RECYCLING | ADDITIVES
has recently submitted requests for food-contact approval from other major global regulatory bodies. Nexam Chemical said that its
Reactive Recycling additive master- batches for rPP can tune flow charac- teristics and enhance processability and quality. The technology elevates the utility of rPP so it doesn’t need to be “downcycled,” the company claims. Nexamite R201 builds molecular weight (ie, decreases melt flow ratio [MFR]) of PP. Nexamite R203 is an enhanced version that also builds molecular weight of rPP. Nexamite R202, on the other hand, is a vis- breaking additive that increases MFR and reduces molecular weight, if needed to match the process.
Tuning flow A study published in March by researchers from the Department of Applied Science and Technology at Politecnico di Torino, Italy, investigat- ed the impact of thermomechanical degradation on PP microstructure during multiple extrusion cycles. PP degrades structurally through chain scission that reduces molecular weight, but a reactive extrusion process with Nexam’s additive was able to rebuild the chains. The experiments showed that Nexamite additive is able to prevent breakdown when added to PP and to restore the molecular weight when added to a simulated post-consumer rPP (as
shown in the graph). The researchers also found that the additive acted differently depending on the resi- dence time in the extruder; a longer residence time introduced some branches onto the polymer back- bone, which improves melt strength and is beneficial for processability. They concluded that the additive would allow “tunable” processability. For PET, a key measure is intrinsic
viscosity. Nexam Chemical said its IV-enhancing additives for rPET are seeing expanded use in multiple regions where rPET use is growing. For example, in the US, IV enhancers are being used in PET foamed sheets, that are used for replacing polysty- rene in food packaging. In Pakistan’s growing packaging market, locally produced rPET sheets and other types of rPET applications are using the IV enhancers, the company reported in a July press release. Nexam said it is seeing growth also in Australia, Mexico, and South America. Techmer PM’s HiTerra rPET Revive is an additive concentrate that counteracts the degradation experi- enced during reprocessing of PET. The additive works by rebuilding the polymer chains to increase viscosity and reduce yellowness. “RPET Revive can allow for a higher
regrind/recycle rate and improve productivity,” said Steve Smith, Techmer PM’s Market Manager for Rigid Packaging, in a release. “We
Polypropylene degrades during reprocessing, and the average molecular weight (MW) typically decreases with each processing cycle. As illustrated in this graph, Nexam’s additive was introduced during the ninth processing cycle to simulate addition to post-consumer recyclate. The additive was able to rebuild the MW of PP.
Source: Nexam
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