Rubber is an elastic polymer that is available as a natural or synthetic derivative. Natural rubber is made from the sap of the rubber tree, while synthetic rubber—including styrene-butadiene (SBR) and ethylene propylene diene terpolymer (EPDM)—is made from oil and natural gas. A vulcanization process heats rubber with sulphur, accelerator, and activator at 140-160 degrees Celsius to strengthen the bonds between long molecules. As a result of this process, rubber is extremely elastic and resistant to water and heat, while also holding good rebound properties. Rubber is most often used for car tires but can also be found in flooring products or in the backings of other flooring materials.