Preparation and characterization of carbon foams from cyanate ester mixtures

Carbon foams were prepared by direct pyrolysis of cyanate ester (CE) resins from the mixtures of phenol novolac cyanate ester (PNCE) and bisphenol A cyanate ester (BACE) at ambient pressure. Pyrolysis behaviors of the CE resins were characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and X-ray diffraction (XRD). In addition, influences of PNCE/BACE mass ratio on the characteristics of the resultant carbon foams were studied. Results show that the CE resin possesses better thermal stability with increasing PNCE/BACE mass ratio, whereas its self-foaming performance becomes worse during pyrolysis. The addition of PNCE to BACE leads to an increase in the bulk density of the resultant carbon foam but a decrease in both its porosity and open cell. Moreover, the compressive strength of the carbon foam increases with an increase in the PNCE/BACE. When the PNCE/BACE mass ratio varies from 0 to 0.75, the compressive strength of the carbon foam prepared increases from 3.25 to 9.6 MPa.