ENR usually comes in 25 percent or 50 percent epoxidized forms, called ENR 25 and ENR 50, respectively. The two can also be blended to produce ENR 37.5, which is particularly useful for truck tires.
Changing natural rubber to ENR changes its physical properties, including decreasing glass transition temperature (the point at which a material becomes molten or rubber-like rather than hard and brittle), increasing damping and decreasing gas permeability. It also reduces rolling resistance and increases wet grip. These properties make it ideal for use in tires.
Over 50 percent of natural rubber becomes ENR in tires. Much of the remainder goes to industrial uses such as hoses, belts and seismic bearings; the rest goes to medical and consumer products such as latex gloves, rubber bands and erasers. In applications for which stretchiness is more important than damping qualities or durability, natural rubber is used.
A competitor for both ENR and natural rubber is synthetic rubber, which can be cheaper because it does not have to be obtained from trees in a labor-intensive process. However, so far, synthetic rubber has not been able to compete with the wide range of grades and applications available with ENR and natural rubber.