ETH Zurich Chemists Turn Waste Polyolefins into Industrial Adhesives
A light-driven chemical grafting method upcycles polyethylene and polypropylene without degrading their polymer backbones.
Chemists at ETH Zurich have engineered a single-step photochemical process that converts discarded plastic bags and bottles into high-strength adhesives. The method tackles polyolefins, which represent about half of the 450 million metric tons of plastic produced each year, bypassing the degraded material quality typical of standard mechanical recycling.
Activating inert carbon chains with light
Polyolefins such as polyethylene (PE) and polypropylene (PP) consist almost entirely of carbon and hydrogen atoms. This simple structure lacks the reactive chemical sites needed for selective chemical breakdown, which typically forces recyclers to rely on pyrolysis, an energy-intensive process that cracks polymers at high temperatures into crude petroleum feedstocks. As reported by Interesting Engineering, the research team led by Tae-Lim Choi, professor of polymer chemistry at ETH Zurich, devised an alternative that preserves the original polymer skeleton while attaching functional chemical side chains.
“Our adhesive is a first-generation product. In the future, plastics with entirely new properties will be possible.”
— Tae-Lim Choi, professor of polymer chemistry at ETH Zurich
A single-step reaction without expensive catalysts
The chemical process dissolves plastic waste in a chlorinated solvent before exposing the mixture to short-wavelength light. This illumination generates reactive chlorine radicals that activate specific carbon atoms along the polymer chain without breaking the backbone apart. These activated sites serve as anchors where chemists can graft new polymer chains carrying tailored functionalities, including acidic, basic, or water-attracting groups. The reaction requires neither high operating temperatures nor costly metal catalysts, and researchers adjust the grafting density by tuning the solvent chlorination and the light wavelength. The resulting material bonds wood, glass, and metals with sufficient strength for load-bearing components in vehicle manufacturing.
Patent protection and industrial testing
Recognizing the commercial potential of the chemical invention, the university secured intellectual property coverage. ETH Zurich filed a patent application covering the grafting technique and nominated the filing for its annual Spark Award, an initiative honouring the institution's most promising commercial inventions. Since the patent publication six months ago, the research group has begun testing formulations with external industrial partners. Beyond adhesives, team members such as senior scientist Hongsik Kim note that the grafted material can act as a structural binder to reinforce lower-grade recycled plastics, advancing material sustainability across secondary manufacturing streams.
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