PROCESSING BEHAVIOUR OF HIGH-CIS POLYBUTADIENES IN RUBBER COMPOUNDS – NdBR vs CoBR

Polybutadiene (BR) is manufactured on a commercial scale using a variety of catalysts such as lithium, cobalt, nickel, titanium and more recently neodymium from the lanthanide series. Depending on the catalyst and conditions used, different microstructure and macrostructure properties can be achieved. Within the high cis-1,4 series, neodymium polybutadienes (NdBRs) in particular are known for their exceptional micro-structural and macro-structural composition. Yet despite providing excellent end product properties such as high resilience, good fatigue behaviour and improved wear characteristics, NdBR has a peculiar processing behaviour in the mixing and extrusion stages. In some cases, this leads to problems in the rubber sheet handling and to the occurrence of high die swell, which prevents the attainment of the outstanding characteristics offered by NdBR´s over other high-cis polybutadienes.
This paper presents countermeasures to ease the processing issues by adjusting mixing and extrusion conditions when using NdBR. Even in the case where the NdBR with the highest molecular weight is used, fast mixing and smooth milled sheets and profiles were obtained. As a result, this paper combines basic knowledge to aid the processing of NdBRs with their excellent vulcanizate characteristics.