Plastic waste and old cooking oil used to make rigid PU foams

Qazvin, Iran – Scientists in Iran have used a mixture of used cooking oil and plastic waste to create polyols. The team at the Imam Khomeini International University then used these polyols in the manufacture of rigid PU foam.
Used cooking oil can be epoxidised, and these epoxides then transformed into biopolyols by reaction with reagents such as glycols, glycerine and triethanolamine. Biopolyols can also be made by a transesterification reaction of the oils.
Crude glycerin is the main byproduct of the transesterification process used to make biodiesel from used cooking oil, but it is far from pure, containing impurities such as water, methanol and acyl glycerides. Purification, however, is economically unfeasible.
Various used plastics can also be used to generate polyols, via a glycolysis reaction. The team used polyol from crude glycerin and epoxidised used cooking oil in the recycling process for three separate plastic wastes – PET, PU and BPA – with the result being new classes of biopolyols, with different viscosities and hydroxyl numbers.
The waste was first depolymerised in diethylene glycol, and then reacted with a heated mixture of PGL and EUO with a magnetic nanoparticle catalyst. These new biopolyols were then blended with commercial polyols, at 20, 40 and 60%, and reacted with an isocyanate to create PU foams.
The apparent density of the foam increases along with the biopolyol content, with high viscosity inhibiting cell growth. The foams made with 20 and 40% of the biopolyol mixtures had what the group described as “insignificant changes” from the thermal, morphological and thermo-mechanical properties of comparative rigid foam samples. At 60%, there was a partial deformity in cellular structure, and greater changes in thermal and mechanical properties.