Composite recycling is in its infancy, but growing environmental concerns and pending policies may require companies to get up to speed quickly.
Recycling composites is more than just a good idea. It’s the law – or it may well soon be. In Europe, the Waste Management Regulations of 2006 required cars, which are increasingly composite-laden, to be 95 percent reused and recycled by average weight per vehicle starting in January 2015. In the United States, more communities are pursuing zero-waste-to-landfill policies: San Francisco has set an ambitious goal of zero waste by 2020.
Such moves toward sustainability – of which recycling is just one component – shouldn’t be perceived as all doom and gloom: Composites do, indeed, provide sustainable attributes. “Everything can be recycled,” says Mathieu Robert, an engineering professor at the University of Sherbrooke in Canada. “Any type of thermoset resin can be recycled. Any type of fiber can be recycled.”
The operative word here is can – meaning it is possible. That does not mean, though, that the reuse of material is profitable. Having the technical means to divert material from the waste stream and create recycled material – a recyclate – is only part of the battle. “Finding an end user or product for the recyclate is key to closing the loop on composite recycling,” says Andrea Kraj, an applications engineer at the Composites Innovation Centre Manitoba in Winnipeg, Canada.
A Concrete Demonstration
The University of Sherbrooke and René Composite Materials, a Sainte-Clotilde-de-Beauce, Quebec, manufacturer of unsaturated polyester resin-based composites for the automotive and transportation industries, have partnered to develop and demonstrate a viable recycling process. They began with truck parts after molding. Using a 75-minute cycle in a ball mill grinder, they pulverized these parts into a mixture of small particles and fine powder. Some 80 percent by weight of the recyclate was less than 80 microns in size, roughly the diameter of a human hair.
Tests of the mixture showed that its incorporation into other materials could improve mechanical properties. For instance, completely replacing the calcium carbonate in a composite material with the recyclate increased the tensile strength from 80 to 115 megapascals.
The demonstration showed that use of the recycled powder as filler in composite materials was feasible at a high rate of production. However, the best use of recyclate is not likely to be as a replacement for existing materials, Robert says. Rather, what is likely to make the most economic sense is when the recyclate can be incorporated into, and provide beneficial properties to, a new material.