SBR, Styrene-butadiene rubber, a synthetic rubber It´s durable, has good anti-slip properties and is flexible. It´s a dense material with good abrasion characteristics but downside is heavy weight. Normally soles with thickness >5 mm are avoided for this reason if not for a specific purpose. To manage a lower weight a midsole of EVA is often used with a bottom sole of synthetic rubber of 3-4mm thickness.

• Good abrasion
• Anti-slip
• Heavy

An alternative is foam rubber which is lighter and can be used for thicker outsoles but with less weight.

References

https://www.drsole2011.com/sbr

https://en.wikipedia.org/wiki/Styrene-butadiene

http://read.nxtbook.com/wiley/plasticsengineering/april2016/consultantscorner.html

http://www.sespoly.com/products/tpr-thermoplastic-rubber/