ADDITIVES | MATERIALS
Cevo-master D-2050 is developed for use in polycarbonates, with the aim to enable production of fast-flowing regenerates and compounds based on regrind (even when the easy-flowing regrinds required are not available). The use of the additive allows production of compounds based on recyclate that have properties very similar to those of virgin material. Further investigation has also shown that Cevo-master D-2050 is suitable for converting high-viscosity cast PA6 into a low-vis- cosity grade via compounding, says Matthies. Cevo-stab F-5510 stabilises the reprocessing
process of polyacetal (POM) copolymer waste. Thermal stress on POM can cause degradation and the formation of formaldehyde. This creates not only an unpleasant odour, but also bubbles in the feeding region of injection moulded parts. The addition of 0.3—0.5% of Cevo-stab F-5510 radically reduces these phenomena, according to Matthies. Finally, Cevo-master B-6000 is designed for a
wide range of applications in recycling of post- consumer and post-industrial polyolefin recyclates, where it acts as a compatibiliser, reducing prob- lems caused by impurities of foreign polymers. The flow behaviour of the recyclates can also be improved in a targeted manner. In parallel, says Matthies, it acts as a process stabiliser and is also suitable as an impact modifier. At Nexam Chemical in Sweden, Chief Market-
ing Officer Lars Öhrn says the company has been working on improving properties in recycled PP. “When studying different streams of recycled PP, we see that they often contain other polymers and most often PE,” he says. “One question often raised by customers is how they can get the processing performance their process demands to be as efficient and reliable as with virgin PP.” Öhrn says products such as Nexam’s Nexamite R202 can help increase MFR in recycled PP to fit the process but to lower MFR in a recycled PP has been less easy unless high amounts of virgin PP with low MFR are blended in. He says the company has now developed a new technology for building molecular weight in recycled PP. Part of Nexam’s Reactive Recycling portfolio,
Nexamite R201 can build molecular weight in PP and can compatibilise with other polyolefins like PE. “Nexamite R201 reacts and forms strong connections both in rPP itself and with rPE,” says Öhrn. Typical dosing of Nexamite R201 is 1-5%, depending on final target, and it is compounded with the recycled PP at temperatures over 200°C. Öhrn cites the example of a PCR PP containing 10% PE, where MW was successfully increased so that it could replace virgin PP.
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Effect of Nexamite R201 on MFR in recycled PP compounded for 90s at 230°C Source: Nexam Chemical
Avient also notes that polyolefin plastic waste
streams can be inhomogeneous and fluctuating, lowering the quality of recycled plastic grades. Incompatibility of polymers in recyclate mixtures may have a direct impact on melt flow index (MFI), the creation of black spots, gels or die build-up and delamination. It says its first generation of compatibilisers, such as Cesa Mix Additives, show good results in minimising the impact of oxidative residues and keeping melt flow index (MFI) in the right process range. The CirKular+ additives from Kraton (best known for its various types of SBS and SEBS elastomers) were launched last year. The product line includes a Compatibilisation Series and a Performance Enhancement Series and the company says that even at low dosages, CirKular+ additives can help raise recycled content and enhance PCR perfor- mance without compromising product performance. The CirKular+ Compatibilisation Series can be used for various normally incompatible mixes, such as PP/PA, PO/PET, PA/PET, and others. Kraton says that as little as 3-5% of CirKular+ additives results in up to 500% improved mechanical performance of PCR and PIR in compositions containing more than 70% recycled resin, as well as improved durability with minimal loss in stiffness. It says that the additives deliver superior performance even after five reprocessing cycles.
*David Eldridge contributed to this article.
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www.crayvalley.com �
www.lbf.fraunhofer.de �
www.altana.com �
www.greenmantra.com �
www.voelpker.com �
www.nexamchemical.com �
www.kraton.com
October 2021 | PLASTICS RECYCLING WORLD 57
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