Fabrication of silicon oxycarbide foams from extruded blends of polysiloxane, low-density polyethylene (LDPE), and polymer microbead

Silicon oxycarbide (SiOC) foams with porosities ranging from 77% to 90% and a cell density higher than 10(8) cells/cm(3) were made from polysiloxane, low-density polyethylene (LDPE), and polymer microbead blends. The polysiloxane, LDPE, and polymer microbeads were compounded directly using a counter-rotated twin-screw extruder. The obtained blends were foamed with gaseous carbon dioxide, cross-linked, and subsequently pyrolyzed. The process resulted in the production of highly porous, open-cell SiOC foams with a bimodal distribution of pore morphology, small spherical pores derived from polymer microbeads and relatively large elongated or equiaxed pores derived from foaming using carbon dioxide and decomposition of LDPE.