Preparation and Properties of Phenolic Foam Modified with Boric Acid and Organosiloxane by Supercritical Co2 Technology

In this study, a modified phenolic foam (SiBPF) is prepared in a reactor under specific pressure and temperature and using supercritical CO2 (scCO2) as a physical foaming agent, to improve phenolic foam (PF) brittle and friable properties and avoid environmental pollution caused by conventional physical foaming. To determine the pre-curing degree for foaming, the influence of pre-curing time at pre-curing degrees between 39.88% and 53.17% was studied. Further, through an orthogonal experimental method, the optimized foaming process parameters—pre-curing time of 6 h, adsorption time of 9 h, foaming pressure of 1 MPa, and foaming temperature of 130℃—were determined. The SiBPF, thus prepared under the optimized conditions, exhibited a density of 0.2356 g/cm3, an average cell size of 86.66 μm, and a cell density of 7.10 × 106 cells/cm3. Its compressive strength was found to be 7.28 MPa, with a specific compressive strength of 30.90 MPa/g·cm-3. At 800℃, the carbon residue rate, thermal decomposition temperature T5%, and Tmax reached 77.61%, 355.21℃, and 702.70℃, respectively. The thermal conductivity of SiBPF was measured to be 0.0644 W/mK, with the rear temperature stabilizing at 60℃ on a hot platform of 100℃.