Pyrolysis of polyurethane by microwave hybrid heating for the processing of NiCr foams

Reticulated polyurethane foams are often used as templates for the processing of metal and ceramic foams, since polyurethane foams with a high homogeneity and uniformity of pores and a wide variety of porosities and pore sizes are commercially available. Current conventional methods to pyrolyse polyurethane have brought attention to issues such as long processing time, high costs and high contents of carbon residue. Microwave hybrid heating, as a new pyrolysis method, has been investigated in this research to overcome these issues. Two microwave hybrid and one conventional heating process as comparison were performed to pyrolyse binder and polyurethane for the processing of NiCr8020 foams, which were fabricated by dip-coating method in a powder metallurgical route. Compared to the conventional process, the processing time and residual carbon content of the pyrolysed and pre-sintered foams can be reduced significantly by utilizing microwave hybrid heating techniques, whereas the stability of microwave hybrid heating must be improved and a compromise must be made between the heating rate and the residual carbon content due to the formation of burst holes during the rapid decomposition of polyurethane.