Researchers from Singapore have developed a new process to recycle mixed plastic packaging without relying on harmful chemical solvents a long-standing barrier in the global push toward more effective plastic waste management. The team, drawn from Nanyang Technological University (NTU), Singapore’s School of Materials Science and Engineering, and the Nanyang Environment and Water Research Institute (NEWRI), has introduced a technique called depolymerization-induced polymer separation, or DIPS. Their findings have been published in the journal Industrial & Engineering Chemistry Research.
Mixed plastic packaging made up of multiple plastic types bonded tightly together has historically been difficult to process through conventional recycling methods. The DIPS approach is engineered to selectively break down one specific plastic in the mix while leaving the remaining materials structurally intact, making individual material recovery and reuse possible. When applied to common mixed plastic packaging, PET reacts with glycerol, a widely available reagent, and breaks down into smaller molecules. The resulting PET-derived material differs physically and chemically from the original plastic, causing it to naturally separate from polypropylene (PP). The entire process runs at room pressure and requires no solvents, which the researchers say makes it both safer and more cost-effective compared to conventional chemical recycling methods.
Hu Xiao, professor and program director for Sustainable Chemistry and Materials at NEWRI, said: “We’re seeing more mixed plastic packaging used in everyday food products, but recycling it safely and efficiently is still a major challenge. Our team set out to tackle this by developing a practical, scalable way to separate these materials without using harmful solvents.” In laboratory tests, the recovered PP retained mechanical properties close to those of virgin plastic, achieving up to 90% of its original tensile strength under optimal conditions. Dr. Liang Yen Nan, co-author of the study and senior research fellow at NEWRI, said: “One of the biggest hurdles in plastic recycling today is the lack of a viable way to deal with mixed plastics. This project was driven by that challenge, and our goal is to help move the industry closer to a solution that works in the real world.”
While the recovered PET cannot be directly reused in packaging applications, the researchers note that it contains chemical groups suitable for specialty material applications including as a potential replacement for epoxy used in wind turbine blades, or for conversion into a monomer. The team also indicates that the DIPS method can be extended to other mixed plastic combinations and scaled up using industrial extrusion equipment. Kathirvel Periasamy, first author of the study, said: “Our process attempts to bridge the gap between laboratory research and industrial application. By simplifying separation and eliminating solvents, we aim to make plastic recycling more economically viable and environmentally sustainable.” As a next step, the research team is set to collaborate with industry partners to validate the approach under scaled-up conditions. The work represents a meaningful development in the field of mixed plastic recycling, offering a pathway that sidesteps the chemical hazards and high costs typically associated with existing separation technologies.
