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
18. The mechanical properties of plastics are affected by
• Rate of loading
• 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
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
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.