Plastic is any of a wide range of synthetic or semi-synthetic materials that are mouldable. There are two main types of plastics: thermoplastics, which soften when heated and harden when cooled, and can be remoulded, and thermosets, which set into a rigid or non-melting shape after heating and cannot be remoulded. Common plastics include polyethylene, polyvinyl chloride, polystyrene, nylon, and polycarbonate. Plastics are formed into objects using various moulding processes like injection moulding, blow moulding, and rotational moulding. Injection moulding is the most common method and involves melting plastic and
2. Definition :-
The word plastic is derived from
the Greek word “plastikos”
meaning capable of being shaped or
moulded. A plastic material is any of a
wide range of synthetic or semi-
synthetic organic solids that
are mouldable.
Plastic are organic polymers of
high molecular mass.
3. Classification Of Plastics :-
Thermoplastic Polymer :- Thermoplastics are the
plastics that do not undergo chemical change in
their composition when heated and can be moulded
again and again. Eg :-
polyethylene, polypropylene, polystyrene, polyvinyl
chloride, and polytetrafluoroethylene (PTFE)
Thermosetting Polymer :- Thermosets can melt
and take shape once, after they have solidified, they
stay solid. In the thermosetting process, a chemical
reaction occurs that is irreversible.
4. Common Plastics :-
• Application :- Fibers, textiles.
• Properties :-
1)It is wrinkle free.
2)It is easy to launder.
3)It dries quickly.
4)It is resistant to stretching and shrinking.
Polyester (PES)
• Application :- Carbonated drinks bottles, peanut
butter jars, plastic film, microwavable packaging.
• Properties :-
• Good gas barrier properties
• Good chemical resistance
• Low moisture absorption
• Food compatible
Polyethylene
terephthalate (PET)
5. Common Plastics Cont.. 1 :-
•Application :- Wide range of inexpensive uses
including supermarket bags, plastic bottles.
•Properties :-
•High impact strength
•High heat resistant
•Excellent weather ability
•Excellent chemical resistance
Polyethylene (PE)
•Application :- Detergent bottles, milk jugs, and
moulded plastic cases, luggage.
•Properties :-
•Low cost
•Impact resistant from -40 C to 90 C
•Moisture resistance
•Good chemical resistance
•Food grades available
High-density
polyethylene (HDPE)
6. Common Plastics Cont.. 2 :-
•Application :- Outdoor furniture, siding, floor tiles, shower
curtains, clamshell packaging.
•Properties :-
•Low cost
•Impact resistant from -40 C to 90 C
•Moisture resistance
•Good chemical resistance
•Food grades available
Low-density
polyethylene (LDPE)
•Application :- Plumbing pipes and guttering, shower
curtains, window frames, flooring.
•Properties :-
•Weathering stability. PVC is resistant to aggressive environmental
factors g.
•Longevity. PVC products can last up to 100 years and even more..
•Barrier properties. PVC can be made impervious to liquids, vapours
and gases.
Polyvinyl
chloride (PVC)
7. Common Plastics Cont.. 3 :-
•Application :- Bottle caps, drinking straws, yogurt
containers, appliances, car fenders (bumpers), plastic
pressure pipe systems.
•Properties:-
•High chemical and corrosion resistance
•Light weight and rigid
•Easy to maintain and clean
•High tensile strength
•Low moisture absorption
•Long life span
Polypropylene (PP)
•Application :- Packaging foam/"peanuts", food
containers, plastic tableware, disposable
cups, plates, cutlery, CD and cassette boxes.
•Properties :-
•High Impact Resistance
•Flame Retardant
•High Heat Resistance
•Expandable
Polystyrene (PS)
8. Common Plastics Cont.. 4 :-
•Application :- Refrigerator liners, food packaging,
vending cups.
•Properties :-
•Good impact resistance
•High dimensional stability
•Easy to paint and glue.
High impact
polystyrene (HIPS)
•Application :- Fibers, toothbrush bristles, tubing, fishing
line, low strength machine parts: under-the-hood car
engine parts or gun frames.
•Properties:-
•Flame Retardant
•Good Dimensional Stability
•High Strength
•High Heat Resistance
•Good Wear Resistance
Polyamides (PA)
(Nylons)
9. Common Plastics Cont.. 5 :-
•Application :- Electronic equipment cases (e.g.,
computer monitors, printers, keyboards), drainage pipe.
•Properties:-
•Dimensionally stable
•Good strength, impact and toughness properties
•Good resistance to abrasion and chemicals
Acrylonitrile butadiene
styrene (ABS)
•Application :- A slippery blend of PE and ABS used in
low-duty dry bearings.
•Properties:-
•Impact resistance and toughness
•ABS is flammable when it is exposed to high
temperatures
•light weight
•shock absorbance
Polyethylene/Acrylonitrile
Butadiene Styrene
(PE/ABS)
10. Common Plastics Cont.. 6 :-
•Application :- Compact discs, eyeglasses, riot shields, security
windows, traffic lights, lenses.
•Properties :-
•Heat and cold resistance
•Can adapt to all kinds of bad weather change from cold to hot, at-
40 ° c to + 120 ° c
•UV-resistant, anti-aging
•80 times the impact strength of glass
Polycarbonate (PC)
•Application :- A blend of PC and ABS that creates a stronger
plastic. Used in car interior and exterior parts, and mobile
phone bodies.
•Properties :-
•High gloss surface finish
•Low moisture absorption
•High tensile strength
•High dimensional stability
•Excellent impact properties, even at low temperature
•Flame retardant.
Polycarbonate/Acrylonitrile
Butadiene Styrene (PC/ABS)
11. Common Plastics Cont.. 7 :-
•Application :- Cushioning foams, thermal
insulation foams, surface coatings, printing rollers.
•Properties :-
•Load bearing capacity
•High tear resistant
•Weather resistant
•Excellent noise abatement properties
•Good Heat and cold resistant
Polyurethanes (PU)
•Application :- Food packaging.
•Properties:-
•High levels of transparency
•Excellent barrier qualities extend the shelf life and
conservation of foods
•Outstanding heat sealing properties
•Highly flexible
Polyvinylidene
chloride (PVDC)
(Saran)
12. Thermosetting Plastics :-
• Applications: Electrical components requiring
strength, tools and dies, fiber reinforced epoxies
are used in structural components, tanks, pressure
vessels, rocket motor casing
• Properties:
• Good dimensional stability
• Excellent mechanical and electrical properties
• Good resistance to heat and chemicals.
Epoxies
• Applications: Laminated panels, handles, knobs,
electrical components; connectors, insulators.
• Properties: Good dimensional stability
• Rigid
• High resistance to heat, water, electricity, and
chemicals.
Phenolics
13. Thermosetting Plastics Cont.. 1 :-
• Applications: Electrical
components requiring
strength at high
temp., waterproof
materials, heat seals
• Properties:
• Excellent electrical
properties over a wide
rang of temperature and
humidity
• Good heat and chemical
properties.
Silicones
14. Additives Used In Plastic :-
Additives are added to polymers in order to obtain or improve certain
properties such as strength, stiffness, color, resistance to weather and
flammability.
Plasticizers are added to obtain flexibility and softness, most common use
of plasticizers are in PVC.
Fillers such as fine saw dust, silica flour, calcium carbide are added to
reduce the cost and to increase
harness, strength, toughness, dimensional stability.
Colorants are added to obtain a variety of colors. Colorants are either
organic (dye) or inorganic (pigments). Pigments provide greater
resistance to temperature and sunlight.
Flame retardants such as chlorine, phosphorus and bromine, are added to
reduce polymer flammability. Teflon does not burn and nylon and vinyl
chloride are self-extinguishing
15. Types Of Moulding :-
Blow moulding
Compaction plus sintering
Compression moulding
Expandable bead moulding
Extrusion moulding
Foam moulding
Injection moulding
•Reaction injection mouldingLaminating
Matched mould
Matrix moulding
Plastic moulding
Pressure plug assist moulding
Rotational moulding (or Roto moulding)
Transfer moulding
•Vacuum forming, a simplified version of thermoformingThermoforming
Vacuum plug assist moulding
16. Injection Moulding :-
Injection moulding is
a manufacturing process for producing
parts by injecting material into a mould.
Material for the part is fed into a heated
barrel, mixed, and forced into a mould
cavity where it cools and hardens to the
configuration of the cavity.
18. Injection Process :-
Granular plastic is fed by gravity from a
hopper into a heated barrel.
Granules are slowly moved forward by a
screw-type plunger.
Plastic is forced into a heated chamber,
where it is melted.
Plunger advances, and the melted plastic is
forced through a nozzle that rests against
the mould, allowing it to enter the mould
cavity through a gate and runner system.
19. Types Of Injection Moulding
Process :-
Metal injection moulding
Thin-wall injection moulding
Injection moulding of liquid silicone rubber
Die casting
20. Application :-
Injection moulding is used to create many bottle caps, automotive
dashboards, pocket combs, some musical instruments (and parts of
them), one-piece chairs and small tables, storage containers, mechanical
parts (including gears), and most other plastic products available today.
Injection moulding is the most common modern method of part
manufacturing, it is ideal for producing high volumes of the same object.
21. Blow Moulding :-
Blow moulding is a manufacturing
process by which hollow plastic parts are
formed. In general, there are three main
types of blow moulding:
i. Extrusion blow moulding
ii. Injection blow moulding
iii. Stretch blow moulding.
22. How It Works ?
In blow molding a tube is extruded and clamped in a split mold. Air
under pressure (50-100 psi) is injected into the tube blowing the
plastic outward to fill the mold cavity.
26. Process :-
Preparing the Mould :- A pre-determined amount of polymer powder is
placed in the mould. With the powder loaded, the mould is closed, locked
and loaded into the oven. The powder can be pre-compounded to the
desired colour.
Heating & Fusion :- Once inside the oven, the mould is rotated around
two axis, tumbling the powder .The ovens are heated by convection,
conduction and, in some cases, radiation. As the mould becomes hotter
the powder begins to melt and stick to the inner walls of the mould. As the
powder melts, it gradually builds up an even coating over the entire
surface.
Cooling :- When the melt has been consolidated to the desired level, the
mould is cooled either by air, water or a combination of both. The polymer
solidifies to the desired shape.
Unloading/Demoulding :- When the polymer has cooled sufficiently to
retain its shape and be easily handled, the mould is opened and the
product removed. At this point powder can once again be placed in the
mould and the cycle repeated.
27. Advantages :-
Molds are relatively inexpensive.
Rotational molding machines are much less
expensive than other type of plastic processing
equipment.
Different parts can be molded at the same time.
Very large hollow parts can be made.
Parts are stress free.
Very little scrap is produced
