Mill Processing Behavior of Polychloroprene and Acrylic Rubbers

Abstract

Mill processing behavior, with respect to front to back roll (F-B) transition, of polychloroprene and acrylic rubbers has been studied. The critical nip gap at which F-B transition occurs has been determined for these rubbers and their filled compounds (including HAF, MT, silica, and whiting) over a range of friction ratios and temperatures. The nip gap increases with friction ratio and temperature. The theoretical model of Tokita based on dimensional analysis, reveals three conditions corresponding to three types of behavior of various rubbers in drop mill operation. Mill band formation indices corresponding to these behavior types have been defined. These indices can be used to determine the conditions for front roll band formation. The systems investigated satisfy one of the conditions of the model. The mill processing behavior of these systems in a continuous milling operation has also been reported.

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

“…In the present investigation the milling behavior of BIMS and its blends with EPDM was investigated over a range of friction ratios and temperatures and the results were analyzed in terms of the theoretical model developed by Tokita10 and Bhowmick et al11–14 In addition, an attempt was made to optimize the mill parameters, to obtain a smooth and regular band. The conclusions from the investigation are as follows: Milling behavior of BIMS changes from a loose nervy band to a tight elastic band, as the temperature of the rolls increased from 30°C to 90°C.…”

“…(1), the two factors ( R 0 / t p U − ) and (2 H 0 / t p U − ) contain no material properties, but only machine parameters. Following Tokita10 and Bhowmick et al11–14 , substituting for t p in these expressions one obtains From the right side of eqs. (3) and (4), the following dimensionless numbers may be defined as where N 1 and N 2 are known as the mill band‐formation indices (MBI), which are of practical importance and provide the information on the conditions for the band formation on the front roll as well as the switchover of the band from the front roll to the back roll during the milling operation.…”

“…Furthermore, the critical nip gap, at which the front‐to‐back roll (F–B) transition occurs was also determined, using a drop mill operation as described by Tokita 10. The mill band‐formation indices (MBI) and the mill band‐formation exponent (MBE) were calculated from the critical nip gap, following the theoretical model of Tokita10 and subsequently modified by Bhowmick et al11, 12…”

“…Studies by Tokita10 revealed that a number of parameters influence the band formation behavior in drop mill operations. Because the number of parameters is large, dimensional analysis approach was applied10–15 and the following dimensionless equation was obtained: where 2 H 0 is the critical nip gap at which the front‐to‐back roll transition occurs; t p is the process time taken by the rubber in passing through the nip area during the milling operation; U − is the speed of the slower roll; F a is the force of adhesion between the rubber and the roll surface; η is the viscosity of the rubber; P is the pressure buildup at the nip gap; R 0 is the radius of the rolls; and k 1 , b , c , and d are constants. The process time ( t p ) is defined10 as where f is the friction ratio defined as the ratio of speed of the front roll to that of the back roll.…”

Rheological behavior and processability of neoprene and acrylic rubbers

“…characterized the flow behavior of neoprene and few other rubber melts. In our earlier communication we reported on milling behavior (27) and rheological behavior (28) of natural rubber and mill processing behavior of neoprene and acrylic rubbers (29). An exhaustive literature search reveals that detailed rheological analysis of gum and filled neoprene and acrylic rubbers is rather inadequate.…”