Flow of Rubber Compound in a Pin Barrel Screw Extruder

Abstract

A cold feed rubber extruder has been rebuilt into a pin barrel extruder with two rows of pins. A comparative experimental study has been made of the initial cold feed extruder, the extruder with a screw with slices in two flights, and the extruder with pins as well as Slight slices. An experimental study of pumping characteristics (Q – Δp screw curves) and of flow patterns obtained from feeding black and white compound with curatives to the extruder with subsequent vulcanization after steady state is achieved. Longitudinal and transverse sections of the rubber compound cured in the flights are studied. It is shown that introducing slices into screw flights reduces pumping capability. The subsequent introduction of pins has little effect on pumping. The flow marker studies show that introduction of slices into screw flights significantly enhances mixing. Both the improved mixing and poorer pumping is due to backflow through the slices. The introduction of pins is shown to again greatly increase mixing. The results of this study are used to discuss the performance and design of commercial pin barrel extruders for the rubber industry.

Modeling and Simulation of the Extrusion Process

“…There is a growing need to be able to accurately model and predict the phenomena occurring within the extruder so that it is possible to optimize both the extruder and the properties of the final product without the use of timely and expensive experiments. Extrusion, the most widely used process in the polymer processing industry-almost all injection molding machines have an extruder (plasticating unit) attached to it, and its flow phenomena have been well studied experimentally [41][42][43][44][45][46][47][48][49] and due to its geometric complexity to a lesser degree numerically [11,[50][51][52][53][54][55][56]. Experimental data is of extreme importance when studying the extruder, however, the time consumption and expense of these experiments creates the need for numerical simulation.…”

Mixing of Polymers

“…The first generation of studies, which relate to flow mechanisms and simulation for Newtonian fluids, is described in the volumes by Schenkel 37 and McKelvey.50 These showed that the flow is dominated by a forward drag of material by the barrel relative to the screw. Menges and Harms 51 and Yabushita et al 52 have made experimental studies of motion in pin barrel screw extruders by curing rubber with markers in place on the machine, removing the screw and unwrapping and sectioning the rubber. Later studies are largely associated with melting behavior and non-Newtonian flow simulation.…”

Investigations of the Elongational Deformation Induced by Pins in Pin-Barrel Cold-Feed Extruders

“…The main role of barrel pins is to continuously conduct (i) diversion orientation, (ii) elongational deformation, and (iii) position replacement for high viscosity rubber, which greatly promotes the interface growth, enhances the distribution mixing, improves the plasticization (softening) efficiency, and achieves the requirements of deformation and temperature uniformity [2-5, 23, 24]. Many experimental and simulation studies have been carried out on the mixing behavior of pin-barrel cold-feed extruder [6][7][8][9][10]. Yabushita et al used a white compound and a black compound to study the mixing performance of pin barrel extruder with two rows of pins and ordinary cold-feed extruder.…”

“…Yabushita et al used a white compound and a black compound to study the mixing performance of pin barrel extruder with two rows of pins and ordinary cold-feed extruder. Their contrastive experimental results showed that the introduction of pins could greatly improve the distribution mixing effect [6]. Shin and White used the flow analysis network method to study the influence of introducing slots in the screw flights and pins on the barrel on the screw pump characteristics.…”