Polymer processing involves converting plastic raw materials into finished products. There are primary, secondary, and tertiary processing methods. The selection of a processing method depends on factors like the product design, material properties, production quantity, and cost. Common primary methods include injection molding, extrusion, blow molding, and compression molding. The polymer properties like water absorption, physical form, thermal stability, and melt flow properties affect the suitable processing technique. Proper consideration of these factors ensures efficient processing and quality product manufacture.

1. Polymer Processing I
Introduction to Polymer Processing

2. INTRODUCTION
 Plastics – The unique class of wonder materials – came into existence by
virtue of their superior performance and cost effectiveness over to
conventional materials.
 Over the years the applications spectrum of plastics have been widened with the
advent of new generation Polymers, blend alloys and composites
 Every day newer and newer application are being promoted in all the key sectors
of Indian Economy viz. Automobiles, Agriculture, Aerospace. Building &
Construction, Infrastructure, Telecommunication, IT, Medical & Bio Medical
engineering, Packaging, etc.
 This in turn necessitates the need for different types processing methods and
machinery to produce quality plastics products at affordable cost
 Today a host of processing methods and machinery are available to manufacture
plastics products meeting stringent quality requirements

3. Definition
Plastics Processing – in a simple layman’s
language – can be defined as the process of
converting the plastic raw materials into Semi-
finished or finished products
Raw Materials
(Powder/granules)
Processing Semi-finished
or
Finished Products

4. Classification of processing methods
1. Primary Processing Methods: Injection,
Extrusion, Blow, Compression and transfer
moulding.
2. Secondary Processing Methods: Rotational
molding, Thermoforming, Coating, Casting,
Fabrication and Calendaring etc.
3. Tertiary Processing Methods: Cutting, Drilling,
Welding and Bending etc.

5. Fundamentals of processing
Performance Requirements
Engineering Approach
Practical Approach
Material Selection
Properties Process Cost/Performance
Ideal Choice

6. The process selection depends on several interrelated factors:
(1) Designing a part to meet performance and manufacturing requirements at the
lowest cost;
(2) Specifying the plastic;
(3) Specifying the manufacturing process, which requires
 Designing a tool ‘around’ the part,
 Putting the ‘Proper Performance’ fabricating process around the tool,
 Setting up necessary auxiliary equipment to interface with the main
processing machine
 Setting up ‘Completely integrated’ controls to meet the goal of zero defects;
(4) Purchasing equipments and materials, and warehousing the materials.

7. 1. Setting up specific performance requirements;
2. Evaluating material requirements and their processing capabilities;
3. Designing parts on the basis of material and processing characterstics, considereing
part complexity and size as well as a product and process cost comparison
4. Designing and manufacturing tools (Moulds, Dies, etc) to permit ease of
processing;
5. Setting up the complete line, including auxliliary equipment;
6. Testing and providing quality control, from delivery of the plastics, through
production, to the product
7. Interfacing all these parameters by using logic and experience and / or obtaining a
required update on technology.
Parameters that help one to select the right options are

8. PROCESSABILITY:
 Processability means generally the ease or difficulty with which a plastic can be
handled during its fabrication into film, moulded products, pipe, etc.
 A plastic with good processability possesses the properties necessary to make it
easy to process the plastics into desired shapes.
 The main characteristics or properties which determine a plastic’s processability
are molecular weight, uniformity, additive type and content, and plastic feed
rates.

9. PROCESSING METHODS:
 The type of process to be used depends on a variety of factors, including product
shape and size, plastic type, quantity to be produced, quality and accuracy
(Tolerances) required, design load performance, cost limitation, and time
schedule.
 Each of the processes provides different methods to produce different products.
As an example, extrusion with its many methods produces films, pipe,sheet,
profile, wire coating, etc.
 Almost all processing machines can provide useful products with relative ease, and
certain machines have the capability of manufacturing products to very tight
dimensions and performances. The coordination of plastic and machine facilities
these processes.

10. PROCESSING METHODS – An Overview:
Machine Operation Terminology
Terminology in the plastics industry regarding the operation of machinery is as
follows:
 Manual Operation
Each function and the timing of each function is controlled manually by an operator.
 Semiautomatic Operation
A machine operating semi automatically will stop after performing a complete cycle
of programmed moulding functions automatically. It will then require an operator to
start another complete cycle manually.
 Automatic Operation
A Machine operating automatically will perform a complete cycle of programmed
moulding functions repetitively; it will stop only for a malfunction on the part of the
machine or mould, or when it is manually interrupted.
Depending upon the configuration of the part, economic viability and the part
tolerance, etc the process can be selected.

11. Plastic Materials
• Thermoplastics start as regular pellets or granules
and can be re-melted.
• Thermosetting materials start as liquids/syrups,
often called "resins", as powders or partially
cured products ("preforms") which need heat for
the shaping phase. The shaping is accompanied
by a chemical reaction, which means that the
material does not soften on reheating. The
reaction may be exothermic (giving heat out), in
which case cooling is required.

12. Plastic Processing Methods
1. Extrusion
2. Injection Moulding
3. Blow Moulding and Stretched Blow Moulding
4. Thermoforming and Vacuum Forming
5. Compression Moulding
6. Transfer Moulding
7. Rotational moulding
8. Casing and Slush Moulding
9. Calendaring
10. Reaction Injection Moulding

13. Extrusion
• Widely used for continuous production of film, sheet, tube, and
other profiles;
• Types of products: Films, Pipes, Strapping, Sheets, Multilayer films,
Profiles etc.
• also used in conjunction with blow moulding.
• Thermoplastic molding compound is fed from a hopper to a screw
pump where it is heated to plasticate
• then pumped out through the shaping orifice (die) to achieve
desired cross section.
• Production lines require input and takeoff equipment that can be
complex.
• Advantages: Low tool cost, numerous complex profile shapes
possible, very rapid production rates, can apply coatings or
jacketing to core materials (Such as wire).
• Limitations: Usually limited to sections of uniform cross section.

14. EXTRUSION

16. Injection Molding
• Very widely used process
• Most versatile for Fast production
• Intricate design is possible
• High automation and robotics can be adopted
• Thermoplastic or thermoset both can be moulded
• Plastic granules or powder is heated to plasticate in cylinder at controlled
temperature, then forced under pressure through a nozzle into sprue,
runners, gates, and cavities of mould.
• The plastic or resin undergoes solidification rapidly by cooling or heating.
• The mould is opened, and the part ejected,
• Injection Moulding can be used for glass-reinforced plastic materials
• Advantages: High production runs, low labour costs, high reproducibility of
complex details, and excellent surface finish are the merits.
• Limitations: High initial tool and die costs; not economically practical for
small runs.

17. INJECTION MOULDING

19. Blow Moulding
• Used or hollow products with Neck to Bottom diameter less than
one
• Used for thermolpastics
• Types of Products: Bottles, Containers, Air ducts, Panels, Portable
toilets, Arm rests, tanks, gas tanks
• A parison or tube formed by extrusion or injection moulding
• heated parison is positioned between two halves of an open split
mould and expanded against the sides of the closed mould via air
pressure.
• The mould is opened and the part ejected.
• Advantages: Low tool and die costs, rapid production rates, and
ability to mould fairly complex hollow shapes in one piece.
• Limitations: Generally limited to hollow or tubular parts; some
versatile mould shapes, other than bottles and containers

20. Types of Blow moulding machine:
1.Extrusion Blow moulding
Extrusion Blow moulding: In extrusion blow molding (EBM), plastic is melted and
extruded into a hollow tube (a parison). This parison is then captured by closing it
into a cooled metal mold. Air is then blown into the parison, inflating it into the
shape of the hollow bottle, container or part. After the plastic has cooled
sufficiently, the mold is opened and the part is ejected.
2. Injection Blow moulding
The process of injection blow molding (IBM) is used for the production of hollow
glass and plastic objects in large quantities. The blow molding process begins with
melting down the plastic and forming it into a parison or in the case of injection.
The parison is a tube-like piece of plastic with a hole in one end through which
compressed air can pass.
3. Stretch Blow moulding
Stretch Blow moulding: In the stretch blow molding (SBM) process, the plastic is
first molded into a "preform" using the injection molding process. the preforms are
heated (typically using infrared heaters) above their glass transition temperature,
then blown using high pressure air into bottles using metal blow molds. The
preform is always stretched with a core rod as part of the process. In the single-
stage process both preform manufacture and bottle blowing are performed in the
same machine.

24. Thermoforming
• Thermoplastic sheets are used
• Heat-softened thermoplastic sheet is positioned over male
or female mould;
• air is evacuted between sheet and mould, forcing sheet to
conform to contour of mould.
• Variations are vacuum snapback, plug assist, drape
forming, etc.
• Advantages: Tooling costs are generally low, large part
production with thin sections possible, and often comes
out economical for limited part production.
• Limitations: Limited to parts of simple configuration, high
scrap, and limited number of materials from which to
choose

25. Thermoforming
• air pressure and plug assisted forming of the softened
sheet. -invariably automated and faster cycle times
• only thermoplastics sheet can be processed by this
method.
• The largest application is for Food Packaging.
• Other industries include Toiletries, Pharmaceuticals and
Electronics
• Food related applications such as Meat Trays, Microwave &
Deep Freeze Containers, Ice Cream and Margarine Tubs,
Snack Tubs, Bakery and Patisserie packaging, Sandwich
Packs and Vending Drink Cups
• Manufacturing Collation trays, Blister packaging and Point
of Sale display trays.

26. THERMOFORMING

30. Compression Moulding
• Usually Used for Thermoset compound,
• Molding powder or a preformed, is positioned in a heated mould
cavity; the mould is closed with the application of heat and
pressure the material flows and fills the mould cavity. Heat
completes polymerization and identification the part of ejected.
• Types of Products: Plugs, sockets, handles, Engine Casing switches,
cistern etc.
• Heat completes polymerization and the part is ejected. The process
is sometimes used for thermoplastics, e.g. Vinyl phonograph
records.
• Advantages: Little material waste is attainable; large, bulky parts
can be moulded; process is adaptable to rapid automation.
• Imitations: Extremely intricate parts containing undercuts, side
draws, small holes, delicate inserts, etc.; very close tolerances are
difficult to produce. Time consuming process.

31. • Advantages of compression molding (compared
with injection molding)
• -Low scrap arisings
• -Low orientation in the moldings
• -well distributed fibrous fillers
• -low residual stress product
• -retained mechanical and electrical properties
• -low mold maintenance
• -low capital and tooling costs

33. Transfer Moulding
• Widely used to produce Thermoset products with part
complexity.
• Types of Products: Plugs, Sockets, Handles, Engine Casing
Switches, Cistern etc.
• Thermoset moulding compound is fed into transfer
chamber where it is then heated to plasticate; it is then fed
by a plunger through sprues, runners, and gates into a
closed mould where it cures; mould is opened and part
ejected.
• Advantages: Good dimensional accuracy, rapid production
rate, and very intricate parts can be produced.
• Limitations:High mould cost; high material loss in sprues
and runners; size of parts is somewhat limited.

35. Rotational Molding
• A predetermined amount of powdered thermoplastic
material is poured into mould; mould is closed, heated,
and rotated in the axis of two planes until contents
have fused to the inner walls of mould; mould is then
opened and part is removed.
• Limited to hollow parts; production rates are usually
slow.

37. Casting
• Liquid plastic which is generally thermoset except for acrylics is poured
into a mould without pressure, cured, and taken from the mould.
• Cast thermoplastic films are produced via building up the material (either
in solution or hot-melt form) against a highly polished supporting surface.
• Advantages: Low mould cost, capability to form large parts with thick cross
sections, good surface finish, and convenient for low-volume production
• Liquid plastic which is generally thermoset except for acrylics is poured
into a mould without pressure, cured, and taken from the mould.
• Cast thermoplastic films are produced via building up the material (either
in solution or hot-melt form) against a highly polished supporting surface.
Low mould cost, capability to form large parts with thick cross sections,
good surface finish, and convenient for low-volume production.
• Limitations: Limited to relatively simple shapes. Most thermoplastics are
not suitable for this method. Except for cast films, method becomes
uneconomical at high volume production rates.

38. casting
• -cast hollow plastic parts with few restrictions
regarding size or complexity Very stable parts
• - no molded in stresses
• Low tooling cost for large parts
• Suited for low volume production
• Can produce complex part geometries
• Can mold in metal inserts and graphics

40. Slush Moulding
• Liquid thermoplastic material (Plastisol) is poured into
a mould to capacity; mould is closed and heated for a
predetermined time in order to achieve a specified
buildup of partially fused material on mould walls;
• mould is opened and excess material is poured out;
and semifused part is removed from mould and fully
fused in oven. Low mould costs and economical for
small production runs.
• Limitations: Limited to hollow parts; production rates
are very slow; and limited choice of materials that can
be processed

41. Calendaring
• Dough-consistent thermoplastic mass is formed
into a sheet of uniform thickness by passing it
through and over a series of heated or cooled
rolls. Calenders are also utilized to apply plastic
covering to the backs of other materials.
• Types of products: Rain boots, Shoes, Hollow
toys, Balls, large pipes and tubes etc.
• Types of Products: Luggage, Rain wear, Tank
lining, Credit cards, Trays, Helmet liner etc.

43. Reaction Injection Moulding
• RIM is a specialized subset of the injection molding technique that
chemically bonds two or more plastics into a polymer before they
are introduced into the mold.
• The most important feature of this process is the plastic
polymerization during molding which can yield properties distinct
from those of the base materials.
• RIM utilizes chemical reactions to produce stronger, tougher, more
lightweight, more complex and more customizable parts in a
significantly more cost-efficient manner than standard injection
molding
• RIM can also fabricate large parts with complex shapes, making it
well-suited for industrial applications that require bulky
components.
• Likewise, issues of cost-efficiency, production cycle rates, and
machinery design can influence the decision to employ this
technique.

45. Effect of polymer properties on Process Technique

46. CORPORATE TRAINING AND
PLANNING
1.6 EFFECT OF POLYMER PROPERTIES ON PROCESS TECHNIQUE
(1) Water absorption of Raw materials,
(2) Physical form of raw material,
(3) Thermal stability of polymer,
(4) Flow properties,
(5) Adhesion of melt to metal,
(6) Thermal properties affecting, Heating and cooling of melt,
(7) Compressibility and shrinkage,
(8) Frozen in Orientation.
When processing thermoplastic melts the following factors should be taken into
account in order both to process efficiently and obtain quality products.

47. Water / Moisture is the greatest enemy for processing of plastics.
 Hygroscopic Materials
 Absorption phenomena - Ex: Nylon, POM, PC.
 Adsorption phenomena - Ex: HIPS, PS, ABS.
 All these materials should be pre-dried.
 Non-Hygroscopic material - Ex: PVC, Polyolefins, etc.
 Need not be predried. Except when completely wet during monsoon.
WATER ABSORPTION

48. CORPORATE TRAINING AND
PLANNING
Actions Necessary
1. Use granules as soon as the bag is opened.
2. Pre-drying ovens, Hopper drier, Dehumidifying drier can be used.
3. For PC - Dehumidifying drier preferable
Physical form of Raw Material
 Powder form, granular form, lumpy/slab form
 Slab Form - Calendering,Compression Moulding
 Granular Form – Preferred - Uniform pellet size ensures even and faster feeding.
 Powder Form - Difficulty in feeding - But savings in cost because of the ability to
avoid pelleting stage - Special feeder attachment essential to ensure proper feeding.

49. Thermal stability of polymers
 PVC thermally sensitive material - Little higher melt temp. may lead to depredation - HCL is
released - This can leads to corrosion and harmful to human being. PID Temperature
controller can be used.
 PMMA, POM upon depredation liberates MMA & formaldehyde respectively - MMA volatilize
and cause bubbles - Formaldehyde gas causes “eye-irritation”.
 PVC & POM (acetal) should never be processed one after the other. This may lead to
explosion
Adhesion of melt to metal:
 Wetting of the polymer melt against the metal wall of processing equipment can
lead to strong adhesion of polymer to metal. Ex: difficulty in removing PVC - Mix
from two roll mill.
 PC has a strong adhesion to metal. It can take away the skin of the barrel if not
properly purged

50. THERMAL PROPERTIES AFFECTING HEATING AND COOLING
In the case of polymer melts the specific heat varies with temperature. For crystalline
polymers such as POM, NYLON etc. latent heat of fusion and sp.heat should be taken in to
account. i.e Total heat content (Enthalpy) =LH of fusion + sp.heat.
POLYMER PROCESS TEMP 0C ENTHALPY / KJ / KG
PS 200 310
LDPE 200 500
HDPE 260 810
PP 260 670
Because of higher enthalpy PP requires more cooling time than LDPE and PS.

51. COOLING SHRINKAGE AND COMPRESSIBILITY
When polymers are in molten stage the vibrations of the molecules results in the polymer
chain being pushed apart so that the volume occupied by a given polymer mass is higher
than when the material is solid.
POLYMER
DENSITY AT 20
C(G/CC)
DENSITY AT PROCESS
TEMP (G/CC)
LDPE 0.923 0.746(210c)
PP 0.905 0.765(210c)
PMMA 1.180 1.105(210c)
SPVC 1.48 1.390(190c)
Because polymer melts are compressible moulding shrinkage is much less than the above
fig.

52. FROZEN-IN ORIENTATION
 When polymer melts are being shaped by either injection moulding or Extrusion
the long polymer chains tend to be elongated or uncoiled in the direction of flow.
 After shaping, the melt is usually cooled rapidly and there is seldom time for the
oriented molecules to return to a random coiled shape by the process known as
relaxation.
 Some orientation is thus “Frozen-in” the product. Such stressed parts are very
weak. Hence annealing is must.

53. PROCESS SELECTION CRITERIA FOR PLASITC PRODUCTS
Introduction:
With the advent of New Generation Polymers, blends alloys and composites,
over the last decade, the application spectrum of plastics has been widened.
Today with the result, the plastics have penetrated deeply in all the key sectors
of economy which includes
Automobiles Telecommunication
Aerospace Defence
Biomedical Building & Construction etc
In the liberalized economy the survival of plastic industries largely depends
upon timely delivery, quality, cost and cost / performance balance of plastics
products.

54. Process Selection Criteria
The following parameters play a key role in selecting the best suited process
to produce a specific product for a specific application.
1. Material Processibility - Limitations
2. Volume of production
3. Size & shape of the product (configuration)
4. Cost to performance balance
5. Quality

55. Material Processibility Limitations
If a specific material is suitable for a particular application, then material
processibility will decide the specific method of Processing / Production.
Case :1
Product : PET bottle
Process : Blow Moulding
Specific process : Injection stretch Blow moulding
Not possible by : Extrusion Blow moulding or Extrusion Stretch blow
moulding
Reason:
PET material used today does not have the required hot melt strength to
hold/self support a parison.

56. Case: 2
Product : PTFE sheets
Process : Compression moulding following by sintering process.-The sintered
sheets are subsequently machined to the required dimension.
Other Conventional Process:
Extrusion - Not possible.
Reason:
PTFE exhibits - very high melt viscosity above its melting temperature. Hence only best
suited process is compression moulding followed by sintering.

57. Configuration of Product
- Size & shape governs the process selection.
Case 1:
Narrow neck containers like Shampoo bottles, Pharmaceutical
containers, soft drink bottles will have to be produced by Blow moulding only.
Case 2:
Hollow containers such as Tanks (20,000ltrs) will have to be produced by
Roto moulding inspite of higher initial cost on plant & machinery.

58. Case 3:
Product : FRP Boat
Raw materials : Fiber glass material, Polyester resin and other
additives
Process : 1. Hand lay-up 2. Spray up
Most suitable process:
If volume of production is less then hand lay up. If more then spray up
technique. Spray up technique calls for higher initial investment.

59. Quality
Mainly due to quality reasons, in spite of higher cost of manufacture, certain products
are produced by a specific process only.
Case:1
PVC – sheets by calendaring
Reason: Stress-free moulding
Case:2
Product: PP Blown film
Process: Only downward extrusion process should be used instead of upward blown
film process.
Reason:
PP, being a crystalline polymer,in order to get transparency, the film emerging out of
die lips needs to be quenched.The best /economical way of quenching is to dip in
water which is possible only in downward extrusion. So due to quality reason this
process is selected.

60. Sl.
No.
Parameter Casting Extrusion
1. Mechanical Properties Lower Higher
2. Optical properties High Low
3. Initial investment Low High
4. Stress built-up
Almost stress
free
Stress built-up
due to
orientation.
Since optical properties are very essential based on cost/performance & quality casting
process is best.

62. CORPORATE TRAINING AND
PLANNING
Cost / Performance Balance
If more than one process is suitable for producing a product based on performance,
then cost plays a crucial role in process selection.
Case: 1
Product : 200 litres chemical container
Material : HDPE
Process : 1. Blow Moulding 2. Roto Moulding

63. CORPORATE TRAINING AND
PLANNING
Case - 2
Product : FRP pipe
Material : Glass fiber, Polyester resin & other additives
Process : 1. Limited lengths & high strengths - Filament winding
2. Continuous lengths & high strength - pultrusion
3. Centrifugal casting - Batch process
If medium strength and relatively stress free pipes are required with better
optical properties, then centrifugal casting is the best method.

64. CORPORATE TRAINING AND
PLANNING
Case: 3
Product : PVC Flexible sheet
Material : Compounded PVC with additives such as plasticizer, stabilizer,
colourants etc.
Process : 1. Calendering 2. Extrusion
Suitable process : Calendering
Reason : Wider width, cost effectiveness
Case: 4
Product : Acrylic sheet
Material : PMMA
Process : 1. Casting 2. Extrusion