Visualization and flow velocity determination of molten polymers

Abstract

The determination of flow vectors of molten polymer by dies and mold cavities filling is a topic of many investigations, realized by various measurement techniques. The non-direct measurements are based on temperature or pressure fields determination along the flow channels, where the sensors are usually positioned in the streaming polymers, leading to flow field disturbance. The Laser Doppler Velocimetry (LDV) is an efficient touchless measurement technique of streaming gases and liquids velocity, deli vering directly values of the flow velocity and its direction. Principle and examples of LDV determined flow velo city distribution, are presented. The direct flow lines determination may be done by using markers with a plate-like form, scanning electron microscopy (seM) observation of fractured product surface.

The Microcellular Structure of Injection Molded Thick-Walled Parts as Observed by In-Line Monitoring

“…The highest shear stresses occurring in the cavity-melt boundary zone resulted in an even greater orientation of the filler in this zone. Those good results of the pore size range can be explained by minimization of the fountain effect during the melt flow [48][49][50], as well as by low shear stresses during the flow and a viscosity decrease. It was caused by a lower flow rate gradient compared to the thin-walled molded part.…”

Deformation Mechanism in Mechanically Coupled Polymer–Metal Hybrid Joints

“…Flow-line distribution in the rivet region was attained by optical visualization of the polymer On the other hand, more probable is the local structure weakness of the rivet resulting from molten-polymer flow instabilities by mold filling [27]. This effect may be related to the disarrangement of fountain flow in the proximity of rivets [29,30], in other words, the local disorientation of the macromolecular structure by molten polymer filling the cylindrical holes may occur. This occurrence was found by observing polymer-flow instabilities in the flow channel with a reduced cross-section, was also revealed and proved by observations done using flow markers like anisotropic inorganic fillers (mica, talc, short fibers) [31][32][33].…”