2023-07-05 17:30:00
Did you know that there is a much stronger material on our planet than steel? Discover Kevlar, a material that resists heat, cuts, and even punctures.
Kevlar is recognized as one of the most fascinating and versatile materials of our time. He was discovered in 1964 by researchers from the DuPont Company. Thanks to its resistance and its exceptional lightness, it quickly conquered a wide range of applications. Whether for personal protection, high-tech equipment or industrial applications, Kevlar established itself as a essential reference.
The extraordinary properties of Kevlar have made it possible to design a new type of bulletproof vest.
In this article, we explore the main uses of this revolutionary material. Let’s see how he pushed the boundaries of science and engineering. Even today it is used in the aerospace industry, military, mining, automotive, construction, high performance sports, etc.
Kevlar: the fabric that stands up to all challenges
What is Kevlar? Kevlar is a synthetic fiber yellow of very high resistance created to exceed the limits of solidity. The material was created from PPD-T (poly-para-phenylene terephthalamide), a thermoplastic polymer made up of aromatic nuclei divided by amide groups. It is therefore a fibre aramidea material with excellent mechanical properties. THE aromatic polyamidesor aramides, are special high heat resistant materials. The PPD-T, being almost identical to the other fibres textilesis not a plastic material.
In 1964, the firm DuPont de Nemours sought to develop a material capable of replacing the steel cord used in the tire industry. After years of polymer research, Stephanie Kwolek et Herbert Blades accidentally created Kevlar. This material then became famous all over the world. It is coveted by many industrial structures.
In 1971, the polymer is marketed under the name « Kevlar ». It is a registered name of the company that created it. It took regarding twenty years for a competing product to appear on the market, such as Twaron de Teijin.
What are the properties of Kevlar?
Kevlar is often used in the product manufacturing requiring great tensile strength. It is said to have a tensile strength of 3,100 MPa and a modulus between 70 and 125 GPa. He owes his great robustness you know rigidity to the existence of hydrogen bonds between the polymer chains. These chains are well aligned and ordered. This is what gives Kevlar its crystalline appearance and its high resistance to any type of cut, shock or heat.
Here are some of its main properties:
Tensile strength : kevlar can withstand considerable forces without breaking. In fact, it is five times stronger than steel for an equivalent weight.
Lightness (d= 1.45): despite its great resistance, kevlar is a very light material. It is therefore an ideal choice for applications where lightness is essential, such as body armor and protective equipment.
Abrasion resistance: Kevlar retains its mechanical properties even when exposed to prolonged wear.
Heat resistance: retains its structural strength even when exposed to high temperatures. It decomposes above 400°C.
High chemical resistance: it is resistant to many chemicals, such as acids, solvents, and even fuels.
Electrical insulation: it is a good electrical insulator, which makes it useful in applications requiring protection once morest electrical currents.
Low thermal conductivity: it has a low thermal conductivity, which means that it does not heat up quickly on contact with heat, thus offering a certain degree of thermal protection.
Challenges and prospects for improvement of Kevlar
Despite his qualitiesKevlar also has a number of defaults related to his utilisation in different domains. For example, it is widely used in the security industry. From an optical point of view, Kevlar unfortunately does not withstand prolonged exposure to rayons UV. This can lead to a deterioration of its properties over time. In terms of safety, it is important to note that this material also loses its ballistic resistance when subjected to humidity. This can compromise its effectiveness in certain situations.
The specificity of Kevlar also makes it difficult to work with. Her machining ask for a huge job and requires a specific equipment adapted to its properties. Unlike more common fabrics such as nylon, denim or polyester, Kevlar cannot be directly made into fabric. He must be combined with a resin to get a usable structure. This observation is particularly valid for the manufacture of resistant clothing.
It should also be noted that other materials, such as ceramiccan be used in addition to Kevlar. This improves its performance in specific applications. These suits improve impact resistance, as well as ballistic protection.
What are the different types of Kevlar?
Here are the different Kevlar grades commonly used:
Basic Kevlar: mainly used to reinforce tires (car, motorcycle…) or other rubber materials.
Kevlar 29 : the most common and widely used type of Kevlar. It offers excellent tensile strength. It is mostly used in the manufacture of body armor, helmets and other personal protective equipment.
Kevlar 49 : it is a stronger variant of Kevlar 29. Kevlar 49 is used in applications requiring higher strength, such as cables, composite fabrics, reinforced tires and marine applications.
Kevlar XP: this type of Kevlar was developed to provide better protection once morest armour-piercing weapons, such as high-velocity handgun bullets. This variant of Kevlar therefore uses a special manufacturing technology to improve ballistic performance.
AP Kevlar: it is an improved version of traditional Kevlar, which offers greater resistance to shocks, heat and cuts. It is used in various industrial applications, such as protective gloves and cut protection equipment.
Kevlar KM2 : this variant is designed specifically for marine applications, such as ropes and cables used in the offshore industry. It offers excellent resistance to abrasion and fatigue.
DuPont, the original manufacturer of the material, continues to develop new new variants of this fiber. These will be tailored to specific applications and will provide increased performance. THE noms and the specifications types of Kevlar can therefore evolve over time.
Are there materials stronger than Kevlar?
Yes, there are materials considered more resistant than Kevlar in some specific contexts. Kevlar is known for its high tensile strength and abrasion resistance, as well as its ability to absorb impact energy. However, other advanced materials may provide superior performance in certain applications.
For example, the carbon fibers offer a exceptional resistance combined with low density. They are used in applications where a high strength-to-weight ratio is essential, such as in the aerospace industry and the vehicle construction high performance. Indeed, carbon fiber can withstand a tensile strength of 7000 MPa and a modulus of 520 GPa.
The dyneema is another material considered more resistant than kevlar in some respects. It’s regarding a polyethylene fiber. This material is often used for the manufacture of bulletproof vests or high performance ropes. Also, it should be noted that the resistance of a material varies depending on several factors. The environmental conditions, manufacturing method and specific properties required for a given application are all elements to take into account. Therefore, the choice of the most resistant material will depend on intended use.
The impact of Kevlar on the evolution of body armor
In the past, the bulletproof vests were made of steel. They were therefore heavy and unwieldy in combat. The extraordinary properties of this material made it possible to design a new type of bulletproof vest. It was now possible to create vests not only flexible and light, but also made with a material stronger than steel. The promising potential of this innovative polymer prompted the US National Institute of Justice to undertake a research series. Several tests have been performed to determine the thickness of Kevlar needed to stop a bullet. So the premier prototype of kevlar bulletproof vest was born.
After the tests were completed in 1973, researchers at the US Army’s Edgewood Arsenal developed a bullet proof vest made up of seven layers of Kevlar, intended for field testing. But the loss of resistance of the material to humidity during cleaning has been confirmed. Indeed, this material, although it is robust, does not tolerate being rubbed often with water. Fortunately, this problem was solved by using a waterproof material et UV resistant to cover vests.
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