Grantee Research Project Results
Final Report: Fluorescence Coding of Plastics for Enhanced Identification and Sorting
EPA Contract Number: 68D99062Title: Fluorescence Coding of Plastics for Enhanced Identification and Sorting
Investigators: Mazel, Charles H.
Small Business: Physical Sciences Inc.
EPA Contact:
Phase: I
Project Period: September 1, 1999 through March 1, 2000
Project Amount: $69,893
RFA: Small Business Innovation Research (SBIR) - Phase I (1999) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , SBIR - Waste , Small Business Innovation Research (SBIR)
Description:
This work addresses the issue of identification of waste plastics prior to recycling. The goal of the Phase I was to explore the feasibility and practicality of incorporating optical tracers in plastic components during manufacture for the purpose of producing optical codes. At the end of the lifetime of these plastic components, the codes can be read in an automated manner to assist in identification for enhanced sorting and recycling. A prime consideration is that the tracers not affect the appearance or the function of the plastic part. This is done by incorporating the tracers at a concentration that is high enough for reliable detection, but low enough so that it does not affect the perceived color of the object.This method will eliminate shortcomings of existing methods by being fast, non-contact, resistant to surface contamination of the waste, independent of plastic color and independent of part orientation. Furthermore, it will eliminate the need to complex identification algorithm required by other methods such as infrared emission.
Summary/Accomplishments (Outputs/Outcomes):
Initially an inventory of commercially available tracers, their properties and suppliers was assembled. Several properties of tracers were identified to be important for our application, including thermal and chemical stability during manufacturing processing, compatibility with various plastic materials, optical properties pertinent to our detection system, photostability, and finally cost.Series of plastic samples doped with tracers were prepared and tested. The samples were specifically prepared to investigate some of the critical characteristics of the identification process. These characteristics are the following:
- Minimum amounts of tracers needed for positive identification for both clear and colored objects;
- The use of tracer combinations to form optical codes;
- Interference between the optical signals from the plastic materials and the traces.
Plastic samples, both clear and colored, containing tracers at various concentrations were prepared. To determine the effects of plastic-tracer interactions, virgin plastics were also examined. All samples, as well as the pure tracers were optically interrogated and their optical signals were compared. Additional measurements were performed to determine changes in the appearance of the samples due to addition of tracers.
For clear plastics, 1 to 10 ppm of tracers are adequate for positive identification, while for dark plastics 100 to 200 ppm are needed. At such concentrations the appearance of plastics does not change, as indicated by chromaticity measurements of spiked and virgin plastics. Furthermore, the signals from individual tracers or combination of tracers are unique and easily distinguishable from the background signal of virgin plastics. The cost of the tracers is estimated to be 1x10-3 - 0.2 cents/lb of plastic, which is negligible with respect to the cost of plastic. It should be noted here that identification of dark colored plastics is especially challenging using existing identification methods. In contrast, dark colors do not present a particular challenge to using our method.
A comprehensive study on potential markets was undertaken. The objective was to find a market with close control over the manufacturing process, which makes possible the use of universal tracers throughout this market. Several industries were investigated and contacted. Finally, a single, multi-billion dollar industry was identified to be the most suitable for our technology. Both manufacturers and recyclers of this industry were contacted and expressed their willingness to work with us in Phase II. In addition a well-known consultant in the industry will be working with us in Phase II to assist us with the implementation of the technology.
Conclusions:
Supplemental Keywords:
Recyclers, plastic manufacturers, recycling, sorting, sensor, tracers., Scientific Discipline, Waste, Sustainable Industry/Business, cleaner production/pollution prevention, Municipal, Chemistry, Technology for Sustainable Environment, Engineering, Hazardous, recyclable design, plastics sorting, hazardous waste, recycling, solid waste, industrial separators, separation selectivitiesThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.