Grantee Research Project Results

Final Report: Permanent Primer/Replaceable Topcoat Aircraft Coating System With Minimum VOC and Chromium Exposure

EPA Contract Number: 68D00239
Title: 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., Sustainable Industry/Business, RFA, Air, Scientific Discipline, Waste, Toxics, Hazardous, Technology for Sustainable Environment, Chemical Engineering, Engineering, Chemistry, Sustainable Environment, HAPS, Environmental Chemistry, 33/50, Engineering, Chemistry, & Physics, Chemistry and Materials Science, Hazardous Waste, VOCs, cleaner production/pollution prevention, Environmental Engineering, chromium & chromium compounds, aircraft coating system, Chromium, permanent primer, Chromium Compounds, permanent primer replacement topcoat (PPRT), non chromated conversion coatings, replaceable topcoat, alternative coatings, alternative aircraft coatings