Kevlar Fiber

Kevlar Fiber

Presented byDevansh Gupta

M.Sc Polymer Science

Semester 1

Contents Introduction History Chemical Reaction Production Structure & Properties Advantages Disadvantages Applications Reference

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Introduction It is DuPont’s registered trademark for para-aramid synthetic

fiber which is made by combining para-phenylenediamine(PPD) and teraphthaloyl chloride(TCl).

Kevlar has not been around for very long. Stephanie Kwolek who worked for DuPont made Kevlar in 1965 to manufacture a stronger tire. Instead of revolutionizing the tire industry, Kevlar revolutionized the entire world. It is a fiber that when woven together has the five times

strength of steel. Kevlar was first commercially used in early ‘70s as a

replacement of steel in racing car tires. Typically it is spun into ropes or fabric sheets that can be used

direct or as an ingredient in composite material components.

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History In 1964, her group began searching for a new

lightweight strong fiber to use for light but strong tires. The chemicals she had been working with at that time, formed liquid crystals while in solution, something unique to those polymers at the time.

The solution was cloudy, opalescent upon being stirred, and of low viscosity and usually was thrown away. However, Kwolek persuaded the technician, Charles Smullen, who ran the "spinneret", to test her solution, and was amazed to find that the fiber did not break, unlike nylon.

After Kwolek discovered Kevlar, she was not very involved in developing the applications of Kevlar.

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Chemical Reaction Kevlar is synthesized in solution from the monomers para-phenylenediamine(PPD) and terephthaloyl chloride(TCl) in a condensation reaction in which molecules of HCl are terminated as a byproduct.

Hexamethylphosphoramide was the solvent initially used for the synthesis, but for safety reasons DuPont replaced it by a solution of N-methyl pyrrolidone and CaCl .

-n HCl

n n

n2

10-20*C

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Another substance which is involved in the synthesis of Kevlar is highly concentrated sulphuric acid.

It is used to keep the crystalline Kevlar in the solution while it spins in the spinneret.

It is very difficult to use highly concentrated sulphuric acid but it’s a necessary process, that’s why it is one of the most expensive step of production.

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Production The product obtained in the laboratory is turned into

fibers by a process called dry-jet-wet spinning; in which a hot and very viscous solution of PPTA through a spinneret to make long, thin, strong, and stiff fibers that are wound onto drums. The fibers are then cut to length and woven into a tough mat to make the super-strong material we know as Kevlar.

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Structure

When Kevlar is spun, the resulting fiber has a tensile strength of about 3,620 MPa, and a relative density of 1.44 gm/cc.

Presence of Amide linkages and other inter-chain bonds like hydrogen bonds give this much high strength.

The presence of salts and certain other impurities, especially calcium, could effect the properties of Kevlar That’s why care is taken to avoid impurities in its production.

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Advantages Strong but relatively Light weight. Tensile strength of Kevlar49 & Kevlar29 is over 8 times

greater than that of steel wire. Bear temperatures up to 450*C (No thermal shrinkage) No embrittlement found on very low temperature (-

196*C). Kevlar can remain virtually unchanged after exposure

to hot water for more than 200 days. Kevlar can be ignited but burning stops when source

removed. Resist attacks from almost all types of chemicals but

long exposure to strong acids or bases will degrade it . Low electrical conductivity. High cut resistance.

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Disadvantages Although Kevlar has very high tensile strength, it has

very low compressive strength. That’s why Kevlar can not replace steel as a primary building material in structures like buildings & bridges where compressive forces are required.

Kevlar fibers quickly absorb moisture, meaning it is more sensitive to its environment than other materials.

It can be difficult to cut & drill. Specially made scissors are usually required to cut the fabric.

Kevlar reacts very badly to UV Light that’s why UV stabilizer is required for outdoor applications.

It suffers some corrosion if exposed to chlorine.

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ApplicationsIndustrial applications Kevlar is used to make industrial equipment such as

hoses, belts, reinforcement materials. It is used to make parts of aircrafts, ship hulls, reinforce tyres.

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Kevlar is used as a reinforcement material for racing car tyres and bicycle tyres. It helps to reduce puncture rate. Generally these tyres are much more expensive than ordinary road tyres.

The best example of Kevlar reinforced car tyre is American President’s car “The Beast”. It’s tyres are so strong even a bullet can not penetrate into it.

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Sports equipment Kevlar is used in making of various sports equipment

due to light weight and strength. These includes tennis, table tennis, badminton, squash rackets, cricket bats and hockey sticks.

F1 race car parts and body, sport shoes, snow boards, skate boards, surf boards, gloves, racquets, motor sport helmets etc are also madeup from Kevlar.

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Brakes Asbestos brake pads were initially used in vehicles but

dust produced from these brakes pads is toxic that’s why chopped Kevlar fiber has been used as a replacement for asbestos in brake pads.

Smart Phones The Motorola RAZR Family, The Motorola Droid Maxx

and the OnePlus 2 have a Kevlar back plate, chosen over carbon fiber due to its less interference in signal transmission and resilience.

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Frying Pans Kevlar is sometimes used as a substitute for Teflon in

some non-stick frying pans.

Personal safety equipment Kevlar is used in production of various personal

protection gear such as riding shoe, helmets, industrial gloves, fire fighting apparel, body pads etc.

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In manufacturing of Military Equipments Because of it’s light weight and high tensile strength

Kevlar is used in production of various Army gear such as Military helmets, Vehicle Armors, Body Armors, Tactical Vests, Fighter Plane’s Wings and other parts etc

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Types Of KevlarAlthough Kevlar is main product, there are

various other grades of Kevlar produced Kevlar29 – In industrial applications such as cables,

asbestos replacement, brake linings and body armors. Kevlar49 - High modulus used in cable and rope

products. Kevlar100 – Coloured version of Kevlar. Kevlar119- Higher elongation, flexible and more

fatigue resistant. Kevlar129- Higher tenacity for ballistic applications. Kevlar AP- 15% lighter tensile strength than

Kevlar29. Kevlar XP- Lighter weight resin and KM2 plus fiber

combination. Kevlar KM2- Enhanced ballistic resistance for armor

applications.

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Sci-fi Part While watching any Batman series Movie have you ever

Thought Without Any Superpowers Like Superman Or Wolverine How Batman Fight with enemies without getting touched by a bullet??

Just because his suit contains more than 50% Kevlar fiber which provides him strength and thus he can avoid bullets like Peanuts..

Due to Kevlar’s light weight Batman can easily jump or glide from one building to another.

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How Bulletproof armor works??

When a bullet strikes on bulletproof body armor, it is caught in a web of very strong fibers. These fibers absorb and distribute the impact energy of the bullet causing the bullet to deform like a mushroom.

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Reference www.safeguardarmour.co.uk/articals/kevlar-uses Kevlarchemistry.neocities.org/about3.html www.safeguardarmour.co.uk/articals/ballistic-plates-su

mmary www.wikipedia.org/wiki/Kevlar www.explainthatstuff.com/kevlar.html www.dupont.co.in/products-and-services/fabrics-fibers-n

onwovens/fibers/brands/kevlar/products www.technologystudent.com/joints/kevlar2.html Event-videek.blogspot.in/2015/03/power-wheels-

obamas-beast.html P K Mallick -Fiber reinforced composites - Materials,

Manufacturing & Design-CRC Press 3rd Addition Manufactured Fibre Technology by V.B Gupta & V.K

Kothari

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