Abstract: A method of making an impeller having inner and outer portions of polyurethane resin having different flexibilities with the outer portion bonded to the inner portion and having greater flexibility than the inner portion, includes rotating a centrifugal casting mold containing a polyurethane resin forming material of predetermined composition, introducing into the inner portion of the mold another polyurethane resin forming composition of different composition than the first material, centrifugal casting the inner and outer portions together, and curing the resulting shape to form a disk having bonded inner and outer portions of polyurethane resin having different flexibilities.

Abstract: A polyurethane impeller for mixing liquids lasts considerably longer than equivalent metal impellers of the prior art. The impeller comprises a disk having inner and outer portions of polyurethane resin having different flexibilities, the outer portion being bonded to the inner portion and having greater flexibility than the inner portion. The polyurethane portions are chemically reacted with each other to form a strong chemical bond.A method is provided for centrifugally casting a polyurethane impeller having inner and outer sections of different flexibility and hardness.