Prague, Czech Republic – Chemists at the Institute of Macromolecular Chemistry in Prague have found a way to convert polyurethane and polycarbonate scrap from end-of-life vehicles into polyols that could be used to make rigid polyurethane foam for thermal insulation.
A paper published in ACS Sustainable Chemistry & Engineering details how the scrap could be turned into liquid polyols using medium chain glycerides of coconut oil. They took semirigid foam from car interiors based on aromatic isocyanate and polyether polyols, and also BPA-based polycarbonate waste from car headlights. The result was a product with a hydroxyl number of about 300 mg/g KOH.
They found that about 50% by weight of virgin petrochemical polyol could be replaced by the recycled polyols when making the rigid PU foam with no negative effect on the foaming process. The foams made in this way had an apparent density of 40–44 kg/m3, and a high closed cell content of 91% by volume.
The rigid PU foams also had compressive strength, greater than 350 kPa in parallel to foam rise direction, when made with 50% by weight of recycled polyol from polycarbonate. The chemists speculate that this probably resulted from the unique structure of recycled polyol combining rigid aromatic segments together with flexible coconut oil glyceride units.
“This approach, utilising the renewable coconut oil-derived reagent, provides a sustainable recycling solution for two major plastics from automotive waste,” the scientists conclude.