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Plastics Identification & Recycling

Recycling plastic packaging.
Recycling plastic packaging.

The wide range of polymer types comprising consumer products make recovering waste plastics a challenging task and it is one that Wolfson Electrostatics has been working towards for some years.

As a conservative estimate, in the UK for example almost 4.5 million tonnes of plastic products are used annually and between 3 and 3.5 million tonnes of waste plastics require disposal. For obvious environmental reasons it is becoming increasingly important to recycle ‘waste’ plastics rather than send them to landfill.

It is necessary to distinguish between certain types of plastic if recycling is to become a practical reality.

Tribopen - a simple hand-held plastics ID tool.
Tribopen - a simple
hand-held plastics ID tool.

Different plastics, particularly different polymer groups, can have significantly different physical and chemical properties which may include mechanical strength, flexibility, chemical resistance, etc. Hybrids of these plastics or those which have been contaminated by the presence of other materials may have these properties seriously affected.

European initiatives are currently in force for waste electrical and electronic equipment (WEEE Directive) and for end-of-life motor vehicles (ELV Directive). The common aim of these directives is to increase the re-use and recycling of WEEE/ELV by setting recovery and recycling targets and by introducing producer responsibility for disposal. The weak link in the recycling loop is material identification and this is an area where Wolfson Electrostatics have been particularly active.

Tribopen & PolyAna

PolyAna - accurate identification from a database of hundreds of materials.
PolyAna - accurate identification
from a database of hundreds of materials.

In the field of plastics identification and recycling, Wolfson Electrostatics has already produced some innovative technology. This includes two plastic identification systems to aid in the recycling of automotive components. Both the Tribopen & the PolyAna are the results of development programmes sponsored by Ford Motor Company and the Landfill Tax Credit Scheme and have won Millennium Product Awards from the UK Government in 2000.

Another invention for identifying asbestos in vehicle clutch plates during recycling gained the ‘Ford of Europe Technical Achievement Award’ - the first time this award has gone outside the Ford Company. This technology is currently in use at recycling plants in Germany.

Onyx Environmental Trust

Automatic sorting - non plastic items such as juice cartons being ejected from the line.
Automatic sorting -
non plastic items such as juice
cartons being ejected from the line.

During 2001 & 2002 Wolfson Electrostatics undertook a major R&D project looking into the use of electrostatic techniques to identify, sort and recycle mixed waste. This work was sponsored by the Onyx Environmental Trust using funds provided from Landfill Tax.

The project which ran for 15 months concentrated on using electrostatic techniques to distinguish between different items of plastic packaging (PET/PE/PVC bottles, PS/PVC/PP food trays & cartons etc.) on an automatic sorting line. An electrostatic method for sorting plastics from non-plastic packaging was also developed.

The pilot sorting line - a five metre long conveyor is currently in use at Southampton University. Mixed plastic and non-plastic waste packaging is loaded onto the conveyor system which automatically recognises the polymer comprising the packaging item and ejects it according to polymer type into the appropriate bin. Non-plastic packaging such as cardboard and wood are automatically directed to a separate bin.

Shanks First Fund

Shanks First - a key partner in the plastics ID development project.
Shanks First - a key partner in the
plastics ID development project.

The first phase of a project entitled ‘Plastics Identification Technology for Recycling’ funded under the Shanks First Fund was recently completed. The work was co-funded by the University of Southampton with Ford as the contributing third party. During this project three new pieces of plastics identification technology have been developed.

These include improved versions of the Tribopen and PolyAna - the latter incorporating the new Nicolet Avatar spectrometer with latest ‘Omnic’ software. A completely new instrument - the ‘tribo-discriminator’ enables the user to quickly distinguish between two or three materials and is particularly useful in identifying contaminant plastics such as PVC from a mixed stream.

Sorting shredded and granulated waste

Shredder residue can be sorted or decontaminated using electrostatic techniques.
Shredder residue can be
sorted or de-contaminated using
electrostatic techniques.

The application of electrostatics provides an ideal means of identifying and manipulating shredder and granulator residue. Due to their size, relatively large surface area and light weight, the particles comprising the stream can be charged and either attracted or repelled using an electric field. Since different materials may have significantly different electrical properties they will often charge to different magnitudes or polarities. Electrostatic techniques can then be used to sort mixed streams or preferentially remove contaminant plastics.

For full copies of reports for Onyx Environmental Trust and Shanks First Fund or for further information on Plastics Indentification & Recycling contact Wolfson Electrostatics.

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