Grantee Research Project Results
Final Report: Permanent Primer/Replaceable Topcoat Aircraft Coating System With Minimum VOC and Chromium Exposure
EPA Contract Number: 68D00239Title: Permanent Primer/Replaceable Topcoat Aircraft Coating System With Minimum VOC and Chromium Exposure
Investigators: Kovar, Robert F.
Small Business: Foster-Miller Inc.
EPA Contact:
Phase: I
Project Period: September 1, 2000 through March 1, 2001
Project Amount: $69,935
RFA: Small Business Innovation Research (SBIR) - Phase I (2000) RFA Text | Recipients Lists
Research Category: SBIR - Pollution Prevention , Pollution Prevention/Sustainable Development , Small Business Innovation Research (SBIR)
Description:
The EPA has identified the need to reduce the release of chromates and VOC's during aircraft coating application, because they endanger personnel and the environment. In Phase I we have developed a 30+ year, Permanent Primer / Replaceable Topcoat (PPRT) aircraft coating system that provides continuous protection against corrosion while reducing VOC and chromate exposure by more than 80 percent. A standard polyurethane topcoat was applied over a low VOC, Self Stratifying Aircraft Primer System (SSAPS) that was designed to bond chemically to conversion coat and topcoat and exhibit high abrasion, producing the PPRT. When the topcoat requires replacement every six years, it is selectively stripped-off without releasing chromates, leaving primer and conversion coats intact. Our SSAPS avoids the danger and expense of reapplying conversion and primer coats and reduces the number of coating application / removal steps over 30 years from more than 15 to only 3 (initial primer and conversion coating + final removal step). In Phase I, we have developed the PPRT, produced coated test panels and analyzed test panels for key performance properties. Feasibility of topcoat stripping was demonstrated.In Phase II, we will refine the PPRT coating and process to ensure sprayability, scale-up to larger quantities, and produce prototype PPRT samples for extensive testing. The committed Phase II involvement of commercial aircraft coating manufacturers will facilitate commercialization of this innovative technology.
Summary/Accomplishments (Outputs/Outcomes):
Successfully stripped off a commercial polyurethane topcoat, leaving behind the Self-Stratifying Aircraft Primer System (SSAPS) containing corrosion inhibitors.Sprayability will be refined in Phase II with solvents such as Dipropylene Glycol Methyl Ether Acetate or reactive diluents. Acetone was tested in the Phase I program, but it is too volatile.
Table 1: Phase I Results of Candidate Self-Stratifying Aircraft Primer System (SSAPS) Coated Test Panels
Properties Evaluated |
Test Method |
Results |
Hardness |
Pencil Test- 6H-hard, 6B-soft ASTM D 3363 ? 93a |
Gouge ? 6H Scratch ? 2H |
Hardness |
Durometer, Shore A ASTM D 2240 |
82 15.0 mm thick |
Impact Resistance |
Ball Drop Modified MIL-PRF-24667A |
No change |
Flexibility |
Mandrel Bend ASTM ? D 522 ? 93a |
23?C No change 177?C No change |
Adhesion |
Tape Test- 5B-No change ASTM D 3359 - 93 |
2.0mm ? 5B 1.0mm ? 3B, When corrosion inhibitor is included ? 5B |
Resistance to Solvent |
MEK Rub ASTM D 5402 93 |
No change |
Resistance to Water |
Immersed in 49? water for 4 days MIL-TT-P-2760 3.7.9.1 |
No change, except discoloration |
Hardness (after water imm.) |
Pencil Test- 6H-hard, 6B-soft ASTM D 3363 ? 93a |
Gouge ? 6H Scratch ? 2B |
Adhesion (after water imm.) |
Tape Test- 5B-No change ASTM D 3359 ? 93 |
2.0mm ? 5B 1.0mm ? 5B |
Resistance to Hydraulic Fluid |
Immersed in 66?C MIL-H-83282 MIL-TT-P-2760 3.7.9.3 |
No change |
Hardness (after H.F. imm.) |
Pencil Test- 6H-hard, 6B-soft ASTM D 3363 ? 93a |
Gouge ? 6H Scratch - B |
Adhesion (after H.F. imm.) |
Tape Test- 5B-No change ASTM D 3359 ? 93 |
2.0mm ? 5B 1.0mm ? 5B |
Mechanical Properties |
Tensile stress @ Max Load (ksi) (free standing film) |
Mean 3.03 C.V. 18.65 |
Mechanical Properties |
Modulus (free standing film) |
Mean 6.26 C.V. 21.86 |
Mechanical properties |
Strain at Break (%) (free standing film) |
Mean 83.90 C.V. 7.75 |
Corrosion Resistance |
Salt Spray ASTM B117 |
Testing in progress No corrosion after 1 week |
Corrosion Resistance |
Filiform ASTM D 2803 |
Testing in Progress No corrosion after 1 week |
Conclusions:
Our efforts on the Phase I program have led us to the following conclusions regarding the Foster-Miller Permanent Primer / Replaceable Topcoat Aircraft Coating System With Minimum VOC and Chromium Exposure:- The feasibility of selectively stripping-off a commercial polyurethane topcoat, and leaving behind intact, the Self-Stratifying Aircraft Primer System (SSAPS) containing corrosion inhibitors was demonstrated.
Foster-Miller's Permanent Primer / Replaceable Topcoat (PPRT) offers several key potential advantages over current commercial aircraft coating systems, including the following:
- Easy, low-cost removal of the topcoat.
- Saves cost, time and danger of replacing the primer.
- Protects personnel and the environment from hazardous chromates.
- Superior adhesion because chemically bonded to conversion coat and
topcoat.
- Excellent durability, and abrasion resistance.
- Solvent Resistant
Supplemental Keywords:
Aerospace, aircraft coating, corrosion protection, durable primer., RFA, Scientific Discipline, Air, Toxics, Waste, Sustainable Industry/Business, Chemical Engineering, cleaner production/pollution prevention, Environmental Chemistry, Sustainable Environment, Chemistry, HAPS, VOCs, Technology for Sustainable Environment, Hazardous Waste, Chemistry and Materials Science, Engineering, Hazardous, 33/50, Engineering, Chemistry, & Physics, Environmental Engineering, permanent primer replacement topcoat, chromium & chromium compounds, permanent primer replacement topcoat (PPRT), Chromium, replaceable topcoat, aircraft coating system, alternative aircraft coatings, permanent primer, Chromium Compounds, non chromated conversion coatingsThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.