Super tough man-made fiber ~
it may be due to the lack of "natural" or the lack of breathability of chemical fiber clothes in the early years, the word "chemical fiber" always has a bad impression in people's minds. However, there are actually many materials with excellent properties in man-made fibers, and today we will introduce one of them with outstanding strength and toughness: Kevlar.
Yes, as a man-made fiber material, its most famous use is to make protective equipment such as bulletproof vests and helmets. This use is due to the unusual tensile properties of this man-made fiber. It has a high strength-to-weight ratio, that is, it is strong and light at the same time. It is often said that Cave is about five times stronger than steel of the same weight.
Kevlar is actually a trade name, and the chemical nature of this material is an aromatic polyamide (polyterephthaloyl-p-phenylenediamine). Because of the structure of p-benzene ring, Kevlar has a long, straight and relatively rigid molecular chain, and under the action of hydrogen bond, the molecular chains often combine closely with each other to form a flake structure. The strength and toughness of the fiber is related to these structural characteristics.
(Kevlar molecular chain bound to each other by hydrogen bond)
in 1965, Stephanie Kwolek, a chemist working for DuPont, discovered the strength and toughness of this polymer in experiments. Kevlar officially entered the market in 1971. Now, there are more superior tough fiber materials on the market, but Kevlar's pioneering position is still recognized by the world.
(Stephanie Kwalak, the female chemist and inventor of Kevlar materials. What she has in her hand is Kevlar's molecular structural unit)
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Stephanie Kwalak may not be familiar with the name, but this account has actually introduced another of her inventions: the nylon rope experiment. The chemist is also a person who is enthusiastic about popular science and education. she participated in inventing this demonstration experiment of forming nylon polymers from the interface. Now it is often seen in chemistry class:
Experimental principle see: experimental dynamic picture: pull a nylon rope
the cover picture is a cartoon of Kvorak. From: https://minidovecomics.wordpress.com/2013/10/28/stephanie-kwolek/
PS: today the 2017 Nobel Prize in Chemistry was awarded to Jacques Dubochet,Joachim Frank and Richard Henderson for their contribution to the development of high-resolution frozen electron microscopy.
you may have heard how x-ray diffraction helps people determine the structure of biological macromolecules (such as the most famous DNA double helix). This is a classical method, but it still has many defects, such as it is difficult if the macromolecules are not crystallized. What won the prize today is a technology that is easier to use than x-ray diffraction, through which you can easily see the fine structure of various complex biological macromolecules and their natural state, which is very important for the development of biochemistry. Related reading → new Nobel Prize: in this unprecedented high-definition world, see the details of life
(regardless of the biophysics professor winning the chemistry prize for the sake of the good use of the technology)