If someone tried to trace their everyday life without plastic today, it would quickly prove to be an almost impossible task. A bottle of water bought on the go, protective film on a parcel, a laptop keyboard, even spectacle lenses. All of these belong to the same, extremely diverse family of polymers. Plastics have become so ubiquitous that it is difficult to notice how quickly everyday objects turn into waste.
The problem arises when this mass of used polymers ends up where it shouldn't. At first glance, plastic waste seems homogeneous, because after all, ‘plastic is plastic’. In reality, we are dealing with a mosaic of materials with different chemical and physical properties that do not cooperate in the recycling process. PET mixes with PE, PP hides among PS, and added dyes or stabilisers further complicate the situation.
The problem of polymer waste diversity does not end with its collection and sorting. This is only the beginning of the journey. Every stream of plastic waste has the potential to be reborn as regranulate, a material that can get a second chance by becoming a bottle, a household appliance casing or a car part again. But the quality of this regranulate is not determined at the sorting stage.
Compromises in regranulate, or why purity is capital
In the plastics industry, the presence of unsuitable polymer in recycled granules acts as a defect in the structure: it reduces strength, impairs appearance and hinders further processing. Therefore, the purity and homogeneity of the feedstock is not only a technical issue, but also an economic and image issue. High-quality regranulate means not only stable mechanical parameters and the aesthetics of the final product. It also means the possibility of realistically replacing virgin raw materials, reducing oil consumption and reducing the carbon footprint. The better the regranulate, the fewer compromises the manufacturer has to make, and thus the greater the chance that recycling will become not an addition, but a full-fledged pillar of the circular economy.
Sorting accuracy as the silent architect of recycling – from waste to full-value raw material
If an error occurs at the beginning of the process, during segregation, the end result is a material of reduced value that is difficult to sell or use in demanding industries. Sorting accuracy therefore acts as a sieve that determines whether waste will be turned into a fully-fledged raw material or just a compromise mixture with limited possibilities.
Every additional percentage of ‘undesirable’ polymer in a batch of waste is a risk of producing defective regranulate. Even a small amount of polyethylene in the PET stream is enough to change its processing properties and reduce its quality. As a result, all the effort of collection, transport and washing is pointless if, at the end of the chain, we do not obtain material that meets market standards.
This is why sorting accuracy is not just a technological parameter. It is a key economic and environmental factor. The cleaner the input material, the higher the value of the output regranulate and the more realistic the vision of a circular economy becomes. In this context, optical sorting methods appear to be the answer to the challenges faced by recycling plants. They allow similar polymers to be distinguished, contaminants to be removed and material to be precisely directed to the appropriate streams, minimising losses.
Infrared in the service of recycling: from colour to plastic identity
Optical sorting is, in a sense, the ‘artificial eye’ of recycling. Where humans see only colourful pieces of plastic, machines equipped with the latest technology can detect subtle differences in the structure of the material. Meyer sorters use near-infrared (NIR) technology, which allows them to ‘read’ the characteristic reflection signal for each type of polymer. PET, PE and PP, although similar at first glance, reveal their identity thanks to this invisible light signature.
In practice, the process looks like a quick show: polymers slide down a chute, a camera records the data, a computer analyses it, and a stream of compressed air ejects the fragment at the right moment. The whole process takes fractions of a second and is repeated hundreds of thousands of times per hour. This makes it possible to separate polymers that would otherwise form a chaotic mixture, difficult to reuse.
The impact of sorting quality on the regranulation process
Regranulate is a material whose true value lies not in tonnes or kilograms, but in purity. It determines whether a plastic granule will become a fully-fledged raw material or merely a substitute for a material that the industry does not really know what to do with. The road to quality begins at the selection stage. This is where it is decided whether the recovered polymers will retain their mechanical and chemical properties or be permanently contaminated by accidental admixtures.
A precisely organised waste stream offers the chance to obtain a material that can compete with virgin plastic without any complexes. However, a little chaos, a few unwanted polymers in the wrong place, and the end product becomes a compromise with limited applications and drastically reduced value.
This is where modern sorting machines, such as Meyer devices, which use near-infrared spectrum analysis, play a key role. They distinguish between polymers that look similar but have completely different properties. Thanks to this technology, there are no longer any stray PE or PP particles in the PET stream that could later ruin the regranulation process.
