MILAN – In the past few years, plastic recycling has come a long way. A result achieved through basic ingredients for preserving our environment. These have combined the efforts of waste sorting, increased demand for recovered materials and technological innovation to enable the maximum waste recovery possible. “Optical sorting” represents one of those ingredients and it continues to promote progress in the recycling of plastic materials.
The technology of sorting
While technological innovation extends across a huge range in shredding processes, the recovery of plastic materials is optimised by optical sorting; a new sorting technology. Basically, information is extracted by computer on materials which are arranged using a blade system. The system comes in various forms:
• Vision technology: This is basically a camera capable of arranging the material based on colour and form.
• Infrared technology: is used to distinguish the types of resin. This category of optical sorting includes near-infrared (NIR), mid-infrared (MIR) and the Raman spectroscope laser.
• X-ray technology (XRF and XRD): enables users to "see through" the plastic at elementary level and detect heavy elements like chlorine and bromine, differentiating PVC from PET and enabling the detection of several elements which cannot be reconstituted in world markets.
Large quantities of material can be sorted in a short time
These technologies are capable of sorting large volumes of material, pieces of plastic or large quantities of flakes. With NIR and XRF, technologies can be miniaturised into units to enable the individual identification of a single piece. In recent years, the recovery programmes have gone way beyond the classic PET bottles, taking into consideration a greater variety of plastic; the right choice for trying to re-use waste in the best ways possible and to enable a larger quantity of plastic to reach the recycling industry.
by editorial staff