Mill processability of brominated isobutylene-co-paramethylstyrene and itsblends with EPDM

Milling behavior of brominated isobutylene-co-paramethylstyrene (BIMS) and its blends with ethylene propylene diene terpolymer (EPDM) rubber, was inve stigated over a range of temperatures and friction ratios in a drop mill op eration. BIMS showed striking changes, that is, from a loose nervy band to a tight elastic band, as the temperature of the rolls was increased from 30 degreesC to 90 degreesC . For EPDM a loose band was observed at all temper atures and friction ratios studied. For the blends of BIMS and EPDM, the mi lling behavior changed from a tight elastic band to a loose bagging band on increasing the EPDM content. The critical nip gap (CNG), at which the fron t-to-back roll (F-B) transition occurred, was also measured. BIMS showed a much higher value of CNG than that of EPDM, indicating that the former had a significantly higher tendency for F-B transition than the latter material . For different blends of BIMS and EPDM, the CNG decreased on increasing th e EPDM content, indicating a decrease in the tendency for F-B transition. T he results were explained in terms of the rubber-to-metal adhesion and the viscosity of the polymers. (C) 2001 John Wiley & Sons, Inc.