GEOPOLYMER FOAM FORMULATION

Abstract

A method for producing a geopolymer foam is proposed, comprising providing a foamable formulation, foaming the formulation, and allowing the foamed formulation to harden. The foamable formulation comprises at least one inorganic binder selected from the group consisting of latent hydraulic binders, pozzolanic binders and mixtures thereof; at least one alkaline activator selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkali metal aluminates, alkali metal silicates and mixtures thereof; at least one surfactant; nanocellulose and water. The mechanical properties of the foam are improved by incorporating nanocellulose.

Claims

1. A method for producing a geopolymer foam, comprising (i) providing a foamable formulation comprising: a) at least one inorganic binder selected from the group consisting of latently hydraulic binders, pozzolanic binders and mixtures thereof; b) at least one alkaline activator selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkali metal aluminates, alkali metal silicates and mixtures thereof; c) at least one surfactant selected from the group consisting of anionic surfactants, cationic surfactants, non-ionic surfactants and mixtures thereof, d) 0.1 to 5 wt.-%, based on the weight of the formulation, of nanocellulose, and e) water, (ii) foaming the formulation; and (iii) allowing the foamed formulation to harden.

2. The method according to claim 1, wherein the inorganic binder is selected from the group consisting of blast furnace slag, microsilica, metakaolin, aluminosilicates, fly ash and mixtures thereof.

3. The method according to claim 2, wherein the inorganic binder comprises metakaolin.

4. The method according to claim 1, wherein the alkaline activator is selected from alkali metal hydroxides of the formula MOH and alkali metal silicates of the formula m SiO.sub.2.nM.sub.2O, where M is the alkali metal, and the molar ratio m:n is 4.0.

5. The method according to claim 4, wherein the alkaline activator comprises a mixture of alkali metal hydroxides and of alkali metal silicates.

6. The method according to claim 1, wherein the surfactant is a non-ionic surfactant, optionally an alkyl polyglucoside.

7. The method according to claim 6, wherein the alkyl polyglucoside has the formula H(C.sub.6H.sub.10O.sub.5).sub.mOR.sup.1, where (C.sub.6H.sub.10O.sub.5) is a glucose unit and R.sup.1 is a C.sub.8-12-alkyl group, and m=from 1 to 5.

8. The method according to claim 1, wherein the nanocellulose is selected from cellulose nanocrystals, cellulose nanofibrils, and tunicate cellulose nanocrystals.

9. The method according to claim 8, wherein the nanocellulose is cellulose nanocrystals.

10. The method according to claim 1, wherein the nanocellulose has a length in the range from 25 to 4000 nm.

11. The method according to claim 1, wherein the nanocellulose has a width in the range from 2 to 70 nm.

12. The method according to claim 1, wherein the nanocellulose has a crystallinity of 40 to 90%.

13. A geopolymer foam obtained by the method according to claim 1.

14. A geopolymer foam comprising regions of a gas separated by a solid film of a geopolymer, the geopolymer having nanocellulose dispersed therein.

15. A foamable formulation for the manufacture of a geopolymer foam comprising: a) at least one inorganic binder selected from the group consisting of latently hydraulic binders, pozzolanic binders and mixtures thereof; b) at least one alkaline activator selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkali metal aluminates, alkali metal silicates and mixtures thereof; c) at least one surfactant selected from the group consisting of anionic surfactants, cationic surfactants, non-ionic surfactants and mixtures thereof; d) 0.1 to 5 wt.-%, based on the weight of the formulation, of nanocellulose, and e) water.

16. A dry formulation adapted for reconstituting with water to form a foamable formulation according to claim 15.

17. A geopolymer foam element comprising the foamable formulation according to claim 15 which is flame-resistant, sound-absorbing, and thermally insulating.

18. A geopolymer foam element comprising the geopolymer foam of claim 13 which is flame-resistant, sound-absorbing, and thermally insulating.

19. The geopolymer foam element according to claim 18 in the form of a sheet or board.

20. The foamable formulation according to claim 15 in the form of cavity filling.

21. A geopolymer foam element comprising the geopolymer foam of claim 14 which is flame-resistant, sound-absorbing, and thermally insulating.

Description

EXAMPLES

Example 1: Production of a Geopolymer Foam from Metakaolin

[0106] The components listed in Table I were mixed using a manual mixer.

TABLE-US-00001 TABLE 1 Description, trade name Mass Component (producer) (g) Wt.-% (1) Potassium K 45 M (Woellner GmbH 216.08 36.8 water glass & Co. KG), 40 wt % aqueous solution (2) Surfactant C.sub.8-10-alkyl polyglucosid 3.44 0.6 (m = 1-5), Glucopon DK225 (BASF SE), 68-72 wt % aqueous solution (3) Metakaolinite Metamax (BASF SE) 123.44 21.0 (4) Hollow Fillite 106 hollow 115.44 19.6 spheres aluminosilicate beads (Omya GmbH) (5) Cellulose Cellulose nanocrystals, 5.84 1 nanocrystals spray-dried (The University of Maine, Process Development Center) (6) Water 123.44 21.0 (additionally added) Total 100

[0107] The components were mixed and finally foamed to a volume of about 6 dm.sup.3. The air content of the foam was approx. 90 vol.-%. The air content was determined by way of the volume change in comparison with the unfoamed suspension by a method based on DIN EN 1015-6.

[0108] The foam was formed into a prisma of 1644 cm and hardened for 24 h at a temperature of 25 C. and a relative humidity of 100%, and afterwards at 25 C., 65% relative humidity for 6 days, the prisma was then subjected to a pressure and bending test in accordance with DIN EN 196-1. The results are shown in table 2 below.

Example 2

[0109] Example 1 was repeated using 1 wt.-% by solid of an aqueous slurry of nanocellulose (11.8 wt % CNC content) and 1 wt.-% by solid of an aqueous slurry of cellulose nanofibrils (NFC, 3.4 wt % NFC content) in the formulation. The results of the pressure and bending test are also shown in table 2.

TABLE-US-00002 TABLE 2 Exam- Exam- Exam- Exam- Refer- ple 1 ple 2 ple 2 ple 2 ence 1 wt % 3 wt % 1 wt % 1 wt % no CNC CNC CNC NFC CNC SD* SD* slurry slurry Density (g/L) 109 176 177 170 155 Tensile bending 14 25 30 22 strength (MPa) 12 51 28 23 15 53 30 23 Compressive 114 124 111 121 122 strength (MPa) 98 100 119 120 111 103 112 120 124 *SD: spray-dried

[0110] As can be seen, the mechanical properties of a foam prepared by using CNC or NFC are significantly improved as compared to a foam without nanocellulose.