MANY MINDEDA chemical fix that rebuilds worn plastic back to near-new strength
Researchers at Tohoku University have developed a way to repair polybutylene terephthalate (PBT), an engineering plastic used in automotive parts, electrical components, and industrial products, at the molecular level during recycling. Heat and moisture break the long polymer chains that give plastics their strength, so recycled material typically comes out weaker than new. The team's method adds a chemical compound called a chain extender — specifically PPDI — to reconnect those broken chains.
At an optimal concentration, the treatment restored the plastic's tensile strength to nearly that of virgin material and recovered much of its flexibility. The team verified the results with tensile testing, gel permeation chromatography, infrared spectroscopy, and end-group analysis, and found the recovered strength followed a Fox-Flory-type relationship linking molecular weight to mechanical strength. The work, led by Koya Otsuka with associate professor Hiroki Kurita, was published in Composites Part A in 2026.
The economics of recycling often break down because recycled plastic is worth less than the virgin material it replaces. A treatment that returns near-original strength changes that calculation: the same material can cycle back into demanding applications rather than being downgraded or discarded, which lowers both material costs and waste.
The caveats are real. The study focused on PBT alone; the researchers believe the approach could extend to other thermoplastics, but that has not been demonstrated. And the findings are presented as a design guideline — real-world scale-up has not yet been shown. Whether the chain extender remains affordable and effective at industrial volumes is the next question.
Source: Phys.org