13. Jul 2026
Iridium catalyst selectively recycles PU from mixed plastic waste
Researchers in Japan have developed a catalytic process that breaks down polyurethane in mixed plastic products while leaving polyester and polyamide components intact for separate recovery.
Researchers from Kyushu University, the University of Tokyo and Japan’s National Institute of Advanced Industrial Science and Technology have developed a method for selectively degrading polyurethane in mixed plastic waste.
The process combines an iridium-based catalyst with a phenolate salt additive and hydrogen gas at temperatures of 130–170°C. It breaks down the PU into smaller, reusable molecules without degrading accompanying polyester or polyamide materials.
The remaining polyester and nylon can then be separated from the PU-derived products by filtration and potentially sent for mechanical recycling. The process therefore combines material separation and chemical recycling in a single step.
The researchers said this selectivity runs counter to the expected order of chemical reactivity. Ester bonds are generally considered more reactive than amide bonds, which in turn are more reactive than urethane bonds. A conventional degradation process would therefore be expected to attack polyester before nylon and PU.
“What I find most remarkable is that it overturns what every undergraduate learns in organic chemistry,” said Takanori Iwasaki, professor in Kyushu University’s faculty of engineering. “By combining iridium catalyst and the right additive, we flipped that sequence entirely. The least reactive bond gets cut first, while the more reactive ones are left untouched.”
The team demonstrated the process on several commercial products containing combinations of PU, polyester and nylon. These included a kitchen sponge, blended underwear, a mobile phone case and an end-of-life automotive seat.
In each case, the PU component was degraded while the polyester and polyamide materials remained intact. The researchers believe the approach could be particularly relevant to automotive seating, mattresses, textiles and other products in which PU is bonded to or blended with other polymers.
The research also potentially reduces the need for manufacturers to replace PU with materials that are easier to recycle but offer different performance characteristics.
“Japan’s Shinkansen trains are a good example,” Iwasaki said. “Newer models have replaced PU seat cushions with polyester. It is easier to recycle but noticeably less comfortable. If we can handle mixed plastics properly, manufacturers no longer need to make that trade-off.”
However, the researchers acknowledged that the cost and scalability of the process remain significant obstacles. Iridium is a scarce and expensive precious metal, and the team said that identifying cheaper catalyst systems or improving catalyst efficiency would be necessary before the method could be considered for commercial-scale recycling.
“Plastic recycling is only the beginning,” Iwasaki said. “As an organic chemist, what excites me most is the ability to selectively override chemical reactivity rules. My hope is that this opens more bridges between fundamental chemistry and real-world problems, from plastic waste to pharmaceutical synthesis and beyond.”
The research was published in Angewandte Chemie International Edition under the title “Selective Degradation of Polyurethanes in Mixed Plastic Wastes via Ir-Catalyzed Hydrogenolysis.” The paper, by Yuto Yamada, Takanori Iwasaki, Shinji Tanaka and Kyoko Nozaki, was selected by the journal as a Hot Paper.