Polymers.

Polymers

Introduction and Historical Development
Stone age → Bronze age → Iron age → Polymer age Development of civilization Application of polymeric materials ｏ PE……….. milk bottles ｏ Polyamide ………bulletproof vests ｏ Polyurethane ……..artificial heart

Classification polymers
Addition polymers and Condensation polymers Thermoplastic and thermosetting polymers Linear, branched and cross linked polymers Natural and Synthetic polymers

Polymerization

Polymerization techniques
Bulk polymerization Solution polymerization Suspension polymerization Emulsion polymerization

Bulk Polymerization The simplest technique
It gives the highest-purity polymer Ingredients : Monomer(l), Monomer-soluble initiator, Chain transfer agent

Model of Batch Polymerization
Monomer PMMA, POLYSTYRENE, LDPE

Obtain purest possible polymer Conveniently cast to shape
Pros & Cons of Bulk Polymerization Advantage Disadvantage Obtain purest possible polymer Conveniently cast to shape Obtain highest polymer yield per reactor volume Difficult to control….auto acceleration… viscosity …difficult Difficult to remove last traces of unreacted monomer

Ingredients- Monomers Initiator organic solvent
2. Solution Polymerization Solution Polymerization : Monomers dissolved into oranic solvent Ingredients- Monomers Initiator organic solvent Solvent helps controlling heat transfer from reaction. PVC, Polybutadiene, polyacrylamide

Model of Solution Polymerization
Monomer I I Initiator I I I Solvent

The effect of solvent solubility on the molecular weight of polyurethane produced by solution method
Viscosity of polymer solution Precipitation of polymer out of the solution Xylene Chlorobenzene Nitrobenzene Dimethyl sulfoxide 0.06 0.17 0.36 0.69 Precipitate immediately Precipitate within 0.5 hr. Polymer remain dissolved in solution Viscosity of polymer  MWpolymer  High viscosity = high molecular weight !

Need solvent separation & recovery Have traces of solvent, monomer
Pros & Cons of Solution Polymerization Advantage Disadvantage Solvent waste Need solvent separation & recovery Have traces of solvent, monomer Lower yield Reduces the tendency toward auto acceleration Reduces viscosity The product in the solution can be directly used as a adhesive

Suspension polymerization
Homogenous …..heterogenous Water insoluble monomers Ingredients Monomer (water)…droplets Initiator (soluble in monomer)

Suspension Polymerization
Coalescense of sticky droplets is prevented by PVA Near the end of polymerization, the particles harder and they can be removed by filtration, then washing Ingredients : water-insoluble monomer, water-insoluble initiator, chain transfer agent

Pros & Cons of Suspension Polymerization
Advantages 1. Easy heat removal and control 2. Obtained polymers pure 3. Economical Disadvantages yield ….. Difficult to control the particle size Reactor cost …….

Emulsion Polymerization
What is emulsion…dispersion of ……..immiscible Ingredients : water(l)-insoluble monomer, water-soluble initiator, chain transfer agent, dispersing medium (water), surfactant such as sodium salt of a long chain d

Process Liquid monomer is emulsified in water
Emulsion ….soap/detergent Initiator + chain transfer agent

Ref: S.L. Rosen, John Wiley & Sons 1993

Emulsion Polymerization – Schematic

Advantages and disadvantages
Viscosity …. Polymer….high molecular weight Purity….. Separation of polymer…..

Pros Cons Pros & Cons of some polymerization techniques Bulk - easy
- No contamination - Difficult to control temp. and heat transfer - High viscosity Solution -good heat transfer -easy to control reaction temp. -low viscosity -polymer produced may be used directly in the solution form - Need to use solvent –adding cost Difficult to eliminate solvent entirely Solvents sometimes act as chain transfer agent  leading to lower MW polymer Suspension - Good heat transfer - easy to control reaction temp. - low viscosity - polymer produced may be used directly as polymeric suspension -Need extra process in washing out suspending agent/contaminants and drying the polymer beads -Polymer beads may stick together and maybe contaminated with suspending agent -Good only for addition polymerization using hydrophobic free radical initiator. Emulsion -- Good heat transfer - polymer produced may be used directly as polymer latex -Need extra process in washing out emulsifier/ contaminants and drying -Good only for addition polymerization using hydrophilic initiator.

Phenol Formaldehyde resins:
(P/F˃1)

(P/F<1),

Crosslinking Take linear polymer chains & link using covalent bonds

Properties 1. Bakelite is resistant to water, acids, and organic solvents. 2. Due to the presence of phenolic –OH group it is attacked by alkalies. 3. Good electrical insulator and got excellent adhesive properties. 4. Rigid, hard and scratch resistant thermosetting polymer.

Applications Used in the manufacture of heater handles, TV and radio cabinets, because of it high temperature resistance. 2. As Bakelite is good insulator, it is used for making electric insulator parts liks switches, plugs, and switch boards. 3. For making brake linings, abrasive wheels and sand papers. 5. For making decorative laminates and wall papers. 6. In the production of ion exchange resins used in the purification of water.

Bakelite - Material of a Thousand Uses
Clear Bakelite items Phenolic resin/celluloid clock Bakelite telephone Bakelite camera Bakelite radio Bakelite microphone

Biodegradable Polymers
These are the polymers which gets decomposed by the process of biodegradation. Biodegradation is defined as a process carried out by biological systems usually fungi or bacteria wherein a poly chain is cleaved via enzymatic activity.

Degradation Mechanisms
Enzymatic degradation Hydrolysis (depend on main chain structure: anhydride > ester > carbonate) Homogenous degradation Heterogenous degradation

Requirement of biodegradation
Micro-organisms: These micro-organisms must exist with the appropriate biochemical machinery to synthesize enzymes specific for the target polymer to initiate the depolymerization process. Environment: Temperature, Pressure, Moisture, Oxygen, Type and concentration of salts, Light etc.

Requirement of biodegradation
Substrate: i) Suitable functional groups ii ) Hydrophilicity iii ) Low molecular weights iv ) Less crystallinity

Types of biodegradable polymers
Natural biodegradable polymers Natural rubber, collagen, lignin, poly(gamma-glutamic acid), starch, cellulose, gelatin, silk, wool etc. Synthetic biodegradable polymers Polyvinyl alcohol, polyanhydrides, PHBV or poly-(3-Hydroxybutyrate-CO-3-Hydroxyvalerate), Polycaprolactum, Polylactic acid, Polyglycolide.

Synthetic or Natural Biodegradable Polymers
Synthetic or Natural Biodegradable Polymers? Why We Prefer Synthetic Materials: Tailor-able properties Predictable lot-to-lot uniformity Free from concerns of immunogenicity Reliable source of raw materials

Poly caprolactam: (Nylon-6):

Polyesters

PCL (Poly caprolactone)
It is a thermoplastic biodegradable polyester synthesized by chemical Conversion of crude oil, followed by ring opening polymerisation. PCL has good water, oil, solvent and chlorine resistance. This polymer is often used as an additive for resins to improve their processing characteristics and their end use properties (e.g., impact resistance). Being compatible with a range of other materials, PCL can be mixed with starch to lower its cost and increase biodegradability or it can be added as a polymeric plasticizer to PVC. Polycaprolactone is also used for splinting, modeling, and as a feedstock for prototyping systems such as a RepRap, where it is used for Fused Filament Fabrication

PolyBIOPOL RESIN noates
Polyhydroxy buterate valerate (PHBV)

Need for biopolymers Solid waste problems, particularly with regard to decreasing availability of land fills Litter problems Entrapment or ingenious hazards to marine life.

Medical Applications of Biodegradable Polymers
Wound management Sutures Staples Clips Adhesives Surgical meshes Orthopedic devices Pins Rods Screws Tacks Ligaments Dental applications Guided tissue regeneration Membrane Void filler following tooth extraction Cardiovascular applications Stents Intestinal applications Anastomosis rings Drug delivery system Tissue engineering

Applications of biodegradable problems
The use of packaging materials produced from biopolymers (bio based polyesters) offers ecological advantages over synthetic plastic packaging because they can be produced from renewable PHB or poly(β-hydroxy butyrate) is used in the manufacture of shampoo bottles. PLA or poly lactic acid: It breaks down in the environment back to lactic acid which can be metabolized which has application in medical science such as sutures, drug delivery systems and wound clips. It has also agricultural applications such as time release coatings for fertilizers and pesticides.

Limitations Biodegradable polymers are very expensive.
They are not easily available. In order to store potentially hazardous materials, landfills are built to be free of moisture and air tight. These anaerobic conditions which serve to guard against the release of hazardous chemicals from landfills also retard biodegradation. Biodegradable polymers are not suitable candidates in the recycling of commingled plastics.

Carbon fibers PAN

Synthesis Step-1 Oxidative stabilization- Stretching & Oxidation 2000C- 3000C Thermoplastic PAN Non Cyclic Non plastic PAN Cyclic Step-II- Carbonization Nonplastic PAN Inert Atmosphere 4000C-6000C PAN ( 50%) Volatiles + Step-III-Graphatization ( -N2) The fibres are treated at temperature between 6000C C to improve order and orientation of crystallites in direction of fiber axis.

Chemical Structure

Properties of Carbon fibre
Carbon fibre has tensile strength 3 times greater than steel & 4.5 times lighter. Exceptional Impact properties- Good energy dissipation mechanism Low coefficient of thermal expansion compared to metals Better corrosion resistance High chemical inertness

CARBON FIBERS – The 21st Century Material
Specific Strength Relative stiffness

CARBON FIBERS – The Enabling Material for Energy
Alternate Energy -- Wind Turbines, Compressed Natural Gas Storage and Transportation, Fuel Cells Oil Exploration -- Deep Sea Drilling Platforms, Buoyancy, Umbilical, Drill Pipe Automotive/Fuel Conservation -- Light Weight Automobiles for better performance with alternate fuel sources

Carbon Fiber Applications

Application of carbon fibres in composites
Applications in Sports: Ice Hockey Sticks rack Spikes Bicycle Frames Helmets Motor Racing Tennis Rackets Golf Clubs Cricket Bats Gliders Surfboards Rowing Shells

Application in the Automotive Industry:
Racing car chassis Hoods Car emblems Mufflers Interior panels of a car Steering wheels Application in Civil Engineering Carbon Fiber Reinforced Polymer is can be applied to reinforce concrete structures The high strength of carbon fiber enables it to be used as a prestresser High corrosion resistance allows for use in offshore environments Used in PCCP (Prestressed Concrete Cylinder Pipe ) lines to reinforce the pipes

Applications in Aerospace Engineering
Aircraft: main wings, Tail units, Rudders, Elevators, Floor panel, Beams, Lavatory units, Seats Rockets: Nozzle cones, Motor cases Satellites: Antennas, Solar battery panels

Chevrolet Corvette Z06 & ZR-1

Conducting Polymers

Introduction Polymers (or plastics as they are also called) are known to have good insulating properties. Polymers are one of the most used materials in the modern world. Their uses and application range from containers to clothing. They are used to coat metal wires to prevent electric shocks.

Noble Prize in Chemistry 2000
Conjugated polymers Polyacetylene σ ~10-5 Scm-1 ~103 Scm-1 I2doping Noble Prize in Chemistry 2000

What is conductivity? Conductivity can be defined simply by Ohms Law.
V= IR Where R is the resistance, I the current and V the voltage present in the material. The conductivity depends on the number of charge carriers (number of electrons) in the material and their mobility.In a metal it is assumed that all the outer electrons are free to carry charge and the impedance to flow of charge is mainly due to the electrons "bumping" in to each other. Insulators however have tightly bound electrons so that nearly no electron flow occurs so they offer high resistance to charge flow. So for conductance free electrons are needed.

What makes the material conductive?
Three simple carbon compounds are diamond, graphite and polyacetylene. They may be regarded as three- two- and one-dimensional forms of carbon materials . Diamond, which contains only σ bonds, is an insulator and its high symmetry gives it isotropic properties. Graphite and acetylene both have mobile π electrons and are, when doped, highly anisotropic metallic conductors.

How can plastic become conductive?
Plastics are polymers, molecules that form long chains, repeating themselves. In becoming electrically conductive, a polymer has to imitate a metal, that is, its electrons need to be free to move and not bound to the atoms. Polyacetylene is the simplest possible conjugated polymer. It is obtained by polymerisation of acetylene, shown in the figure.

Two conditions to become conductive:
1-The first condition for this is that the polymer consists of alternating single and double bonds, called conjugated double bonds. In conjugation, the bonds between the carbon atoms are alternately single and double. Every bond contains a localised “sigma” (σ) bond which forms a strong chemical bond. In addition, every double bond also contains a less strongly localised “pi” (π) bond which is weaker.

Doping process The halogen doping transforms polyacetylene to a good conductor. Oxidation with iodine causes the electrons to be jerked out of the polymer, leaving "holes" in the form of positive charges that can move along the chain.

The iodine molecule attracts an electron from the polyacetylene chain and becomes I3ֿ. The polyacetylene molecule, now positively charged, is termed a radical cation, or polaron. The lonely electron of the double bond, from which an electron was removed, can move easily. As a consequence, the double bond successively moves along the molecule. The positive charge, on the other hand, is fixed by electrostatic attraction to the iodide ion, which does not move so readily.

DOPING - FOR BETTER MOLECULE PERFORMANCE
Doped polyacetylene is, e.g., comparable to good conductors such as copper and silver, whereas in its original form it is a semiconductor. Conductivity of conductive polymers compared to those of other materials, from quartz (insulator) to copper (conductor). Polymers may also have conductivities corresponding to those of semiconductors.

Factors that affect the conductivity
1-Denesity of charge carriers. 2- Thier mobility. 3-The direction. 4-presence of doping materials (additives that facilitate the polymer conductivity) 5-Temperature.

Synthesis of Polyaniline
It is prepared by redox polymerization of aniline using APS ( Ammonium Peroxydisulfate) NH4S2O8 as oxidant. Distilled aniline(0.2M) is dissolved in 300cm3 of 1M Hcl. APS (0.5M) is dissolved in 200ml Hcl (1M)and added to the aniline solution maintaining the temoerature 0-5 oC.

Synthesis of Polypyrrole

Bipolaron Chemical structures of polypyrrole in neutral aromatic and quinoid forms and in oxidized polaron and bipolaron forms

Applications Conducting polymers have many uses. The most documented are as follows: anti-static substances for photographic film Corrosion Inhibitors Compact Capacitors Anti Static Coating Electromagnetic shielding for computers "Smart Windows" A second generation of conducting polymers have been developed these have industrial uses like: Transistors Light Emitting Diodes (LEDs) Lasers used in flat televisions Solar cells Displays in mobile telephones and mini-format television screens

Energy Harvesting Polypyrrole can be used as catalyst support for fuel cells and to sensitize cathode electrocatalysts. Inexpensive microporous polyaniline (PANI) is used as a substitute for platinum to construct the counter electrode in dye-sensitized solar cells (DSSCs). Nano Polypyrrole incorporated graphene oxide can be used as an efficient counter electrode for platinum-free dye-sensitized solar cells. Biocompatible polypyrrole cathode (PPyDS) and a Mg alloy anode in Mg/air battery. These batteries are sufficient to drive some implantable devices requiring low power densities such as a pacemaker or biomonitoring systems.

2. Sensing applications Polypyrrole nanowire doped FeCl3, assessed for chemical sensing application, specifically pH monitoring. Bovine serum albumin (BSA), a protein incorporated polypyrrole film can be used for detection of Urea. Single Polypyrrole nanowires-based sensors showed good limit of detection and sensitivity and excellent selectivity for gaseous ammonia. Polyaniline can be used in conductometric sensors. PANI/CuCl2 as a hydrogen sulphide sensor PANI nanofiber reinforced nanocomposite crystal microbalance sensor as HCl sensor

3. Defence applications Conducting PANI and Polypyrrole can be used in Radar Absorbing materials Materials that absorb incident electromagnetic energy and convert that energy to other forms—typically heat. Conducting polymers, such as polypyrrole (PPY), polyaniline (PAni), and polyethylenedioxythiophene (PEDOT) have been deposited onto various textiles in the forms of woven fabrics, knit fabrics, felts, other nonwoven structures, and fibers. Potential property of any conductive fabric is its ability to shield against electromagnetic radiation. Conformable Polypyrrole Antennae for soldiers

Application of conjugated polymers

Solar cell Shield for computer screen against electromagnetic "smart" windows radiation smart" windows Light-emitting diodes Photographic Film

Fluorescence behavior of P1-P20 under UV irradiation

COMPOSITES A composite material is a material made from two or more constituent materials with significantly different physical or chemical properties that, when combined, produce a material with characteristics different from the individual components. The individual components remain distinct within the finished structure. The new material may be preferred for many reasons: common examples include materials which are stronger, lighter, or less expensive when compared to traditional materials.

CONSTITUENTS OF A COMPOSITE
Matrix phase Continuous phase, the primary phase. It holds the dispersed phase and shares load with it. Reinforcing phase The second phase is imbedded in the matrix in a continuous/discontinuous form. Dispersed phase is usually stronger than the matrix, therefore it is sometimes called reinforcing phase. Interface Zone across which matrix and reinforcing phases interact (chemical, physical, mechanical)

The matrix is basically a homogeneous and monolithic material in which a fiber system of a composite is embedded. It is completely continuous. The matrix provides a medium for binding and holding reinforcements together into a solid. It offers protection to the reinforcements from environmental damage, serves to transfer load, and provides finish, texture, color, durability and functionality.

Reinforcement usually adds rigidity and greatly impedes crack propagation. Thin fibers can have very high strength, and provided they are mechanically well attached to the matrix they can greatly improve the composite's overall properties. Fiber-reinforced composite materials can be divided into two main categories normally referred to as short fiber reinforced materials and continuous fiber-reinforced materials.

The interphase is the region in which loads are transmitted between the reinforcement and the matrix. The extent of interaction between the reinforcement and the matrix is a design variable, and it may vary from strong chemical bonding to weak frictional forces. This can often be controlled by using an appropriate coating on the reinforcing fibers. Generally, a strong interracial bond makes the coupling is often intermediate between the strong PMC more rigid, but brittle.

Types of Composite Matrix Materials
CERAMIC MATRIX METAL MATRIX POLYMER MATRIX Types of Composite Matrix Materials

Ceramic MATRIX They consist of ceramic fibers embedded in a ceramic matrix, thus forming a ceramic fiber reinforced ceramic (CFRC) material. CMC materials were designed to overcome the major disadvantages such as low fracture toughness, brittleness, and limited thermal shock resistance, faced by the traditional technical ceramics.

Metal matrix Metal matrix composites (MMCs) are composite materials that contain at least two constituent parts – a metal and another material or a different metal. The metal matrix is reinforced with the other material to improve strength and wear. MMCs are fire resistant, operate in a wide range of temperatures, do not absorb moisture, and possess better electrical and thermal conductivity.

Polymer matrix Polymer matrix composites (PMCs) can be divided into three sub-types, namely, thermoset, thermoplastic. PMC's consist of a polymer matrix combined with a fibrous reinforcing dispersed phase. They are cheaper with easier fabrication methods. PMC's are less dense than metals or ceramics, can resist atmospheric and other forms of corrosion, and exhibit superior resistance to the conduction of electrical current.

Polymer Matrix Composites
Thermosets Thermoplastic

Thermosets Thermosetting resins include polyesters, vinyl- esters, epoxies and polyamides. Thermosetting polyesters are commonly used in fiber-reinforced plastics, and epoxies make up most of the current market for advanced composites resins. Initially, the viscosity of these resins is low; however, thermoset resins undergo chemical reactions that crosslink the polymer chains and thus connect the entire matrix together in a three-dimensional network. This process is called curing. Thermosets, because of their three-dimensional cross-linked structure, tend to have high dimensional stability, high -temperature resistance, and good resistance to solvents. Recently, considerable progress has been made in improving the toughness and maximum operating temperatures of thermosets.

Thermoplastics Thermoplastic resins, sometimes called engineering plastics, include some polyesters, poly ether-imide, polyamide, poly-phenylene sulfide, polyether-ether ketone (PEEK), and liquid crystal polymers. They consist of long, discrete molecules that melt to a viscous liquid at the processing temperature and, after forming, are cooled to an amorphous, semi-crystalline, or crystalline solid. The degree of crystallinity has a strong effect on the final matrix properties. Thermoplastics, although generally inferior to thermoses in high-temperature strength and chemical stability, are more resistant to cracking and impact damage. Thermoplastics offer great promise for the future from a manufacturing point of view, because it is easier and faster to heat and cool a material than it is to cure it.

FABRICATION OF POLYMER COMPOSITES
Given the many different fibers and matrices from which PMCs can be made, the subject of PMC manufacturing is an extremely broad one. However, more than any other single area, Iow-cost manufacturing technologies are required before advanced composites can be used more widely. The basic steps include: 1 impregnation of the fiber with the resin 2 forming of the structure 3 curing (thermoset matrices) or thermal processing (thermoplastic matrices) 4 finishing.

P M C S H A I N G R O E OPEN MOULD PROCESS
To lay resins and fibres onto forms CLOSED MOULD PROCESS Basically plastic moulding method FILAMENT WINDING Continuous dipping in liquid resin and wrapping around a rotating mandrel, producing a rigid, hollow, cylindrical shape PULTRUSION PROCESS Similar to extrusion only adapted to include continuous fibre reinforcement

APPLICATIONS AND MARKETS

PMCs are a more mature technology than structural ceramics
PMCs are a more mature technology than structural ceramics. Advanced polymer composites have a good record of performance and reliability and are rapidly becoming the baseline structural material of the defense/aerospace industry among others.

AEROSPACE INDUSTRY The aerospace industry is estimated to consume about 50 percent of polymer composite production. Composites are used extensively today in small military aircraft, commercial rotorcraft and prototype business aircraft. The primary matrix materials used in aerospace applications are epoxies, and the most common reinforcements are carbon/graphite, aramid (e.g., Du Pont’s Kevlar), and high-stiffness glass fibers.

Reciprocating Equipments
PMC materials have considerable potential for use in many different kinds of high-speed industrial machinery. Current applications include components as centrifuge rotors, weaving machinery, hand-held tools, and robot arms. All of these applications take advantage of the low inertial mass and varying degrees of tailorable characteristics. CONSTRUCTIONS A potentially high-volume market for PMCs lies in construction applications especially in construction of buildings, bridges, and housing. Additional applications include lampposts, smoke-stacks, and highway culverts. Construction equipment including cranes, booms, and outdoor drive systems, could also benefit from use of PMCs. Because of the many inexpensive alternative building materials currently being used, the cost of PMC materials will be the key to their use in this sector.

Medical Devices PMC materials are currently being developed for medical prostheses and implants. The impact of PMCs on orthopedic devices is expected to be especially significant. Metallic implant devices, such as the total hip unit that has been used since the early 1960s, suffer a variety of disadvantages: difficulty in fixation, allergic reactions to various metal ions, poor matching of elastic stiffness, and mechanical (fatigue) failure. PMC materials have the potential to overcome many of these difficulties. It is also possible to create implants from biodegradable PMC systems that would provide initial stability to a fracture but would gradually resorb over time as the natural tissue repairs itself.

Naval Applications The light weight and corrosion resistance of PMCs makes them attractive for a number of naval applications. Advanced composites are currently in production in molded propeller assemblies for the Mark 46 torpedo, at a cost savings of 65 to 70 percent over the previous aluminum design . The Navy is also evaluating PMCs for hatch doors, bulkheads, and propeller shafts. PMCs could also be used for an advanced technology submarine hull, providing weight savings and thus speed advantages over metal hulls currently in use.

FUTURE WORK

High-Temperature Matrices
Bio-production Living cells can synthesize polymeric molecules with long chains and complex chemistries that cannot be economically reproduced in the laboratory. Plants are being evaluated for commercial production of lubricants, engineering nylons, and other PMCs. Biotechnology may offer a novel approach to the synthesis of biological polymers in the future. High-Temperature Matrices The maximum continuous service temperature of organic polymers in an oxidizing atmosphere is probably around 700°F. Although brief exposures to higher temperatures can be tolerated. Currently, the most refractory matrices are polyamides, which can be used at a maximum temperature of 600°F. If stable, high-temperature matrices could be developed, they would find application in a variety of engine components and advanced aircraft structures.

Space Station Military
Graphite/epoxy advanced composites and aluminum are both being considered for the tubular struts in the space station reference design. The goal of reducing launch weight favors the use of advanced composites however, their lower thermal conductivity creates problems in service. To reduce the effects of thermal cycling, advanced composites are being developed. Military Composites of all types, including ceramic, polymer, and metal matrix composites, are ideal materials for use in space-based military systems, such as those envisioned for the Strategic Defense Initiative. A program devoted to the development of new materials and structures has been established within the Strategic Defense Initiative Office.

CONCLUSION Beyond the turn of the century, PMCs could be used extensively in construction applications such as bridges, buildings, and manufactured housing. Because of their resistance to corrosion, they may also be attractive for marine structures. Realization of these opportunities will depend on development of cheaper materials and on designs that take advantage of compounding benefits of PMCs, such as reduced weight and increased durability. In space, a variety of composites could be used in the proposed aerospace plane, and PMCs are being considered for the tubular frame of the NASA space station. Unlike most structural ceramics, PMCs have compiled an excellent service record, particularly in military aircraft. However, in many cases the technology has outrun the basic understanding of these materials. To generate improved materials and to design and manufacture PMCs more research needs to be done.

REFERENCES POLYMER MATRICES www.princeton.edu COMPOSITE MATERIALS
Dr. S.M.K. Hosseini POLYMERS University Sains Malaysia MATERIAL SCIENCE (IIT-K) NPTEL Videos COMPOSITE FABRICATIONS MANUFACTURING COMPOSITES INTRODUCTION TO PMCs Polymer Composites Sdn Bhanda REFERENCES

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