BODY
ARMOUR
Unfortunately, police officers are now regularly faced with the threat of gunfire, therefore it is very important that they take the appropriate steps to minimise the damage sustained. Bulletproof vests are now worn daily by many of the officers, ad even the dogs, who patrol our streets. In 1935, the Dupont Corporation invented nylon, which was subsequently used to protect bomber pilots in the Second World War. In 1965 the same company created Kevlar, a related polymer intended for use in the manufacture of car tyres. Kevlar has 2.5 times the tensile strength of nylon, and is therefore very suitable for the production of lightweight body protection.
The effectiveness of a material as body armour depends on the rate at which it can disperse the energy when a bullet hits it. This property is related to the rate at which sound travels in that material. Sound travels three times faster in Kevlar than it does in nylon, and therefore Kevlar will be much more effective than nylon at dispersing the energy on impact. Bullets made from lead are relatively soft and will deform on collision with Kevlar, thus reducing the chance that the bullet will penetrate the vest. While this prevents the bullet entering the body of the wearer, there is often significant bruising, as the energy cannot be dissipated effectively enough to prevent this.
It has been shown by electron microscopy that the effectiveness of Kevlar is due to the ability of the fibres to stretch on impact, thus absorbing energy before snapping. Nylon is less effective because the fibres simply melt when hit by a bullet.
Teflon is a polymer commonly used as the non-stick coating on many frying pans and also in easy-iron shirts due to its lubrication properties. Teflon coated bullets penetrate the body very easily and their manufacture is banned in many western countries.
An even stronger material is being developed that may be up to three times as strong as Kevlar, and it comes from what may seem a rather surprising host, the spider. The silk that spiders use to spin their webs and to catch prey is extremely strong and lightweight so would be ideal for use in the manufacture of body armour. Scientists are currently working on creating synthetic silk from spiders known as golden orb weavers which originate from Panama and are thought to produce seven different types of silk from various glands. The fibres in Kevlar can be stretched by up to 4% before breaking, whereas the spider silk can stretch by as much as 15%, and would be far more efficient at dissipating the energy.