Polymeric rubber is a family of materials that consists of molecules whose carbon (C) backbones are connected by covalent chemical bonds. Polymers are generally considered to be stiff, inflexible materials, but the chemistry behind some of these compounds allows for a great deal of flexibility. The C atoms that make up the backbone of a polymer can be bonded to other atoms in different ways, giving rise to many different polymer types. One of the more common forms of polymeric rubber is elastomer, which has the ability to return to its original shape after being stretched or deformed. The elasticity of elastomer is derived from the fact that the polymer chains are coiled when it is at rest, but can be stretched to many times their original length without breaking. The coiled chains then snap back into their original position when the tension is released.
The vulcanization process that creates the elasticity and resistance of rubber is a complex reaction that involves many chemicals. During this process, the molecules of the rubber are linked together through strong chemical interactions (van der Waal forces). The strength and ductility of the finished product depend on these interactions as well as other factors, such as the type of monomer used to start the synthesis and the temperature at which it is performed.
Natural rubber (NR) is a plant-derived polymer that has good elasticity, durability and cost efficiency. Its abrasion and vibration-dampening properties are useful in hoses, tires and rollers for printing machines. Its relative gas impermeability makes it suitable as a lining for tanks and processing equipment. Its water resistance and tensile strength are also useful in hoses, pipes and tubing. Its relatively low flammability and high tensile strength combined with a broad operating temperature range make it an ideal material for a wide variety of industrial applications.
It is often combined with fillers and additives such as carbon black, factice or whiting to give it specific physical properties. For example, a rubber coating is typically sprayed on a surface to act as a cushion or shock absorber. This type of surface is commonly used for athletic tracks and other recreational surfaces where a high degree of traction is required as well as a level of impact absorption to reduce injuries.
Synthetic NR and polyurethane (PU) are the primary materials used in most rubber products. They are derived from two monomers, a diol and a diisocyanate. The monomers can be combined in a variety of ways to produce a wide range of polymer structures, from soft foams to hard varnishes. PU has the advantage over NR in that it can be combined with other ingredients to improve its performance in extreme environments and for different applications. It is particularly well suited for use in sport surfaces because it combines excellent elasticity with good endurance, and can be sprayed in a variety of colours to meet individual requirements. It is also suitable for outdoor use, as it is resistant to weathering and ozone.