Polyurethane bonding process for fuel bladders
A method of bonding a metal fitting to a polyurethane structure, the method comprising abrading a surface of the metal fitting with an abrasive; cleaning the metal fitting with a solvent; cleaning a surface of the polyurethane structure with an alcohol; applying a primer to the surface of the metal fitting; applying an adhesive to the surface of the metal fitting and the surface of the polyurethane structure; applying a liquid polyurethane compound to the surface of the metal fitting and the surface of the polyurethane structure; and pressing the surface of the metal fitting against the surface of the polyurethane structure to form an assembly. The primer can comprise a first resin and a first catalyst in a ratio of about 1.1 to 1; the adhesive can comprise a second resin and a second catalyst in a ratio of about 3 to 1; and the liquid polyurethane compound can comprise a third resin and a third catalyst in a ratio of about 10 to 1.
1. A method of bonding a metal fitting to a polyurethane structure, the method comprising:
abrading a surface of the metal fitting with an abrasive;
cleaning the metal fitting with a solvent;
cleaning a surface of the polyurethane structure with an alcohol;
applying a primer to the surface of the metal fitting, wherein the primer comprises a first resin and a first reactant in a weight ratio of about 1.1 to 1;
applying an adhesive to the surface of the metal fitting and the surface of the polyurethane structure, wherein the adhesive comprises a second resin and a second reactant in a weight ratio of about 3 to 1;
applying a liquid polyurethane compound to the surface of the metal fitting and the surface of the polyurethane structure, wherein the liquid polyurethane compound comprises a third resin and a third reactant in a weight ratio of about 10 to 1; and
pressing the surface of the metal fitting against the surface of the polyurethane structure to form an assembly;
wherein the first resin comprises
from about 40% to about 70%, by weight, methyl ethyl ketone,
from about 10% to about 30%, by weight, isopropyl alcohol,
from about 10% to about 30%, by weight, trizinc bis(orthophosphate),
from about 1% to about 5%, by weight, phenol, and
from about 1% to about 5%, by weight, methanol;
wherein the first reactant comprises
from about 40% to about 70%, by weight, ethyl acetate,
from about 10% to about 30%, by weight, isopropyl alcohol, and
from about 1% to about 5%, by weight, phosphoric acid;
wherein the second resin comprises
from about 50% to about 60%, by weight, methyl ethyl ketone, and
from about 15% to about 40%, by weight, bisophenol A diglycidyl ether;
wherein the second reactant comprises
from about 70% to about 80%, by weight, methyl ethyl ketone, and
from about 1% to about 5%, by weight, 4,4-diphenylmethane diisocyanate;
wherein the third resin comprises from about 0.1% to about 1%, by weight, toluene diisocyanate; and
wherein the third reactant comprises
from about 65% to about 85%, by weight, di(methylthio)toluenediamine, and
from about 15% to about 35%, by weight, glycol ether.
2. The method of claim 1 , wherein the metal fitting comprises milled aluminum.
3. The method of claim 1 , wherein the abrading comprises abrasive blasting.
4. The method of claim 1 , wherein the abrasive comprises 24 grit aluminum oxide.
5. The method of claim 1 , wherein the solvent comprises methyl ethyl ketone.
6. The method of claim 1 , further comprising applying the adhesive to an outer perimeter of the assembly.
7. The method of claim 6 , further comprising applying a bead of the liquid polyurethane compound around the outer perimeter of the assembly.
8. The method of claim 7 , wherein the bead is applied with an air-powered fluid dispenser.
9. The method of claim 1 , further comprising allowing the primer to dry for at least 10 minutes.
10. The method of claim 1 , further comprising allowing the adhesive to dry for no more than 10 minutes.
11. The method of claim 1 , wherein the metal fitting is selected from the group consisting of: a fitting port, a hatch frame, and a ring.
12. The method of claim 1 , wherein:
the polyurethane structure is a patch; and
the method further comprises heat sealing the patch to a bladder.
13. The method of claim 1 , wherein the polyurethane structure is a bladder.
14. The method of claim 1 , wherein the pressing step comprises:
aligning the surface of the polyurethane structure over the surface of the metal fitting;
matching an inner diameter of a die cut hole in the polyurethane structure with an inner diameter of the metal fitting; and
pressing the surface of the metal fitting onto the surface of the polyurethane structure.
15. A method of bonding metal fittings to a polyurethane structure, the method comprising:
abrading a first surface of a first metal fitting and a second surface of a second metal fitting with an abrasive;
cleaning the first and second metal fittings with a solvent;
cleaning a first surface of the polyurethane structure and a second surface of the polyurethane structure with an alcohol;
applying a primer to the first surface of the first metal fitting and the second surface of the second metal fitting, wherein the primer comprises a first resin and a first reactant in a weight ratio of about 1.1 to 1;
applying an adhesive to the first surface of the first metal fitting, the second surface of the second metal fitting, and the first and second surfaces of the polyurethane structure, wherein the adhesive comprises a second resin and a second reactant in a weight ratio of about 3 to 1;
applying a liquid polyurethane compound to the first surface of the first metal fitting, the second surface of the second metal fitting, and the first and second surfaces of the polyurethane structure, wherein the liquid polyurethane compound comprises a third resin and a third reactant in a weight ratio of about 10 to 1; and
pressing the first surface of the first metal fitting against the first surface of the polyurethane structure and the second surface of the second metal fitting against the second surface of the polyurethane structure to form an assembly;
wherein the first resin comprises
from about 40% to about 70%, by weight, methyl ethyl ketone,
from about 10% to about 30%, by weight, isopropyl alcohol,
from about 10% to about 30%, by weight, trizinc bis(orthophosphate),
from about 1% to about 5%, by weight, phenol, and
from about 1% to about 5%, by weight, methanol;
wherein the first reactant comprises
from about 40% to about 70%, by weight, ethyl acetate,
from about 10% to about 30%, by weight, isopropyl alcohol, and
from about 1% to about 5%, by weight, phosphoric acid;
wherein the second resin comprises
from about 50% to about 60%, by weight, methyl ethyl ketone, and
from about 15% to about 40%, by weight, bisophenol A diglycidyl ether;
wherein the second reactant comprises
from about 70% to about 80%, by weight, methyl ethyl ketone, and
from about 1% to about 5%, by weight, 4,4-diphenylmethane diisocyanate;
wherein the third resin comprises from about 0.1% to about 1%, by weight, toluene diisocyanate; and
wherein the third reactant comprises
from about 65% to about 85%, by weight, di(methylthio)toluenediamine, and
from about 15% to about 35%, by weight, glycol ether.
16. The method of claim 15 , wherein the first and second metal fittings comprise milled aluminum.
17. The method of claim 15 , wherein the abrading comprises abrasive blasting.
18. The method of claim 15 , wherein the abrasive comprises 24 grit aluminum oxide.
19. The method of claim 15 , wherein the solvent comprises methyl ethyl ketone.
20. The method of claim 15 , further comprising applying the adhesive to an outer perimeter of the assembly.