Polyethylene terephthalate, the plastic of drinks bottles and polyester fibre, is produced in enormous volume yet remains stubbornly difficult to recycle chemically, as depolymerisation normally demands high temperatures and energy. A University of Tokyo group led by Haruo Ishitani and Shu Kobayashi has found that mechanical force can do much of the work: PET treated in a bead mill breaks down into its raw materials, dimethyl terephthalate and ethylene glycol, at a mild 90 degrees Celsius.
A bead mill pulverises material into fine particles using beads under two millimetres in diameter suspended in a solvent. The researchers discovered that the milling itself cleaves chemical bonds within the polymer chains, priming the plastic for low-temperature depolymerisation. Combining the mechanical treatment with catalytic methanolysis allowed the breakdown to proceed without external heating at all.
Reported in Chemical Science, the approach suggests a lower-energy route to genuinely circular plastics, in which waste PET is broken back into monomers suitable for making fresh polymer rather than being downcycled into lower-value uses. With plastic waste accumulating globally and chemical recycling still constrained by its energy demands, chemistries that swap thermal intensity for mechanical ingenuity could prove an important addition to the recycling toolkit.