Strong composites made by combining recycled PET with biobased monomers

About 30% of the 26 million metric tons of poly(ethylene terephthalate) (PET) produced each year gets fashioned into single-use beverage bottles. But according to a report from the National Association for PET Container Resources and the Association of Plastic Recyclers, only 18% of that material has a second life after recycling—the rest ends up in landfills. The problem, in part, is that the properties of recycled PET just aren’t as good as those of the virgin polymer. Looking for a way to add value to reclaimed PET, Gregg T. Beckham and colleagues at the National Renewable Energy Laboratory have devised a way to transform it into useful composites by combining it with biobased chemicals (Joule 2019, DOI: 10.1016/j.joule.2019.01.018). The scientists first deconstructed the reclaimed PET and glycolized it with linear diols. They then reacted the resulting material with renewable monomers to create either unsaturated polyesters or diacrylic polymers. These polymers were dissolved in the presence of a free-radical initiator to form a resin. Finally, the researchers applied that resin to a woven fiberglass mat. The resulting composites are strong and durable, making them promising materials for car parts, wind-turbine blades, or surfboards. What’s more, analyses suggest that using the new composites instead of petroleum-based, fiberglass-reinforced plastics could save 57% in energy costs and reduce greenhouse gas emissions by 40%.