QUALITY | PROCESSING


Finding consistency using in-line rheology control


Meet your new best friend: an in-line rheometer – this is the basis of new offerings from European institutes aiming to help compounders smooth out the variations of recycled content. David Eldridge finds out more


For compounds containing recycled plastics to be used in high-value applications, they need to be as consistent in quality as compounds based entirely on virgin polymers. That is a major challenge for companies reprocessing post-consumer material with all its variability in quality. Usually PCR input material requires additives to be applied during compounding to restore mechanical properties, but with unpredictable quality fluctuations and flow behaviour, the compounder must do time-consum- ing testing offline and/or rely on estimates for the correct amount of additives to dose. Two organisa- tions are now offering to take the time and guess- work out of dealing with feedstock material variability using rheometers in line with the com-


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pounding system and thereby ensure consistently high quality products with recycled content. The Fraunhofer LBF institute in Germany has carried out test work using in-line (alternatively called online) rheometers with post-industrial recycled (PIR) and PCR polypropylene material, researching how to improve application of antioxi- dants when producing compounds containing rPP. “Until now, when developing new compounds, the optimum proportion of antioxidants has been determined in extensive and therefore cost-inten- sive test series,” said Fraunhofer LBF. “Ultimately, the processor wants to optimise the properties of the plastic. However, lengthy pre-tests are not profitable when producing recyclate from old


Main image: In-line


rheology at Fraunhofer LBF supports compound developers and makes formulations more cost- effective, says the institute


November/December 2024 | PLASTICS RECYCLING WORLD 23


IMAGE: FRAUNHOFER LBF/RAAPKE


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