Sulfur-containing organic-inorganic hybrid gel compositions and aerogels

Abstract

Methods and materials are described for preparing organic-inorganic hybrid gel compositions where a sulfur-containing cross-linking agent covalently links the organic and inorganic components. The gel compositions are further dried to provide porous gel compositions and aerogels. The mechanical and thermal properties of the dried gel compositions are also disclosed.

Claims

1. A dry gel composite comprising an organic polymer incorporated into a silica network, wherein the organic polymer is covalently bound to the silica network through a sulfur-containing cross linking agent.

2. The dry gel composite of claim 1 wherein the dry gel composite is an aerogel composite.

3. The dry gel composite of claim 1 or claim 2, wherein the organic polymer is selected from the group consisting of unsaturated polyesters; prepolymers based on vinylesters, acrylates, methacrylates or polyurethanes; polybutadienes; styrene-butadiene copolymers; butadiene-isoprene co-polymers; butadiene-isoprene-styrene terpolymers; copolymers or terpolymers of isobutylene, para-methylstyrene and bromo-para-methyl-styrene; ethylene propylene diene monomer rubber; and a combination thereof.

4. The dry gel composite of claim 1 or claim 2, wherein the organic polymer is in the form of latex particles or polymer resin.

5. The dry gel composite of claim 1 or claim 2, wherein the sulfur-containing cross linking agent is a hexasulfide compound, a tetrasulfide compound, or a disulfide compound.

6. The dry gel composite of claim 1 or claim 2, wherein the sulfur-containing cross linking agent is selected from the group consisting of polysulfide alkyl silanes, mercapto aryl silanes, polysulfide aryl silanes, silated core polysulfides, sulfur-containing silanes, sulfanylsilanes, sulfur-containing siloxanes, sulfur-functional polyorganosiloxanes, bis(triethoxysilylpropyl) tetrasulfide, 3-thiocyanatopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane and any combination thereof.

7. The dry gel composite of claim 1 or claim 2, wherein the sulfur-containing cross linking agent is a sulfidosilane of a general formula
(R.sub.1O).sub.3SiR.sub.2S.sub.xR.sub.2Si(R.sub.1O).sub.3 or of a general formula
HSR.sub.1Si(OR.sub.2).sub.3 where R.sub.1 and R.sub.2 are same or different alkyl or aryl groups; and x is a number between 1 and 8.

8. The dry gel composite of claim 1 or claim 2, wherein the organic polymer in the dry gel composite is present in an amount of up to 50 wt % based upon the weight of the dry gel composite.

9. The dry gel composite of claim 1 or claim 2, wherein the sulfur-containing cross linking agent in the dry gel composite is present in an amount up to 50 wt % based upon the weight of the dry gel composite.

10. The dry gel composite of claim 1 or claim 2, wherein the organic polymer in the dry gel composite is present in an amount of at least 3 wt % based upon the weight of the dry gel composite.

11. The dry gel composite of claim 1 or claim 2, further comprising fibers in an amount of up to 75 wt % based upon the weight of the dry gel composite.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1. Schematic depicting the use of coupling agents to improve the adhesion of rubber to silica

(2) FIG. 2. Schematic depicting the modification of poly(styrene-butadiene) latex with TESPT.

(3) FIG. 3. Particle size distribution of treated and untreated UCAR 313 latex emulsions.

(4) FIG. 4. FT-IR spectra of neat MPTS and a Me-1 latex emulsion before and after vulcanization.

(5) FIG. 5. FT-IR spectra of MEPST, vulcanized TV-1 latex and vulcanized TV-2 latex.

(6) FIG. 6. Photographs of hybrid silica/SB rubber aerogels prepared with 50% TV-2 (left) and 30% TV-2 (right) latex emulsions.

(7) FIG. 7. FT-IR spectra of silica/SBR hybrid aerogels prepared using vulcanized latex TV-1 and TV-2.

(8) FIG. 8. DSC curves in air of latex/aerogel composites prepared at a 10% loading.

(9) FIG. 9. TGA curves in air for latex/aerogel composites prepared at a 10% loading.

(10) FIG. 10. Nitrogen physisorption isotherms for vulcanized latex/aerogel composites.

(11) FIG. 11. Pore size distributions for vulcanized latex/aerogel composites.

(12) FIG. 12. Compressive stress strain curve of prototype aerogel composites prepared at a nominal target density of 0.05 g/cc.

(13) FIG. 13. Compressive recovery for hybrid aerogel composites prepared from the vulcanized SBR emulsions.

(14) FIG. 14. Change in thermal conductivity and density for hybrid aerogel composites prepared with vulcanized SBR emulsions.

(15) FIG. 15. Schematic depicting the vulcanization process.

(16) FIG. 16. Molecular structure of polybutadiene and TESPT. Chain length of PBD is longer than that shown in this figure.

(17) FIG. 17. FT-IR spectrum of WD-32 vulcanizate in comparison to pure polybutadiene.

(18) FIG. 18. GPC chromatograms of vulcanized polybutadiene prepared at a concentration of 0.65 g/cc and an olefin/TESPT molar ratio of 12.5 (a) in comparison to pure polybutadiene (b).

(19) FIG. 19. Molecular weights and product yields determined for the vulcanization of PBD with TESPT according to GPC analysis.

(20) FIG. 20. Photographs of a fiber-reinforced hybrid rubber/silica aerogels exemplifying the highly flexible and resilient nature of this material.

(21) FIG. 21. Thermal conductivity values (1 atm, 100 F.) as a function of organic content for hybrid silica/PBD aerogels prepared with a variety of PBD vulcanizates.

(22) FIG. 22. Measured density values as a function of organic content for hybrid silica/PBD aerogels prepared with various PBD vulcanizates.

(23) FIG. 23. FT-IR of a rubber/silica aerogel prepared with a low molecular weight vulcanizate (WD23).

(24) FIG. 24. Nitrogen isotherms (top panel) and pore size distribution of PBD-silica hybrid aerogels (bottom panel). PBD content in WD-35C1, D1, E1, and F1 are 0, 17, 33 and 50 wt %.

(25) FIG. 25. Compressive stress-strain curve for Silica-BD/PESPT aerogel with 33% PBD-PESPT.

(26) FIG. 26. Photograph displaying the inherent hydrophobicity of WD-23d.

(27) FIG. 27. Schematic depicting a typical ASTM C177 guarded hot plate apparatus.

(28) FIG. 28. Thermal conductivity (ASTM C177) of a hybrid aerogel composite as a function of atmospheric pressure at 38 C. (100 F.).