PROCESS CONTROL | INLINE MEASUREMENT
Figures 1a and 1b: Comparison and example measurements with Bagley correction for a twin die capillary rheometer (top) and Göttfert’s RTS inline rheometer (bottom) with long and short dies
Source: Göttfert
contamination through a blow-out unit. While the three-camera set-up provides a higher detection rate, optimisation of the sorting is important and it has developed a hybrid blow-out feature for this rea- son. This allows the customer to define in advance which impurities in the material represent uncritical contamination, for which there is a smaller blow-out unit. This might include, for example, small, light- coloured black specks that frequently occur in material. The larger blow-out unit is then specified for critical contaminants, such as metal inclusions, that can impair the functionality of the end product.
Pellet inspection Italy-based Industrie Polieco-MPB is a large European compounder of polyethylene and polypropylene. It uses Sikora sorting systems for quality control to inspect and sort pellets used for production of films for food packaging. It is using a Purity Scanner Advanced unit to inspect for impurities at the final step of its process for production of maleic-anhydride grafted functional polymers. These polymers are used as adhesives and/or coupling agents and are used in products that will come into contact with food and/or drinking water including tie-layers in multilayer food packaging films or multilayer pipes for hot and cold water installations.
32 PLASTICS RECYCLING WORLD | November/December 2023
Sikora says that its system is reliably detecting pellets with colour deviations, as well as pellets with small black spots on the surface. These are both defects that can occur due to side-reactions during production of grafted polymers. The system automatically sorts out all detected contamination starting at a size of 50 microns. Furthermore, it provides various statistics as well as an image gallery of the detected contamination, which helps in optimising production.
“During the development and continuous
improvement of our production processes, we have been able to minimise the formation of black spots and of pellets with colour deviations,” says Marina Ausonio, Research & Development Execu- tive at Industrie Polieco-MPB. “However, the presence of such defects cannot be completely avoided. Sorting systems like Sikora’s Purity Scanner Advanced have the essential task to get rid of such residual defects so that we can provide our clients with a superior quality material.” German company Göttfert has developed an inline rheometer for continuous measurement of extensional viscosity during extrusion. The company says that online process monitoring of rheological properties is essential for fast and effective process control of polymer production in polymerisation and pilot plants, as well as in compounding operations.
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