PROJECTS OF CFC - RECYCLING
Did you know that 35 percent of landfill materials is plastic and 85 percent of that plastic could be recycled?
A team of researchers here at the CFC along with the National Resource Center for Coal and Energy, the Polymer Alliance Zone in Parkersburg and other industries have mounted a many-prolonged investigation into the economics, logistics and engineering aspects of the problem of recycling electronic plastics. Several issues are in play. The first consideration is the quality and ingredients of different plastics.
Some ingredients are more easily broken down than others and some have more uses than others. The second major consideration is supply of the "raw material." It is easier and cheaper to recycle material of a known quantity and quality. For example, if a large business turns over its computers and peripherals every three or four years, chances are these machines are from one or two (perhaps three) known manufacturers? This is much easier than trying to collect electronics from individual homes or from small businesses that may have only a half dozen items of differing content. Separation in such cases becomes a real issue and logistics is a real problem in identifying and separating various polymers.
There are three levels of recycling: primary, secondary and tertiary. Primary recycling is taking the recycled material and putting it back into the same product; secondary recycling is using the material in some other end product; tertiary recycling requires breaking the material down into its original components.
Polymers come in many varieties and are classed into seven grades for ease of recycling. Each grade of plastic has different characteristics derived from its chemical make-up. Polymers used in electronics are pure plastics, but they can just as well be used in composite materials composed of fibers (usually glass) bound by polymer.
Electronic equipment uses polymers with certain flow properties and those solidify quickly and do not degrade or decompose during the process. Because different polymers melt, deform and flow at different temperatures, and because a mix of different plastics loses desirable characteristics (tensile strength compression, elongation or ductility toughness, harness and impact strength) the researchers needed to determine what mix of virgin and recycled polymers would yield the necessary engineering and temperature-related properties.
After extensive and painstaking testing, the research team is finding that the primary polymers used in monitor casings, computer covers and printer housings - called PC and ABS - can be recycled by mixing as much as 20 percent post consumer plastic with 80 percent of virgin plastic of the same type.
Since recycling is the aim, the team is also interested in using other hard-to-recycle items such as tires. They have found that it is possible to mix some compatible rubber into the electronic polymers. Primary aim is to make a polymer that is suitable for injection molding and to do so in a cost-competitive way. The researchers' are making several parts with recycled polymers such as guard rails and spacer blocks to test the recycled polymers they formulate and compound.
The focus is on secondary recycling to develop high-volume applications. Because the engineering properties of a composite depend primarily on the resin used in its manufacture, the researchers are examining the engineering properties of composites made from 100 percent recycled to 100 percent virgin plastics.
Right now development is on a highway guardrail assembly, and in the process using yet another item that needs to be recycled: rubber tires. But why highway guardrails? Along the Eastern seaboard, highway departments purchase two million wood blocks each year (this is the part of the assembly that holds the W-shaped rail to the upright posts). Reducing that number by even one-fourth would take a substantial amount of plastic out of landfills.
One-quarter-size test blocks are already made. These blocks are unusual in that they are a sandwich construction with a slice of rubber tire embedded in the composite. The tire is an additional shock absorber. Tests indicate that a mix of 20 percent recycled plastic and 80 percent virgin plastic yields the best results from an engineering perspective. Considering cost versus performance, the mix could be as much as 50-50.
Researchers at the CFC are aiming to reduce the amount of plastics going into landfills while leading the way to more value-added products that would, eventually, represent real financial savings.