Rabu, 26 April 2017

Chemical articles

Kevlar As Bulletproof Vest Material
Bulletproof vests are protective clothing to minimize bullet injury. Usually used by military and police personnel in certain tasks. Materials for bulletproof vests include metal (steel or titanium), ceramic or polymer type which can provide extra protection against the vital parts of the wearer.
This vest protects the wearer by holding back the bullet. The bullet is stopped before penetrating into the body. When the vest holds the bullet penetration, the drive from the bullet is reduced by spreading its momentum throughout the body. Users will still feel the kinetic energy of the bullet, this can cause bruises, swelling or serious internal injuries.
One of the polymers developed as a modern anti-bullet vest material is kevlar. Kevlar is also known as twaron and poly-paraffenylene terephthalamide, a synthetic fiber whose strength is five times the strength of copper, of the same weight. Kevlar is extremely resistant to heat and decomposes above 400 oC without melting. Kevlar was invented by the DuPont company in the early 1960s, the work of Stephanie Kwolek. Kevlar is a registered trademark by E.I. De Pont de Nemours and Company.
Properties
Kevlar is one type of aramida, which consists of long chain polymers with parallel orientation. Aramide itself is a synthetic fiber in the form of a long chain of synthetic polyamides with at least 85 percent of its amid link attached directly to two aromatic chains (amide groups and alternating aromatic groups). Kevlar strength is obtained from intra-molecular hydrogen bonds and interaction of aromatic powders between sheets. These interactions are stronger than the interactions of Van der Waals contained in other synthetic polymers and fibers such as dyneema (fibers made from very long polyethylene chains, arranged in the same direction). The presence of other salts and impurities, usually calcium, may interfere with the interaction of polymer sheets and must be eliminated in the production process. Kevlar consists of relatively rigid molecules, which form structures such as flat sheets on silk proteins.

Of these properties obtained fiber with high mechanical strength and heat resistance.
Kevlar has free groups that can form hydrogen bonds on the outside, so they can absorb water and have good 'wet' properties. It also makes it feel more natural and 'sticky' compared to polymers in general, such as polyethylene.
The main weakness of kevlar is that it can decompose under alkaline conditions or when exposed to chlorine. Although it can support large tensile stress, kevlar is not strong enough under compressive pressure. To overcome this problem, kevlar is often used in conjunction with strong materials against compressive pressures.
Production
Kevlar is synthesized from monomers 1, 4-phenyliamylamine (para-phenylenediamine) and terephthaloyl chloride. The result is an aromatic amido polymer (aramide) with a benzene ring and an alternating amide group. With this production step, randomly assembled polymer sheets are produced. To make kevlar, the materials are dissolved and stirred, resulting in a fiber-oriented polymer chain.
Kevlar is expensive because of the difficult use of concentrated sulfuric acid in its production. This extreme condition is required to maintain the high polymer toxicity in solution during synthesis and stirring.
DSM's Dyneema, Akzo's Twaron, Toyobo's Zylon (controversial, recent study, the material is rapidly degraded so that the wearer is not as protected as expected), or Honeywell's GoldFlex - all trademarks. The new materials are lighter, thinner, and more resistant than kevlar, but the price is more expensive. (Reader: From various sources).

Literature:


14 komentar:

  1. what is meaning of kevlar?

    BalasHapus
    Balasan
    1. Kevlar is a registered trademark for synthetic aramid fiber fibers, this material is still in contact with Nomex and Technora. Poly-paraphenylene terephthalamide / Kevlar was created in 1965 by Stephanie Kwolek when she worked at DuPont. Furthermore, this material was developed by DuPont company. This powerful material was first used commercially in the 1970s as a substitute for steel in tire products for racing purposes. This material is widely used on tires and ship screens to materials for the manufacture of bulletproof vests, this is due to the strength and elasticity of the material and the light weight that is the nature of this material. This material is touted as a material that is five times stronger than steel of the same weight.

      Hapus
  2. Whether to make household appliances using kevlar?

    BalasHapus
    Balasan
    1. I thought it might be just a very heavy kevlar so not used for household purposes. Besides kevlar made of carbon. But carbon fiber (kevlar) proved to provide a very significant benefit for human life. One of them in the manufacture of bulletproof vests. This vest is made of steel or titanium type of metal, ceramic or polymer type which can provide extra protection against the vital parts of the wearer. Kevlar also known as twaron and poly-paraffenylene terephthalamide was created by Stephanie Kwolek, an inventor from Kensington, Pennsylvania, USA.

      Hapus
  3. Kevlar is synthesized from monomers 1, 4-phenyliamylamine (para-phenylenediamine) and terephthaloyl chloride. Would you like to tell isomer that?

    BalasHapus
    Balasan
    1. I think it is not a type of isomer because Monomer is a polymer constituent. They can be simple or complex molecules with double bonds or other functional groups such as -OH, -NH2, -COOH, etc. of unsaturated double bonds or functional groups required in the polymerization process, when some monomers are connected to form polymers.

      Hapus
  4. "The new materials are lighter, thinner, and more resistant than kevlar, but the price is more expensive" Are there any links to the compounds used?

    BalasHapus
    Balasan
    1. Yes, the excess kevlar compared to other carbon compounds is Kevlar also known as twaron and poly-paraffenylene terephthalamide, which is a synthetic fiber whose power is five times the strength of copper, with the same weight. Kevlar is extremely resistant to heat and decomposes above 400 oC without melting.

      Hapus
  5. Why the presence of salt and other impurities, usually calcium, can interfere with polymer sheet interactions and should be eliminated in the production process?

    BalasHapus
    Balasan
    1. These interactions are stronger than the interactions of Van der Waals contained in other synthetic polymers and fibers such as dyneema (fibers made from very long polyethylene chains, arranged in the same direction).
      So salt salt is easy to react and interfere with other reactions

      Hapus
  6. What the component of kevlar?

    BalasHapus
    Balasan
    1. Kevlar is synthesized from monomers 1, 4-phenyliamylamine (para-phenylenediamine) and terephthaloyl chloride. The result is an aromatic amido polymer (aramide) with a benzene ring and an alternating amide group. With this production step, randomly assembled polymer sheets were obtained. To make the kevlar, the materials are dissolved and stirred, resulting in a fiber-oriented polymer chain forming the fibers.

      Hapus
  7. Kevlar used as a bullet vest material other than kevlar used as what?

    BalasHapus
    Balasan
    1. Aramid (Kevlar)
      This material was discovered by Stephanie Kwolek in 1964, an American chemist, who worked as a researcher at the DuPont company. Aramid is an acronym of the word aromatic polyamide. Aramid has a strong structure, tough, has a good damping properties (vibration damping), resistant to acid (acid) and base (leach), but it can withstand heat up to 370 ° C, so it is not flammable. The marketed product is known as Kevlar. Kevlar has a light weight, but 5 times stronger than iron.This material is widely used on tires and ship sails up material for the manufacture of bulletproof vests, this is due to the strength and elasticity of materials and light weight which is the nature of this material. This material is touted as a material that is five times stronger than steel of the same weight

      Hapus

A chemical learning video about the difference in the number of bonds between alkanes and alkenes

Differenrate The Number Of Bond  Between Of Alkanes And Alkenes 1. Alkanes Alkane compounds are the simplest carbon chains. Alkane...