An Experimental Study of Flow and Stress Fields in a Pressurized Mooney Viscometer

Abstract

The boundary conditions of rubber compounds on solid surfaces during extrusion has long been a subject of question. The concerns of Mooney on this topic date back 60 years. He continued to return to this question throughout his career. In more recent years Vinogradov and his coworkers have called attention to slip phenomena occurring in the extrusion of elastomers through dies. This is associated with fluctuating pressure losses which occur at the onset of extrudate distortion. Such behavior has also been observed with rubber-carbon-black compounds. More recently, Turner and Moore have developed a pressurized rotational rheometer to characterize this type of behavior in rubber compounds. We have recognized the importance of this problem in our own laboratories. Marker experiments have been used in extrusion of rubber compounds to detect slippage. In the present paper, we describe an experimental study of the response of gum elastomers and their carbon black compounds in a pressurized Mooney viscometer of the general design of Turner. We look first specifically at the variations of steady torque (shear stress) with the magnitude of applied pressure. We then look at the characteristics of sheared samples and the responses to pressure transients.

Rest-time effects in repeated shear-startup runs of branched SBR polymers

“…Similar biconical rotors were used in a subsequent work by Galvin and Whorlow (1975) on the shear stress growth of HDPE, LDPE, ethylene-vinyl acetate copolymer, while Best and Rosen (1968) adopted a biconical rotor with sharp edge in order to determine the flow curves of a natural rubber, and of a SBR, in a wide range of temperatures and shear rates. More recently, Montes et al (1988) Also used a variable speed Mooney viscometer equipped with a biconical rotor, emphasizing the role played by several operating variables (chamber pressure, grooves, etc. ) in avoiding slip at the wall.…”

Extrusion characteristics of thermoplastic melts containing fluoropolymers

“…Studies of fluoroelastomer coated dies have also supported this (16). There is a long associated history of slippage of elastomers over metal sixfaces (17)(18)(19)(20)(21)(22)(23).…”

Influence of carboxylic acid additives on the flow behavior of molten thermoplastics

“…Vinogradov et al19, 20 have observed slip in polyisoprene and polybutadiene under similar conditions. It was also observed that elastomers at low applied pressures exhibited slip 21, 22…”

“…It was also observed that elastomers at low applied pressures exhibited slip. 21,22 There has been a limited literature on additives inducing slippage in the literature. We have already mentioned the work of Turner and Moore 8 with stearic acid in rubber compounds.…”