Beijing – Scientists at Peking University have developed a catalytic process for transforming waste polyurethane into useful intermediates. These can then be used to make various functional polymers.
The heterogeneous catalytic process combines methanolysis and hydrogenation using a CO2/H2 reaction medium. The products are used to make, for example, polyimide, with good thermal and electrical insulation properties, and the biodegradable plastic polylactone. They claimed that both of these polymers have enhanced performance when compared to existing commercial products.
A zinc-copper catalyst was used to achieve the breakdown of the PU into diamines, diols and lactones. These were then used to make polyimide and polylactone.
They tested the efficiency of the process on four different commercial PU products: shoe soles, tubes, tyres and safety strips. For example, 5g of predominantly PU-containing tyre waste gave a total product yield of 86%. These were then used to make about 2.2g of polyimide film that acts a dielectric capacitor, and 0.44g of polylactone with satisfactory ductile properties.
The depolymerisation yields of the other three products were 77% for the shoe sole, 80% for the tube, and 82% for the safety strip. This, they said, illustrated the effectiveness of their reaction on several different PU compositions, showing its potential as a pathway for converting waste into high-performance materials.
The work has been published in the journal National Science Review.
