SBR, or Styrene-butadiene rubber, is the most consumed synthetic rubber, widely used in place of natural rubber for similar applications. SBR is a general purpose rubber made up of 75% styrene and 25% butadiene joined in a co-polymer. The co-polymer means the molecules of these two materials connect into combined molecules with multiple units. The styrene added makes SBR cheaper while adding bonding and blending capabilities. The styrene also lends SBR its wear and abrasion resistance, as well as its strength.

SBR rubber is so widely used because of its cheapness and availability, although it also has high tensile and impact strength, resilience, and abrasion resistance. It’s flexible in low temperatures (though not as flexible as natural rubber) and has decent heat resistance as well. SBR is also water, organic acid, ketone, chemical, alcohol, and aldehyde resistant. This type of rubber also ages better than natural rubber and is crack resistant while able to accommodate large amounts of filler, which is used to enhance its properties.

• Carbon black gives SBR enhanced strength, as well as more abrasion and UV resistance.
• China clay also adds strength and reinforcement, and is used for rubbers that aren’t black.
• Calcium carbonate is added to make the final product cheaper.
• Silica gives SBR better thermal conductivity, electrical insulation, and dimensional stability.
• Filaments keep the rubber from being too stretchy in the finished product.