Recycling plastics, unlike other materials, poses several unique challenges, including difficult identification and separation, high contamination levels and costly equipment. In an effort to reduce these risks and boost recovery rates, the American Plastics Council (APC), Washington, D.C., is investing in innovative technologies.
In 1994, the American Plastics Council opened the Multi-Products Recycling Facility (MPRF) located in Boston, Mass., and operated by wTe Corp. The MPRF, reportedly the first large-scale U.S. research and development facility for plastics recycling, transforms plastic contaminated with material such as metals and fabric coverings into clean, reusable plastics.
To date, the facility has processed more than 100,000 pounds of used plastics from automobiles, computers, business equipment and appliances. In addition, the MPRF periodically is upgraded with new, off-the-shelf equipment such as classifiers, shredders and grinders.
Last spring, Berkeley, Calif., became home to the Advanced Plastics Recycling Pilot Line Facility operated by MBA Polymers Inc. and sponsored by the APC. As its name implies, this 10,000-square-foot plant aims to develop and demonstrate advanced mechanical recycling technologies for plastics.
Specific goals include: improved recycling economics resulting from higher throughput and reduced capital costs; post-processed plastics that are cleaner and purer, contain less contamination and are more uniform in size; and an investigation of new separation processes.
The pilot recycling line (see diagram) reportedly can process all types of plastic materials including those containing foreign materials such as ferrous and nonferrous metals, labels, foam and wiring. The facility uses high-temperature, high-pressure water to remove paints and coatings.
The Advanced Plastics Recycling Pilot Plant includes: a size reduction operation, a three stage air classification system, a low energy, high-throughput wet grinding operation and a series of hydrocyclone systems.
Another American Plastics Council goal is to improve identification methods for used plastics. For example, the P/ID 28, a near-infrared instrument developed by Bruker Instruments Inc., Billerica, Mass., under APC sponsorship, reportedly can classify at least 23 different types of plastics, including normally hard-to-identify black plastics.
The P/ID 28 uses the unique make-up of different plastics, namely the long chains of specific chemical species which determine not only plastic type, but also its mechanical, chemical and physical properties. When infrared light impinges on the various chemical species along a polymer chain, they vibrate at different frequencies, absorbing energy at wave lengths that are characteristic of the specific type of plastic.
Therefore, the reflected infrared light from a plastic sample will vary in intensity at different wavelengths. This spectrum of intensity versus wavelength acts as a "fingerprint" which can then be matched with spectra from known samples to identify the unknown material.
Currently, a sample reportedly can be prepared in a few seconds, and then held up to the PI/D 28's window for an additional five seconds for identification. In the future, the technique could be modified into a probe for identifying plastics in a dismantling yard. This probe could also be added to a conveyor line to identify plastics during separation.
The APC Automotive Committee, founded there years ago, includes plastic producers, car companies, automotive parts suppliers and members from the dismantling/ recycling community.
As part of its education program, the APC offers four condensed reports: Disposal Practices for Post-Use Automotive Plastics, Economics of Recovery and Recycling, Sorting and Processing Automotive Plastics-Emerging Technologies and Repair and Reuse of Automotive Plastic Parts.
For more information on the reports, contact the American Plastics Council, 1275 K St., NW, Suite 400, Wash., D.C. 20005. (800) 243-5790.