Recycled materials: properties and standards
What are the properties of recycled materials (recyclates)? How about their strength, toughness, odour or colour? For which processing methods and applications can they be used? Although recyclates often have somewhat different properties than starting materials, they are usually still suitable for many applications. Thanks to our many years of research into material properties, Wageningen Food & Biobased Research has sound insights into the criteria that recyclates of components such as plastic must meet in order to make them suitable for the production of new products. With this background, we advise government bodies and industry on the development of standards for recyclable raw materials.
A large part of the plastic recyclates made from household waste is currently still too contaminated for high-end applications. They may have an unattractive smell, a greyish appearance or reduced functionality due to the presence of polymeric contaminants, for instance. Common polymeric contaminants are other plastics than the main stream, such as polypropylene (PP) caps in sorted polyethylene (PE) streams (from bottles) or a polystyrene (PS) tray that is wrongly sorted.
These contaminants affect the properties of the material but can also prevent processing methods such as film extrusion or blow moulding. The reuse of plastic recyclates from household waste in food packaging is a major challenge as it must be proven that the recyclates contain no toxic (harmful) components. That said, the use of recycled PET in soda bottles shows that the possibility exists.
We study the extent to which recyclates are suitable for specific applications, and work on developing technological solutions for contaminants in recyclates. This includes determining which components most affect the quality of the material, and whether there are alternatives which could improve quality.