The rolabilities of raw rubbers of high cis 1

4-polybutadienes prepared by four different catalytic systems were examined as a function of temperature and nip width.The critical temperatures at which the flow curves change from continuousness to di-scontinuousness may be used as a criterion of the rolability. The higher the critical temperature

the higher the 2-3 transition temperature

i.e. the better the rolability. But the long chain branching of the polymer has some influence on the rolability

especially at the wide mill nip. The causes of these phenomena have been suggested.