The document discusses advanced polymers and their applications in engineering sciences. It describes how polymers are increasingly being used for structural applications instead of conventional materials due to their good mechanical properties. Thermally stable polymers, photoconducting polymers, photonic polymers, electroluminescent polymers, electrically conducting polymers, and polymer composites are some examples of advanced polymers discussed in the document along with their properties and applications. The document concludes that advanced polymers offer a wide range of materials that can improve strength, durability and other properties for use across many industries.

1. ADVANCED POLYMER MATERIALS IN
SCIENCE AND ENGINEERING
Ch. Rajyalakshmi, Asst.Prof.,
Department of Basic Sciences,
Vishnu Institute of Technology, Bhimavaram-2, W.G.Dt, A.P
Email: rajyalakshmi.ch@gmail.com
ABSTRACT---Materials have always played a
significant and defining role in human development,
from the Stone Age to the material world of today.
Materials are central to our prosperity and new
materials hold the key to our future development.
Material engineers therefore have an essential role in
developing the materials of today and the future and in
taking performance to the next level. Material related
issues can be found in all areas of life and engineering
e.g. in biomedical, telecommunications, aeronautical,
construction, chemical and mechanical, and in all
aspects of a products life, from an idea or discovery to a
prototype or finished product and recycling. In the
puzzle of innovation, material engineers focus on the
application of materials, where they test, develop and
modify materials that are used in a wide range of
products, from jet engines and snow skis to smart
phones and diapers. Most of the materials are prepared
from polymers. The commercial applications of
polymers have increased over the years, for a wide
variety of engineering and medical uses. The demand
for polymers with engineered properties for specific end
uses increased, resulting in the development of new
materials based on polymers. Such materials include
electrically thermally conducting polymers, photo
conducting polymers, photonic materials,
electroluminescent polymers, electrically conducting
and composite polymers. This paper reviewed the some
of advanced polymers and their applications in
engineering sciences.
Key words: Materials, Engineering applications,
Advanced polymers, thermally conducting,
photoconducting, photonic, composite,
electroluminescent, electrically conducting polymers.
INTRODUCTION
Polymers are macromolecules having very
large chains, contain a variety of functional groups,
can be blended with low and high molecular weight
materials. Polymers are becoming increasingly
important in the field of drug delivery. Advances in
polymer science have led to the development of
several novel drug delivery systems. A proper
consideration of surface and bulk properties can aid
in the designing of polymers for various drug
delivery applications.
Polymers with good mechanical properties
have replaced conventional materials such as metals,
wood or glass for structural applications
Engineeing and specialty thermo plastics
offer some remarkable properties like high thermal
stability, high flexural, tensile and impact strength,
low creep compliance and good chemical resistance
as compared to commodity plastics like polystyrene
and polyolefines and that too with reasonable price
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2. tags. Hence these polymers offer in many cases a
viable alternative for metals, especially where high
strength-to-weight ratio is a prime consideration, as
in aerospace and automotive applications.
Engineering polymers generally include
those polymers which are used in the manufacture of
premium plastic products that exhibit high impact
strength, high temperature resistance, high chemical
resistance and such special properties. Example
aliphatic polyamides (Nylon-6, Nylon66),
polysulfones, polycarbonates, Acrylonitrile butadiene
and styrene (ABS) resin,poly phenylene oxide resin,
poly p-phenylene sulfide, fluroplastics (teflon), and
polyesters. These engineering plastics are generally
priced 1 to 5 times the cost of the commodity
plastics.
Speciality polymers are usually priced at 10
times more than the commodity plastics. Examples
are polyetherimide, polybismaleimides, ionic
polymers, polyphosphazines, poly aryl ether ketones,
polyarylates and related aromatic polyesters and ultra
high molecular weight polyethylene. These polymers
exhibit exclusively remarkable performance in
certain special, limited but critical applications such
as in aerospace composites, membrane for gas liquid
separations, fire retardant textile fabrics used by fire
fighters and race car drivers and as sutures and
surgical implant. Polymides represent the most
important group of speciality polymers. This paper
reviewed the some of advanced polymers and their
applications in engineering sciences.
Thermally stable polymers
Most commonly used polymers as plastics
such as polyethylene, polystyrene, polyvinyl chloride
and ABS soften close to 1000
c and hence cannot be
used for load bearing applications. Though polymers
are stable even upto 3000
c in the absence of air or
oxygen they are susceptible to atmospheric oxidation
particularly at higher temperatures, which further
reduces their usefulness at higher temperatures. The
need for thermally stable polymers is growing in
electrical insulator, construction, transport
applications, and aerospace industries. Polymers for
high temperature applications should have high
melting point, high degree of crystallinity and high
bond dissociation energy. The presence of aromatic
rings in the polymer backbone enhances the thermal
stability as well as rigidity. Some of the commonly
used high temperature resistant polymers include
polysiloxanes, fluoropolymers (PTFE), aromatic
polymers (polyphenylene, Bisphenols A,
polycarbonate, polyphenylenevinylene), heteroatom
containing polymers such as polyphenylene oxide,
polyphenylene sulphide, polysulphones, poly p
hydroxy benzoic acid, polyimides, polyamides such
as Nomex and Kevlar, etc.
Photo conducting polymers
The ability of certain materials to be
electrically conductive on exposure to light is known
as photoconductivity. Typically these materials are
good insulators in the dark but become electrically
conductive when exposed to light because they are
capable of absorbing electromagnetic radiation to
generate charge carriers and facilitate the migration
of these carriers to the electrodes. Photoconducting
and charge transporting polymers are of p-type or n-
type depending on the majority carrier. Most of the
photoconducting polymers are p-type as thy transport
only holes. An important example of
photoconducting polymer is poly(N-Vinyl
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3. carbazole)(PVK). PVK is an insulator in dark but
becomes conducting on exposure to ultraviolet
radiation. The photoconductive response of the
polymer may be extended to visible and infrared
radiation by incorporating electron acceptors such as
2,4,7-trinitrofluorenone or sensitizing dyes. Other
examples of photoconducting polymers include poly-
p-phenylene sulphide, polyvinylpyrene and polymers
containing arylamine groups and inorganic polymers
such as poly {bis(2-naphthyloxy)phosphazene}.
Photo conducting polymers are of importance in laser
printers, xerographic copiers and duplicator
machines.
Photonic polymers
Polymers with non linear optical properties,
i.e, optical properties vary with the intensity of the
light (glass in contrast is linear in its optical
properties) have a variety of uses such as photo
responsive sun glasses and optical processing and
storage of computer data (as in CD-ROM and
WORM devices).polymers with extended pi electron
structures exhibit non-linear optical properties when
the electrons are optically excited. Photonic materials
include 6F-polyimide and 4-methoxy-4’-nitrostilbene
moiety connected by a six carbon spacer.
Polymers used in optical data storage discs
should have high transparency, non-scattering, low
water absorption and permeability, low stress,
thermally stable, tough and hard surface
characteristics and should be mouldable with high
accuracy at a fast throughput. Acrylic polymers have
good optical properties but have high water
absorption characteristics. Polycarbonate and
transparent amorphous polyolefins have good optical
properties, ease of moulding and low water
absorption.
Electroluminescent polymers
Electroluminescence refers to the
phenomenon of production of light by electrical
excitation as seen in a large number of
semiconductors. The process occurs as electrons from
one electrode are captured by holes at the other
electrode followed by Radiative decay of the excited
electron-hole combine (exciton).
Polymers with conjugated pi electron
systems such as poly-p-phenylene vinylene (PPV)
exhibit electroluminescence. Electroluminescent
polymers have potential applications in light emitting
diode (LED) devices and colour pixels in ink-jet
printing.
Electrically conducting polymers
Genrally polymers including plastics,
elastomers and fibers are regarded as insulators
because of the intrinsic property of carbon carbon
covalent bonds and were used as insulating materials
in electric wires. Polyethylene, PVC, rubber used as
insulating sheath. Under certain circumstances they
can be made to behave like a metal. Conductivity
generally increases with decreasing band gap. Metals
have zero band gaps, whereas insulators like many
polymers have large band gap which hinder electron
flow. By careful design of the chemical structure of
the polymer backbone, it may be possible to obtain
band gaps as low as 0.5 to 1ev. In becoming
electrically conductive its electron need to be free to
move. The polymer should have conjugated double
bond and the polymer has to be disturbed either by
Proceedings International Conference On Advances In Engineering And Technology
ISBN NO: 978 - 1503304048
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4. removing electron from oxidation or inserting
electron on reduction of polymer. The process is
known as doping. Extrinsically conducting polymers
are polymers whose conductivity is due to externally
added ingredients. They are conductive element filled
polymers and blended conducting polymers. In case
of Conductive element filled polymers, the
conducting materials like carbon black, metal oxides,
etc. are added to the polymers. In case of blended
conducting polymers, the conducting polymers are
mixed with conventional polymer.
Some important electrically conducting
polymers are poly sulphur nitrile PSN, Polyacetylene
PA, Poly-p-phenylene PPP, polypyrrole PPY,
polythiophene PTh, polyaniline PAni, etc.
Conducting polymers have many uses
because they are light weight, easy to process and
have good mechanical properties. They are used in
chargeable light weight batteries based on perchlorate
doped polyacetylene lithium systems. These are
approximately 10 times lighter than conventional
lead storage batteries. They have flexibility to fit into
different designs. In optical display devices, based on
polythiophene and polyaniline. When the structure is
electrically biased, the optical density of the film
changes and its colour changes. Such electrochromic
systems produce colour displays with faster
switching time and better viewing than conventional
liquid display device. Polyaniline, due to redox
activity in conducting state, is green; under reducing
condition, it is in yellow colour, and oxidizing
condition, it apprears blue. A LED consists of a
semiconductive polymer in the middle and at the
other end a thin metal foil as electrode. When a
voltage is applied between the electrodes, the
semiconductive polymer will start emitting light.
These are used in telecommunication systems (LED),
in electromagnetic screening materials, in electronic
devices such as transistors and diodes, in wiring in
aircrafts and aerospace components, in solar cells
and used as biosensors in metabolic reactions and
drug delivery system for human body, in photo
voltaic devices, in non linear optical material, and in
molecular wires and molecular switches. Conducting
polymers such as polyfuran and polythiophene have
profound uses in humidity sensors and as radiation
detectors as well as gas sensors.
Composites
A composite is multiphase material that
exhibits a significant proportion of the properties of
both the constituent materials. Scientists and
engineers haves designed various composite
materials by the combination of metals, ceramics and
polymers to produce a new generation of
extraordinary materials having combination of
superior mechanical characteristics such as
toughness, stiffness and high temperature strength.
Fibre reinforced composites are those composites in
which the dispersed phase is in the form of fibre.
Technologically these composistes are very important
as they provide high strength and stiffness are their
high specific strength and high specific modulus.
Fibre glass composites are widely used in automotive
parts, marine bodies, storage tanks, plastic pipes and
industrial floorings. Fibre glass reinforced plastics are
extensively used in transportation industries to reduce
vehicle weight and boost fuel efficient. Carbon fibers
have much higher specific modulus than glass fibers
and possess better resistance to temperature and
corrosive chemicals. However, carbon fibres are
more expensive and have only limited short fiber
utilization. The aircraft industry is currently using
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ISBN NO: 978 - 1503304048
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International Association of Engineering & Technology for Skill Development
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5. carbon reinforced composites. Composite materials
haves evolved as sophisticated materials. The extent
of mechanical properties that can be attained with
carbon fibres depends on crystallinity and the
structure which in turn depend upon the quality and
composition of the starting material and on the
production technology. Reinforcing fibers are
relatively new entrants in industry.
CONCLUSION
Advanced Polymes offers a range
of materials designed for use across a broad spectrum
of products and industries. Advanced polymer
products can improve strength and durability; impart
water, stain and chemical resistance; enhance color,
increase gloss, reduce dust and dirt pick-up, promote
adhesion and more. Further technological innovations
and cost reduction is likely to extend their
applications to weight savings in automobiles and
components for light weight engines, robots and
various other machineries.
Proceedings International Conference On Advances In Engineering And Technology
ISBN NO: 978 - 1503304048
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