Viscosity Analysis of Polypropylene-Kaolin Composites Measured Using Single-Screw Extruder

Deviations between data for the apparent and true viscosity measurement are commonly observed in the rheological studies of thermoplastics. To validate the significance on the usage of these data on the processing side, filling analysis for the apparent viscosity and true viscosity of polypropylene-kaolin (PP-kaolin) composites was conducted by using CadMold (R) software on the dumbbell Computer Aided Design model for comparative purposes. The raw apparent viscosity data were generated from a single-screw extruder by using different sets of die geometries. Bagley and Rabinowitsch corrections were implemented to get a corrected set of true viscosity measurements. It was found that the true viscosity curves are lower compared with the apparent viscosity curves of PP-kaolin. By constructing the corresponding data from PP-kaolin composite rheological results, it was discovered that the high viscosity of the apparent viscosity melt data has shown a large variation in the mold distributions filling temperature, reduces the total pressure loss and melt shear stress, and increases the melt velocity during mold filling. Although the corrections were made on the calculated results, however, the significance is relatively small and it does not prove the changes in the overall physical property of the composite. Therefore, correcting the data by using the Bagley and Rabinowitsch corrections is not necessary in mold-filling analysis. (c) 2014 Society of Plastics Engineers