New Method to Detect Flaws of High- and Medium-Pressure PIMFeedstocks

摘要

The flowability of feedstocks is usually used to characterize their consistency. Mistakes in thernbinder/powder ratio and in the mixing homogeneity can be detected by viscosityrnmeasurements. Various methods for testing the viscosity are known and described in thernliterature, e.g. melt-indexer, capillary viscosimeter, RheoNoz (rheological nozzle) etc. Eachrnmethod has its specific advantages but also its specific disadvantages. Typical factors takenrninto consideration for choosing a proper method for feedstock characterization are the costsrnand the time needed for measuring. The paper presents a new apparatus for a quick checkrnof the feedstock consistency which is based on a by-pass nozzle of the injection mouldingrnmachine. During PIM-parts production and between two consecutive shots the injectionrnmoulding machine injects the molten feedstock through a capillary die. The pressure neededrnto keep a certain speed is used as an indicator for the flowability and therefore the quality ofrnthe feedstock. The applicability of the method with a polystyrene and a high-pressure PIMrnfeedstock will be presented.