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Transcript of Kevlar
- purely chemical process
- Kevlar is a complex polyamide which are formed through condensation reactions of ammonia-like chemicals and organic acids Forming the Fibers:
-Kevlar naturally forms rod-like shapes due to molecular structure
-through a process called "wet spinning" the rods line up in the same direction, increasing the number of hydrogen bonding opportunities
- the fiber that forms is super strong The hydrogen bonds formed in the synthesis of Kevlar are directly responsible for its high-tensile strength. Kevlar is five times stronger than steel and is therefore the material of choice for things like cables in suspension bridges. One of Kevlar's competitors comes from the company, Novana, which recently received a federal grant to produce what they call ABC-Matrix. Thank You! Alternatives Though currently the most widely-used product of its kind, other similar creations threaten to eliminate Kevlar as the leading high-tensile material ABC-Matrix is considered to be equal in durability and strength, but costs a fraction of what Kevlar does. In addition, this new polymer is created by melting polymers together from certain recycled plastics, making it eco-friendly as well. And if that wasn't enough, the polymer has the capability of melding back together after damage has incurred. Kevlar is made up of "light elements" like carbon, nitrogen and oxygen, as opposed to strong, but heavy elements like iron. This is what allows it to remain lightweight, despite its strength and thus can be woven into fabrics to make comfortable things like cut-resistant gloves or bullet-proof vests. Intermolecular interactions:
The individual strands within the chain are bonded using hydrogen bonding. The hydrogen from an amide at the end of one chain bonds to an oxygen which is double-bonded to a carbon on another chain.
Functional groups of polymer backbone:
Throughout the chain are benzenes, which is an aromatic functional group. Functional groups of side chains:
Kevlar is a polyamide, so it contains amide functional groups within it. Shape:
- The shape of Kevlar is complex. The presence of the aromatic rings make it too rigid to adjust in a linear fashion.
- The polymer chain is orientated as a crystalline, another reason why the strength of Kevlar is so great.
- It is a condensation polymer; a water is removed between the -COOH and -NH2 groups when one chain is bonded to another. Kevlar is an alternating copolymer of phenylene diamine (para H2N-C6H4-NH2) and terephthalic acid (para HOOC-C6H4-COOH) condensed together. Unfortunately, Kevlar is not biodegradable, recyclable, or renewable and producing Kevlar requires a lot of energy and has toxic by-products. The life cycle of Kevlar depends on what material it is used in. For example, DuPont recommends that bullet-proof vests be replaced every 5 years to account for changes in technology as well as damage due to wear. However, cables in bridges don't have to be replaced for decades. In addition, the durability of Kevlar decreases significantly when exposed to certain harsh chemicals such as bleach. It also degrades with exposure to UV light, so prolonged exposure to direct sunlight will decrease its life span. Now and Future: Finally Kevlar has incredible heat resistance, up to about 800 degrees F. This makes Kevlar useful in high-heat situations such as in the brakes of cars or as heat-resistance gloves for welders or glass blowers. Researchers are constantly testing new blends of Kevlar. One promising study observes the effects of coating Kevlar with a chemical called Acyclic N-Halamine. When subjects wore Kevlar material coated with this and were exposed to biohazards such as E. Coli, the Kevlar material was found to be resistant. Almost no traces of bacteria were found on the clothing. This could mean a brighter and safer future for hospital staff and biomedical researchers. The overall polymer has a formula of [-CO-C6H4-CO-NH-C6H4-NH-]n The chemical formula of the monomer units is C14H10N2O2 By Dilpreet Mayall and Courtney Pasco
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Luo J., Yuyu, S., “Acyclic N-Halamine Coated Kevlar Fabric Materials: Preparations and Biomedical Functions,” ACS Ind. Eng. Chem. Res., 2008, 47 (15), pp 5291-5297. doi:10.1021/ie.800021p.
McCorvey J. J., Innovation: A Cheaper Alternative to Kevlar. http://www.inc.com/magazine/201110/innovation-a-cheaper-alternative-to-kevlar.html. (accessed April 25, 2013).
UC Davis ChemWiki. http://chemwiki.ucdavis.edu/Organic_Chemistry/Polymers/Condensation_Polymers. (accessed April 25, 2013).