁰C )
Cure timevariables:-
The period required to harden thermosetting material to partial and complete
polymerization is called cure time. Cure times typically range from 1 - 5 min

9. 2. TRANSFER MOLDINGS : -
 It is similar to compressionmoulding.
 Thermoset polymers can be formed when a preset
amountof material is placed in a
separate cavity andheated.
 A plungermoves the material into theshaped
mould with high pressure.

10. 3. INJECTION MOULDING : -
It isa manufacturing technique for making parts from
thermoplastic and thermoset materials.
Injection moulding is a highly automated productionprocess
for producing large quantities of identicalitems.
A measured amountof molten thermoplastic is driven bya
ram pasta heating system into the mould.
The mould is split toallow finished object to be removed after
cooling.
Example : - Polystyrene, Nylon, Polypropylene, PVC,
Acrylonitrile Butadiene Styrene

12. PROCESS : -
contains a rotatingscrew.
material.
barrel.
 Plastic powderare fed from a hopper intoa hollow steel barrel which
 The barrel is surrounded bya jacketof heaterswhich melt the plastic
 The screw is forced back as the melted plasticcollects at theend of the
 Once a sufficient charge of melted plastic has accumulated a hydraulic
ram forces the screw forward injecting the thermoplastic through a sprue
into the mouldcavity.
 Thisone is capable of exerting forces of up to 250 tonnes.
 Pressure is kepton the mould until the plastic has cooled sufficiently for
the mould to beopened and thecomponent ejected.

14. 4. EXTRUSION MOULDING: -
 Continuous process used to produce both solid and hollow products that havea
constantcross-section.
 Ex: - Window frames, hose pipe, curtain track, gardentrellis.
 Thermoplasticgranulesare fed froma hopper by a rotating screw through a heated
cylinder.
 The tapered screw compacts the plasticas it becomeselasticised. Thediewhich is fitted to
the end of theextruder barrel determines the cross-section of the extrusion.
 Thicker cross-sections are extruded more slowly as more time is required for the initial
heating and subsequent cooling of the larger quantities of material which are involved.
 As the extrusion leaves the die itis cooled by passing through a coolingtrough
containing cold water.

16. 5. BLOW MOULDING:-
 Blow Moulding is an automated process that is used extensively to make
bottles and other lightweight, hollow parts from thermoplastic materials.
 A hollow length of plastic, called a parison, is extruded down betweenthe
two halves of the mould.
 The mould closes
 Compressed air is blown into the inside of the parison which inflates it,
pushing thesoft plastic hard against thecold surfaces of the mould.
 The mould is then opened the moulding ejected and the waste (called
flash) is trimmed off with aknife.
 Example : - high density polytheneand lowdensitypolytheneare used.

17. 1. 2.
3. 4.

19. Blow Moulding Process
Extrusion
Blow
Moulding
Injection
Blow
Moulding
Stretch Blow
Moulding

20. 6. CALENDARING : -
 It is a intermediateprocess where theextruded plasticsectionsare reduced to sheet.
 Only used forthermoplastics.
 Involves rolling outa massof premixed plastics material between large rollers to form a
continuous and accurately sized film.
 The process beginswith the ingredients being blended and fluxed in a mixing mill
at approx. 100°c.
 Nip rollers control the thicknessof the sheet material can begradually reduced in thickness.
 Rolls of semi-rigid PVC which will be used to manufacture transparentA4 folder

21. Example: -
1. Flexible PVC :- Rainwear, Shower curtains, Tapes,etc.
2. Rigid PVC: - Credit cards, Lamination

22. 7. THERMOFORMING: -
 Process used to shape thermoplasticsheet intodiscrete parts.
 Basic principles: -
i. Heata thermoplasticsheet until it softens.
ii. Force the hot and pliable material against thecontoursof a mold by using
eithermechanical, airorvacuum pressure
iii.Held against mold and allow to cool, and plastics retains its shape
 This can bedone by: -vacuum and pressure forming.
 Lower pressures are required tothermoform.

24. 8. ROTATIONAL MOULDING : -
 Rotational moulding is a process used forproducing hollow plasticproducts.Such
as road conesand storage tanks up to 3m³ capacity.
 A measured weightof thermoplastic is placed insideacold mould.
 Heated toa temperatureof 230-400⁰Cwhilst being rotated around both vertical
and horizontal axes.
 The mould moves intoacooling area orchamberwhere it is cooled by airor
water jets.
 The hollow moulding can be removed as soon as it is cool enough to hold its
shape.

25. The rotational molding (roto-molding
or roto- casting) process.Trash cans,
buckets, and plastic footballs can be
made by this process.
90% of rotational mouldings are made
from polyethylene

26. 9. LAMINATING: -
 Layersof materialsare bonded with a resin intoa strong solid structure, often
with heat andpressure.
 This can be done in followingways: -
 Gravurecoating
 Wet bond laminating
 Dry bond laminating
 Solvent less laminating
 Extrusion laminating
 Example: -Snack food bag, Saran- coated nylon, Metallized propylene,etc.

27. Substrate A
Extrusion die
Substrate B
Strip-off roll
Nip roll
Extrudate
Pressure
roll
Three ply
laminate
Extrusion laminating Dry bond laminating
Gravurecoating

28. Rotational Moulding