Organically modified hybrid aerogels
View Patent ↗Disclosed and claimed herein are hybrid aerogels which are compositions of tetraalkoxysilanes and bis-(trialkoxysilyl)imides that exhibit low thermal conductivities and high compressive strengths. Methods for their preparation are also provided.
1. Hybrid aerogels comprising the reaction product of:
a. at least one tetraalkoxysilane which may optionally be partially hydrolyzed,
b. at least one bis-trialkoxysilane diimide, and
c. a selected amount of water,
wherein a gelation catalyst was admixed to condense and gel the siloxanes, and dried to obtain an aerogel.
2. The hybrid aerogels of claim 1 , wherein the selected amount of water is calculated from a water to silicon ratio.
3. The hybrid aerogels of claim 2 , wherein the water to silicon ratios are between about 8 and about 20.
4. The hybrid aerogels of claim 3 , wherein the final density of the aerogel is less than about 0.7 grams/cubic centimeter.
5. The hybrid aerogels of claim 3 , wherein the thermal conductivity of the aerogel is less than about 30 milliwatts/meter-degree Kelvin or below.
6. The hybrid aerogels of claim 3 , wherein the compressive modulus is greater than about 175 pounds/square inch.
7. The hybrid aerogels of claim 1 , wherein the at least one tetraalkoxysilane is partially hydrolyzed tetraalkoxysilane.
8. The hybrid aerogels of claim 7 , wherein the selected amount of water is calculated from a water to silicon ratio.
9. The hybrid aerogels of claim 8 , wherein the water to silicon ratios are between about 8 and about 20.
10. The hybrid aerogels of claim 8 , wherein the final density of the aerogel is less than about 0.7 grams/cubic centimeter.
11. The hybrid aerogels of claim 8 , wherein the thermal conductivity of the aerogel is less than about 30 milliwatts/meter-degree Kelvin.
12. The hybrid aerogels of claim 8 , wherein the compressive modulus is greater than about 175 pounds/square inch.
13. The hybrid aerogels of claim 1 , further comprising a fibrous material, comprising microfibers, mats, felts, woven fabrics, non-woven fabrics, fibrous battings, lofty battings or a combination thereof.
14. A method of producing hybrid aerogels comprising:
a. combining at least one tetraalkoxysilane or optionally at least one partially hydrolyzed tetraalkoxysilane, at least one bis-trialkoxysilane diimide, and a selected amount of water;
b. admixing a gelation catalyst to condense and gel the siloxanes; and
c. drying the gel to obtain an aerogel.
15. The method of claim 14 , wherein the selected amount of water is calculated from a water to silicon ratio.
16. The method of claim 15 , wherein the water to silicon ratios are between about 8 and about 20.
17. The method of claim 14 , further comprising an aging step after the gelation step, comprising contacting the siloxanes with an amine containing material.
18. The method of claim 17 , wherein the final density of the aerogel is less than about 0.7 grams/cubic centimeter.
19. The method of claim 17 , wherein the thermal conductivity of the aerogel is less than about 30 milliwatts/meter-degree Kelvin or below.
20. The method of claim 17 , wherein the compressive modulus is greater than about 175 pounds/square inch.