Mixing and kneading

Mixing and kneading of the thermosetting resin, rubbery components and other additives. 

Twin screw extruders introduce the necessary shear to thoroughly compound the dry blend into a polymer melt. They achieve this by utilizing aggressive mixing and kneading elements on the screw. Unfortunately, processing speeds are limited by the requirement that temperatures must be kept low to prevent excessive degradation. 

Fig. 173. Diagrammatic illustration of a Drais mixing and kneading machine with two tanks. The drive and switchgear is in an adjacent room for safety reasons (Courtesy Draiswerke Maschinenfabrik G.m.b.H., Mannheim-Waldhof, G.F.R.).

If a twin-screw extruder is stopped and opened, several zones can be clearly distinguished [9]. Depending on whether the extruder is fed with a solid or a liquid material, two different situations occur. In the case of a solid feed (a polymer or solid monomer), the channels near the feed hopper are more or less filled with solids. This material melts, resulting in a zone where the channels are only partly filled. At the end of the screw, close to the die, a zone exists where the channels are completely filled with polymer. If the extruder is fed with a liquid monomer, the first part does not necessarily need to be partly empty but, as will be explained later, for reasons of stability it is advisable to create a zone where the channels are not fully filled. In particular, the fully filled zone is very important for correct functioning of the extruder. In this zone the pressure is built up, the mixing and kneading mainly... 

The patent vacuum has also prompted new applications from several areas. Apparatus patents are among the foremost of these, i.e., numerous variants of innovative screw, mixing, and kneading elements from mechanical engineering companies, while process patents employing co-rotating extruders are proposed by the chemical industry. 

The previous chapters have shown how screw machines are comprised of successive zones that perform specific process tasks. The most common process task is a combination of transporting materials and generating pressure. At the head of the machine, higher pressure needs to be applied, in particular, where typically an extrusion die or a nozzle plate is attached however, most mixing and kneading zones are also pressure consumers that require pressurization of the melt. 

Reid, R. W (1979) Mixing and kneading equipment, in Solids Separation and Mixing, M. V. Bhatia and P. E. Cheremisinoff (eds.) (Technomic). 

The first crushing machine, after the war club, was the mortar and pestle. Except as a laboratory implement, this has become more of a mixing device and is described under Mixing and Kneading. The bucking board of the assayer may be considered a mortar that has been flattened out. 

L. C. Reese. Ph. D. Consulting Chemical Engineer. Mixing and Kneading. 

All materials were mixed and kneaded in kneader (Mikami Machinery Co., MND-10) for 3 minutes of dry mixing and 8 minutes of wet kneading. After kneaded, fresh mortar was measured its hardness by a rubber hardness tester. Then the mortar was extruded immediately. 

Also Mix-Muller. Originally, a device that used a heavy stone roller to grind and/or mix particulate solids. Today, a blender with one, two or four large metal rollers that mix and knead (densify) material. Often used prior to pressure agglomeration. (See also pan grinder.)... 

Erdmenger, R. Mixing and kneading machine US2670188. U.S. Pattern Organization, Farbenfabriken Bayer, 1954, p. 6. 

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