ADDITIVES | RECYCLING
Table 2: Melt flow and physical propertied of recycled PC compounds containing Cevo additives Formulation
MVR300°C/ 1.2 kg
PC-regrind + 0.4% Cevo J-3400 PC-regrind + 0.4% Cevo J-3400 + 1.5% CEVO-master D-2055 Lexan 121R 1) 1)
Values taken from supplier’s TDS Source: Völpker Spezialprodukte
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 recy- clate that have properties very similar to those of virgin material (Table 2). Further investigation has also shown that Cevo-master D-2050 is suitable for converting high-viscosity cast PA6 into a low-viscosi- ty 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.
Compatible ideas In something of an understatement, developing new additives is no simple matter, according to Salvatore J Monte, President of Kenrich Petro- chemicals. “Besides the R&D to come up with something different/better, the costs related to registering a new chemical in the various global inventories is significant. The challenges to recycle — such as lower cost virgin polymer — remain the same. What is changing is the perception of a need to move the sustainability needle.” Kenrich has several projects under evaluation, many covered by NDAs, and Monte says the company is finding there is a strong market interest in compati-
70 COMPOUNDING WORLD | October 2021
bilisation of dissimilar polymers. Also working in this area is Intermix Perfor- mance Materials, a start-up based on technology developed in the lab of Prof Geoffrey Coates at Cornell University in Ithaca, NY, US. Coates says Intermix is commercialising a suite of PP/PE block copolymers that “provide non-covalent compatibili- sation of PE and PP via entanglement and co-cryst- allisation.” Unlike current commercial compatibilis- ers for PE and PP, the company says block copolymers function with as little as 0.5% compati- biliser, allowing economically-viable development of superior performance polymer PE/PP alloys.
Focused on PP At Nexam Chemical in Sweden, Chief Marketing Officer Lars Öhrn says the company has been work- ing 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 (Figure 4). Avient also notes that polyolefin plastic waste
www.compoundingworld.com
cm³/10 min 7
20 21
Vicat B50 ° C
145 138 140 Tensile
strength MPa
68 67 65 Notched
impact strength kJ/m²
79 49 65
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