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• A plastic material is any of a wide range of synthetic or semi-
synthetic organic solids that are mouldable.
• Plastics are typically organic polymers of high molecular
mass, but they often contain other substances.
• They are usually synthetic, most commonly derived from
petrochemicals, but many are partially natural.
• Synthetic resigns may be phenol, formaldehyde, cellulose
vinyl, alkyl, etc. The moulding compounds are catalysts,
fillers, hardeners, lubricants, pigments, plasticizers, solvents,
• POLYMERIZATION: The simplest substances consisting of one
primary chemical are known as the monomers or monoliths. They
are to be combined or synthesized to form polymers by the process
known as the polymerization.
• POLYMER : The word polymer literally means “ many parts “. A
polymeric solid material may be considered as to be one that
contains many chemically bonded parts or units which themselves
are bonded together to form a solid.
• Two industrially important polymeric materials are:
• Plastics are a large and varied group of synthetic materials which
are processed by forming or molding into shape. Just as we have
many types of metals such as aluminium and copper, we have
many types of plastics such as polyethylene and nylon.
• Plastics can be divided into two classes.
1. Thermo plastics
2. Thermo setting plastics,
depending on how they are structurally and
• Thermo plastics: These plastics can be softened by heating and hardened
by cooling any number of times without changing the properties of the
• It is thus possible to shape and reshape these plastics by means of heat and
• One important advantage of this variety of plastics is that scrap obtained
from old and warnout articles can be effectively used again.
• Properties :
1. Softens and liquefies on heating and hardens up to cooling.
2. Retains shape after manufacture.
3. Suitable for recycling.
4. Can be reshaped by heat.
5. It may melt before passing to a gaseous state.
6. Allow plastic deformation when it is heated.
7. They are soluble in certain solvents.
8. Swell in the presence of certain solvents.
• Examples and applications of thermoplastic plastic materials:
1. High pressure polyethylene as applied to rigid material covered
with electrical machines, tubes, etc...
2. Low pressure polyethylene elastic material used for insulation of
electrical cables, etc...
3. Polystyrene applied for electrical insulation, handles of tools...
4. Polyamide used for making ropes, belts, etc...
5. PVC or polyvinyl chloride for the manufacture of insulation
materials, pipes, containers, etc.
• Examples of thermoplastic adhesives:
3. Epoxy cured by ultraviolet radiation
4. Acrylates cured by ultraviolet radiation
• THERMO PLASTIC MATERIALS :
1. Polyvinyl chloride ( P V C )
PROPERTIES : Rigid , tough , elastic to feel.
Uses : Plumbing pipes and sanitary fittings are manufactured out of this
material. Shower curtains , window frames, flooring , corrugated roofing
sheets , plastic coating to steel sheets tanks, water cisterns, etc.
2. Acrylic :
PROPERTIES: Glass clear , some what brittle sound when tapped.
Uses : Glazing , bath rooms and sinks.
3. Polyethylene ( or polythene ) – low density:
PROPERTIES: Flexible, feels like paraffin wax.
Uses ; bottles, buckets, sheeting water tanks.
4. Polyethylene ( or polythene )- high density :
PROPERTIES: stiff and hard, coarser than the polythylene of low density
used as large storage bottles, water tank.
5. Polypropylene :
PROPERTIES : smooth, rigid, lightest of all plastics – it floats in water.
Uses : wc cisterns, sink traps, washing machine bids, food containers,
appliances , car fender.
6. Polystyrene : Solid ( glassy ) state at room temperature, but flows if heated
above its glass transition temperature and becoming solid again when
cooling off. Pure solid polystryrene is a colourless, hard plastic with
limited flexibility. Polysterene can be transparent or can be made to take
on various colours.
Uses : Refrigerator containers , food trays, packaging, food containers,
disposable cups, plates, cutlery, CD and cassette boxes.
7. Nylon : PROPERTIES : High density polythene but smoother to feel.
Uses : Textiles , brush bristles, carpeting , surgical trays , bearings ,
• These plastics are either originally soft or liquid or they soften once
upon heating, they harden permanently.
• When they are heated in the temperature of 127 degree centigrade to
177 degree centigrade , they set permanently and further application
of heat does not alter their form of soften them.
• But at temperature of about 343 degree centigrade, the charring
occurs. The thermo setting plastics are durable, strong and hard.
• They are available in a variety of beautiful colours.
• They are mainly used in engineering applications of plastics.
• Properties :
1. Permanently hard on heating above a certain temperature.
2. Undergoes chemical changes during manufacture.
3. Cannot be melted and reshaped.
4. Little potential for recycling.
• Examples and uses:
1. Polyester fibreglass systems: sheet molding compounds and bulk molding
2. Polyurethanes: insulating foams, mattresses, coatings, adhesives, car parts, print
rollers, shoe soles, flooring, synthetic fibers, etc. Polyurethane polymers are formed
by combining two bi- or higher functional monomers/oligomers.
3. Vulcanized rubber
4. Bakelite, a phenol-formaldehyde resin used in electrical insulators and plasticware
5. Urea-formaldehyde foam used in plywood, particleboard and medium-density
6. Melamine resin used on worktop surfaces.
7. Epoxy resin used as the matrix component in many fiber reinforced plastics such as
glass-reinforced plastic and graphite-reinforced plastic)
• THERMOSETTING PLASTIC MATERIALS
1. Melamine formaldehyde ( formica ):
PROPERTIES : Hardest of common plastics , heat resistant.
2. Phenolics ( bakelite ) :
PROPERTIES : The cheapest. Heavy solid plastic material, fishy smell
when burnt dark in color. Heat resistant.
Uses : Bottle caps, plastic automobile parts, bonding plywood and chip
board, glues, laminates with other materials.
3. Urea formaldehyde :
PROPERTIES : Similar to phenolic but can be produced in lighter
Uses : Door furniture, light switches, and electrical fittings, glues,
bottoms, radio cabinets, etc.
PROPERTIES: Resin and hardener.
Uses: Used as adhesives.
5. Polyesters :
PROPERTIES: produced as fibres and films.
Uses ; Used for reinforced plastics.
TO STRUCTURE OF ATOMS
According to this classification , the plastics are divided into 2 groups.
• HOMOGENEOUS PLASTICS : This variety of plastic contains
carbon chain ie, the plastics of this group are composed of carbon
atoms only and they exhibit homogeneous structure.
• HETEROGENEOUS PLASTICS : This variety of plastic is
composed of the chain containing carbon and oxygen, the nitrogen
and other elements and they exhibit heterogeneous structure.
Physical and mechanical
• According to this classification, plastics are divided into four groups.
1. Rigid plastics
2. Semi –rigid plastics
3. Soft plastics
• RIGID PLASTICS : These plastics have high modulus of elasticity and they retain
their shape under exterior stresses applied at normal or moderately increased
• SEMI- RIGID PLASTICS: These plastics have a medium modulus of elasticity and
the elongation under pressure completely disappears, when pressure is removed.
• SOFT PLASTICS: These plastics have a low modulus of elasticity and the
elongation under disappears slowly, when pressure is removed.
• ELASTOMERS : These plastics are soft and elastic materials with a low modulous
of elasticity. They deform considerably under load at room temperature and return
to their original shape, when the load is released. The extension can range up to ten
times their original dimensions.
PROPERTIES OF PLASTICS
The following properties are common with most of the plastics.
1.They are light in weight.
2. They have good resistance to most of the chemical.
3. They have high electrical strength.
4. They have good corrossive resistance.
5. Plastics can be moulded to any desired shape and size.
6. They can be made transperent or color.
7. They are cheap compared to metals.
8. All operations like drilling ,sawing, punching can be done on
9. Painting and polishing is not necessary.
10. The plastics posses excellent electric insulating properties.
11. The plastics, have low specific gravity, the average being 1.3 to
• Polyvinyl chloride, commonly abbreviated PVC, is the
third-most widely produced plastic, after polyethylene
• PVC is used in construction because it is more effective
than traditional materials such as copper, iron or wood
in pipe and profile applications.
• It can be made softer and more flexible by the addition
of plasticizers, the most widely used being phthalates.
• In this form, it is also used in clothing and upholstery,
electrical cable insulation, inflatable products and many
applications in which it replaces rubber.
PVC's relatively low cost, biological and chemical resistance and workability have
resulted in it being used for a wide variety of applications.
1. It is used for sewerage pipes and other pipe applications where cost or
vulnerability to corrosion limit the use of metal.
2. With the addition of impact modifiers and stabilizers, it has become a popular
material for window and door frames.
3. By adding plasticizers, it can become flexible enough to be used in cabling
applications as a wire insulator.
4. The material comes in a range of colors and finishes, including a photo-
effect wood finish, and is used as a substitute for painted wood, mostly for
window frames and sills when installing double glazing in new buildings,
or to replace older single-glazed windows.
5. Other uses include fascia, and siding or weatherboarding.
6. This material has almost entirely replaced the use of cast iron for
plumbing and drainage, being used for waste pipes, drainpipes, gutters
7. uPVC does not contain phthalates, since those are only added to flexible
PVC, nor does it contain BPA. uPVC is known as having strong resistance
against chemicals, sunlight, and oxidation from water.
• In the plastics industry most acrylics are polymers of methyl
• Acrylics may be in the form of molding powders or casting
syrups, and are noted for their exceptional clarity and
• Acrylics are widely used in lighting fixtures because they
are slow-burning or even self-extinguishing, and they do not
produce harmful smoke or gases in the presence of flame.
• The most important properties for acrylic (PMMA) are its
optical clarity, low UV sensitivity, and overall weather
resistance. Acrylic is often used as a glass substitute.
1. Transparent glass substitute.
2. Acrylic paint essentially consists of PMMA suspended in water;
however since PMMA is hydrophobic, a substance with both
hydrophobic and hydrophilic groups needs to be added to facilitate
3. Laser cut acrylic panels have been used to redirect sunlight into a
light pipe or tubular skylight and, from there, to spread it into a
4. panels have been commercialized for purposes of day lighting, to
be used as a window or a canopy such that sunlight descending
from the sky is directed to the ceiling or into the room rather than
to the floor. This can lead to a higher illumination of the back part
of a room, in particular when combined with a white ceiling, while
having a slight impact on the view to the outside compared to
• Plastic film/Polymer film is a thin continuous
polymeric material. Thicker plastic material is often
called a “sheet”.
• These thin plastic membranes are used to separate areas
or volumes, to hold items, to act as barriers, or as
• Plastic films are used in a wide variety of applications.
• These include: packaging, plastic bags, labels, building
construction, landscaping, electrical fabrication,
photographic film, film stock for movies, video tape,
FIBRE REINFORCED PLASTIC
• Fibre-reinforced plastic (FRP) (also fibre-reinforced polymer) is a
composite material made of a polymer matrix reinforced with fibres.
• The fibres are usually glass, carbon, basalt or agamid, although
other fibres such as paper or wood or asbestos have been sometimes
• The polymer is usually an epoxy, vinylester or polyester
thermosetting plastic, and phenol formaldehyde resins are still in
• FRPs are commonly used in the aerospace, automotive, marine, and
• FRPs have been used widely in the design of new construction.
Structures such as bridges and columns built completely out of FRP
composites have demonstrated exceptional durability, and effective
resistance to effects of environmental exposure.
• Pre-stressing tendons, reinforcing bars, grid reinforcement , and
dowels are all examples of the many diverse applications of FRP in
• One of the most common uses for FRP involves the repair and
rehabilitation of damaged or deteriorating structures.
• Several companies across the world are beginning to wrap damaged
bridge piers to prevent collapse and steel-reinforced columns to
improve the structural integrity and to prevent buckling of the
• Architects have also discovered the many applications for which
FRP can be used. These include structures such as siding/cladding,
roofing, flooring and partitions.
• Synthetic rubber, invariably a polymer, is any type of artificial
elastomer mainly synthesised from petroleum byproducts.
• Synthetic rubber, like natural rubber, has uses in the automotive
industry for door and window profiles, hoses, belts, matting,
flooring and dampeners (antivibration mounts).
• Synthetic rubber displays the capacity of elasticity, synonymous in
colloquial terms to bounciness, flexibility or pliability.
• Water-repellent materials are those that do not allow water
molecules to penetrate or pass through. Thus, synthetic rubber
absorbs little to no water.
• Another property that makes it possible for synthetic rubber
products to be used in the electrical industry is electrical
• Synthetic rubbers exhibit high resistance to heat, meaning
the material poorly conducts heat energy transference.
• Certain synthetic rubbers display properties of chemical
resistance, which in this instance means the chemical
composition of the material cannot be readily changed
through contact with other materials.
ASBESTOS CEMENT PRODUCTS
• Asbestos Cement is primarily a cement-based product where about
10% to 15% w/w asbestos fibres are added to reinforce the cement.
• Asbestos cement is weatherproof in that although it will absorb
moisture, the water does not pass through the product.
• It was used for corrugated sheets, slates, moulded fittings, soffits
and undercloak, water cisterns, rainwater gutters, down pipes,
pressure pipes, underground drainage and sewer pipes, sills,
copings, chalkboards, fascias, infill panels, etc.
• It is sometimes difficult to tell the difference between an asbestos
cement product and a low-density insulation board.
• Where the product has been used as a roofing or cladding product,
open to the weather, you can be confident that the product is
• ADVANTAGES OF PLASTICS OVER
1. It can be moulded into finished products at a relatively low
cost, compared to the machining and fabricating costs for
wood and metal.
2. It resists chemicals.
3. It poses a high strength to weight ratio.
4. It does not rust like iron.
5. It is non conductor of electricity.
6. It is light in weight.
7. It is easy to fabricate.
• DISADVANTAGE OF PLASTICS:
1. It has low modulus of elasticity.
2. It is not reliable with respect to weathering