ADDITIVES | MATERIALS
Coming to the aid of recycled compounds
Additives help solve a range of problems in the processing and use of recycled compounds. New products include stabilisers, antioxidants and processing aids, writes Jennifer Markarian
As brand owners and part manufacturers seek to use increasing amounts of recycled plastic in their products, it becomes more important to provide recycled compounds that can be used at higher levels without negatively impacting the converting process or the end-product performance. Additives are needed to accomplish this goal. In the “first life” of plastics, additives are an essential part of the formulation of virgin resin and of specialised plastic compounds. Antioxidants and stabilisers, for example, protect the polymer from degradation during processing and end-use. Each time the plastic material is melted and reformed (undergoes a “heat history”), some of these degradation-protecting additives are consumed. And while some antioxidants may remain in the post-industrial or post-consumer recycled (PIR/ PCR) material, there may not be enough to protect the polymer, resulting in problems such as gels, black specks, discolouration, changes in viscosity, or poor properties. These defects can cause waste in the next
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processing step, such as gels that cause the film web to break, or may make the PIR/PCR unusable for some applications. In some types of polymers, additives can help repair the damage (chain extenders for condensation polymers such as PET and polyamides, for example). In polyolefins, such as polyethylene (PE) and polypropylene (PP), however, the key is to prevent this degradation from occurring. BASF has conducted multiple studies with
recycled plastics, looking at issues such as gel formation, the impact of degradation on perfor- mance, and incorporating recycled plastics from various sources. An advanced pre-stabilisation package incorporated into the virgin resin is an effective way to both protect the virgin resin and allow more recycled content to be incorporated while maintaining properties. “Ideally, pre-stabilisation should anticipate the
recycling phase of the resin after the first life cycle,” said Sebastian Heitkamp, Global Industry Segment Head, Packaging and Consumer Goods, Plastic
March/April 2024 | PLASTICS RECYCLING WORLD 25
Main image: Milliken developed DeltaMax performance modifier to help com-
pounders using recycled PP
IMAGE: MILLIKEN
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