Mill processability of brominated isobutylene‐co‐paramethylstyrene and its blends with EPDM

Abstract

Milling behavior of brominated isobutylene-co-paramethylstyrene (BIMS) and its blends with ethylene propylene diene terpolymer (EPDM) rubber, was investigated over a range of temperatures and friction ratios in a drop mill operation. 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°C to 90°C. For EPDM a loose band was observed at all temperatures and friction ratios studied. For the blends of BIMS and EPDM, the milling 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 front-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 the EPDM content, indicating a decrease in the tendency for F-B transition. The results were explained in terms of the rubber-tometal adhesion and the viscosity of the polymers.

Study on the milling behavior of chloroprene rubber blends with ethylene–propylene–diene monomer rubber, polybutadiene rubber, and natural rubber

“…The milling behavior of rubber compounds can be classified into four states in terms of mill band formation characteristics, and the most favorable state to mixing of rubber compounds and dispersing of compounding ingredients in rubber is that rubber can enter into nip gap of two rolls automatically, at this time rubber is plastic flow and forms a tight elastic band adhering to roll (named for Region 2) [1,2]. Another state is that the rubber compound forms a transparent fluid film band and it is very soft to be lack of elasticity, meanwhile green strength of rubber is low so that the rubber compound adheres to the roll (named for Region 4) [1,2]. At this time, compounding ingredients can be added into rubber easily, but they cannot be dispersed well in rubber.…”

“…When the compound is mixed on an open mill, the state of the compound is not only related with the recipe of rubber, but also dependent on conditions of mixing. Certainly, the temperature of rolls is one of the most important factors that affect milling behavior of rubber compounds [1,2]. Table 2 shows the tight milling behavior of the compounds at different roll temperatures.…”

“…Table 2 shows the tight milling behavior of the compounds at different roll temperatures. From Table 2, at low temperatures, every compound didnot stick to the rolls and could be milled up well and peeled from the rolls that was similar to Region 2, as described in related document [1,2]. When the temperature increased, CR compound and 70/30 CR/NR blend became sticky to the rolls and the bulk compound entered into the clearance of two rolls hardly, meanwhile it was hard to be milled up and peeled from the rolls that was similar to Region 4, as described in related document [1,2].…”

“…From Table 2, at low temperatures, every compound didnot stick to the rolls and could be milled up well and peeled from the rolls that was similar to Region 2, as described in related document [1,2]. When the temperature increased, CR compound and 70/30 CR/NR blend became sticky to the rolls and the bulk compound entered into the clearance of two rolls hardly, meanwhile it was hard to be milled up and peeled from the rolls that was similar to Region 4, as described in related document [1,2]. Pure EPDM compound and pure BR compound as well as the CR/EPDM blend with high EPDM blend ratio could be milled up well and peeled from the rolls easily even at higher temperatures, and it was not sticky to the rolls.…”

“…Generally, the mixing of rubber compound is carried out in its elastic state, because the elastic shear forces can make the compounding ingredients disperse well [1][2][3]. Chloroprene rubber (CR) has outstanding antiaging and self-reinforcement properties, and it is not easy to stick to rolls at or close to room temperature.…”