Effective Recycling by Repairing Damaged Plastics at the Molecular Level
According to scientists at Japanese Tohoku University, plastic recycling could become far more effective thanks to a new technique that restores the strength of damaged engineering plastics by repairing them at the molecular level.
The researchers have developed a method to restore the mechanical strength of degraded polybutylene terephthalate (PBT), a durable engineering plastic widely used in automotive parts, electrical components, and industrial products. By adding a chemical compound known as a chain extender (called PPDI) during recycling, they were able to reconnect broken polymer chains and recover the material’s strength to a level close to that of new plastic. As underlined, the findings would address one of the biggest challenges facing plastic recycling. “Many plastics gradually weaken during use as heat and moisture break apart the long molecular chains that give them their strength. Although these materials can be melted and remolded, conventional recycling methods often fail to restore their original mechanical performance, limiting how they can be reused.” Furthermore, the team also found a clear relationship between molecular weight and mechanical strength. “By analyzing the recycled material using tensile testing, gel permeation chromatography, infrared spectroscopy, and end-group analysis, they showed that the recovered strength follows a Fox-Flory-type relationship,” the university gave account. “This means the future performance of recycled plastics can be predicted from their molecular characteristics rather than relying on trial-and-error processing.”
“This study demonstrates that recycling can be approached scientifically,” Hiroki Kurita, Associate Professor of Tohoku University’s Graduate School of Engineering, was quoted. “By understanding how molecular weight affects mechanical strength, we can transition from empirical methods of recycling to predictive ones.”
The researchers would hope their approach would contribute to a more circular materials economy by enabling high-performance plastics to be reused instead of discarded, Tohoku University stated. “As demand for sustainable manufacturing continues to grow, repairing polymers at the molecular level could help reduce plastic waste, conserve valuable resources, and extend the lifespan of engineering materials.”
(Published in GLOBAL RECYCLING Magazine 3/2026, Page 31, Source: Otsuka et al.)
