Structural Foams of Improved Strength and Thermal Stability From Random-Coil and Rigid-Rod Polymers

摘要

The most significant accomplishments were determining the conditions forpreparing microcellular structural foams from high-temperature polymers of interest to the US Air Force. The primary system was rodlike polybenzobisthiazole blended with poly(etherketoneketone) with 5% rod content. This gave microcellular foams with densities about 0.92 g/cc, and a yield strength about 9.4 ksi. A modified foaming technique gave foams with high porosity, a density of 0.65 g/cc, and pore sizes from 10to 40 micrometers. Also, some sulfonated poly(p-phenyleneben zobismidazole) /poly(2-vinylpyidine) molecular composites gave foams of uniform microstructures and a cell size less than 10 micrometers, but with some brittleness. Molecular composites based on polysulfone (PSF) and polybenzimidazole (PBI) were also successfully prepared. PSF and PBIare immiscible, but introduction of functional groups into the PSF or PBI resulted in miscible polymer blends. Very homogeneous microcellular foams were obtained from them, and their thermal behavior and mechanicalproperties were encouraging.