Polymers are organic materials made up of a chain of single units called monomers. They are manufactured in a process called polymerisation which involves joing monomers together to form long chains of propylene, joined together to form a long chain. A polymer product may contain a large number of the long chains.
Synthetic and Natural Polymers
Polymers can be made from synthetic and natural polymers. Synthetic polymers are most common and are chemically manufactured using carbon based materials like crude oil.
Natural Polymers are made by processing natural materials like plants. The most common natural polymer is latex which comes from trees and it is a form of rubber. As people are becoming more conscious of the environment there is an increasing interest in natural polymers.
Thermosets are formed by a moulding process where they create lots of links across the different polymer chains. This stop the chains from moving and make them harder and more rigid than thermoplastics. This gives them a good resistance to electricity and heat. Once they have been moulded they cannot be re-shaped or recycled.
Thermosetting polymers include melamine formaldehyde, phenol formaldehyde, urea formaldehyde and epoxy resin. They are used for things like electrical fitting, electrical equipment, electrical insulators and domestic appliances.#
Thermosets are available in powder or granular form, they can be mixed with fillers and colouring agents. A filler is a cheap material that is used to add bulk therefore reducing the amount of polymer needed. This makes it cheaper and can change the properties of the polymer.
Thermoplastics do not have links between the chains so they are softer and more flexible. They soften when they are heated and can be re-shaped when hot. They then harden when cooled. They can usually be recycled. They are available in sheets or in glanular form. Granular form is used in the moulding processes.
There are many thermosetting plastics including polypropylene, high impact polystyrene, acrylic, nylon, high density polyethylene, low density polyethylene and polyvinyl chloride. They all soften at different temperatures and have different properties.
I will focus on HDP (high density polyethylene) because this is the material used to create the body of the pedalos along with fibreglass
HDP is a polymer made from petroleum. It has strong intermolecular forces, this means the bonds between the molecules are strong. It also has a high tensile strength meaning it stays strong when it is being pulled apart. These properties are stronger than that of LDP (low density polyethylene). It can withstand a constant temperature of 110 degrees. It is hard and opaque so you cannot see through it. HDP is lighter than water, therefore it floats. It can be moulded, machined and welded, making it appropriate for rotational moulding. A similar material would be polypropylene. To create 1kg of HDP you need 1.75kg of oil therefore it is not very environmentally friendly, although it can be recycled the quality is not as good. It is very resistant to acids, alkalines and solvents therefore if there was any of these impurities in the water it would not be a problem. It is dense because it does not branch like many other polymers. When a material branches the molecules stop going in a straight line and instead they branche off into different lines of molecules.