High cis polybutadiene
This type is characterized by a high proportion of cis (typically over 92%)[14] and a small proportion of vinyl (less than 4%). It is manufactured using Ziegler-Natta catalysts based on transition metals.Depending on the metal used, the properties vary slightly.
Using cobalt gives branched molecules, resulting in a low viscosity material that is ease of use, but its mechanical strength is relatively low. Nodymium gives the most linear structure (and therefore higher mechanical strength) and a higher percentage of 98% cis. Other less used catalysts include nickel and titanium.
http://en.wikipedia.org/wiki/Polybutadiene

Styron Buna® cis 132 este un cauciuc polibutadienic (BR) cu conţinut mare de unităţi cis, peste 95%, şi este produs cu ajutorul unui sistem catalizator pe bază de nichel.
http://www.resinex.ro/produse/styronbr.html