Effect of Heterogeneous Secondary Pyrolysis Reactions on the Thermal Decomposition of Polyurethane Scrap

Pyrolysis is an effective resource recovery technology for many polymeric materials but is unsuitable for polyurethanes because the liquid product is extremely viscous and can solidify over time. We have pyrolyzed reaction injection molded polyurethane (RIM) scrap in a batch, laboratory-scale reactor and have used a packed carbon bed to influence the composition and yield of the pyrolysis products. We find that carbon surfaces are effective in eliminating the high-viscosity liquid product. Both activated carbon and polyurethane char improve the liquid product by promoting heterogeneous secondary pyrolysis reactions. The polyurethane char provides the additional benefit of increasing the amount of char produced. Char yields as high as 40% can be obtained when polyurethane char is used as the carbon bed material, as compared to 15-25% with other bed materials. These results will be useful in developing pyrolysis as a resource recovery technology for thermosetting polymer waste.