Low density, resorcinol-formaldehyde aerogels
First Claim
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1. A process for the synthesis of a low density, organic aerogel of ultra-fine pore size, said process comprising the steps of:
- mixing in a predetermined ratio a polyhydroxy benzene and formaldehyde in the presence of a base catalyst;
heating the mixture to a predetermined temperature for a sufficiently long period of time to form a stable gel;
washing the gel in a suitable organic solvent to exchange the aqueous solvent for the organic solvent;
critical point drying the gel; and
characterizing the gel.
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Abstract
The polycondensation of resorcinol with formaldehyde under alkaline conditions results in the formation of surface functionalized polymer "clusters". The covalent crosslinking of these "clusters" produces gels which when processed under supercritical conditions, produce low density, organic aerogels (density ≦100 mg/cc; cell size ≦0.1 microns). The aerogels are transparent, dark red in color and consist of interconnected colloidal-like particles with diameters of about 100 Å. These aerogels may be further carbonized to form low density carbon foams with cell size of about 0.1 micron.
231 Citations
15 Claims
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1. A process for the synthesis of a low density, organic aerogel of ultra-fine pore size, said process comprising the steps of:
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mixing in a predetermined ratio a polyhydroxy benzene and formaldehyde in the presence of a base catalyst; heating the mixture to a predetermined temperature for a sufficiently long period of time to form a stable gel; washing the gel in a suitable organic solvent to exchange the aqueous solvent for the organic solvent; critical point drying the gel; and characterizing the gel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A process for the synthesis of a low density, microcellular resorcinol-formaldehyde aerogel, said process comprising the steps of:
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(a) mixing resorcinol and formaldehyde in a molar ratio of about 1;
2, in the presence of catalytic amounts of sodium carbonate;(b) adjusting the pH of the mixture to a value in the range of about 6.5 to about 7.4; (c) decanting the mixture into a glass ampoule; (d) sealing the glass ampoule; (e) heating the mixture to about 85°
C. in an oven for about seven days to facilitate formation of a gel;(f) removing the ampoule from the oven and cooling it to room temperature; (g) breaking the ampoule and removing the gel from the ampoule; (h) washing the gel in an agitated bath of trifluoracetic acid at 45°
C. for three days;(i) transferring the gel from the acid bath to an agitated acetone bath maintained at about 45°
C., to remove water;(j) removing the gel from the acetone bath and critical point drying the gel; and (k) characterizing the gel. - View Dependent Claims (15)
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Specification