This document discusses various types of polymers including thermoplastics like acrylic, ABS, and PVC. Acrylic is clear and weather resistant but more expensive than glass. ABS is impact resistant but not very durable. PVC is lightweight and inexpensive but less flame resistant than other materials. The document also covers properties of polymers like strength to weight ratio, manufacturing advantages over metal, and common applications of different plastics.

2. Muhammad Umair Bukhari
Engr.umair.bukhari@gmail.com
www.bzuiam.webs.com
03136050151

3.  Polymers. Macromolecules.
 Natural & synthetic
 Their unique properties have allowed
them to replace metals.
1. strength: weight ratio
2. Designing with plastics
3. Cost of using plastics
4. Ease of manufacturing

4.  plastic is cheaper than most metal
 weighs a lot less (better fuel economy).
 Plastic can be injection molded, vacuum
molded, cast and generally machined or
"worked" faster and cheaper than metal.
 for winter cold areas where the roads are
salted, the corrosion resistance of plastics

5. Bio-plastic green phones
Urethane bumpers

6.  Thermoplastics:
Amorphous structure. Secondary bonds.
Linear & branched polymers have weak
secondary bonds. Return to their original
hardness when cooled. Reversible
heating possible.
 Examples: acrylics, nylon, PVC,
polyethene

7.  Thermosets:
Cross-linked in a 3d network. Strength of
bond. Hardness & strength in material not
affected by temperature.
 Polymerization will require heat &
pressure so that the shape of the part is
permanently set.(curing)
 Irreversible. Decomposes. Chars.

8.  Tg not sharply defined. Become rubbery
over a narrow range.
 Polymerization in 2 steps. At chemical
plant & at parts-producing plant.
 Phenolics. Pots & pans.
 Possess better insulating, mechanical &
chemical properties. Also better
dimensional stability.

9.  they need to be painted for UV
protection.
 Tooling: Normally more expensive for
plastic because of the surface finish
required (in the mold) and the number of
cavities are larger, thus increasing the
cost.

10.  Various chemical reactions were used to
make cellulose in to cellulose acetate.
Photographic films. Packaging sheets.
 So additives are added to impart certain
specific properties.
 Modify properties like stiffness, strength,
color, flammability, weatherability.

11.  Fillers: improve mechanical properties.
Decreases the cost/unit weight.
 Plasticizers: add flexibility & softness to
the polymer by reducing Tg .
 Stabilizers: UV rays & oxygen tend to
weaken & break the primary bonds.
Degradation.
 Colorants
 Flame retardants

12.  Cellulosics
 Fluorocarbons
 Polyamide (nylons)
 Polycarbonates
 Polyesters
 Polyethylenes
 Polypropylenes
 Polystyrenes
 PVC

14.  Acrylic is a useful, clear plastic that
resembles glass, but has properties that
make it superior to glass in many ways.
Common brands of high-grade acrylic
include Plexiglass.
 moderate strength, good optical quality &
weather resistance. Transparent but can be
made opaque. Generally resistant to
chemicals.
 Typical applications: lenses, signs,
automotive lenses, window glazing, artificial
nails, paints

15.  For all of its advantages, there are two
disadvantages of acrylic: it is more
expensive than glass, and if exposed to a
direct flame it will melt and eventually burn.
 Has good impact strength, higher than that
of glass or polystyrene, but significantly
lower than that of polycarbonate or
engineering polymers. In the majority of
applications, it will not shatter but instead
breaks into large dull pieces.

16.  ABS is impact resistant, abrasion &
chemical resistant. Resistance to
chemicals & corrosion. Does not ignite
easily.
 Typical applications: pipes & fittings, tool
handles, telephones & appliances.
 High performance at high & low
temperatures. (-400 F to 1800 F)

17.  The main disadvantage to using ABS pipe
fittings are that it is not very durable
when it comes to solvents or fatigue
resistance. It also has minimal UV
resistance, so should not be left exposed
to the sun.
 The nitrile groups from neighboring
chains, being polar, attract each other
and bind the chains together, making
ABS stronger than pure polystyrene

19.  PVC has many advantages over pipes
made of galvanized steel and copper.
 To begin with, it is the most lightweight of
the three. This makes it easier to install.
Also, it is the least expensive of the three
types.
 Also, it can withstand higher water
pressure than the copper. Also, PCV is
non-conductive, will not rust, and is not as
conducive to condensation.

20.  Another advantage is that PVC can be
placed under concrete slab without
reacting to the concrete. Moreover, it is
self-insulating. That is why it can handle
hotter temperature water.

21.  Even though it can withstand hot water
temperatures, it is less flame resistant.
That is one of the biggest disadvantages
of PVC.
 Also, PVC contains volatile compounds
which are harmful to the environment.
Furthermore, some people have
complained that PVC pipes cause water
to have a slight plastic taste.

22.  ElasticModulus & tensile strength
decrease with increasing temperature.
Toughness increases.
 Water absorption. Adverse affect.
 Solvents. Residual stresses.
 Radiation & visible light.
 Anisotropy due to cold rolling.

23.  Friction& wear (self-lubricating,
TEFLON) (gears, roller skate wheels,
prosthetic joints)
 Thermal & electrical conductivity
 Low specific gravity (0.9-2.2)
 High coefficient of thermal expansion