Professor Hiroshi Uyama and his research team at the Graduate School of Engineering, Osaka University, have recently developed a technology that selectively decomposes and removes polyurethane (PU) from blended textile materials, enabling the recovery of cotton.
This process utilizes microwave heating—similar to that used in microwave ovens—allowing for rapid treatment. PU has long been considered the final barrier to textile recycling due to its complexity, and this breakthrough offers a promising solution.
In March 2024, the team had announced a method for separating cotton and polyester blends. Building on that technique, the new approach uses chemical agents and ethylene glycol, heated by microwaves, to selectively break down PU and extract only the cotton. Although the PU content in clothing is minimal and not yet recyclable on its own, the ethylene glycol containing PU can be reused through distillation, minimizing waste through a closed-loop system.
The method also supports three-component blends of cotton, polyester, and PU. By applying a two-step process—first decomposing polyester, then removing PU—the team successfully recovered both cotton and BHET (bis(2-hydroxyethyl) terephthalate), a precursor to PET (polyethylene terephthalate). The cotton remains largely undamaged throughout the process, with a recovery rate exceeding 95%, making material recycling feasible.
The procedure is simple: mix the fibers with chemicals and heat them for a few minutes using microwaves. It eliminates the need for hazardous solvents or high-pressure vessels, allowing for safe, low-pressure treatment with common reagents and reduced environmental impact. “Microwave heating enables highly efficient processing in a short time, and the low-pressure conditions ensure safe operation,” explains Professor Uyama.
As demand for stretchable, comfort-focused fabrics grows, PU-containing garments have expanded from sportswear to everyday clothing. However, recycling such blended materials has been challenging. Around 65% of clothing collected in Japan is made from blended fabrics. “Many companies show little interest in recycling inexpensive polyester, but there’s strong demand for reusing cotton if it can be extracted intact,” he notes.