Strong Enough To Stop A Bullet

What do color-changing pens, bullet resistant vest, and calculators have in common? The chemicals that make each of them function are called liquid crystals. These chemical find numerous applications; you are probably most familiar with liquid crystal displays (LCD) for example the LCD screens on our TV and computers and the color-changing products we see everyday, but these chemicals are also used to make super strong synthetic fibers.

Molecules in a normal crystal remain in an orderly arrangement and this arrangement can be viewed using powerful microscopes, but in a liquid crystal the molecules can flow and maintain an orderly arrangement at the same time. Liquid crystal molecules are both linear and polar. When viewed under a forensic microscope using forensic comparison microscopy techniques, the atoms tend to lie in a quite straight line, the molecules are commonly much longer than they are wide. These polar molecules are attracted to each other and are able to line up in an orderly form, without transforming into solid.

Liquid crystal with twisted arrangements of molecules that can only be classified with the aid of microscopes which can give us a unique specimen view especially when applied with forensic comparison microscopy techniques. In these liquid crystals the molecules lie side by side in nearly flat layer. The next layer is similar, but at an angle to the one under it. The closely packed flat layers have a special effect on light. As the light strikes an object, some of it is reflected from the top layer and some on lower layers. When the same wavelength is reflected from many layers, we see a color. This is the same as what we see on rainbows, the rainbow colors formed by oil in a pond on the street or the layer of a soap bubble, we normally see this on ordinary days. As the temperature increased, the molecules moved faster, causing a change in the angle and the space between the layers. This will result to a color change in the reflected light. Different compounds change its color within different temperature ranges, allowing a variety of practical and amusing applications. The color changes can be viewed under a microscope such as a forensic comparison microscope.

Liquid crystal molecules that lie parallel to one another are used to manufacture very strong synthetic fibers and these fibers are also viewed using different kinds of microscopes, although for lower magnification a simple microscope can be used. However if you want it magnified into a thousand times then you can use high-powered microscopes such as an electron microscope. Perhaps the best example of these liquid crystals is Kevlar, a synthetic fiber used in bullet proof vests, canoes, and some parts of the space shuttle. Kevlar is synthetic polymer, like nylon or polyester that gains force by passing through a liquid crystal state during the manufacturing stage.

Using forensic comparison microscopy techniques, a typical polymer can be seen as long molecular chains jumbled together, somewhat like spaghetti. This is an interesting view and you can see it using a microscope such as a forensic microscope. A forensic comparison microscope can compare two materials side by side.

The strength of this type of material is limited by the disorderly arrangement. The trick is to get the molecules to line up parallel to each other, it is an interesting fact that one can see under a microscope. Once the giant molecules have been synthesized, they are dissolved in sulfuric acid. At the proper concentration the molecules align, and the solution is forced through tiny holes in a nozzle and further alignment. One thread of Kevlar is stronger than an equal sizes strand of steel. It has a much lower density as well, making it a material of choice in bullet resistant vest that saved many lives nowadays. Read more on this subject

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