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BOEING PAINT HANGAR PRESSURE SENSITIVE TAPE APPLICATIONS Craig Ungerecht, Senior Research Engineer, Boeing Commercial Airplane Group, Seattle, WA Michael Andrews, Technical Principal, Boeing

1 BOEING PAINT HANGAR PRESSURE SENSITIVE TAPE APPLICATIONS Craig Ungerecht, Senior Research Engineer, Boeing Commercial Airplane Group, Seattle, WA Michael Andrews, Technical Principal, Boeing Commercial Airplane Group, Seattle, WA Introduction Masking tape is a critical component of the painting process for commercial aircraft. The tape must adhere to several different substrates, remove cleanly, and provide a sharp paint line. The tape must withstand, exposures to solvent, water, abrasives, and multiple 120 degrees F heat cure cycles. The tape may remain on the airplane for several days before removal. The performance of the tape must be consistent and predictable. The cost and schedule impact when the masking tape fails is significant on commercial aircraft. Variation during manufacturing of the tape can change the expected performance causing adhesive residue, difficulty applying or removing the tape, poor paint lines, and ultimately rework and delays. Rework and delay costs easily run into thousands of dollars per day. For this reason, Boeing performs several qualification tests prior to accepting a masking tape for use in the paint hangar. However, these tests cannot guard against variability and manufacturer changes in the production of the masking tape. The tape may pass the lab and shop tests only to fail in production on theairplane. Variation of the tape from batch to batch or within a batch often results in intermittent and unpredictable failures. The Paint Hangar Process The paint process for 737 and 757 aircraft is typically three days. Wide body aircraft like the 747 take 4-5 days to clean and paint. The tape is exposed to alkaline cleaners, water, and intermittent solvent exposure during the cleaning process. The tape masks aluminum, primer, composite, and topcoat. The paint hangar is heated to 120 degrees F for 4 hours to cure the primer and topcoat.!ili!i!iiiii!iiiiil i i!ii.!ii!::- :!~ii~:i:ili ~i!!iii~!!~i~!'~:i~!?iii!iii~i:~i!i:: ~:~i!~!~i.~!!~!~!i~!~!~!~!i~iii~:i~!!i!j~iiii~iii~i~iii~:~i~ii~!i!!~i~i~i~i!!i!!!~!~i~i~i~i~i!~ii!~i~!ii~!~!~i : : i ~:i:?.:~:?:... ::::: : ~!~!i!i!~:~..~i~ii~i~ii~i~i~i:~i~i~!iiiiii~iiii~ii~!iii~i!~i~i~i!~ii!ii~i~i~ii~iii~i~i~i~i~i~i~ii~....:.:..,,>,- ;. =========================================================================================================== : :. i-'ii~.:: : ~ii~:~ii~i~i~ii~iii~i~i~i~i~i~i~i~i~i~i~i:~i~i~i~:i~i~i~i~iii~iii~i~i~b~!iiiiiii~i:~i~i~i~iiiii~iiii~iiiii!iiiiiiii~i!iiiiiiii~iii~ii~i~ " :ii~!~ii. ~i< i:.~:~:i::::::::::..:~iii~!ii!i~iiii!iii~ii~i~!i!ii~i~!~i~!iiii~i!~i!i!iii~ii!~i!~i!~ii~i~!i!ii~!ii~iii~ii~iiiii~ii!!~i!ii~iii~iii~!!..`~i~i~!~i~!~ii!~iiii~i~iii~i!~i~ii!i~.~iii~ :.::::::~:~::~::!i:~... :i:::~... ~iii~i~i!~:~!~!ii~i~i~!iiii~i!!~iiiiiii~i~ii!~i~iii~iiii~i~!;i~i!i!i~i!~!~!~i!i~!~!i!ii~!~!~!!!~i!ii~.~i~i~i~i~!~i~i~!~!~!~ Figure 1. Painting in progress Figure 2. Example of masking 315 i. ~

2 Clean And Prep The airplane is rolled into the paint hangar and prepped for paint. The fuselage has a temporary protective coating, which must be removed. Previously painted components, landing gear, wings, and windows are masked. An alkaline cleaner is applied to the airplane and rinsed off with large amounts of water to remove the temporary protective coating. Spot solvent cleaning removes residual temporary protective coating or other contamination. The entire airplane is power abraded and a chemical conversion coating is applied. The airplane is then masked for primer application.!i i i i!il i~i!iiiiiii;iiil;iiiljiii iii!i~i;ii~ ;iiiiiii~"~!!i!~' ~'. ~!!ii~is~ii!ii~ i~i~i~ i~i~ii~i~i,~ i,i~,~, ~:~ ~., ~,~',',!~,!i!iii;iii~,!!iiiiiiiiii',i',iii~,ii!i!!,,~:~ ~..-~i~!ii'~',iiiiiiiili! :::~:~ ~ ~ ~.... : Figure 3. Window masking Figure 4. TPC removal 316

3 Primer/Topcoat The airplane is masked prior to primer and topcoat application. Boeing uses a high solids epoxy primer and polyurethane topcoat. Two different primers and two different topcoats are currently qualified. The tape must be compatible with any of these paint systems. The tape must remove easily with little adhesive transfer and produce clean paint lines. The process is slowed if the tape splinters upon removal and causes additional adhesive transfer that can be difficult to remove without damaging the fresh paint. The tape must not allow paint to bleed through to the substrate or around rivets. Adhesive residue can compromise both the appearance and paint integrity. Figure 5. Ready for topcoat ~::i ::~:::~:::i:ii:: ~::::~: ~ :.:: ~- '::~!iiiiiiiiiiiii!i~iiiiii::ii!~i~::~:~~::~: :i ii->~-:~iiiii~iliiiiiiii!ii!!!i:i~iii~ii:/:!:!i!~::~:ii::~ii~:~!~i!il, :... ::~:?'ili: i~i :,: ~!~ii~i~i~i!!~ii~i!~i~!~i~!~!~!ii~i~ii!ii~i~i~i~i~!~i~!~i~iii~!i~!~i~ i i iiiiiiii ii!i :~i!:: ~i::ii::::iiiiiiiiii~i::ii!iiiiii!iiiii~!iiii!~i:~i~iii::.. Figure 6. Topcoat application 317

4 . Qualification Testing Release Coating Compatibility The masking tape cannot incorporate any silicone in its construction. The release coating on the tape can be swiped with a solvent laden rag during cleaning and be smeared onto the airplane surface. For this reason, the release coating must not cause appearance or adhesion problems. Silicone has a very low surface energy compared to paint. Silicone contamination will cause significant de-wetting and paint adhesion problems. For this reason, masking tapes may not contain silicone in the adhesive or release coating. Silicone is often used as a release coating in many tape constructions. Tape manufacturers are made aware that no silicone may be part of the tape construction prior to submitting samples. The compatibility of the release coating is tested by applying the tape to an aluminum panel and lightly solvent wiping with Methyl Propyl Ketone across the tape onto the panel. The panel is topcoated and allowed to cure. The panel is checked for fisheyes and other defects in the area of the wipe. Observations are also conducted to see if the topcoat buries any visible defects after one, two, or three coats. A scribe adhesion test is conducted on the wipe area. We have also seen problems where the paint will run off the masking tape and produce runs on the airplane which must be repaired. Figure 7. Release coatingtest _; 318

5 Paper Hang Test The masking tape must be able to hold heavy drapes of masking paper through various chemical exposures and extended heat cycles. It is important that the masking tape not lose adhesion to the surface. A common example of this is lifting when the tape edge curls up and away from the airplane. If lifting is severe, the masking will peel completely off the plane. If lifting is not corrected prior to painting, paint will seep under the tape causing rework. The paper hang test is used to check the compatibility of the tape with the process. A sheet of masking paper is hung directly from a large aluminum panel. In addition, tape is applied to the panel and the masking paper is hung off the first line of tape. This is to test the "A to B" or adhesive to backing adhesion. The paper is soaked with water and run thorough a 120 degrees F heat cycle for 4 hours. This test is repeated for the primer and topcoat applications. < ii~,,ii!iii:s!i',ii:::~:i: ~ <.,':':: ::.: 2 ~,,~:~::,!!!!!<::x~iiiiiii~{iii~iii~... ~..::~::~ i, % i'::::: ;i;ii {<!!!'::.i :'::: <i~i;i~!:l: i iiiiii',iiiiiiiiiiiiiiii!i!~iiiii~'. ~iiii::" <:.:;i~i:~!:.:::.~!!::::isii i,i~,i~i,~:,i:,', i iii!~,i!'~i~,}!i~i},iiil;i~ii!i'~',',',~'<: }ii i', ': ~',':~,i ~',',~, i: ',iiii', ',i',~,i ',',',!i', iii~iii',',iil ~,i!ii i', i~i',i ',i~!i~il ii~!i',i~ ii ~, ~i~iiii~iiii',!il ~',ii~!~,~ii~i ',iii!~ ~ ~ ' :: ~::::.~.~<<~ii~ii!!%~!~i}i~!~i;ii!ii~i~iiiii~ii!iii~i};!i~i!ii~ii!!iii~;~i!}~ii!i~i!}~iiiiiii!iiii~i!~i!~iiii!ii!i~iii~ i~i~iii~i~i~i~;~!iiii~!i~iii~iiiii~ii!i!~i~ii~i~;i~i~ip~ %.... "~ :~:: : ': " '"'<~ :~'~::+:::::::::~ ~:w:::'<:~:~:~-4~-~:i~:~%~'~'~\~ N ======================== I%~i!:i::::%.. :::i:<i@i~!:~::!i::::::~:<::~i<:;:~<<:)!!!! ~ iiiiiiiiii! i:;:~:i:::::~:i~i.~:!~%.<...!~i:::!):::::!ii::::i::::~::i::ii::~ii::i::::::::ii:~i<;ilil ::...:.:~ii!ii!~i::i:::::::~::~i[ : Figure 8. PaPer hang in hangar Figure 9. Paper hang test in lab 319

6 Primer and Topcoat Testing Clean line/adhesive Transfer Testing It is important to utilize the same materials and match the paint hangar process as closely as possible when conducting the testing. Clad aluminum panels are primed or top-coated and cured at 120 degrees F for 4 hours. Tape is applied to the panels and top-coated and cured again. The tape is removed and inspected for adhesive transfer or paint penetration under the masking. Figure 10. Adhesive transfer Figure 11. Paint bleed Rivet Bleed Testing Tape that does not conform well to rivets and lap joints, or tape with poor adhesive strength can allow seepage or wicking of paint. Time-consuming touch up is the result. A riveted panel is used to conduct this test. Imitation rivets can be used if a panel is not available. Punched circles from aluminum tape will make an acceptable imitation rivet. Lay the tape in a line crossing the rivet center on one primed and one painted panel. Apply topcoat and cure. Remove the tape and look for seepage around rivets. "'):". L: Figure 12. Rivet bleed test 320

Ghosting Tests Occasionally, tape lines are visible in the cured topcoat of areas that were masked, but seem free of all adhesive prior to painting.

7 Ghosting Tests Occasionally, tape lines are visible in the cured topcoat of areas that were masked, but seem free of all adhesive prior to painting. This is referred to as ghosting, telemarring, or telegraphing. The problem has been seen on bare metal, primed, and painted surfaces. The tapelines can manifest themselves as de-wetting or a change in reflectance so that the paint appears raised, or as an apparent dip along the edge of the masking line. Laying tape on the primer before its two-hour dry-to-tape time causes the majority of ghosting seen in the paint hangars. This test is conducted by priming or top coating an aluminum panel and allowed to cure. Tape is applied to the panel and left on for at least 24 hours. We often run the panel through a 4-hour 120F cure cycle. Remove the tape and topcoat the panel with three coats of paint and allow to cure. Note if a tapeline is visible under the paint where the tape was removed. Also note if the topcoat was able to bury the tapeline after one, two, or three coats. There should be no de-wetting or tapeline visible. Hands-on Handling Tests These tests are often subjective and the painters are the best judges of tape acceptability. A masking tape that is difficult to handle or apply will slow the painting process and produce substandard quality. A good masking tape must be able to pull long straight lines without deforming and still be conformable enough to mask around windows and door bands. The tape cannot cup when pulling long tapelines. These tests are quick and easy to conduct. To check for cupping, a metal file cabinet will work well. Squeegee 1 to 2 feet of tape to a wall or cabinet and pull a 10' to 20' line. Check out of roll (too fast or too tight), cupping (edges curl toward each other), necking (too much tape deformation will make wavy lines), and adhesion when pulled. Conformability for masking around the windows and door bands is checked by trying to mask a 3" radius circle without tearing along the edge. The tape must have sufficient adhesion to the roll to prevent free unwind. The tape if often left hanging from the airplane between stacker positions for up to 20 minutes. If a tape comes off the roll too easily, it will unwind and end up on the floor of the hangar. There are two simple tests. The first test is to hang a full roll of tape from a vertical surface for 20 minutes. Does it unwind by itself?. The second test is to pull about a 4-inch lead from a full roll of tape. Give the tape a light jerk like throwing a yo-yo, only softer. The tape should not unwind to the floor with a simple jerk. Conclusion The Boeing Commercial Airplane Group cleans and paints large commercial aircraft. Our customers demand a high quality product and the decorative paint system on the aircraft is a critical component the customer gauges the quality. Poor paint quality is not acceptable. Boeing is also trying to efficiently use its resources and minimize manufacturing costs. Rework, overtime, and delivery delays can cost a considerable amount of money. The performance of our masking tape directly affects the product quality and our ability to meet our production cost targets. The masking tape may seem like a minor component but tape failures have delayed delivery of aircraft and affected our product quality. For these reasons, Boeing requires the masking tape to pass certain testing and qualification requirements as described above. Several components of the tape construction are considered. The release coating must be compatible with the application process, and have an acceptable unwind. The backing must be able to pull long paint lines, quickly stick when masking, and be conformable to mask tight radiuses and seal around rivets. The backing must also remove easily without slivering. The adhesive system must adhere during the paint application and cure cycle and remove cleanly without adhesive transfer. 321

8 These tests are conducted with the same materials used in production and follow the actual production process. It is important for the tape manufactm'es to provide a consistent product with little manufacturing variability. Individual rolls within a batch of tape or sometimes the entire batch of tape will fail and cause considerable rework. The manufacturer must consider the tapes end use when making changes to the product or their production process. Even minor changes can and have produced severe impacts to the end user. 11, 322

8 x 10 Sandwich Panel

*Before starting, please read entire manual *Changes can be made in order for this manual to work for you 8 x 10 Sandwich Panel Follow all applicable sections of the attached Manufacturing Plan. Objectives: