Screw-compression ratio determination

Extrusion. For processing of TPEEs by extrusion, the single-screw machines are recommended. The screws should have hardened surfaces for good wear resistance. A general purpose extruder barrels may be used with preferable length to diameter (L/D) ratio 24/1 to provide the best melt quality for precision extrusion. The barrel should have at least four independently controlled heating zones. Compression ratios should be between 2.5/1 and 3.5/1, as determined by the depth of the feed zone divided by the depth of the metering zone channel. 

Air-dried S- -PMA powder y5% H2O) was extruded from a C. W. Brabender Plasticorder extruder equipped with a 3/4-in. diameter 20 1 length-to-diameter barrel. The screw had a 3 1 compression ratio and was operated at 40 RPM. Temperature of the slit die (1x0.020 in.) and the end of the barrel was 140°C whereas the inlet zone was 90°C. Dumbbell-shaped tensile specimens were tempered 4 days at 22.2 C and 50% relative humidity before testing on an Instron testing machine at 5 or 50 cm/min cross head speed. Average UTS values were determined from five specimens of each sample. Relative standard deviation for the reported UTS values is 3.7%. 

Compression ratio. A measure of the amount of work the screw is able to do. It is determined by the ratio of the feed section flight depth to the metering section flight depth. (Rigorously, the ratio of the volume of material is contained in one turn of the feed section compared to the... 

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