Abstract
The solid bed (SB) break-up phenomenon in which the SB in the screw channel breaks and becomes discontinuous can be observed during the single screw plastication process. An analysis of this continuous extrusion process using the visual heating cylinder described in previous reports clarified that SB break-up occurs during crystal resin plastication, and generation models were proposed. In this study, analyses of polypropylene, polyamide, and general-purpose polystyrene were added, and the validity of the generation models proposed was verified. The results are summarized below:1) The break-up phenomenon was found to occur during the plastication process of both amorphous resins as well as crystalline resins.2) The results of the verification of previously proposed break-up generation models-stretch-breakup type and mechanically compressed-breakup-confirmed the validity of the stretch-breakup model.3) The mechanically compressed-breakup model was generalized as a formation mechanism of the interference between the SB and wall in the screw compression zone, and the following new model was proposed:In the screw compression zone, unmelted pellets collide strongly with the screw and cylinder wall. This generates a large tension in the SB at the collision area due to the rise in the screw surface speed and the shear rate in the melted resin layer of the SB boundary surface along the channel that becomes shallow, resulting in the break-up of the SB.
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