THERMOSET RECYCLING

We’ve always heard that thermoset resins can’t be recycled like thermoplastics. But Randy Lewis doesn’t buy that. “There’s no such thing as non-recyclable. Everything can be recycled,” he told PlasticsToday. Lewis has his own consulting firm, P.R. Lewis Consulting (Charlotte, NC), and is a 50% owner in ZeMC² (Salisbury, NC), a specialty material bulk molding compound (BMC) company that develops new materials for pump and down-hole applications, among others.

Lewis likes to tell the story of his experience in a plant that was injection molding phenolic parts with a molding compound he had hand mixed in a box beside the press. “The virgin phenolic molding compound contained 20% phenolic regrind,” he said. “The molded parts were to be inspected by QC, built into finished product and tested in the plant. If the internal in-house tests were successful, the assembled product was to be submitted to UL for approval. As I was standing there watching the parts fall out of the mold (using the same cycle that was used for the virgin parts), a gentleman with a masters in mechanical engineering walked up behind me and asked what I was doing. I explained to him that we were molding 20% phenolic regrind into his parts for testing, and his exact words were, ‘Thermosets can’t be recycled.’”

That was January 3, 2000, Lewis said, who noted that he has spent as much time molding thermoplastics as thermosets. “I have worked with recycling both phenolic and BMC, and I’m starting to work on a project to recycle epoxies. Based on this, I feel I can be forward enough to tell you that recycling thermosets is no more or less difficult than recycling any engineering-grade thermoplastic—with the exception of polypropylene, polyethylene, styrene, PVC and maybe ABS,” he explained. “Many of the thermoplastics such as Ectar, Ultem, Torlon and so forth are exponentially harder to recycle than thermosets because of the inherent drying problems caused by the shape of the ground material. An even shape dries evenly; ground material does not have an even shape, therefore myriad inconsistencies come with trying to dry and mold regrind engineering thermoplastic.”

All of these thermoplastic materials cost $2 to $20 per pound, yet they exist to give the thermoplastic molder properties they could not get from a $0.50 to $2 per pound thermoset material, Lewis explained. “In many applications requiring dimensional stability, chemical resistance and heat resistance we outshine them, but are never even considered,” said Lewis. “One of the major reasons, and becoming more so every day, is the perception that thermosets cannot be recycled.”

Lewis has applied for a patent for recycling phenolics and BMC, noting that the recycled phenolic material is difficult to get. Lewis grinds the thermoset material into tiny pieces that look like coral and lock into the virgin material. Using recycled phenolics make the thermoset cure faster and give a shiner surface. “Using recycled thermoset materials as filler provides a perfect adhesion band for the virgin material,” he added.

Recycling thermosets can be done if people have the imagination and the desire to do it,” said Lewis. “It might also work if we put monetary incentive into doing it.”