PS foam VS Phenol

Hi there, Just question the Phenol whether it can be used for the foam blank. Its much stiffer than those PS. When shapes, it produces fine dust/powder like stuff, similar to those Clark Foam. As PS shaped by planer, it gives out coarse foam particle. But I worry it gives more weight as the mass is much heavier than PS/PU. Do your guys have any idea about this? Thanks for your attention. Regards, Crabie