What is Kevlar?
Born in the late 1960s, Kevlar is a new type of high-tech synthetic fiber. It is widely used in the field of bulletproof products and is one of the ideal bulletproof materials. So what kind of material is Kevlar, and why does it have such strong bulletproof performance? What are the usual applications? Let's start with Kevlar's molecular structure and bulletproof principle.
1. Molecular structure of Kevlar
Kevlar was originally a kind of aramid fiber material developed by DuPont (DuPont) in the United States. Its chemical name is polyparaphenylene terephthalamide, which is polymerized from p-phenylene diamine and terephthaloyl chloride. into high molecular weight polymers. The molecular formula is (C14H10O2N2)n, which means that it is composed of repeating units connected to each other to form a chain structure, and these chain structures are connected by hydrogen bonds to form a network.
The molecular structure of Kevlar determines that it has strong heat resistance and flame retardancy. Very good tensile properties.
Usually the manufacturing process of Kevlar fiber is divided into two stages:
1) Polycondensation of p-diphenylamine and terephthaloyl chloride into p-phenylene terephthalamide (PPTA).
2) The polymer is dissolved in a solvent and then spun to form the required mesh fiber material.
1. The bulletproof mechanism of Kevlar
As mentioned earlier, unlike hard bulletproof materials such as ceramics and metals, Kevlar has ultra-high strength, good toughness and tensile properties due to the tight combination of chemical bonds in the molecule. The Vla fiber will produce elastic deformation due to the stretching and shearing of the projectile. During this process, the energy of the bullet is forced to diffuse to the area other than the impact point. The loss of kinetic energy will greatly reduce the speed of the bullet, and it will eventually be intercepted by the fiber net. The application of Kevlar in the field of bulletproof has greatly improved the protective performance of various bulletproof products, and at the same time greatly reduced the weight of bulletproof equipment, which is a great progress in the field of bulletproof.
2. Application of Kevlar
With good heat resistance, tensile strength and high strength, Kevlar has been widely used in the manufacture of various daily life products and bulletproof equipment. For example, beverage straws and safety gloves that are often used in our daily life; parachute ropes for aerospace, cables for ships; racing suits, firefighters’ heat-insulating protective clothing; military body armor, bulletproof plates, bulletproof helmets, etc. Wait. The application of Kevlar greatly facilitates our life and promotes the progress of the manufacturing industry.
But aramid also has two fatal shortcomings:
1) It will degrade when exposed to ultraviolet rays;
2) Easy to hydrolyze, even if it is stored in a dry environment, it will absorb moisture in the air and gradually hydrolyze.
Therefore, some aramid products are not suitable for long-term use in strong ultraviolet and humid environments, which will greatly reduce their service life.
The above is the introduction to Kevlar, if you have any questions, please come to consult us.
