Journal
JOURNAL OF SUPERCRITICAL FLUIDS
Volume 180, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.supflu.2021.105424
Keywords
Epoxy resin; Microcellular foam; Curing reaction; CO2 diffusion; Foamable window
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The rapid depressurization foaming process using supercritical CO2 as blowing agent is effective in preparing microcellular epoxy foams, with curing reaction and CO2 diffusion playing crucial roles in controlling cell morphology. Experimental and molecular simulation results demonstrate that higher CO2 pressure promotes curing reaction and CO2 diffusion, while there is an optimal curing degree range where unsaturated CO2 concentration and curing degree contribute to good cell structure.
Directly rapid depressurization foaming process has been successfully applied to prepare microcellular epoxy foams using supercritical CO2 as blowing agent. It is found that both curing reaction and CO2 diffusion are crucial for controlling cell morphology. For epoxy of tetraglycidyl-4,4 '-diaminodiphenyl-methane (TGDDM) and 4,4-diaminodiphenylsulfone (4,4-DDS) system, the experimental and molecular simulation results displayed that higher CO2 pressure always promotes curing reaction, and CO2 diffusion is more sensitive to pressure at low curing degree, while limited by high curing degree. The foaming experimental results showed that there existed a suitable curing degree range, in which both unsaturated CO2 concentration and curing degree contribute to good cell structure. Higher CO2 pressure can broaden this foamable window. The microcellular epoxy foam with an average cell diameter of 14.6 mu m and cell density over 109 cells/cm3 as well as volume expansion ratio of 14.5 has been obtained at 85% curing degree under 22 MPa CO2 pressure.
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