Chemistry behind Parachutes

The choice of materials to make a parachute is essential for it to function well. Its main components are a fin fabric, suspension lines and support tapes. One essential feature is that the components have to have a low density. Density is defined as the mass of a material per unit volume and is normally measured in kg/m³ or g/cm³. So if there are two materials with the same volume , the one with the lowest mass, weight, and therefore the least dense one will be more beneficial for the parachute production because the denser the parachute, the faster will be the speed in which the chute will come down. So as density also depends on the mass of the materials, it’s better to use equipments with low relative molecular mass like carbon, nitrogen and hydrogen rather than elements with high molecular mass such as iron. That’s why most of the fibers used in parachutes are organic ones such as nylon 6,6 ([(-OC-( CH2)4-CO-NH-(CH2)6-NH-]n) , Terylene ([OC-(C6H6 )-CO – (CH2 )2 –O]n) and Kevlar( [C14H10N2O2]n). All of these fibers have a low density, hence, a low molecular mass and are strong, which are essential features for parachutes materials. The strength of, Kevlar, for example, is due not only because of the strength of the bonds but how the molecules are aligned. Kevlar is a polyamide and is made in a process called condensation polymerization. It’s produced, together with a water molecule, when reacting a molecule with two amines groups, which have the functional group NH2 , and a dicarboxylic acid. This polymer will contain a dipole-dipole bonding (C=O)and a hydrogen bonding (N-H) which are very strong bonds making the molecule strong. In addition to that, the molecules of the fiber are extended and perfect aligned. They need to be in a lattice chain configuration. This alignment also contributes to the stiffness and rigidity of the fiber making it more rigid. If you increase the rigidity of the material it will affect its shape which can then affect the stability of the parachute. If the parachute is stable then an air drag will be created and the parachute will descend slowly but if the parachute is unstable then the air drag won’t be produced and it will come down in a higher speed. The fact that the fiber made in parachutes is foldable, which means that it can be put in different shapes without breaking, is due to its malleability. This basically means that the layers of molecules are able to slide past each other rearranging the overall structure of the solid. Nylon and Terylene are also produced in condensation polymerization but nylon is a polyamide, like Kavlar, and Terylene a polyester ( polymer formed, together with a water molecule, by reacting diols (compounds containing two alcohol functional groups O-H) and dicarboxylic acids (compounds containing two carboxylic acids functional groups COOH).
Nylon is the material which is used the most to make parachute’s canopy because not only it has these characteristics of high strength, low density and high flexibility and rigidity but it’s also less expensive and more available than the other materials. Not only the canopy (top part of the parachute) but also the harness and the suspension lines (look at the pictures above) are made of nylon. The ripcord , the part you pull to open the parachute, is made of stainless steel and the metal connectors, used to join the suspension lines, are coated with cadmium, a d block element. Both the stainless steel from the ripcord and the cadmium coat from the connectors prevent rusting, which occurs when the iron or an alloy of iron reacts with oxygen in the presence of water. The cadmium serves as a coat and a sacrificial protection occurs, which is when a layer of a metal that is more reactive than iron, in this case, cadmium, is put over the iron metal so that as long as the “sacrificial” metal is present, it will corrode first. The stainless steel also contains a layer of chromium (III) oxide, which is more reactive than iron. This is another example of sacrificial protection.
When you practice these types of extremes sports, the hormone adrenaline starts to work in your body resulting in an adrenaline rush, which causes stress to the body. This hormone makes the blood vessels and air passages dilate. This will increase the concentration of blood into the muscle and of oxygen into the lungs. So as there’s a larger number of reactant particles in our body, therefore more collisions will happen more frequently. As there are more particles, the number of successful collisions will increase. These only occur when the particles have the activation energy, minimum energy needed for a reaction to take place. So if there are more successful collisions, more reactions inside our body will happen in a given time, increasing the rate of the reactions that happen in our body.