Open-celled gypsum core, gypsum acoustic panel, and method for making same
An open cell set gypsum core includes an interlocking matrix of gypsum having air voids distributed therein. The air voids define cells having cell walls formed by the interlocking matrix. The interlocking matrix further includes channels distributed therein. The channels interconnect the air voids and comprise openings in the cell walls.
1. An open cell set gypsum core comprising:
a. an interlocking matrix of gypsum having air voids distributed therein, the air voids defining cells having cell walls formed by the interlocking matrix;
b. the interlocking matrix further having channels distributed therein, the channels interconnecting the air voids, the channels comprising openings in the cell walls formed by starch granules after dissolving, the starch granules being disposed in the cell walls of the set gypsum core before dissolving, wherein at least 30% of the air voids are interconnected to another of the air voids by at least one of the channels.
2. The core of claim 1 , wherein at least 60% of the air voids are interconnected to another of the air voids by at least one of the channels.
3. The core of claim 1 , wherein the openings are generally circular or elliptical in cross-sectional shape.
4. The core of claim 1 , wherein each of a plurality of the channels comprises a first opening in a first cell wall of a first air void and a second opening in a second cell wall of a second air void.
5. The core of claim 1 , wherein the core is not externally perforated.
6. The core of claim 1 , wherein the air void volume is at least 60% of the core volume.
7. The core of claim 1 :
a. wherein the air voids have a mean diameter between 50 and 200 microns;
b. wherein the channels have a mean diameter between 10 and 50 microns; and
c. wherein the mean diameter of the channels is smaller than the mean diameter of the air voids.
8. The core of claim 1 , wherein the gypsum comprises synthetic gypsum.
9. The core of claim 1 , wherein the gypsum comprises natural gypsum.
10. The core of claim 1 , further comprising reinforcing fiber distributed throughout the interlocking matrix.
11. The core of claim 1 , wherein the reinforcing fiber comprises glass fiber.
12. A set gypsum core, the core being formed from an air-foamed stucco slurry comprising stucco, at least one uncooked starch and an aqueous foam, the uncooked starch being in the amount of at least 4% by weight of the dry stucco, the air-foamed stucco slurry having air bubbles distributed therein;
a. wherein the core is set to provide an interlocking matrix of set gypsum, wherein the air bubbles form air voids distributed within the interlocking matrix, and wherein granules of the uncooked starch are distributed within the interlocking matrix between the air voids and within cell walls of the air voids, wherein the uncooked starch is included in the air-foamed stucco slurry in an amount that is at least a 2× multiple of a binding amount of the uncooked starch for the interlocking matrix; and
b. wherein the set core is heated to at least a gelatinizing temperature, wherein the granules of the uncooked starch gelatinize to provide channels distributed within the interlocking matrix and interconnecting the air voids, wherein at least 30% of the air voids are interconnected to another of the air voids by at least one of the channels.
13. The set gypsum core of claim 12 , wherein the air-foamed stucco slurry further comprises a reinforcing fiber that is distributed throughout the interlocking matrix of the set gypsum core.
14. The set gypsum core of claim 12 , wherein the stucco comprises synthetic gypsum.
15. A gypsum acoustic panel, comprising:
a. an acoustic layer comprising an open cell set gypsum core, the open cell set gypsum core comprising an interlocking matrix of at least gypsum, the interlocking matrix having air voids distributed therein, the air voids defining cells having cell walls formed by the interlocking matrix, the interlocking matrix further having channels distributed therein, the channels interconnecting the air voids, the channels comprising openings in the cell walls formed by starch granules after dissolving, the starch granules being disposed in the cell walls of the set gypsum core before dissolving, wherein at least 30% of the air voids are interconnected to another of the air voids by at least one of the channels; and
b. at least one backing sheet facing an outer surface of the acoustic layer.
16. The gypsum acoustic panel of claim 15 , wherein at least 60% of the air voids are interconnected to another of the air cells-voids by at least one of the channels.
17. The gypsum acoustic panel of claim 15 , wherein the set gypsum core further comprises reinforcing fiber distributed throughout the interlocking matrix.
18. The gypsum acoustic panel of claim 15 , wherein the gypsum comprises synthetic gypsum.
19. The gypsum acoustic panel of claim 15 , wherein the backing sheet comprises one or more of non-woven glass face, metallic foil, paper, a laminate comprising paper and a metallic foil, or combinations thereof.