Sulfur-linked hybrid gel compositions and aerogels thereof
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.
1. A gel composition comprising an organic polymer, a silica network, and a cross-link comprising sulfur, wherein the gel composition is characterized by a thermal conductivity of from 11.6 milliWatts/meter-K (mW/m-K) to 18.2 mW/m-K measured according to ASTM C177 at 38° C. at atmospheric pressure and under an applied compressive load of 0.4 psi and wherein residual strain in the gel composition after release to 0 psi of a 14.7 psi compressive force applied using a cross-head speed of 0.05 inches/minute is from 1% to 3%.
2. The gel composition of claim 1 wherein the gel composition is an aerogel composition.
3. The gel composition of claim 1 , wherein the organic polymer is selected from the group consisting of unsaturated polyesters; prepolymers based on vinylesters, acrylates, methacrylates or polyurethanes, polybutadiene, polystyrene, or polyisoprene; 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 gel composition of claim 1 , wherein the organic polymer is in a form of latex particles or polymer resin.
5. The gel composition of claim 1 , wherein the cross-link is a sulfidosilane of a general formula (R 1 —O) 3 —Si—R 2 —S x —R 2 —Si—(R 1 —O) 3 or of a general formula HS—R 1 —Si—(O—R 2 ) 3 where R 1 and R 2 are same or different alkyl or aryl groups; and x is a number between 1 and 8.
6. The gel composition of claim 1 , wherein the organic polymer in the gel composition is present in an amount of up to 50 wt % of the weight of the gel composition.
7. The gel composition of claim 1 , wherein the cross-link comprises up to 50 wt % of the weight of the gel composition.
8. The gel composition of claim 1 , wherein the organic polymer in the gel composition is present in an amount of at least 3 wt % of the weight of the gel composition.
9. The gel composition of claim 1 , further comprising fibers in an amount of up to 75 wt % of the weight of the gel composition.
10. The gel composition of claim 1 , wherein the silica network defines a plurality of macropores and wherein the gel composition is characterized by a density of from 0.065 grams (g)/cubic centimeter (cm 3 ) to 0.17 g/cm 3 both pre-compression and post-compression.