SUSTAINABILITY | ADDITIVES FOR RECYCLING
hand. Having one type of PP resin of low MFI would allow for any number of higher MFI possibilities,” the company says. Struktol says the VMO series products have been designed to allow for some PE present in the PP, in some cases upwards of 35%, adding that PE contamination is a common issue that PP recyclers encounter. The grades in the series – VMO 058, VMO 108, VMO 208, VMO 308 and VMO 408 – range in activity from low to high. Struktol says the range of activities is helpful for recyclers as it allows for high percentage dosing in cases where weighing or dosing small quantities could be problematic.
Compatibiliser update Compatibilisers are key for effective recycling as, after sorting, a recyclate feedstream may still be contaminated with materials that are incompatible with the main polymer. These incompatibilities can cause problems, such as delamination or poor physical properties, when the recycled plastic is processed into a new part. Compatibilising additives improve interfacial adhesion between, for example, a mineral filler and the polymer matrix, or between two incompatible polymers, resulting in a polymer blend with more uniform and better strength properties. Compatibilisers can also be used to improve reyclate from mixed plastics streams, such as where it is difficult to mechanically separate polymers. Ampacet’s ReVive compatibiliser masterbatch contains a blend of additives designed to enable film manufacturers to re-use in-house scrap generated from edge trim of multilayer films as well as recyclate from post-consumer barrier films (these films contain multiple materials, such as PA,
EVOH, and PE, and would not typically be recy- cled). The additive technology, however, allows the material to be recycled and reprocessed in the PE layer of film construction, explains Doreen Becker, Sustainability Manager at Ampacet. The company says independent tests have demonstrated improved optical properties using ReVive com- pared to PE/PA recyclate without the additive. The masterbatch is part of the company’s R3 Sustain- able Solutions portfolio. Building on its long experience in styrenic block copolymers as compatibilisers and modifiers, Kraton has launched its CirKular+ portfolio of additives for use in PCR and post-industrial recyclate. Three products in the compatibilisation series and two products in the performance enhancement series are already commercially avail- able, with samples currently being tested in potential applications, says Yuliya Streen, Global Marketing Manager at Kraton Corporation. The new additives are designed to improve
processing and properties of mixed-material recyclate streams. For example, the C2000 and C3000 additives can enhance properties such as stress cracking and impact strength in polyolefin PCR streams in which, particularly in the US, PP and HDPE are frequently commingled. The C1000 and C1010 compatibiliser additives are useful in polyolefin blends contaminated with PET, as well as for improv- ing processability and properties of the mixed PCR stream (resin codes 3-7). The additives are also said to improve processability of recycled PET carpet fibres, which may contain PET, PA, PP, and fillers. “The CirKular additives allow mechanical
CirKular+ additives from Kraton can enhance the performance of mixed PCR blends of HDPE and PP with PET Source: Kraton
42 COMPOUNDING WORLD | October 2020
recycling of mixed PCR, which can increase circularity by reducing the amount of material going to incineration or chemical recycling,” says Streen. “We understand that the balance of performance and value is critical in recyclate because it competes with the low cost of virgin resin,” she adds. Kraton’s C1010 is available in a grade that contains 50% post-industrial recycled block copolymers; this grade is a more affordable option but does not have the FDA clearance that the other grades offer. As compatibilisers, the addi- tives are typically used at approximately 3-5wt% in the formulation but in some cases only 1-2% is needed to improve homogeneity of the blend, according to Streen. Kenrich Petrochemicals’ neoalkoxy titanate additives achieve compatibilisation through a different method to the more commonly employed silanes, maleic anhydride modified polymers, or block copolymers, claims President Salvatore J
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