Durable, electrically conductive transparent polyurethane compositions and methods of applying same

1. A polyurethane composition suitable for coating a surface of a substrate, the composition comprising:

an aliphatic polyester urethane matrix; and

a fluorinated ionic antistatic additive;

wherein the aliphatic polyester urethane matrix comprises:

an aliphatic diisocyanate;

a polyester polyol having

a polyester diol, and

a polyester triol; and

a sulfonated polyester urethane polyol; and

wherein the fluorinated ionic antistatic additive comprises a quaternary ammonium salt of a fluorinated sulfonimide.

2. The composition of claim 1 , wherein the aliphatic diisocyanate is selected from the group consisting of: hexamethylene diisocyanate, methylene bis (4-cyclohexylisocyanate), and isophorone diisocyanate.

3. The composition of claim 2 , wherein the polyester diol has an average molecular weight of about 830 g/mol and comprises a polycaprolactone diol initiated with dimethyl glycol.

4. The composition of claim 3 , wherein the polyester triol has an average molecular weight of about 540 g/mol and comprises a polycaprolactone triol initiated with trimethylol propane.

5. The composition of claim 4 , wherein the polyester polyol further comprises a chain extender selected from a group consisting of: ethylene glycol, 1,4-butanediol, and 2-ethyl-1,3-hexanediol.

6. The composition of claim 4 , wherein the sulfonated polyester urethane polyol comprises an anionic dispersion of an aliphatic polyester urethane resin.

7. The composition of claim 6 , wherein the sulfonated polyester urethane polyol is from about 5% to about 10%, by weight, of the composition.

8. The composition of claim 7 , wherein the aliphatic polyester urethane matrix is about 85% to about 98%, by weight, of the composition.

9. The composition of claim 8 , wherein the quaternary ammonium salt is selected from a group consisting of: tri-n-butylmethylammonium bis-(trifluoromethanesulfonyl)imide and quaternary alkyl ammonium bis-(trifluoromethanesulfonyl)imide.

10. The composition claim 9 , wherein the fluorinated ionic antistatic additive is from about 3% to about 8%, by weight, of the composition.

11. A method of preparing a polyurethane composition suitable for coating a surface of a substrate, the method comprising:

mixing a polyester diol and a polyester triol with a sulfonated polyester urethane dispersion to form a homogeneous sulfonated polyol mix; and

mixing the homogenous sulfonated polyol mix with components comprising an aliphatic diisocyanate, a fluorinated ionic antistatic additive, and a catalyst, to form the polyurethane composition;

wherein the fluorinated ionic antistatic additive comprises a quaternary ammonium salt of a fluorinated sulfonimide.

12. The method of claim 11 , wherein the sulfonated polyester urethane dispersion is mixed with the polyester diol and the polyester triol at about 90° C. to about 105 ° C. for about 48 hours.

13. The method of claim 12 , wherein the polyester diol has an average molecular weight of about 830 g/mol and comprises a polycaprolactone diol initiated with diethylene glycol.

14. The method of claim 13 , wherein the polyester triol has an average molecular weight of about 540 g/mol and comprises a polycaprolactone triol initiated with trimethylol propane.

15. The method of claim 14 , wherein the sulfonated polyester urethane dispersion comprises an anionic dispersion of an aliphatic polyester urethane resin and is from about 5% to about 10%, by weight, of the composition.

16. The method of claim 15 , wherein the aliphatic diisocyanate comprises methylene bis (4-cyclohexylisocyanate).

17. The method of claim 16 , wherein the fluorinated ionic antistatic additive quaternary ammonium salt comprises tri-n-butylmethylammonium bis-(trifluoromethanesulfonyl)imide and is from about 3% to about 8%, by weight, of the composition.

18. A method of coating a surface of a substrate with a polyurethane composition, the method comprising:

coating the surface with the polyurethane composition of claim 1 to form a coated surface;

curing the coated surface at a first cure temperature from about 50° C. to about 60° C. for about 12 hours; and

re-curing the coated surface at a second cure temperature from about 75° C. to about 85° C. for about 24 hours.

19. The method of claim 18 , wherein:

the polyurethane composition is transparent and

the substrate is a transparent acrylic.

20. The method of claim 19 , wherein the surface is an outer surface of an aircraft transparency.

21. The method of claim 20 , wherein the first cure temperature is about 54° C. and the second cure temperature is about 82° C.

22. The method of claim 21 , further comprising a step of preparing the surface before coating it with the transparent polyurethane composition, wherein the preparing step comprises:

coating the surface with a polysiloxane coating to form a base-coated surface;

coating the base-coated surface with a three-layer indium tin oxide (ITO)/gold/ITO film stack to form an ITO-coated surface;

coating the ITO-coated surface with a 0.1% silicate coating solution to form a silicate-coated surface;

heating the silicate-coated surface at about 82 ° C. for about 1 hour;

coating the silicate-coated surface with a 0.1% aminosilane primer solution to form an aminosilane-coated surface;

coating the aminosilane-coated surface with a 18% polyurethane thermoset adhesive solution to form a polyurethane thermoset-coated surface; and

curing the polyurethane thermoset-coated surface at about 20° C. to about 25 ° C. for about 16 hours.

23. A laminate comprising:

a coating disposed on a surface of a substrate;

wherein the coating comprises a polyurethane composition comprising:

an aliphatic polyester urethane matrix, and

a fluorinated ionic antistatic additive;

wherein the aliphatic polyester urethane matrix comprises:

an aliphatic diisocyanate,

a polyester polyol having

a polyester diol, and

a polyester triol, and

a sulfonated polyester urethane polyol; and

wherein the fluorinated ionic antistatic additive comprises a quaternary ammonium salt of a fluorinated sulfonimide.

24. The laminate of claim 23 , wherein the coating has a thickness from about 75 μm to about 100 μm.

25. The laminate of claim 24 , wherein the coating has an electrical volume resistivity less than or equal to about 10 11 ohm·cm at about −40° C.

26. The laminate of claim 25 , wherein the coating has a luminous transmittance from about 65% to about 70%.

27. The laminate of claim 26 , wherein the coating has a haze from about 0.90% to about 1.40%.

28. The laminate of claim 27 , wherein the coating does not include ionizable metal salts of perfluoroalkylsulfonate or a colloidal indium tin oxide nanoparticle dispersion.

29. The laminate of claim 27 , wherein the coating is transparent and the substrate is a transparent acrylic.

30. The laminate of claim 29 , wherein the surface is an outer surface of an aircraft transparency.