Fibre-reinforced plastics, Biodegradable polymers, preparation and their properties

1. FIBRE-REINFORCED PLASTICS
&
BIODEGRADABLE POLYMERS
BY
CH. SAI SRI RAMA CHANDRA
MURTHY

2. Fiber – reinforced plastics (FRPs)
These are prepared by reinforcing a plastic matrix with a high-strength fiber
material and therefore, also referred as composite materials. The original plastic
without fiber reinforcement is known as matrix. Main reinforcing fibers used are
glass, graphite, alumina, carbon, boron, beryllia, aromatic polyamide which increase
the strength and elasticity of plastics.
Natural fibers are also used for reinforcement such as sisal, asbestos etc. The
nature of the fiber used depends upon the properties of the final reinforced
composite desired. fibers reinforced plastics find extensive use in space-crafts, aero
planes, boat hulls, acid-storage tanks, motor cars and buildings.
FRPs replace traditional materials such as metal and as users look for better
performance than plastics. These FRPS have advantages over traditional materials
which include design freedom, reduced weight and corrosion resistance.

3. 1. Glass fiber is the most extensively used and is the work –horse of the FRP
industry.
Preparation:
Glass fibers are basically made by mixing silica sand, lime stone, folic acid and
other minor ingredients. The mixture is heated until it melts at about 1260°C and is
allowed to flow through fine holes in a platinum plate. The glass strands are cooled,
gathered and wound. The fibers are then woven in to various forms for use in
composites.
Most attractive features/properties of glass fiber are–low coefficient of thermal
expansion, high dimensional stability, low cost of production, good tensile strength,
low dielectric constant, non-flammability, corrosion resistance and chemical
resistance.

4. Important applications of GRPs
1. In the house building market: used for the production of roofing laminate, door
surroundings, over-door canopies, window canopies and dormers, chimneys,
coping systems, heads with keystones and sills.
2. Piping: GRP pipe systems can be used for a variety of applications, above and
under the ground such as firewater systems, cooling water systems, drinking
water systems, waste water systems/sewage systems, and gas systems.
3. Others include- gliders, kit cars, sports cars, micro cars, karts, body shells,
boats, flat roofs, kayaks (small boats), lorries, wind turbine blades, domes and
architectural features where a light weight is necessary, bodies for automobiles,
such as Chevrolet Corvette and Studebaker Avanti, and DeLorean DMC-12
under body etc.

5. 2. Carbon fiber reinforced plastics (CFRPs): These do not absorb water and are
resistant to chemicals, electrically conductive and might give galvanic corrosion in
direct contact with steel.
Features/Properties:
These are alkali resistant, corrosion resistant, low thermal conductivity, high
strength, fatigue resistance, both thermosetting and thermoplastics are suitable for
these CFRP. Thermosetting are epoxies or polyesters, phenolics, vinyl esters.
Thermoplastics are polyamides, polycarbonates etc.
Applications:
1. In structural components requiring high specific stiffness and strength.
2. Used in air frame structures, space vehicles and satellites, high temp machinery
etc.
3. Also used in sports equipment and high speed reciprocating parts for industrial
machinery.

6. Biodegradable polymers
Polymers are generally stable, but they undergo degradation when exposed to
oxygen, ozone and micro organisms, moisture, heat, stress or radiation. The
degradation may be due to a loss in toughness or strength (physical properties).
Degradation also may be by thermal degradation (~150°C). It may adversely
change mechanical and electrical properties due to dehydrochlorination in PVC
polymers.
Biodegradable polymers are such polymers in which the degradation is mediated
at least partially by a biological system.
The biodegradable polymers may be naturally occurring or they may be synthesized
my chemical means.
Natural biodegradable polymers:
Cellulose, starch, casein, etc. are known to be naturally occurring biodegradable
polymers. Natural polyester poly-3-hydroxy butyrate is used for energy storage by
bacteria.

7. Synthetic biodegradable polymers: examples include polyester polyglycolide,
polyacetide, ethylene-ether-copolymer, polyamino-triazole, etc.
A variety of natural and synthetic biodegradable polymers are known to man-kind
but only a few of them have been successfully marketed.
Biodegradable plastics are of two types in the market. These are hydro-
biodegradable plastics (HBP), which undergo chemical degradation by hydrolysis
and oxo–biodegradable plastics (OBP), which undergo chemical degradation by
oxidation.
HBP tend to degrade and biodegrade somewhat more quickly than OBP, but the
end results are same, both are converted to CO2, water and biomass. OBP are
generally less expensive, possess better physical properties and can be made with
current plastics processing equipment. Polyester plays a predominant role in HBP due
to their easily hydrolysable ester bonds. HBP can be made from agricultural resources
such as corn, wheat, sugarcane and fossil. OBP‟s can be made from byproducts of oil
or natural gases.

8. Biodegradable polymers are mainly used in medical devices to avoid a second
operation to remove them or to gradually release a drug.
Properties:
1. They are non-toxic.
2. They maintain good mechanical integrity until degraded.
3. They are capable of controlled rates of degradation.
Applications:
1. They are used in sutures, tissue engineering.
2. They are used in case of controlled drug release.
3. They are used in drug delivery systems.
4. They are used to coat a stent and release drugs in a controlled way.
5. They are used in dental devices.
6. They are used in orthopedic fixation devices.

9. THANNK YOU