Today, Kevlar fabric is widely used in sewing clothes and equipment for people who are exposed to danger during their work: military, astronauts, police, athletes, etc.
Kevlar fabric was developed by DuPont in 1965 and is a registered trademark of a para-aramid synthetic fiber.
Later, fibers were created with properties similar to Kevlar, but all materials belonging to this type began to be called Kevlar. The widespread use of Kevlar began in 1970, when this high-strength material began to be used in racing tires to replace heavy steel.
Currently, Kevlar fiber is used in a variety of fields: in the production of bicycle tires, yacht sails, in body armor, to increase the strength of parts of carbon fiber feet in prosthetics.
What type of fabric is this?
Kevlar is a synthetic fabric with a crystalline structure. This material is durable due to the benzene ring located in the cross section of the crystal. Kevlar is stronger than metal in its properties.
This material is produced in America at the DuPont chemical plant. Kevlar production begins only when low temperatures are reached.
Kevlar colors
Calcium chloride and methylpyrrolidone are mixed, then reagents are added. All these substances enter into a chemical reaction, and a polymer is obtained that has the properties of liquid crystals.
The resulting polymer looks like a gel or fine crumbs. It is thoroughly washed, then dried and then dissolved in sulfuric acid. The resulting solution is passed through dies. The result is fibers. By twisting them, threads are created and fabric is obtained from them.
Structure and properties
Molecular structure of Kevlar: monomer in bold, dotted lines indicate hydrogen bonds.
Once formed, Kevlar fibers have a tensile strength of about 3620 MPa and a relative density of 1.44. The polymer owes its high strength to the many bonds between monomers. These bonds have a greater effect on the properties of Kevlar than van der Waals forces and chain length, which typically affect the properties of other synthetic polymers and fibers such as Dyneema. The presence of salts and some other impurities, especially calcium, can affect the properties of the final product, and during production they try to avoid the inclusion of impurities in the composition of Kevlar.
Origin story
Kevlar was created in America in 1964 at the DuPont chemical plant. The creator of this material is American chemist Stephanie Kwolek. Kevlar began to be produced on an industrial scale in 1970.
Initially, the material was created for reinforcing cables and tires for cars. Subsequently, the scope of application of Kevlar became extensive.
Kevlar fabric is a registered trademark of a para-aramid synthetic fiber.
How to buy Kevlar fabric
You can buy Kevlar fabric at almost any fabric store. The cost of Kevlar varies depending on the density and type - canvas, tape or thread. Average price of 1 sq. m. Kevlar fabric is 2,500 rubles.
Kevlar fabric impresses with its physical and chemical properties. This is a modern, high-strength material, the characteristics of which have been appreciated and used in a wide variety of areas from clothing production to strengthening aircraft engine parts.
Companies developing aramid fabrics do not stop at Kevlar alone, improving this fiber and creating analogues with properties superior to Kevlar.
Types of fabric
Types of Kevlar are presented in the table.
| View | Peculiarities | Application area |
| Kevlar K-29 | Was produced very first, has standard properties | Reinforcement of cables, car tires, strengthening of car elements |
| Kevlar K49 | Fiber structure: high modulus | Manufacturing of cables, ropes, plastic reinforcement |
| Kevlar K100 | Yarn Dyed | Sewing special clothing (military uniforms) |
| Kevlar K119 | Increased elongation and flexibility | Reinforcement of rubber products |
| Kevlar K129 | Increased strength | Making armor |
| Kevlar AP | Slightly stronger than Kevlar K-29 | Reinforcement of cables, car tires, strengthening of car elements |
| Kevlar XP | Contains high viscosity resin with added KM2plus fiber | Manufacturing of body armor |
| Kevlar KM2 | Special fibers for making high-strength fabrics | Manufacturing of body armor and helmets |
Material characteristics
- thin and light – the thickness of the produced fibers is 1 micron;
- the finished fabric does not stretch even with frequent wear;
- resistant to fire - it begins to melt only at temperatures above 430 degrees, but a certain amount of time must pass (therefore the material is suitable for special services uniforms);
- it cannot be damaged by solvents;
- despite the lack of stretching properties, elastic;
- not subject to corrosion;
- negative temperatures do not make the material worse, but only enhance its strength;
- the material does not conduct electric current and does not accumulate static electricity;
- Kevlar fibers cannot be cut even by running a sharp knife blade through them.
Pros and cons of fabric
Pros:
- Increased strength, cut resistant.
- Keeps its shape well.
- Fire resistance. Does not burn or melt, can withstand temperatures up to 480°C.
- Does not corrode.
- High wear resistance.
- At low temperatures, strength increases.
- Quite low level of electrical conductivity.
Minuses:
- Long exposure to direct sunlight leads to loss of material properties.
- When wet, the strength of the material decreases.
- Needs special careful care.
- Poor air exchange, the body “does not breathe.”
- Very high price.
Rules of care
When caring for protective devices, you need to remember that Kevlar is a polymer that does not tolerate moisture, ultraviolet rays and dry cleaning, so when caring for it you must follow the manufacturer's recommendations. DuPont guarantees the preservation of the protective properties and durability of its Kevlar products for up to 10 washing cycles. Washed items should be dried indoors, but exposure to heat does not harm them. As for exposure to various chemicals, especially those containing chlorine, contact with them is extremely undesirable, although cleaning with oxygen bleaches is quite acceptable.
What standards are used in production? What do they take into account?
Kevlar fabric is a registered trademark of a para-aramid synthetic fiber. When manufacturing it, it is necessary to rely on GOST 33842-2016 “Para-aramid fiber”.
When producing this material, the following are taken into account:
- linear density;
- tensile modulus of elasticity;
- twist;
- sagging thread;
- moisture contents;
- dressing content;
- tensile strength;
- elongation at break.
Carbon fabrics
Carbon fabric (carbon fabric or carbon fabric, from “carbon”, “carbone” - carbon) - fabrics woven from carbon fiber threads. Such threads are very thin (approximately 0.005-0.010 mm in diameter[1]), they are very easy to break, but quite difficult to break. Fabrics are woven from these threads. They can have different weaving patterns (herringbone, matting, etc.). The materials are distinguished by high tensile strength, rigidity and low weight, often stronger than steel, but much lighter (in terms of specific characteristics it surpasses high-strength steel, for example 25KhGSA).
Carbon filaments are usually produced by heat treating chemical or natural organic fibers, which leaves primarily carbon atoms in the fiber material. Heat treatment consists of several stages:
- The first of them is the oxidation of the original (polyacrylonitrile, viscose) fiber in air at a temperature of 250 °C for 24 hours. As a result of oxidation, ladder structures are formed.
- After oxidation, the carbonization stage follows - heating the fiber in nitrogen or argon at temperatures from 800 to 1500 °C. As a result of carbonization, graphite-like structures are formed.
- The heat treatment process ends with graphitization at a temperature of 1600-3000 °C, which also takes place in an inert environment. As a result of graphitization, the amount of carbon in the fiber is increased to 99%.
In addition to ordinary organic fibers (most often viscose and polyacrylonitrile), special fibers from phenolic resins, lignin, coal and petroleum tars can be used to produce carbon filaments. In addition, carbon parts are stronger than fiberglass parts, but at the same time, they are much more expensive than similar fiberglass parts.
Carbon fabric is most often used to create carbon fiber plastics, carbon fiber, using the following technologies:
Pressing.
The carbon fabric is lined in a mold pre-lubricated with an anti-adhesive (for example, soap, wax, wax in gasoline, Ciatim-221, silicone lubricants). Impregnated with resin. Excess resin is removed in a vacuum (vacuum molding) or under pressure. The resin polymerizes, sometimes when heated. After polymerization of the resin, the product is ready.
Contact molding.
Using the example of making a bumper: take a metal original bumper (“boob”) and lubricate it with a separating layer. Then polyurethane foam (gypsum, alabaster) is sprayed onto it. After hardening, it is removed - this is the matrix. Then it is lubricated with a separating layer and the fabric is laid out. The fabric can be pre-impregnated, or it can be impregnated by brushing or pouring directly into the matrix. The fabric is then rolled with rollers to compact and remove air bubbles. Then polymerization (if the hardener is hot-curing, then in an oven, if not, then at room temperature - 20 ° C). Then the bumper is removed, if necessary, sanded and painted.
Pipes and other cylindrical products are produced by winding. Fiber form: thread, ribbon, fabric. Resin: epoxy or polyester. It is possible to make molds from carbon fiber at home, if you have experience and equipment.
link: Carbon fiber reinforced plastics - Wikipedia
go to Fabric Catalog
What purposes can this fabric be used for?
Kevlar is used in various fields:
Sports and tourism. Equipment for tourists and athletes is made from this material.
Orthopedic industry. Kevlar is used to produce the part of the bionic prosthesis that connects the limb and the prosthesis.
Armor protection. This material is used in the manufacture of body armor and armored helmets for intelligence officers.
Protective clothing. Kevlar fabric is used to produce gloves and clothing for protection against fire, welding, shrapnel and other things.
Aviation. Kevlar is used to make skins for airplanes and helicopters.
Automotive industry. Kevlar is used to reinforce tires and strengthen car parts.
Applications of Kevlar
As mentioned above, the goal of the developers was to create a lightweight but at the same time durable material that could replace heavy steel in the production of tires.
Later, thanks to the excellent properties of Kevlar, they began to use it in sewing clothes, overalls, military uniforms, etc.
Armor
Kevlar is a well-known component for the production of personal armor and protection products.
Combat helmets, ballistic face masks and body armor are made using Kevlar. The armed forces of various countries use Kevlar to create bulletproof masks and balaclavas for armored vehicle crews.
Kevlar is so strong that it is used as armor for Nimitz-class aircraft carriers.
In the civilian sphere, the properties of Kevlar are used to create equipment to protect emergency response workers. The body armor of police officers, private security companies and special forces soldiers is also made of Kevlar.
Sport equipment
Kevlar is used to line bicycle cleats, which increases their puncture resistance.
Kevlar fibers are also used to increase the rebound of tennis rackets and reduce their weight. In motorsports, Kevlar is used to produce safe clothing for motorcycle athletes and to strengthen elements in the shoulder and elbow areas.
The properties of Kevlar have been successfully used in other sports - creating jackets, trousers, elements of masks in fencing, in the Japanese art of archery Kyudo to strengthen the bowstring, to improve performance in sails for racing boats, etc.
Musical instruments
Kevlar has excellent acoustic properties, which are used in the creation of acoustic speaker cones for transmitting low and mid frequencies.
Kevlar is used as a base material in strings for stringed instruments. Kevlar strings become stronger, more flexible and more resistant to temperature changes.
Other Applications
Due to its physical properties, Kevlar is used as a reinforcing fiber, allowing parts to be made lighter and stronger.
Kevlar fiber is used to strengthen cables, which protects the wires from stretching and breaking. The ability to combine Kevlar with other polymers through a chemical reaction allows the creation of more advanced materials used in specific areas.
As an example, carbon-Kevlar, which is characterized by high heat resistance and lightness, is used for the construction of high-speed boat hulls.
Flaws
Kevlar fabric has virtually no disadvantages when considering its purpose. But aramid fiber also has weak points. Prolonged heating and exposure to sunlight reduces the strength of the material. But we are talking about intensive use for hundreds of hours in a row. Wet fabric also loses some of its unique properties, so when Kevlar is used in conditions of high humidity, it is strengthened and impregnated.
The material does not have aesthetic appeal, but this cannot be called a minus if you remember for what purpose the polymer was invented. It is not used for sewing street clothes, and therefore does not need improved decorative properties.
Kevlar thread
What is Kevlar thread? The resulting aramid fibers are twisted into threads, and their number may vary, giving different thicknesses of the finished product. For example, threads with no more than 1000 fibers are used to create Kevlar fabric - the finished material is thin, light and, at the same time, durable. If up to 10,000 fibers were used, such a thread is used for technical purposes, for example, for reinforcing certain materials, as well as in the production of high-strength cable, ropes, etc.
Manufacturing Principles
Kevlar is an expensive process to produce, so the material costs more. One linear meter can cost more than $30, but this price is due to its ultra-durable properties.
Expert opinion
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To obtain polymer threads, you need to go through more than one chemical reaction. A solution of calcium chlorine and methyl pyrrolidone is used as a base. Special reagents are poured into them, which precipitate and form a liquid crystalline substance. This is a cross between gel and powder.
Before loading the substances into the machine, they are washed to remove any remaining solution and dried. Then the future polymer is passed through molds (special equipment does this). This is how a homogeneous substance turns into the finest threads (or fibers, depending on the scope of application). For this to happen, a lot of sulfuric acid is needed - this is what makes the production process expensive for the manufacturer.
Compound
It's time to find out what Kevlar is made of - such a durable material that cannot be replaced by anything else. It is a para-aramid fiber with a yellowish tint. It is a polymer, so the resulting threads are synthetic. They are added to the composition of fabrics from which durable workwear and equipment (for example, gloves) are sewn.
Kevlar is also used as a composite (tires), but here, in addition to it, carbon fiber and fiberglass are added, although Kevlar is many times stronger than them. If it is the main material, then the item made from it will be too expensive.
Strength averages 360 kg per 1 mm2, but in some species it can reach up to 550 kg. In terms of structure and properties, they tried to bring Kevlar as close as possible to a durable, natural material - spider web. Compared to steel, for which this figure only reaches 150 kg, Kevlar is much stronger. It also has a low density (about 1500 kg per cubic meter), which is slightly more than water (1000 kg/m3).
