Foam formation from fluorinated polyphosphazenes by liquid C[O.sub.2] processing

Three dimensional foams of fluorinated polyphosphazenes were prepared using liquid C[O.sub.2] to solvate polymer films, which were then expanded by volatilization of liquid C[O.sub.2] within the polymer matrix. The polymers dissolved in C[O.sub.2] at 1.5 x [10.sup.7] Pa (2200 psi) and room temperature. Materials were examined using Raman spectroscopy before and during high pressure C[O.sub.2] exposure. The solubility in liquid C[O.sub.2] 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., 48:683-686, 2008. © 2008 Society of Plastics Engineers
INTRODUCTION Only a limited number of polymers such as fluorinated polyacrylates, fluoroalkoxy polysiloxanes, and poly(difluoroethylene) are soluble in or are swelled by liquid carbon dioxide [1-3]. Thus, the discovery of [...]