Curable composition containing rice husk ash biosilica toughened epoxy resin

1 . A curable composition, comprising:

at least one polyamine;

an epoxy resin; and

a silane-modified biosilica material;

wherein the silane-modified biosilica material is derived from rice husk;

wherein the silane-modified biosilica material is present in the curable composition at a concentration of 0.01 to 10 wt. %, based on a total weight of the curable composition; and

wherein the silane-modified biosilica material has an average particle size of 1 to 10 micrometers (μm).

2 . The curable composition of claim 1 , wherein the at least one polyamine comprises a polyalkylene polyamine, and wherein the polyalkylene polyamine comprises at least one polyamine selected from the group consisting of piperazine, aminoethylpiperazine, ethylenediamine, ethyleneimine, diethylenetriamine (DETA), pentaethylenehexamine (PEHA), hexaethyleneheptamine (HEHA), tetraethylenepentamine (TEPA), triethylenetetramine (TETA), and a mixture thereof.

3 . The curable composition of claim 1 , wherein the epoxy resin comprises at least one resin selected from the group consisting of a bisphenol A epoxy resin, a bisphenol F epoxy resin, a novolak epoxy resin, an aliphatic epoxy resin, a glycidylamine epoxy resin, an epoxidized vegetable oil, and a mixture thereof.

4 . The curable composition of claim 3 , wherein the epoxy resin is a bisphenol A epoxy resin, and wherein the bisphenol A epoxy resin is bisphenol A diglycidyl ether.

5 . The curable composition of claim 1 , wherein a volume ratio of the at least one polyamine to the epoxy resin is in a range of 20:1 to 1:1.

6 . A cured composition obtained by curing the curable composition of claim 1 , wherein the silane-modified biosilica material particles are uniformly distributed throughout the cured composition.

7 . A method of making a cured composite material, comprising:

mixing an epoxy resin and a silane-modified biosilica material, and sonicating to form a mixture;

adding at least one polyamine to the mixture to form the curable composition of claim 1 ; and

curing the curable composition by mixing thereby allowing the epoxy resin, the silane-modified biosilica material and the at least one polyamine to react and form the cured composite material;

wherein the silane-modified biosilica material is present in the curable composition at a concentration of 0.2 to 5 wt. %, based on a total weight of the curable composition; and

wherein a volume ratio of the at least one polyamine to the epoxy resin is in a range of 15:1 to 5:1.

8 . The method of claim 7 , wherein the cured composite material has a tensile strength of 50 to 90 MegaPascal (MPa) according to ASTM D-638 standard test method.

9 . The method of claim 7 , wherein the cured composite material has a flexural strength of 60 to 120 MPa according to ASTM D-790 standard test method.

10 . The method of claim 7 , wherein the cured composite material has a hardness of 80 to 130 shore-D according to ASTM D-2240 standard test method.

11 . The method of claim 7 , wherein the cured composite material has a water vapor permeability of 2 to 4 water content (WC %) according to ASTM F1249-90 standard test method.

12 . The method of claim 7 , wherein the cured composite material has an oxygen permeability of 2 to 3.5 (10 −2 cc·mm/(m 2 ·d·atm)) according to ASTM D-3985 standard test method.

13 . The method of claim 7 , wherein the cured composite material has a thermal conductivity of 0.2 to 0.5 Watts per meter-Kelvin (W/mK) as determined by TGA.

14 . The method of claim 7 , further comprising:

preparing the silane-modified biosilica material from rice husk by:

cleaning raw rice husk and steeping in a first acid solution to form acid-treated rice husk in a first mixture;

removing the acid-treated rice husk from the first mixture and heating at a temperature of at least 400° C. to form rice husk ash (RHA);

mixing the rice husk ask in an alkaline solution, heating, and filtering to form a sodium silicate solution;

neutralizing the sodium silicate solution with a second acid solution under agitation to form a gel-like precipitate in a second mixture;

removing the gel-like precipitate from the second mixture, washing, drying and pulverizing to form a silica xerogel;

mixing the silica xerogel in a solvent mixture to form a silica solution;

adjusting the pH of the silica solution to 4 to 6;

dropwise adding a silane coupling agent to the silica solution and mixing to form precipitated particles of the silane-modified silica material in a reaction mixture;

removing the precipitated particles from the reaction mixture, washing, and drying to form the silane-modified biosilica material.

15 . The method of claim 14 , wherein the first acid solution comprises at least one acid selected from the group consisting of a hydrochloric acid, a sulfuric acid, a nitric acid, a phosphoric acid, and a citric acid.

16 . The method of claim 14 , wherein the alkaline solution comprises sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, lithium hydroxide, and lithium carbonate.

17 . The method of claim 14 , wherein the second acid solution comprises at least one acid selected from the group consisting of a hydrochloric acid, a sulfuric acid, a nitric acid, a phosphoric acid, and a citric acid.

18 . The method of claim 14 , wherein the solvent mixture comprises at least two solvents selected from the group consisting of a ketone solvent, an ester solvent, an alcohol solvent, an amide solvent, an ether solvent, and water.

19 . The method of claim 14 , wherein the solvent mixture comprises an alcohol solvent and water, and wherein a volume ratio of the alcohol solvent and water is in a range of 50:1 to 10:1.

20 . The method of claim 14 , wherein the silane coupling agent is an amino-silane coupling agent selected from the group consisting of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, (aminoethylaminomethyl) phenyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyl tris(2-ethylhexoxy) silane, 3-aminopropyltrimethoxysilane, trimethoxysilylpropyldiethylenetriamine, bis(2-hydroxyethyl)-3-aminopropyltrimethoxysilane, aminopropyltriethoxysilane, and 4-aminobutyltriethoxysilane.