TECHNOLOGY | ODOUR REDUCTION


LDV1035T compounded in PP + Talc 20% LDV 1035T


Loading


1.5% 2% 2%


VW PV3900 VW PV3341


Odour Test Emissions of Organic Compounds by Headspace GC VW PV3015 Condensable Constituents


volatile, semi-volatile and non-volatile residues by means of supercritical agents or additives. CAI Additives’ products – LDV 8010 for ABS and


LDV 1035T for other polymers including PP, TPO, TPV, TPE, and POM – remove odour-causing organic molecules during the compounding process. The company says that the additives create active microfoams in the melt in the compounding extruder. These microfoams attract and bind the polar organic molecules, and the foams containing the compounds are then vented from the extruder at the end of the barrel. Thus, the offending VOCs are physically removed from the material in conven- tional compounding equipment. Applications include recycled PP (rPP) and talc-filled compounds. The additives also include certain fragrance actives for additional odour control in the resulting compound and part. These are particularly useful for the automotive OEM VOC tests for odour, which include a subjective test by a panel of people. In some cases, the additional fragrances are what brings the material over the threshold into the acceptable range, says CAI. Recent data from CAI demonstrates that the additives enable users to achieve automotive standards. In the table above, for example, CAI’s LDV1035T compounded at 2% loading into a 20% talc-filled PP was able to meet the VW PV 3900 odour test (threshold of 3.0) with a vacuum drawn from the vent port near the exit of a twin-screw compounding extruder.


Additives and absorbers AFI Chemical’s Addisperse odour-eliminating additives work by binding with the odour-causing molecules so that they can be removed by venting during compounding as well as subsequent converting steps. The odour eliminator is designed to volatilise at the same time as the odour-causing compounds. Formulations must be optimised for a specific application, says Paul Albee, Consultant with AFI Global. “Every volatile material has a specific flashpoint, and its compatibility with the polymer varies as


40 PLASTICS RECYCLING WORLD | October 2024


well,” he explains. “We evaluate each application in house to balance the chemistry of the odour-neu- tralising additive with the formula and design it to primarily work at the conversion step. In addition, a certain amount of odour-causing material can deposit on the moulded or extruded part, and you want the odour eliminator to also be on the surface at that same point, to neutralise any remaining odour in the finished part.” Albee says that as companies are looking to use


more mixed PCR streams, the challenge for removing odour becomes more complex, but says that their iterative optimisation process can find a solution. The company’s ON106 and ON108 additives are good starting points for optimisation because they neutralise the main odour compo- nents found in polyolefins, he says. Albee says that eliminating, not just masking, is


crucial. “In some cases, however, we add an ‘identity scent,’ such as a leather or ‘new car’ scent for an automotive part, to mask any remaining odours.” Albee sees an increase in washing and cleaning


of PCR before it arrives at the recycler, which can help with removing some of the odour-causing contaminants. Washing doesn’t always solve the problem, however. For example, for recycled (non-biodegradable) mulch film from strawberry fields, the overripe strawberry scent is absorbed into the film and remains after washing and pelletising. Albee says that the neutraliser ON106 is useful for this application. AFI Global has a development product for


neutralising odours in bio-based polymers, such as PLA, and in compounds with natural fillers, such as hemp. Albee says the odour compounds are different than those in PCR, but the need to eliminate the odour is similar. Evonik’s TEGO Sorb PY 88 TQ is a zinc ri-


cinoleate that absorbs odour and is effective for controlling odours from products such as hydrogen sulphide, mercaptane, thioether, isovaleric acid, amines and ammonia, as well as odours from pigments (eg, ultramarines, yellow pigments, or


www.plasticsrecyclingworld.com


Screw speed (rpm)


250 250 250 250


Vacuum (Mpa)


0.078 0.078 0.078 0.1


PV3900


4.5 3.5 3.0 3.0


PV3341 (µgC/g)


57 40 28 19


PV3015 (mg)


1.2


0.34 0.3


0.34 Source: CAI Additives


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