Use of chemical markers to enable identification and separation of different plastics from mixed plastics wastes

Chemical markers will be identified which are suitable for adding to plastics used for packaging applications, and which can be readily identified and discriminated by a spectroscopic or other technique (preferably noncontacting). The compatibility of the chemical markers with commonly used plastics will be evaluated. Finally, it will be shown that the markers can be added to the plastics materials (a different marker for each polymer) by a blending/compounding or coating method. An investigation was made of the use of chemical markers to enable identification and separation of different plastics from mixed wastes. Good progress has been made in developing the specifications for such a system, identifying and testing a range of marker compounds, proving compatibility with real packaging products and demonstrating a range of techniques considered suitable for identification. The concept appears feasible and work is being pursued on 2 fronts; production of specialist tracer compounds with enhanced response and diversity to ease identification and, developing a preproduction sorting machine to enable the technique to be applied to real waste materials. This latter development addresses the practical problems of presentation and separation as well as the identification and decision making software aspects. A separation at a rate of 10 particles per s is the aim. Some concern has arisen over the longer term feasibility and acceptability of the chemical marking concept (eg effect of recycling on discrimination and gaining the widespread acceptance of polymer manufacturers necessary for an effective system). This system is competitive with the direct polymer identification methods developed. State of the art review. Screening of spectroscopic and other techniques. Preliminary screening of chemical markers. Examples of chemicals to be evaluated: Fluorescent markers: substances based on stilbene sulphonic acid Ultraviolet markers: substances based on 2 (o-hydroxyphenil)-benztriazole substance based on o-hydroxy benzophenone X-ray fluorescent markers; substances containing metals/elements such as copper, manganese, phosphorus All chemical markers would be selected from the plastics additives list in the draft EC document for a Directive on plastic materials and articles intended to come into contact with foodstuffs' or selected from other current EC Member States national lists of substances approved for use in plastics intended to come into contact with foodstuffs. Preliminary blending and coating trials Sheet evaluation Pilot plant blending tests Material conversions Method assessment Control of safety Physical property check Proving and final trial