Foam formation from fluorinated polyphosphazenes by liquid CO2 processing



Three dimensional foams of fluorinated polyphosphazenes were prepared using liquid CO2 to solvate polymer films, which were then expanded by volatilization of liquid CO2 within the polymer matrix. The polymers dissolved in CO2 at 1.5 × 107 Pa (2200 psi) and room temperature. Materials were examined using Raman spectroscopy before and during high pressure CO2 exposure. The solubility in liquid CO2 is attributed to interactions between the solvent and the fluorine atoms in the polymer side groups. Fluoroalkoxy polyphosphazenes are known for their hydrophobicity and fire retardant properties, and these characteristics are retained in the foams. Scanning electron microscopy, water swelling, and preliminary fire retardance tests were conducted to determine the morphology and properties of the foams. These materials are possible candidates for a number of different engineering applications. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers