Views:22 Author:Site Editor Publish Time: 2017-08-07 Origin:Site
① The history of the screw extruder
Because of production demand, the screw extruder also has been improving its function and efficiency. According to the principle of screw extruder, the defect of screw extruder is corrected step by step to meet the needs of people. These improvements of the screw extruder are hard-won and measured.
Extrusion using a screw extruder has been playing very important roles in polymers processing as one of the basic processing technologies for producing compounds and various products such as pipes, car parts, films, etc. In this paper the history and recent technology progress in screw extrusion are reviewed, mainly focused on Japan. Screw extrusion has a long history starting from food processing to rubber and plastics, and is now applied to various fields, such as compounding, fiber spinning, film making, blow molding and injection molding. Recent progress in extrusion technology allows for precise selection of conditions, providing for production of polymers and nanocomposites with required properties, morphology/structure, as well as significant improvement in production efficiency and energy consumption. Today extrusion technology has been divided into two major streams. The first stream goes towards higher efficiency using larger scale processing lines, and the other towards the production of functional products with special properties, such as nanocomposites and/or polymer blends with specified nanoscale morphology starting from the wide range of extrusion technologies against the historical background.
Following the increase in plastics consumption, the demand for larger extrusion capacity and better mixing performance of the screw extruder drastically raised and therefore a twin--screw extruder has been playing more important role in capacity increase than a single-screw extruder in the field screw/barrel geometries. The flow behaviors around grooved barrels and kneading disks were calculated by a particle tracing method. From these results the combination of grooved barrels with kneading disks was optimized so as to obtain more homogeneous flow behavior at lower polymer temperature. Lately the optimum combination of grooved barrels and kneading disks has been successfully applied, for example in practical use of polypropylene-carbon nanotube compounding.
The pace of improvement of the screw extruder has not stopped, because the change in environment and demand, the screw extruder’s improvement is endless.