INORGANIC POLYMER CERAMIC-LIKE COATINGS AND METHODS FOR THEIR PREPARATION

Abstract

An inorganic polymer coating. Low cost thermal barrier coatings thermal barrier coating and a process that starts with an aqueous suspension which may be sprayed, dipped, rolled or painted on a surface and cured. The cured thermal barrier coating has high thermal performance, low emissivity, high adhesion to multiple substrates, thermal cycle and thermal shock stability, high hardness, high elasticity and toughness.

Claims

1. Method of producing an alkali aluminosilicate coating on a substrate, said method comprising: a. providing a solubilized alkali silicate solution; b. providing a compound selected from the group consisting of i. aluminate and, ii. aluminosilicate; c. admixing said alkali silicate solution and said compound and placing the admixed composition on a substrate as a coating; d. curing said admixture at two or more predetermined, distinct temperatures such that said aluminate becomes at least partially solubilized and said alkali aluminosilicate condenses out of said admixture onto said substrate.

2. A method as claimed in claim 1 wherein said aluminate sources are solid components.

3. A method as claimed in claim 1 wherein said alkali aluminate sources are liquid components.

4. A method as claimed in claim 2 wherein said solid component includes a silicon source.

5. A method as claimed in claim 1 wherein the silicon to aluminum ratio is between 1:1 and 5:1.

6. A method as claimed in claim 2 wherein the silicon to aluminum ratio is between 1:1 and 5:1.

7. A method as claimed in claim 3 wherein the silicon to aluminum ratio is between 1:1 and 5:1.

8. A method as claimed in claim 1 wherein the silicon to aluminum ratio of the matrix is preferably between 1.5:1 and 2.5:1.

9. A method as claimed in claim 2 wherein the silicon to aluminum ratio of the matrix is preferably between 1.5:1 and 2.5:1.

10. A method as claimed in claim 3 wherein the silicon to aluminum ratio of the matrix is preferably between 1.5:1 and 2.5:1.

11. A method as claimed in claim 1 wherein the silicon to aluminum ratio of the entire compound is preferably between 1:3 and 2.5:1.

12. A method as claimed in claim 2 wherein the silicon to aluminum ratio of the entire compound is preferably between 1:3 and 2.5:1.

13. A method as claimed in claim 3 wherein the silicon to aluminum ratio of the entire compound is preferably between 1:3 and 2.5:1.

14. A method as claimed in claim 1 wherein the aluminum to alkali ratio of the matrix is between 1.2:1 to 0.8:1.

15. A method as claimed in claim 2 wherein the aluminum to alkali ratio of the matrix is between 1.2:1 to 0.8:1.

16. A method as claimed in claim 3 wherein the aluminum to alkali ratio of the matrix is between 1.2:1 to 0.8:1.

17. A method as claimed in claim 1 wherein, in addition, a filler is present.

18. A method as claimed in claim 2 wherein, in addition, a filler is present.

19. A method as claimed in claim 3 wherein, in addition, a filler is present.

20. A method as claimed in claim 1 wherein said filler is partially reactive.

21. A method as claimed in claim 2 wherein said filler is partially reactive.

22. A method as claimed in claim 3 wherein said filler is partially reactive.

23. A method as claimed in claim 17, wherein said filler is mullite.

24. A method as claimed in claim 17, wherein said filler is glass.

25. A method as claimed in claim 17, wherein said alkalinity is adjusted to prevent the dissolution of fillers.

26. A method as claimed in claim 17, wherein said filler is steel.

27. A method as claimed in claim 17 wherein said filler is selected from one or more of the group consisting of: aluminum oxide, titanium oxide, zirconium oxide, mullite, and Wollastonite.

28. A method as claimed in claim 17, wherein said filler is ceramic microspheres.

29. A method as claimed in claim 17 wherein said filler is selected from the group consisting of non-oxide ceramic, silicon carbide, boron nitride, boron carbide, titanium nitride.

30. A method as claimed in claim 1 wherein the humidity during cure is controlled between 5% to 95%.

31. A method as claimed in claim 1 wherein the initial cure is below 150° C. and the final cure is an additional step above 200° C.

32. A method as claimed in claim 1 wherein said substrate is selected from the group consisting of: metal, glass, ceramic, wood, PVA, and polyurethanes.

33. A substrate coated by the method as claimed in claim 1.

34. A coated substrate as claimed in claim 33 wherein the emissivity of the coating is below 0.4 at 0° C. to 550° C.

34. A coated substrate as claimed in claim 33 wherein the emissivity of the coating is below 0.7 at a temperature of from 800° C. to 1200° C.

35. A coated substrate as claimed in claim 33 wherein the coating has a thermal conductivity of 0.8 to 2 W/mK.

36. A coated substrate as claimed in claim 33 wherein the adhesion of the coating to said substrate is greater than 400 psi.

37. A coated substrate as claimed in claim 33 wherein said substrate will bend over a mandrel by more than 8 degrees for coating thicknesses of between 100 um and 300 um.

38. A coated substrate as claimed in claim 33 wherein the surface hardness is above Mohs 8.

39. A coated substrate as claimed in claim 33 wherein the surface scratch hardness is at least 250 Kpsi.

40. A coated substrate as claimed in claim 33 wherein said coating has an elasticity of at least 0.2%.

41. A coated substrate as claimed in claim 33 having an elongation to break of at least 2%.

42. A coated substrate as claimed in claim 33 wherein said coating having a CTE mismatch at 400° C. is less than the elasticity of said coating.

43. A coated substrate as claimed in claim 33 that is stable to UV radiation ASTM G154.

44. A coated substrate as claimed in claim 33 that is capable of passing GMW 14380 thermal shock test.

45. A coated substrate as claimed in claim 33 that is capable of passing gravelometery test ASTM D3170-03.

46. A coated substrate as claimed in claim 33 that is capable of passing a corrosion test equivalent to 200 h salt spray chamber.

Description

DETAILED DESCRIPTION OF THE SPECIFICATION

[0021] The polymer material is processed as a reactive two-part material, similar to epoxy. The material as mixed can have a viscosity from 200 to 25,000 cPS. The lower viscosity is better for spraying thin films, while the higher viscosity is suitable as a rolled out thin sheet and applied directly. The spray techniques may include air spraying, airless spraying, electro spraying, rotary cone spraying, ultrasonic spraying.

[0022] The final cure reaction occurs when the substrate is exposed to temperatures of 160-250° F. for 2-24 hours. Longer curing times yield stronger materials. This cures the polymer to an advanced ceramic-like state. Shrinkage is in the range of less than 0.01%, allowing very fine tolerances. A molecularly smooth surface allows for low cost high performance, rapid, complex parts manufactured with excellent surface texture. The texture may be smooth and high gloss or may be made matt as desired. The advanced hybrid is a suitable alternative for critical and strategic coatings. The final cure may be between 250° C. and 450° C. Pigments many be added to the bulk of the coating or to the surface of the coating prior to curing.

[0023] These properties will allow the ceramic coating to fulfill several material needs, which include high temperature bonding or adhered structural component coating requirements that do not delaminate or crack, thermal barrier coatings to reduce heat flow to or from a substrate, wear coating, corrosion coatings or aesthetic coatings.

EXAMPLES

[0024] Table 1 shows the comparison data sheet of various coatings. The substrates used were 409 SS plates.

[0025] The coating Example 1 is the alumina silicate base coat labeled TWR-228 with pigment topcoat labeled TCA5000.

[0026] Example 2 is a comparative example alumina silicate as in example 1 without the topcoat.

[0027] Example 3 is Cerakote W400Q with pigment topcoat TCA5000 and Example 4 is Cerakote C-7700 with pigment topcoat TCA5000. Comparative examples 5 and 6 are Cerakote W400Q and Cerakote C-7700 applied as per Cerakote directions. Cerakote W400Q and Cerakote C-7700 are two high temperature coatings.

[0028] The advantage of TWR-228/TCA5000 vs. the Cerakote coatings is significantly higher scratch hardness, higher Mohs hardness, higher abrasion resistance, higher reflectivity at temperatures up to 550° C., and providing corrosion resistance (tested on 1008 steel in 192 h aerated salt bath). On the other hand, Cerakote coatings provide more convenient curing conditions.

Examples 1 and 2

[0029] Alumina silicate is (labeled TWR-228) is a mixture of premixed Part A consisting of Metastar 501HP, Maxfil 104 and spherical alumina and premixed part B consisting of water, KOH, Kasil 6, Borax, Sodium PMA and PolyDAMAC 20% formed in a slurry which was sprayed on the substrate with an air spray gun. The coating was cured in a 60 degrees C. oven for 8 hours at 30% relative humidity followed by a final cure at 300 C for 5 hours at ambient humidity.

[0030] Examples 2, 3, 4, and 5 were sprayed from the commercial spray can and cured as per the Table 1.

[0031] Examples 1, 2 and 3 topcoat TCA5000 process was to dry dust the uncured coating with a pigment from a dry media sprayer then the coating was cured as above.

[0032] Cerakote W400Q/TCA5000 and C-7700/TCA5000 are W400Q and C-7700 Cerakote coatings used as base coat with PetraForge TCA5000 as topcoat. These coatings combine the convenient curing process of Cerakote with higher reflectivity of the instant invention.

TABLE-US-00001 Example 3 Example 4 Example 1 Example 5 Example 6 Cerakote Cerakote TWR-228/ Cerakote Cerakote W400Q/ C-7700/ Example 2 TCA5000 W400Q C-7700 TCA5000 TCA5000 TWR-228 409SS surface treatment Sonication cleaning Alumina blast Alumina Alumina Alumina Sonication blast blast blast cleaning Topcoat Yes No No Yes Yes No Curing Conditions Initial Cure 30-60° C./ air dry 30 air dry 5 air dry 30 air dry 5 30-60° C./ 3-24 h/ minutes, days minutes, days 3-24 h/ 20-70% RH 80° C./20 min 80° C./20 min 20-70% RH Post Cure 100-500° C./1- 315° C., None 315° C., None 100-500° C./1- 12 h/ambient 60 minutes 60 minutes 12 h/ambient humidity humidity Specific Gravity of slurry (g/ml) 2.41 ± 0.05 1.5 1.18 1.5 1.18 2.41 ± 0.05 SEM Microstructure No cracks Many Medium to No cracks No cracks No cracks No cracks large cracks Cohesion - Scratch Hardness - Dip 85 ± 10 <1   <1    <1   <1    85 ± 10 Coating (MPa) Hardness (Mohs) .sup. 7 ± 0.5 2.5 ± 0.5 2.5 ± 0.5 2.5 ± 0.5 2.5 ± 0.5 6.5 ± 0.5 Thickness - Spraying (um) 140 ± 15  70 ± 5  12 ± 3  75 ± 5  17 ± 3  135 ± 15  Adhesion - Bend Test (deg) 28 ± 3  no failure no failure no failure no failure 28 ± 3  up to 40 up to 40 up to 40 up to 40 Total Reflectivity (unpolished) 0.70 ± 0.03 0.50 ± 0.03 0.55 ± 0.03 0.78 ± 0.03 0.80 ± 0.03 0.10 ± 0.03 400-550° C. Max Operating Temp (° C.) 550° C. 550° C. 550° C. 550° C. 550° C. 1100° C. Corrosion Inhibition (192 h) Pass: corrosion is Catastrophic Failure: steel Catastrophic Failure: steel Pass: completely inhibited Failure: Corrosion reacts under Failure: Corrosion reacts under corrosion is propagates and the coating propagates and the coating completely cause complete throughout cause complete throughout inhibited delamination the whole delamination the whole of coating sample of coating sample Taber Abrasion testing (cycles/mil) 8100 ± 100  2700 ± 100  Outside test Outside test Outside test 8100 ± 100  lab - in lab - in lab - in process process process Part A 30 um Part B Panadyne Poly Metastar Maxfil Spherical DADMAC 501HP 104 Alumina 20% H2O KOH Kasil Borax Formula (g) (g) (g) (g) (g) (g) 6 (g) (g) NaPMA Total TRW-288 2.33 0.54 20.18 0.02 7.55 7.83 59.08 2.17 0.30 100