University at Buffalo reports method to separate layers of plastic packaging

University at Buffalo researchers said on September 30 that they had developed solvent-based ways to separate the bonded layers of multilayer plastic packaging in tests on selected films. The work could help recover plastic from packaging that is difficult to recycle, but it has not established a way to process mixed household wrappers in ordinary recycling systems.

The university said the separation, called delamination, took less than an hour at atmospheric pressure and temperatures below 90°C. The researchers aimed to recover the plastic as solid film, rather than break it down, and said the solvent used in the process could be recovered by distillation. Those are reported experimental results, not measurements of a commercial recycling operation.

What the polyethylene recovery tests showed

An accessible abstract of a related paper by the team identifies the materials more precisely: commercial post-industrial films with polyethylene, an intermediate layer and polyester. It describes two combinations, PE/PEI/PET and PE/PU/PET. These selected factory films are a narrower test than the assortment of used packaging collected from homes.

For those combinations, the paper reports using a solution of 88% formic acid in water at 70°C. It says the solvent dissolved the adhesive layer, allowing the materials to separate in under an hour while polyethylene remained an intact solid film. The paper was published on June 22, before the university's September account of the wider work.

Paschalis Alexandridis, a corresponding author, said the team designed the process to recover polyolefin at high purity as solid film. The university also names Marina Tsianou as a corresponding author and Jacob S. Licht as first author of the work it discusses. It says the research received support from the US Department of Energy through the REMADE Institute and from the National Science Foundation.

Why multilayer wrappers are difficult to recycle

Multilayer packaging joins materials that serve different purposes. According to the university, polyethylene can help a package seal and resist moisture and gas, while polyester and nylon add strength or a barrier to liquid. Those layers are bonded for the package's useful life, which makes recovering individual materials difficult after disposal.

An independent review of structural separation technologies, published in June, says existing systems often struggle to identify, sort and separate multilayer packaging. That matters for a household recycling route: a process that separates a known film composition still needs a reliable way to receive suitable material from a mixed collection stream.

The university says its researchers explored more than one way to induce delamination, including disrupting adhesion between adjacent layers or dissolving a minor component. The accessible abstract gives detailed conditions for the formic-acid tests on the two specified film combinations. Neither source establishes that the same conditions will work for every food wrapper or medicine package.

What remains to be tested for household packaging

The independent review identifies contamination control, solvent management, energy use and validation at larger scale as important questions for separation methods. Those issues are relevant to any attempt to move from selected post-industrial films to used packaging collected from consumers. The university's statement that solvent can be recovered by distillation addresses one part of that challenge, but gives no commercial-scale solvent-loss or net-energy figure for this process.

The available sources also give no commercial processing cost or life-cycle assessment for the Buffalo method. Without results from mixed post-consumer packaging and a complete collection and processing system, its reported material recovery cannot be translated into a claim that household wrappers can now go into ordinary recycling bins.

For now, the clearest finding is that selected bonded films can be separated under the conditions reported by the researchers, with polyethylene recovered in a form that performed well in their stated tests. Further evidence on collection, sorting, contaminated packaging, solvent handling and scale is needed to judge whether the method can divert consumer packaging from disposal.