Silicone rubber foam with ablation resistance and high-efficiency heat insulation and preparation method thereof
The present disclosure provides a room-temperature-vulcanizing (RTV) silicone rubber foam with ablation resistance and high-efficiency heat insulation and a preparation method thereof. In the present disclosure, hydroxyl-terminated polydimethylsiloxane, vinyl-terminated polydimethylsiloxane, a catalyst, an inhibitor, a ceramifiable emulsion foaming agent, a functionalized ceramic filler, and a heat-resistant additive are placed in a planetary stirring tank, and stirred to obtain a base rubber A. The hydroxyl-terminated polydimethylsiloxane, the vinyl-terminated polydimethylsiloxane, a hydrogen-containing silicone oil, a functionalized low-melting glass powder, and functionalized hexagonal boron nitride are placed in the planetary stirring tank, and stirred to obtain a base rubber B. The base rubber B is transferred to the base rubber A, vulcanization is conducted, followed by after vulcanization in an oven to obtain a final product.
1 . A silicone rubber foam with ablation resistance and high-efficiency heat insulation, comprising the following components in parts by weight for blending and foaming:
a hydroxyl-terminated polydimethylsiloxane
100 parts;
a vinyl-terminated polydimethylsiloxane
20 parts to 60 parts;
a hydrogen-containing silicone oil
20 parts to 40 parts;
a catalyst
0.4 parts to 1.5 parts;
an inhibitor
0.1 parts to 0.5 parts;
a ceramifiable emulsion foaming agent
5 parts to 10 parts;
a functionalized ceramic filler
3 parts to 15 parts;
a functionalized low-melting glass powder
3 parts to 15 parts;
a functionalized hexagonal boron nitride
1 part to 5 parts; and
a heat-resistant additive
1 part to 3 parts;
wherein the ceramifiable emulsion foaming agent is a mixture of the following substances in parts by weight:
the hydroxyl-terminated polydimethylsiloxane
100 parts;
an emulsifier
5 parts to 15 parts;
a high-melting glass powder
10 parts to 70 parts;
a ceramic filler
10 parts to 70 parts; and
a hydroxyl-modified hexagonal boron nitride
10 parts to 20 parts; and
wherein:
the hydroxyl-terminated polydimethylsiloxane of the ceramifiable emulsion foaming agent has a viscosity of 1,500 mPa·s to 50,000 mPa·s;
the emulsifier is one or more selected from the group consisting of sorbitan monolaurate, sorbitan monostearate, and sorbitan monooleate;
the high-melting glass powder has a melting point of 650° C. to 900° C.;
the ceramic filler is one or more selected from the group consisting of montmorillonite, kaolin, wollastonite, and halloysite;
the hydroxyl-modified hexagonal boron nitride is obtained by treating a hexagonal boron nitride at a high temperature of 900° C. to 1,200° C., cooling, and washing with deionized water; and
wherein the emulsifier and the hydroxyl-terminated polydimethylsiloxane are dissolved by heating in a water bath and mixed uniformly, and the high-melting glass powder, the ceramic filler, and the hydroxyl-modified hexagonal boron nitride are added into the obtained mixture and mixed uniformly to obtain the ceramifiable emulsion foaming agent.
2 . The silicone rubber foam with the ablation resistance and the high-efficiency heat insulation according to claim 1 , wherein the hydroxyl-terminated polydimethylsiloxane of the silicone rubber foam has a viscosity of 5,000 mPa·s to 20,000 mPa·s; the vinyl-terminated polydimethylsiloxane has a viscosity of 20,000 mPa·s to 50,000 mPa·s; and the hydrogen-containing silicone oil has a hydrogen content of 0.5% to 1.6%.
3 . The silicone rubber foam with the ablation resistance and the high-efficiency heat insulation according to claim 1 , wherein the catalyst is a Karstedt's platinum catalyst with a chemical formula of C 24 H 54 O 3 PtSi 6 and a platinum concentration of 2,000 ppm to 5,000 ppm.
4 . The silicone rubber foam with the ablation resistance and the high-efficiency heat insulation according to claim 1 , wherein the inhibitor is a silylene-propargyl compound with a structural formula as follows:
R 1 , R 2 , and R 3 each are selected from the group consisting of H, methyl, and ethyl, and R is selected from the group consisting of cyclohexyl and isopropyl.
5 . The silicone rubber foam with the ablation resistance and the high-efficiency heat insulation according to claim 1 , wherein:
the functionalized ceramic filler is obtained by grafting the same ceramic filler as used for making the ceramifiable emulsion foaming agent with a silane coupling agent;
the functionalized low-melting glass powder is obtained by grafting a low-melting glass powder with the silane coupling agent, and the low-melting glass powder has a melting point of 350° C. to 600° C.; and
the functionalized hexagonal boron nitride is obtained by grafting the same hydroxyl-modified hexagonal boron nitride as used for making the ceramifiable emulsion foaming agent with the silane coupling agent.
6 . The silicone rubber foam with the ablation resistance and the high-efficiency heat insulation according to claim 5 , wherein the silane coupling agent is selected from the group consisting of vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltris (β-methoxyethoxy) silane.
7 . The silicone rubber foam with the ablation resistance and the high-efficiency heat insulation according to claim 1 , wherein the heat-resistant additive is one or more selected from the group consisting of SnO 2 , Fe 2 O 3 , CeO 2 , and Al 2 O 3 .
8 . A preparation method of the silicone rubber foam with the ablation resistance and the high-efficiency heat insulation according to claim 1 , comprising the following steps:
step (1), placing 50 parts by weight of the hydroxyl-terminated polydimethylsiloxane, 10 parts to 30 parts by weight of the vinyl-terminated polydimethylsiloxane, 0.4 parts to 1.5 parts by weight of the catalyst, 0.1 parts to 0.5 parts by weight of the inhibitor, 5 parts to 10 parts by weight of the ceramifiable emulsion foaming agent, 3 parts to 15 parts by weight of the functionalized ceramic filler, and 1 part to 3 parts by weight of the heat-resistant additive in a planetary stirring tank to obtain a rubber material A, turning on a cold circulation system to control a temperature of the rubber material A at 15° C. to 25° C., and stirring at a speed of 1,000 rad/min to 2,000 rad/min for 20 min to 30 min to obtain a base rubber A;
step (2), placing 50 parts by weight of the hydroxyl-terminated polydimethylsiloxane, 10 parts to 30 parts by weight of the vinyl-terminated polydimethylsiloxane, 20 parts to 40 parts by weight of the hydrogen-containing silicone oil, 3 parts to 15 parts by weight of the functionalized low-melting glass powder, and 1 part to 5 parts by weight of the functionalized hexagonal boron nitride in the planetary stirring tank to obtain a rubber material B, turning on the cold circulation system to control a temperature of the rubber material B at 15° C. to 25° C., and stirring at a speed of 1,000 rad/min to 2,000 rad/min for 20 min to 30 min to obtain a base rubber B;
step (3), transferring the base rubber B to the base rubber A to obtain a mixed rubber, turning on the cold circulation system, and stirring the mixed rubber at a speed of 4,000 rad/min to 6,000 rad/min for 1 min to 2 min; transferring an obtained mixed rubber to a mold, conducting vulcanization at a room temperature for 10 min to 20 min, followed by after-vulcanization in an oven at 60° C. to 80° C. for 1 h to 2 h to obtain the silicone rubber foam with the ablation resistance and the high-efficiency heat insulation.
9 . The preparation method according to claim 8 , wherein the hydroxyl-terminated polydimethylsiloxane of the silicone rubber foam has a viscosity of 5,000 mPa·s to 20,000 mPa·s; the vinyl-terminated polydimethylsiloxane has a viscosity of 20,000 mPa·s to 50,000 mPa·s; and the hydrogen-containing silicone oil has a hydrogen content of 0.5% to 1.6%.
10 . The preparation method according to claim 8 , wherein the catalyst is a Karstedt's platinum catalyst with a chemical formula of C 24 H 54 O 3 PtSi 6 and a platinum concentration of 2,000 ppm to 5,000 ppm.
11 . The preparation method according to claim 8 , wherein the inhibitor is a silylene-propargyl compound with a structural formula as follows:
R 1 , R 2 , and R 3 each are selected from the group consisting of H, methyl, and ethyl, and R is selected from the group consisting of cyclohexyl and isopropyl.