a Chemical Reaction > Kevlar is synthesized in solution from the monomers prrra- phenylenediamine(PPD) and terephthaloyl chloride(TCl) ina condensation reaction in which molecules of HCI are terminated as a byproduct. > Hexamethylphosphoramide ~~ O-0 "BOte was the solvent initially used for the synthesis, but for safety ee oame reasons DuPont replaced it by a solution of is N-methyl pyrrolidone and fu Ofrn-t| (O) a n CaCly. Polymerization in solvent -n Hcl PPTA oF Kevlar; repeat unit ‘Scanned with CamScanner5 % 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. ‘Scanned with CamScanner6 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. $ Piston anached to reversible drive Coagulation Sate A dry-jet wet-spinning process for PPTA fibre [20] ‘Scanned with CamScamner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. ‘Scanned with CamScanner8 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) > Noembrittlement 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. ‘Scanned with CamScanner9 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. ‘Scanned with CamScanner10 Applications + industrial 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. ‘Scanned with CamScanner1 > 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. KEVLAR® KEVLAR® REINFORCED REINFORCED BICYCLE TYRE CAR TYRE RUBBER |KEVLAR, - ‘Scanned with CamScammer12 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. > FI race car parts and body, sport shoes, snow boards, skate boards, surf boards, gloves, racquets, motor sport helmets etc are also madeup from Kevlar. ‘Scanned with CamScanner3 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 LS EUROFIGHTER PANELS AND WINGS ‘Scanned with CamScanner18 Types Of Kevlar * Although 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. > Keviar119- 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. ‘Scanned with CamScanner