KEVLAR

Properties and Applications

ByG.SAI PRAVEEN 11671A0334

AbstractThe objective of the paper is to explain about Kevlar, a synthetic polymer. To examine the structure, properties, advantages, disadvantages and various applications of the Kevlar which is a super strong material in detail. Thus by learning about this material enables its appreciation in various fields.

IntroductionKevlar is a registered trademark for a synthetic

fiber produced by DuPont, a chemical company.

Kevlar was developed in 1965 and being used

commercially since 1970. DuPont can also be

credited for the development of other polymers

such as Neoprene, Nylon, Teflon, Nomex etc..

Chemical name for kevlar is poly-para-

phenylene terephthalamide

Description Kevlar is a polymer Kevlar is a high strength material It is very light when compared to its strength It is 5 times stronger than steel of same weight It has very high tensile strengthThus it can be said as a Super strong plastic

Production step 1 (chemical synthesis)

Kevlar is synthesized in solution from the monomers 1,4-phenylene-diamine (para-phenylenediamine) and terephthaloyl chloride in a condensation reaction yielding hydrochloric acid as a byproduct.

Step 2 (wet spinning) The chemical obtained is turned into fibers by a process

called wet spinning, which involves forcing a hot, concentrated, and very viscous solution of poly-para-phenylene terephthalamide through a spinneret (a metal former a bit like a sieve) 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, super-stiff finished material we know as Kevlar. Later, this fiber is woven into sheets.

Structure

Kevlar is a polymer chain with cross linkages which owe to its high strength. The hydrogen bonds also strengthen the bonds.

Types of KevlarAlthough Kevlar is main product, there are various other grades of Kevlars produced

Kevlar Kevlar K29 Kevlar K49 Kevlar K100 Kevlar K119 Kevlar K129 Kevlar AP Kevlar XP Kevlar KM2

Properties Strength to weight ratio is more

Withstands temperatures upto 450

C and as low

as -196

C Self extinguishable Resistant to almost all types of chemicals Negative co-efficient of thermal expansion Abrasion resistance

These all properties enable the usage of Kevlar in various products individually and in composites.

Advantages DisadvantagesHigher strength

to weight ratio Impact resistanceAbrasion

resistanceDoesn’t expand

on heating

Absorb moisturePoor

compressive strength

Difficult to cut and drill

APPLICATIONS Industrial applicationsKevlar is used to make industrial equipment such as hoses, belts, reinforcement materials. It is used to make parts of aircrafts, ship hulls, reinforce tires.

Military applicationsKevlar is used to make military equipment such as Bulletproof vests, helmets, reinforcements for military vehicles and in making other light weight military equipment

Sports equipmentKevlar is used in making of various sports equipment due to light weight and strength. These include Kanoe hulls, race car parts and body, sport shoe, snow boards, skate boards, surf boards, gloves, racquets, motor sport helmets

Personal safety equipmentKevlar is used in production of various personal protection gear such as riding shoe, helmets, industrial gloves, fire fighting apparel, vests, body armors, body pads

Comparison between steel and KevlarImpact of bullet on steel

Comparison of Computer Predicted andExperimental Impact Crater – Steel Only

Impact on Kevlar® Panel

Comparison of Computer Predicted andExperimental Impact Crater – Kevlar®

HOW IT WORKS? When a bullet strikes body armor, it is caught in a “web” of very strong fibers. These fibers absorb and disperse the impact energy that is transmitted to the bullet proof vest from the bullet, causing the bullet to deform or “mushroom.”

Future of Kevlar A lot of development has been made in using

kevlar properties. It has predominantly entered many fields . Although Kevlar is mostly exploited, still a lot has to be done in this field.

Kevlar has poor compressive property, so innovations to be made to improve compressive property.

The Kevlar fiber is also too stiff, and it should be made flexible for more usage.

The cost also should be reduced to make it more affordable and usable by common public.

ConclusionKevlar is now being used in many high end products, but still has a large usage and made very fast foray into a vast range of products. This is all due to the virtue of the properties it possesses. And in very near future Kevlar is going to be used commonly in all walks of life