Evaluation of the Melting Behavior and the Melt Penetration into the Solid Bed Using a Model Experiment

This work deals with the melting of polymeric bulk materials and the melt penetration into the solid bed utilizing a model experiment that simulates the melting process in single screw plasticating units. The polymer granules are pressed onto a heated rotating shaft. The thickness distribution of the resulting melt film is measured according to the principle of optical triangulation (light intersection). This new method and the measurement of the bulk density using a piston position measurement were presented earlier by the authors. The combination of these different principles allows the determination of the melt penetration into the solid bulk as it takes place in the delay zone of single screw plasticating units. The melting behavior of spheroidal and cylindrical shaped polypropylene-homopolymer (PP-H) bulk solids is analyzed at different applied pressure. Spheroidal bulk solids show significant advantages compared to cylindrical shaped granules which melt much slower, particularly at higher pressures. The melt clearly penetrates deeper into the spheroidal bulk compared to cylindrical bulk.