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An environment friendly process to produce low density foam from PAES |
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| An environmental friendly and benign process has been developed by scientists from Virginia Polytechnic Institute and State University of Virginia to produce low density foam from poly (arylene ether sulfone) (PAES). Carbon dioxide (CO2) and water as well as nitrogen and water were used as physical blowing agents in a one-step batch process. A large amount of blowing agents (up to 7.5%) was able to diffuse into the PAES in a 2 hour saturation time. Water and CO2 gave foam better properties than nitrogen and water because both the water and CO2 are plasticizers for the PAES. PAES foam produced from CO2 and water had a large reduction in foam density of 80% and a cell size of 50 lm, while maintaining a primarily closed cell structure. The small cell size and closed cell structure enhanced the mechanical properties of the foam when compared with the PAES foam produced from nitrogen and water. The lower compression strength of 39 MPa and lower compression modulus of 913 MPa of the produced PAES foam is comparable to polyetherimide and poly (vinylchloride) structural foams.
PAES foam that was produced in the experiments had a foam density ranging between 350 and 490 kg/m3. This correlates to a density reduction of 62�72%. The cell size and cell nucleation density of the foam were 156 lm and 7.03 3 105 cells/cm3, respectively. The foam exhibited better properties. The foam density was 250 kg/m3, an 81% reduction in foam density, which is comparable to several commercially avail-able structural foams. The cell size was 54 lm and the cell nucleation density was 1.85 3 107 cells/cm3, which are both improvements upon the PAES foam produced from N2 and water.
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