Scientists use plastic waste and waste cooking oil to make rigid polyurethane foam

Scientists in Iran use a mixture of waste cooking oil and plastic waste to make polyols. The team at Imam Khomeini International University uses these polyols to make rigid polyurethane foam.

Used cooking oils can be epoxidized, and these epoxides are then converted into bio-based polyols by reacting with some chemical agents such as ethylene glycol, glycerol and triethanolamine. Bio-based polyols can also be prepared by transesterification of oils.

Crude glycerin is the main by-product of the transesterification process of biodiesel preparation from used cooking oil, but it has a high content of impurities, including water, methanol and acylglycerides. Therefore, it is not economically feasible to purify it.

Various waste plastics can also be used to produce polyols, which are reproduced by glycolysis. The team used polyols from crude glycerin and epoxidized waste edible oils in the recycling of three different plastic wastes – PET, PU and BPA – resulting in a new bio-based polyol with different viscosities and hydroxyl values.

The waste is first depolymerized in diethylene glycol and then reacted with a heated mixture of PGL and EUO under the action of a magnetic nanoparticle catalyst. These new bio-based polyols are then mixed with commercial polyols in 20%, 40% and 60% ratios and react with isocyanates to produce polyurethane foam.

The apparent density of foam increases with increasing bio-based polyol content, and high viscosity inhibits bubble growth. Foams made with 20% and 40% bio-based polyol blends have "insignificant changes" in insulation, morphology and mechanical properties under heat compared to relatively rigid foam samples. At 60%, the bubble structure is partially deformed, and the mechanical properties under heat have undergone a relatively large change.