2. PLASTICS
PLASTICS ARE A WIDE RANGE
OF SYNTHETIC OR SEMI-SYNTHETIC
MATERIALS THAT USE POLYMERS AS A
MAIN INGREDIENT.
THEIR PLASTICITY MAKES IT POSSIBLE
FOR PLASTICS TO
BE MOULDED, EXTRUDED OR PRESSED IN
TO SOLID OBJECTS OF VARIOUS SHAPES.
3. THERMOPLASTICS
POLYMERS
• Examples of thermoplastics
include polyethylene, polypropylene,
polyvinyl chloride, polystyrene,
polybenzimidazole, acrylic, nylon, and
Teflon.
Thermoplastic polymers can be very
broadly classified as amorphous or
crystalline. Most thermoplastics suitable
for use as matrices for high performance
composite exhibit some degree of
crystallinity because this type of
structure has better resistance to
chemical attack by field, hydraulic oil
and paint stripper. Thermoplastic
polymers have linear and branched
they soften when heated and harden
cooled.
4. THERMOPLASTIC
POLYMERS PROPERTIES
I. Nylon is a thermoplastic that is self-
lubricating and resists abrasion. Often
it comes in use for making ropes,
fishing line and the zippers.
II. Acrylics are usable for the making
goggles, lenses, and the windows
because of their transparency and
impact strength.
III. Polyethylene is very tough and strong
and tends to resist impact, and so it
comes in use for making buckets and
toys.
IV. PVC is a very less expensive plastic,
generally visible in the floor tiles, hose
pipes and some cable coatings as
well.
5. THERMOSETTING
POLYMERS
• examples of thermoset plastic polymers
include silicones, vulcanized rubber,
epoxies, polyesters and phenolics.
A thermosetting polymer which is also
known as a thermoset or thermosetting
plastic is a polymer consisting of cross-
linked structure or heavily branched
molecules.
These polymers which are in the soft solid or viscous
state on heating undergo extensive cross-linking in
moulds and become irreversibly hard as well as
insoluble products.
6. THERMOSETTING
POLYMERS PROPERTIES
•One of the main properties of thermoset plastics
or polymers is that they harden during the moulding process
and after solidifying they cannot be softened.
•Typically, when the polymers are moulded and shaped they
acquire a three-dimensional cross-linked structure along with
strong covalent bonds that further help them retain their
strength as well as a structure even if the temperatures are
set high.
•However, thermoset plastics are brittle and tend to char and
burn if heat is applied for a prolonged state. Normally,
thermosets decompose before melting. Meanwhile,
thermoset resins are insoluble in most of the inorganic
solvents.
7. CHEMISTRY OF SOME
IMPORTANT THERMOPLASTIC
AND THERMOSET RESINS
• Poly vinyl chloride is
produced by free radical chain
polymerisation of vinyl
chloride in presence of
benzoyl peroxide or hydrogen
peroxide.
• Vinyl chloride is prepared by
treating acetylene with
hydrogen chloride at 60-80°c
and presence of metal oxide
catalyst
8. PROPERTIES OF PVC
APPLICATIONS
• Plasticized PVC is used in flooring or (PVC-U) unplasticized PVC
is used in making window frames.
• It is used in making sewage pipes and other pipe applications
where cost or vulnerability to corrosion limit the use of metal.
• Used in construction fields for insulation on electrical wires or in
flooring for hospitals, schools, homes, and other areas where a
sterile environment is a priority.
• It is used in various industries like building, electronics, electrical,
automotive, medical and packaging.
• PVC fabric is used in the manufacture of aprons shower curtains,
raincoats, jackets and sports bags.
• It is used in the garden hose and imitation leather upholstery.
• PVC is a colourless, non-
inflammable and chemically
innert powder.
• It has specific gravity 1.33 and
melting point 148*C.
• Resistance to atmospheric
conditions.
• PVC is strong, brittle.
• It is resistant to atmospheric
conditions like O2, CO2 and
moisture.
• PVC is not stable to heat and
U.V.radition. It undergoes
degradation.
9. TEFLON (POLYTETRA FLUORO
ETHYLENE) OR FLUON
• Teflon is obtained by
chain polymerization of
tetrafluoroethylene in
presence of benzoyl
peroxide as initiator.
• Tetra fluoro ethylene is
produced by
dichlorination of syn
dichlorotetrafluoroethan
e within presence of
catalyst.
10. PROPERTIES OF TEFLON
ENGINEERING USES
• Teflon is a very good insulating material for motors,
Transformers, cables, wires, fittings etc..
• It is used for making gaskets, pump parts, tank linings, tubing
etc…
• Jio 2 it’s extreme chemical resistance it is used for making
chemical carry pipes.
• Non lubricating bearings and non stick stopcock for burettes
are made from TEFLON.
• It is also used for coting as impregenating glass fibre,
asbestos fibres.
Due to the presence of highly
electronegative fluorine atoms Teflon as
got.
• High melting point greater than 350
degrees centigrade
• Exceptionally high chemical resistance
[except heart alkali metals and
fluorine].
• High density 2.1 to 2.3 GM by CC.
• It is very strong, hard polymer that
can be machined to drilling, punching
etc..
• Teflon is a very good electrical
insulator.
• It possesses very good abrasion
resistance.
11. BAKELITE OR PHENOL -
FORMALDEHYDE RESIN
Bakelite is an important thermoset
resin named after the scientist
Bakeland. who synthesised this resin in
the year 1909. it is prepared by step
polymerization of phenyl with
formaldehyde in presence of an acid or
alkali as a catalyst. Depolymerization
takes place in the 3 stages.
1. phenol is made to react with
formaldehyde in presence of acid
or alkali to produce non polymeric
mono, di and Tri methylol phenols
depending on the phenol
formaldehyde ratio (P/F ratio).
12. 2.The mono, di and tri
methylol phenols are
heated to produce two
types of straight chain
resins by condensation of
the methylol group with
hydrogen atom of
benzene ring or another
methylol group.
13. 3.This stage of
preparation includes
heating of ‘A’ stage
resin and ‘B’ stage
resin together, which
develops cross
linkings and bakelite
plastic resin is
produced.
14. PROPERTIES OF BAKELITE
APPLICATION
• For making electrical insulator parts like switches,
switch boards, heater handles etc.
• In paints and varnishes.
• As an anion exchanger in water purification by ion
exchange method in boilers.
• As an adhesive (binder)for grinding wheels etc.
• For making tarpulines, wood laminates and glass
laminates.
• Bakelite plastic resin is hard, right
and strong.
• It is a scratch resistance and
water resistance polymers.
• Bakelite has got good chemical
resistance, resistant to acids,
salts and many organic solvents,
but it is attacked by alkalis due to
the presence of – OH with any
other anion.
• It is a very good adhesive.
