2. used to describe any of a group of
synthetic or natural organic materials that
can be shaped when soft and then
hardened.

3.  It comes from the Greek words “Poly” meaning
“Many” and “Meros” ,meaning “Part”.

5.  Can be defined as a unit consisting of
relatively few hydrogen atoms joined to
other units to form a polymer.

6. the process of building up small
molecules in a long chain to form a
large molecule.

7. Hydrocarbons are
substances
containing only
the chemical
elements carbon
and hydrogen.

10.  Thermoplastic Materials – is a polymer that softens
and melts gradually when heated and can be
reshaped when still warm.
 Thermosetting Materials – is a polymer that
cannot be reshaped after manufacture.

12.  Thermoplastic resins do not undergo permanent
change on reheating.
 Thermosetting resins first soften on heating and on
continuous heating harden or set to become
relatively rigid like an egg.

14.  Thermoplastic products are manufactured using a
number of methods; the most common in mass
production are extrusion and molding.
 Thermosetting products are generally made by a
combination of compression molding, transfer
molding, or injection molding.

16. Light cross-linking of certain linear
polymers produces an additional class
of plastics : rubberlike materials called
ELASTOMERS.

18. The mechanical properties of plastics are affected by
several factors:
• Rate of loading
• Temperature
• Environmental conditions

19.  Polystyrene – one of the most common
thermoplastics, was discovered in 1831.
 Pure polystyrene – which is crystal clear, is used for
storage containers and cups.
 Polyvinyl chloride (PVC) – is a commonly used
thermoplastic material with a sp. gravity of about 1.39

21.  Polyethylene – is also a common thermoplastic,
with a sp. gravity of about 0.92
 Polypropylene – is another thermoplastic that has a
low sp. gravity (the same as polyethylene) and low
modulus of elasticity.
 Acrylics – are thermoplastic materials that are
crystal clear in natural form but are commonly
manufactured in a wide range of colors and shades.

23.  Polyester – is a thermosetting resin that has a sp.
gravity ranging between 1.6 and 2.2
 Phenol-formaldehyde – is a common
thermosetting resin with a high sp. gravity (1.9)

25.  Plastics are less elastic than steel or concrete.
 Generally, plastics do not transmit vibrations very
well.
 Plastics retain their color in indoor applications.

26.  Fire resistance is an important property in buildings.
Most plastics are flammable.
 Most plastics have low water-absorption properties.
 Poisson’s ratio is a measure of the reduction in cross-
section that accompanies longitudinal elongation. For
most brittle plastic materials, poisson’s ratio is around 0.3.
For flexible plastics, its value is close to 0.4

28.  Fiber-reinforced plastic (FRP) (also fiber-
reinforced polymer) are composite materials made of
a polymer matrix reinforced with fibers.

29.  Graphite or carbon fiber is produced by subjecting
organic precursor fibers (such as polyacrylonitrile,
pitch or rayon) to a sequence of heat treatments,
converting the precursor to carbon.
 Aramid fiber(also called kevlar) was originally
developed for radial tires and has a density about half
that glass fibers.

31. USES OF PLASTICS
 Plastics have a favorable strength/weight ratio.
 Because of their lightness, plastics present ease in handling,
transportation, storage, and assembly.
 Plastics can be molded to any shape and pattern.
 Most plastics are generally maintenance free and have good corrosion
resistance.
 Plastic products come in variety of colors and texture.
 Plastics can be manufactured with consistent quality. They are easy to
manufacture into components.
 Plastics are very economical.