1. MODULE 6
 OUTLINES
 Polymers
 Ceramics

2. Why Plastics?
 Plastic products can be mass-produced & require less skilled
staff.
 Light weight, high weight to strength ratio, particularly when
reinforced
 Relatively low cost compared to metals & composites
 Corrosion resistance & generally waterproof
 Plastics require little or no finishing, painting, polishing etc
 Low electrical and thermal conductivity, insulator
 Easily formed into complex shapes, can be formed, casted &
joined.
 Wide choice of appearance, colors and transparencies

3. Disadvantages of using Plastics
 Low strength
 Low useful temperature range
 Less dimensional stability over period of time (creep effect)
 Aging effect, hardens and become brittle over time
 Sensitive to environment, moisture and chemicals
 Poor machinability
 It can harm the environment when it is not being used
properly by humans

4. Additives in polymers
• To impart certain specific properties, polymers are usually
compounded with additives.
• Additives improve polymers stiffness, strength, colour,
weather ability, flammability and arc resistance for electrical
applications.
Some examples are:
1. Fillers
2. Plasticizers
3. Colorants
4. Flammability
5. Lubricants

5. Thermosetting plastics
• The molecules of thermosetting
plastics are heavily cross-linked. Cross-linked molecules
They form a rigid molecular
structure.
• The molecules in thermoplastics
sit end-to-end and side-by-side.
• Although they soften when
heated the first time, which
allows them to be shaped they
become permanently stiff and
solid and cannot be reshaped.
• Thermoplastics remain rigid and
non-flexible even at high
temperatures.

6. Thermo sets: Behavior and Properties
 During polymerization, the shape of the part is
permanently set.
 Curing is irreversible.
 Polymerization process takes place in 2 stages:
1) molecules are partially polymerized into linear
chains
2) cross-linking is completed under heat and pressure
 Strength and hardness of thermo sets are not
affected by temperatures or rates of deformation.

7. Some examples of thermo sets are:
Polyurethanes,
Vulcanized rubber
Bakelite,
Duroplast,
Urea-formaldehyde
Melamine resin
Epoxy resin
Polyamides

8. Applications---Thermo sets:
 Phenolic is commonly used for circuit boards,
automotive parts, handles for cutlery and ovens.
 Epoxy is used in automotive equipment, electrical,
sports equipment and adhesives.
 PU (Polyurethane) is used as car seats, mattresses,
cushions, diaphragms, gears, finishes and coatings.

9. Thermoplastics
Long chain molecules
• The molecules of
thermoplastics are in lines
or long chains
• The process of heating,
shaping, reheating and
reforming can be repeated
many times.

10. Some major thermoplastics are;
1. Acetals
2. Acrylics
3. Acrylonitrile-butadiene-styrene
4. Cellulosics
5. Fluorocarbons
6. Polyamides
7. Polycarbonates
8. Polyesters

11. Applications---Thermoplastics
PVC (polyvinyl chloride) is used in medical products, credit cards, cable
insulation, packaging film, bottles, flooring and window frames.
PS (polystyrene) is used in cups, plates, tape cassettes and dairy product
containers.
PP (polypropylene) is used in fibers, automotive parts, bottle crates,
battery cases and food containers.
PET (polyethylene terephthalate) is used in food packaging, carpets and
bottles.
LDPE (low density polyethylene) is used in flexible containers, cling film
and plastic bags.
HDPE (high density polyethylene) is used in toys, bottles, automotive fuel
tanks and piping.

12. Thermoplastic polymers Thermosetting polymers
(1) These soften and melt on These do not soften on heating but
heating. rather become hard in case
prolonged heating is done these
start burning.
(2) These can be remoulded recast These can not be remolded or
and reshaped. reshaped.
(3) These are less brittle and These are more brittle and
soluble in some organic solvents. insoluble in organic solvents.
(4) These are formed by addition These are formed by condensation
polymerization. polymerization.
(5) These have usually linear These have three dimensional
structures. cross linked structures.
Ex. Polyethylene, PVC, teflon. Ex. Bakelite, urea, formaldehyde,
resin.

13. Processing of Plastics
1) Extrusion
2) Injection molding
3) Structural foam molding
4) Blow molding
5) Rotational molding
6) Thermoforming
7) Compression molding
8) Transfer molding
9) Casting
10) Process of reinforced plastics

14. Ceramics
A ceramic is an inorganic, nonmetallic solid prepared by the action
of heat and subsequent cooling.
Ceramic materials may have a crystalline or partly crystalline
structure, or may be amorphous (e.g., a glass).
Ceramics now include domestic, industrial and building products ,
art objects & semiconductors
A wide-ranging group of materials whose ingredients are clays,
sand and felspar.

15. Comparison metals v ceramics
Metals Ceramics

16. Ceramics Applications:
 Refractories
 Sensors
 Capacitors
 Semiconductors
 The magnetic strip on a credit card
 Spark plug
 Cutting tools
 Die blanks
 Piston coating of Automobile engine

17. Classification of Ceramics
Ceramics
materials
abrasives Advance
glasses Clay products refractories
ceramics
Structural
glass fireclay
clay products
Glass- White ware silica
ceramic
s
basic
special

18. Based on chemical composition ceramic are classified as
oxides, carbides, nitrides, sulfides and fluorides.
 Alumina ( Al2O3)
 Graphite
 Diamond (C)
 Silica (SiO2)
 Silicon Carbide (SiC)
 Tungsten Carbide (WC)
 Titanium Carbide (TiC)
 Silicon nitride (Si3N4)
 Titanium oxide (TiO2)
 Zirconia (ZrO2)

19. Refractory Brick
Glass Containers
White ware:
Glass in
Bathrooms
Buildings

20. Automotive
Ceramic Brake Discs Components in Silicon
Carbide