Because different polymers have different qualities, multiple types will often be layered together in products such as food packaging. And while such multilayer plastics are currently non-recyclable, a new technique may change that.
Known as Solvent-Targeted Recovery and Precipitation (STRAP) processing, the experimental technology is being developed by scientists at the University of Wisconsin-Madison.
It incorporates a computer system called the Conductor-like Screening Model for Realistic Solvents (COSMO-RS), which calculates the solubility of specific polymers when exposed to different solvents at different temperatures. Discarded multilayer plastics are thus put through a series of solvent washes, based on this system's recommendations.
As a result, the various polymers are dissolved one layer at a time. Each one can then be chemically separated from the solvent, and reused in new products.
STRAP has already been utilized to separate and reclaim the polymers from a multilayer plastic composed of polyethylene, ethylene vinyl alcohol, and polyethylene terephthalate. The researchers now want to try the system out on other combinations, plus they hope to scale it up for commercial use.
They're also looking into more eco-friendly solvents, in order to decrease the technology's environmental footprint.
A paper on the research – which is being led by professors George Huber and Reid Van Lehn – was recently published in the journal Science Advances.
Source: University of Wisconsin-Madison