AF31 3M | Alldatasheet

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Technical content

Introduction 3M™ Scotch-Weld™ Structural Adhesive Film AF 31 is an unsupported, thermosetting structural film adhesive designed for metal-to-metal bonding. It is especially designed for high-temperature resistant application (up to 500°F [260°C]). Scotch-Weld AF 31 film adhesive offers the following advantages:

  • Good flexibility and shear strength at service temperatures from -67°F to 500°F (-55°C to 260°C).
  • Easy application in a dry film which can be pressure, heat, or solvent tacked in position.
  • Excellent retention of strength after aging in many environments.
  • Scotch-Weld AF 31 film adhesive with 3M™ Scotch-Weld™ Structural Adhesive Primer EC-2174 on stainless steel, known as the AF-7431 system, meets, and is qualified to, MMM-A-132 Types III and IV . Technical Data March, 2006

Description

Form: Flexible unsupported film, protected by suitable liner. Color: Yellow to brown. Nominal Caliper: 9-11 mils (uncured). Volatile Content: Less than 5% (2-4 gm. sample cured 1 hr. at 350°F [177°C]). Shrinkage: 5% maximum (24 hrs. at 75°F ± 5°F [24°C ± 2°C] in horizontal position). Note: The following technical information and data should be considered representative or typical only and should not be used for specification purposes.

  • 2 - 1. 3M™ Scotch-Weld™ Structural Adhesive Film AF 31/3M™ Scotch-Weld™ Structural Adhesive Primer EC-2174 Overlap Shear on Stainless Steel The following product performance data has been obtained in the 3M Laboratory under the conditions specified. All data reported in this section except as noted, were developed under a cure cycle using 100 psi bonding pressure applied by a platen press. A 10°F/minute bond line temperature rise from 80°F to 350°F (27°C to 177°C) with 120 minutes ± 1 minute at 350°F (177°C) ± 2°F was used. The panels were then removed from the press and post cured for 20 hours at 500°F (260°C). The primer was air dried 30 minutes plus force dried 30 minutes at 200°F-250°F (93°C-121°C). All properties were measured on pre-slotted, .050" thick, 17-7PH-TH 1050 stainless steel panels. The properties were measured on 1" wide by 1/2" overlap specimens. Tests were conducted according to MMM-A-132 Types III & IV methods. Product Performance Note: The following technical information and data should be considered representative or typical only and should not be used for specification purposes. Test Condition Scotch-Weld AF 31/ Scotch-Weld EC-2174 A. Tensile Shear 1. Standard Temperature 75°F ± 5°F (24°C ± 2°C) 6166 psi 2. 10 minutes at 300°F ± 5°F (149°C ± 2°C) 2828 psi 3. 192 hours at 300°F ± 5°F (149°C ± 2°C) 3166 psi 4. 10 minutes at 500°F ± 5°F (260°C ± 2°C) 1983 psi 5. 192 hours at 500°F ± 5°F (260°C ± 2°C) 2268 psi 6. 10 minutes at -67°F ± 5°F (-55°C ± 2°C) 6012 psi 7. Standard Temperature 75°F ± 5°F (24°C ± 2°C) after 30 days Salt Spray 5693 psi Exposure at 95°F (35°C) 8. Standard Temperature 75°F ± 5°F (24°C ± 2°C) after 30 days at 120°F (49°C) 5635 psi and 90-100% relative humidity 9. Standard Temperature 75°F ± 5°F (24°C ± 2°C) after 30 days Tap Water 5764 psi Immersion at 75°F (24°C) 10. Standard Temperature 75°F ± 5°F (24°C ± 2°C) after 7 days Immersion in 5912 psi Anti-icing Fluid (MIL-F-5566) at 75°F (24°C) 11. Standard Temperature 75°F ± 5°F (24°C ± 2°C) after 7 days Immersion in 5867 psi Hydraulic Oil (MIL-H-5606) at 75°F (24°C) 12. Standard Temperature 75°F ± 5°F (24°C ± 2°C) after 7 days Immersion in 5722 psi JP4 Fuel (MIL-J-5624) at 75°F (24°C) 13. Standard Temperature 75°F ± 5°F (24°C ± 2°C) after 7 days Immersion in 6042 psi in Hydrocarbon Fluid (MIL-S-3136) at 75°F (24°C) B. Creep Rupture 14. Standard Temperature 75°F ± 5°F (24°C ± 2°C) after 192 hours at 1600 psi 0.0000 inches 15. 300°F ± 5°F (149°C ± 2°C) after 192 hours at 800 psi 0.0000 inches 16. 500°F ± 5°F (260°C ± 2°C) after 192 hours at 800 psi 0.0017 inches C. Fatigue Strength 17. Standard Temperature 75°F ± 5°F (24°C ± 2°C) at 750 psi for 106 + cycles No failures
  • 3 - 2. 3M™ Scotch-Weld™ Structural Adhesive Film AF 31/3M™ Scotch-Weld™ Structural Adhesive Primer EC-2174 Overlap Shear on Aluminum The following data shows typical values obtained with Scotch-Weld AF 31 film adhesive over Scotch-Weld EC-2174 primer in overlap bonds. All properties were measured on 1" wide 1/2" overlap specimens cut from .063" thick 4" x 7" bonded panels of 2024 T3 clad aluminum. Tests were conducted according to MMM-A- 132 methods. All data reported in this section was developed using the following cures. Product Performance (continued) Note: The following technical information and data should be considered representative or typical only and should not be used for specification purposes. Scotch-Weld AF 31/Scotch-Weld EC-2174 Test 350°F (177°C) for 120 min. 350°F (177°C) for 60 min. Test Temperature 100 psi 10°F rise rate/min. 45 psi 10°F rise rate/min. Shear Strength -67°F ± 2°F (-55°C ± 1°C) 2750 psi 2310 psi 73.5°F ± 2°F (23°C ± 1°C) 4430 psi 4070 psi 260°F ± 2°F (127°C ± 1°C) 2700 psi — 300°F ± 2°F (149°C ± 1°C) 2550 psi 2330 psi 350°F ± 2°F (177°C ± 1°C) 2350 psi — Creep Rupture 73.5°F ± 2°F (23°C ± 1°C) .003" 3. Scotch-Weld AF 31 Film Adhesive T-Peel on Aluminum T-Peel bonds consist of bonded areas of 1" x 6" 2024 T3 clad 1" x 8" x .032" panels with one layer of Scotch- Weld AF 31 film adhesive. Each metal skin of the T-Peel panels were pulled at a 90° angle to the bond line or 180° in relation to themselves with a jaw separation rate of 20 inches per minute. A. Original Properties T-Peel (lbs./inch width) -40°F 75°F 180°F 250°F 350°F 450°F Cure Cycle (-40°C) (24°C) (82°C) 121°C (177°C) (232°C) 350°F (177°C), 60 min., 150 psi, 200°F 4 25 12 8 7 4 (93°C) per min. rise rate to cure temperature. 450°F (232°C) press temperature, 350 psi, 4 27 11 8 7 4 15 seconds in the press, maximum bond line temperature attained 412°F (211°C).
  • 4 - 4. 3M™ Scotch-Weld™ Structural Adhesive Film AF 31 Overlap Shear on Aluminum Using Varied Cure Times, Temperatures, and Pressures The following data shows typical values obtained with Scotch-Weld AF 31 film adhesive in aluminum overlap bonds. All properties were measured on 1" wide, 1/2" overlap specimens cut from .063" thick 4" x 7" bonded panels of 2024 T3 clad aluminum. Tests were conducted according to MMM-A-132 methods. All bonds were formed in a platen press. Product Performance (continued) Note: The following technical information and data should be considered representative or typical only and should not be used for specification purposes. Cure Cycle Overlap Shear (psi) Temp. Time Pressure Rise Rate Test Temperature 350 177 60 150 200 2700 3700 2850 2500 2390 1700 1150 1100 800 250 350 177 10 150 200 2850 4200 2430 1975 350 177 5 150 200 2260 4200 2260 1610 350 177 60 45 200 2675 3740 2050 350 177 60 45 9 2800 3700 2100 1300 350 177 120 100 10 2647 2165 1790 250 121 120 75 10 4285 1225 250 121 24 hrs. 75 10 4375 2090 260 127 120 75 10 4150 1510 260 127 8 hrs. 75 10 4360 2000 325 163 60 20 200 2720 3360 1830 1370 840 350 177 60 20 200 2820 3280 2020 1720 1530 Cure Cycle Platen Time at Time in Pressure Test Overlap Shear Temp. Temp. Press (psi) Temp. (psi) 450°F (232°C) 5 sec. 85 sec. 300 75°F (24°C) 3000 450°F (232°C) 1 min. 140 sec. 300 75°F (24°C) 2900 450°F (232°C) 10 min. 11.25 min. 300 75°F (24°C) 2800 450°F (232°C) 384* 10 sec. 300 75°F (24°C) 2350 450°F (232°C) 412* 15 sec. 350 -40°F (-40°C) 3400 450°F (232°C) 412* 15 sec. 350 75°F (24°C) 3050 450°F (232°C) 412* 15 sec. 350 180°F (82°C) 2400 450°F (232°C) 412* 15 sec. 350 250°F (121°C) 1850 450°F (232°C) 412* 15 sec. 350 350°F (177°C) 1650 450°F (232°C) 412* 15 sec. 350 450°F (232°C) 1240 450°F (232°C) 419* 30 sec. 350 75°F (24°C) 3200 *Maximum bondline temperature attained (°F). Bond line did not attain platen temperature.
  • 5 - 5. Environmental Aging of 3M™ Scotch-Weld™ Structural Adhesive Film AF 31 Using a 350°F (177°C) Cure for 120 Minutes, 100 psi, 10°F rise rate/minute. Product Performance (continued) Note: The following technical information and data should be considered representative or typical only and should not be used for specification purposes. Overlap Shear Strength (psi) -67°F 75°F 200°F 300°F 350°F 400°F 450°F 500°F 600°F Control 3500 3700 2390 1700 1150 1100 800 250 Air @ 300°F (149°C) for 222 hours 4750 4200 2540 2510 1960 320 Air @ 350°F (177°C) for 216 hours 1578 1130 Air @ 450°F (232°C) for 100 hours 2600 1920 1430 Air @ 450°F (232°C) for 200 hours 2250 1560 1470 Air @ 500°F (260°C) for 192 hours 1600 1440 1080 1060 1Air @ 400°F (204°C) for 1 hour 2840 2300 1930 2Air @ 450°F (232°C) for 10 hours 2350 3590 2450 1910 Salt Spray @ 95°F (23°C) for 30 days 3950 Tap Water @ 75°F (24°C) for 30 days 3790 Anti-Icing @ 75°F (24°C) for 7 days 3720 (MIL-F-5566) Hydraulic Oil @ 75°F (24°C) for 7 days 3790 (MIL-O-5606) Type III Hydrocarbon @ 75°F (24°C) 3750 for 7 days (MIL-H-3136) JP-4 @ 75°F (24°C) for 7 days 3970 (MIL-F-5624) JP-4 @ 140°F (60°C) for 7 days 3740 (MIL-F-5624) 60% H 2O – 40% Methyl Alcohol by volume, plus 1% soluble oil: @ 170°F (79°C) for 7 days 32430 @ 170°F (79°C) for 30 days 32246 60% H 2O – 40% Ethylene Glycol by volume, plus 1% soluble oil: @ 200°F (93°C) for 7 days 32450 @ 200°F (93°C) for 30 days 32430 99% H 2O – 1% soluble oil: @ 200°F (93°C) for 7 days 32220 @ 200°F (93°C) for 30 days 32210 1Cure Cycle – 350°F (177°C), 2 hours, 150 psi – 10°F/min. rise rate. 2Cure Cycle – 350°F (177°C), 60 min., 45 psi – 9°F/min. rise rate. 3Specimens cut to one inch width prior to immersion.
  • 6 - 6. Heat aging of 3M™ Scotch-Weld™ Structural Adhesive Film AF 31/3M™ Scotch-Weld™ Structural Adhesive Primer EC-2174 on Aluminum and Titanium. The adhesive was cured as indicated below. The primer was air dried 30 minutes plus force dried 30 minutes at 250°F (121°C). Product Performance (continued) Note: The following technical information and data should be considered representative or typical only and should not be used for specification purposes. Exposure Time and Cure Overlap Shear Strength (psi) Temperature Cycle 75°F (24°C) 300°F (149°C) 400°F (204°C)

2024 T-3 Alclad Aluminum

500 hours at 300°F (149°C) A 3410 2180 1000 hours at 300°F (149°C) A 2980 2070 2000 hours at 300°F (149°C) A 3240 2150 3000 hours at 300°F (149°C) A 3170 2190 Control B 4150 1710 192 hours at 400°F (204°C) B 3850 1730 Control C 3390 1240 192 hours at 400°F (204°C) C 2790 1420 6,4 Titanium Alloy Control B 880 880 192 hours at 400°F (204°C) B 640 820 Control C 1490 630 192 hours at 400°F (204°C) C 1310 1030 Cure Cycle A – 350°F (177°C), 45 minutes, 100 psi, 10°F/minute rise rate. Cure Cycle B – 350°F (177°C), 120 minutes, 100 psi, 10°F/minute rise rate. Cure Cycle C – Cure Cycle B plus post cured 120 minutes at 500°F (260°C). 7. Long Term Aging at 500°F (260°C) on Stainless Steel using a 350°F (177°C) cure for 120 minutes, 100 psi, 10°F rise rate/min. Effect of 500°F (260°C) Aging on Overlap Shear Strength of Scotch-Weld AF-31 / Scotch-Weld EC-2174

Environmental Aging of 3M™ Scotch-Weld™ Structural Adhesive Film AF 31 on Aluminum Using Short Time Cure Cycle (Specimens Cut to 1" Width Prior To Immersion) Cure Cycle – 15 seconds in a 450°F (232°C) platen press, 350 psi, maximum bond line temperature attained 412°F (210°C). Product Performance (continued) Note: The following technical information and data should be considered representative or typical only and should not be used for specification purposes. Overlap Shear Strength (psi) Environment -40°F (-40°C) 75°F (24°C) 180°F (82°C) 250°F (121°C) 350°F (177°C) Control 3400 3050 2400 1850 1650

7 Days 3450 3000 2400 1800 1400

14 Days 3400 3200 2600 1800 1700

30 Days 3950 3300 2400 1900 1500

60 Days 3950 3400 2400 1800 1000

1/2 Year 4300 3900 2000 1800 1300

1 Year 4300 3300 2000 1900 1200

Tap Water @ 120°F (49°C)

7 Days 3450 2800 2600 1600 1400

14 Days 3800 3200 2500 1900 1600

30 Days 3950 3200 2400 1700 1500

60 Days 3800 3200 2450 1600 1100

1/2 Year 3800 3750 2200 2200 1300

1 Year 3300 2250 2200 1800 900

Gasoline @ 75°F (24°C)

7 Days 3800 3100 2400 1600 1450

14 Days 3800 3100 2200 1350 1350

30 Days 3800 3100 2350 1550 1400

60 Days 3800 3150 2400 1550 1350

1/2 Year 3400 3200 2600 2050 1300

1 Year 3000 2850 2400 1550 1150

Methanol @ 75°F (24°C)

7 Days 3950 3200 2350 2100 1250

14 Days 3250 3350 2050 2000 1600

30 Days 3800 2800 2250 1900 1250

60 Days 3750 3000 1950 1000 750

1/2 Year 3800 2500 1600 1000 600

1 Year 4050 2700 2400 1250 900

Salt Spray @ 75°F (24°C)

7 Days 3700 2950 1900 1750 1400

14 Days 3800 3250 1900 2000 1600

30 Days 4300 3300 2300 1700 1550

60 Days 4000 2950 2100 1800 1000

1/2 Year 3200 3100 1750 2000 1050 - 7 -

  • 8 - 9. Environmental Aging of 3M™ Scotch-Weld™ Structural Adhesive Film AF 31 on Steel The following data shows typical values obtained with Scotch-Weld AF 31 film adhesive in steel overlap bonds. All properties were measured on 1" wide, 1/2" overlap specimens cut from .035" thick 4" x 8" bonded panels of 1020 cold rolled steel. The 1020 steel was cleaned with toluene solvent. Tests were conducted according to MMM-A-132 methods. A. Original Properties Product Performance (continued) Note: The following technical information and data should be considered representative or typical only and should not be used for specification purposes. Overlap Shear Strength (psi) -40°F 75°F 250°F 350°F 450°F Cure Cycle A 350°F (177°C), 60 min., 150 psi, 200°F (93°C) 2600 2195 1800 1720 660 per minute rise rate to cure temperature. Cure Cycle B 450°F (232°C) press temp., 350 psi, 250 2510 1520 1400 480 15 seconds in the press, maximum bond line temperature attained 412°F (212°C). B. Environmental Aging Properties (Specimens cut to 1" width prior to immersion) 75°F (24°C) Overlap Shear (psi) Environment Cure Cycle A Cure Cycle B Control 2195 2510 100% RH @ 100°F (38°C) for 7 days 1910 2530 120°F (49°C) Tap Water for 7 days 1650 1530 75°F (24°C) Gasoline for 7 days 2090 2530 75°F (24°C) Methanol for 7 days 2020 2410 95°F (35°C) Salt Spray for 7 days 1760 2810 10. Effect of Overlap Length on Scotch-Weld AF 31 Film Adhesive Shear Strength The effect of overlap length on shear strength of Scotch-Weld AF 31 film adhesive was determined on 1" wide specimens of varying length overlap, cut from .063" thick bonded panels of 2024 T3 clad aluminum. The cure cycle used was 350°F (177°C), 60 minutes, 150 psi, 200°F (93°C)/min. rise rate. Length of Actual Overlap Load (lbs.) psi 1/4" 1425 5700 3/8" 1740 4640 1/2" 2000 4000 3/4" 2500 3340 1" 2900 2400 1/2" 3230 2150 2" 3270 1634 3" 3600 1200
  • 9 - 11. Shear Strength of 3M™ Scotch-Weld™ Structural Adhesive Film AF 31/3M™ Scotch-Weld™ Structural Adhesive Primer EC-2174 on 410 Stainless Steel Surface Preparation – Abraded with a Scotch-Brite™ Hand Pad soaked in methyl ethyl ketone – rinsed with methyl ethyl ketone and air dried.* Primer Dry – two brush coats – (30 minutes between coats) – air dried overnight. Cure Cycle – 350°F (177°C) for 60 minutes, 50 psi, 10°F rise rate/minute. *Note: When using solvents, extinguish all ignition sources and follow manufacturer’s precautions and directions for use. Product Performance (continued) Note: The following technical information and data should be considered representative or typical only and should not be used for specification purposes. Scotch-Weld AF 31/Scotch-Weld EC-2174 Overlap Shear Strength 4365 psi 2230 psi 12. Scotch-Weld AF 31 Film Adhesive Outgassing The outgassing data at 10-6 torr was obtained on Scotch-Weld AF 31 film adhesive which had been cured for 60 minutes at 350°F (177°C). The total weight loss and volatiles condensed were measured using SP-R-0022A procedures. Total Weight Loss = 2.34% V olatile Condensible Material = 0.33% Coefficient of Thermal Expansion Below 35°F (2°C) 550 x 10 -7 per °F Above 35°F (2°C) 1360 x 10 -7 per °F 13. Scotch-Weld AF 31 Film Adhesive Coefficient of Thermal Expansion The coefficient of thermal expansion was obtained on Scotch-Weld AF 31 film adhesive cured at 350°F (177°C) for 60 minutes under 100 psi with a rise rate to cure temperature of 200°F (93°C) per minute.
  1. Dynamic Mechanical Properties of Scotch-Weld AF 31 Film Adhesive The dynamic mechanical properties were obtained using a Maxwell rotating beam apparatus on Scotch-Weld AF 31 film adhesive cured at 350°F (177°C) for 60 minutes under 100 psi pressure with a rise of 10°F per minute. E1 = Storage Modulus E11 = Loss Modulus E* = Complex Young’s Modulus Scotch-W eld TM Structural Adhesive Film AF 31 - 10 - 14. Effect of Radiation on 3M™ Scotch-Weld™ Structural Adhesive Film AF 31 Bonds The effect of radiation was determined using a spent fuel source (Particle energy .75 MEV avg.) Dosage 1.0 megarads per hour on 1" wide 1/2" overlap shear specimens cut from 4" x 7" x .064" thick bonded 2024 T3 clad aluminum panels. Bonds were formed with a 350°F (177°C), 60 minutes, 150 psi, 200°F (93°C)/minute temperature rise rate cure cycle. Radiation temperature was 75°F (24°C). Overlap shear tests were run per MMM-A-132 Methods. Product Performance (continued) Note: The following technical information and data should be considered representative or typical only and should not be used for specification purposes. Megarad Overlap Shear (psi) Dosage -67°F (-55°C) 75°F (24°C) 300°F (149°C) 0 3500 4200 2390 100 3120 4200 1620 200 2950 4070 1500 300 2840 3910 1500 500 2340 3020 1500 700 1850 2180 1330 900 1400 1340 870 Tanδ = E11 Frequency Temperature Cycles/minute E 1, psi E 11, psi Tan δδ E*, psi -67°F (-55°C) 1 498600 34000 .0682 499800 10 527100 28000 .0531 527800 100 557200 22850 .0410 557600 500 557200 19330 .0347 557500 3700 534400 26780 .0501 535100 77°F (25°C) 1 62660 6900 .1101 63040 10 72500 11050 .1524 73330 100 87670 17270 .1969 89350 500 103200 23150 .2244 105700 3700 104900 28110 .2679 108600 180°F (82°C) 1 34620 3340 .0964 34790 10 37950 2400 .0895 38100 100 42270 2890 .0684 42370 500 44000 3620 .0821 44190 3700 46800 4730 .1011 47030 300°F (149°C) 1 29390 2160 .0737 29470 10 31990 2745 .0858 32110 100 34360 3300 .0970 34520 500 36220 2920 .0805 36330 3700 37280 2820 .0756 37390
  • 11 - Note: Prior to using or handling chemicals or solutions listed below, read and follow supplier’s environmental, health and safety information. Proper adhesive application is as important as proper bond design and adhesive choice to obtain maximum joint properties. Improper adhesive application techniques can result in partial or complete failure of an assembly. A thoroughly cleaned, dry, grease-free surface is essential for maximum performance. Cleaning methods which will produce a break-free water film on metal surfaces are generally satisfactory. Surface preparations should be fully evaluated with the adhesive, especially if resistance to specific environments are anticipated. 1. Surface Preparations A. Suggested Surface Preparation for Aluminum 1. Vapor Degrease – Perchloroethylene condensing vapors for 5-10 minutes. 2. Alkaline Degrease – Oakite 164 solution (9-11 oz./gallon water) at 190°F ± 10°F (88°C ± 5°C) for 10-20 minutes. Rinse immediately in large quantities of cold running water. 3. Acid Etch – Place panels in the following solution for 10 minutes at 150°F ± 5°F (66°C ± 2°C). Sodium Dichromate (Na2Cr2O 72H 2O) 4.1 - 4.9 oz./gallon Sulfuric Acid, 66° Be 38.5 - 41.5 oz./gallon 2024-T3 aluminum (dissolved) 0.2 oz./gallon minimum Tap Water as needed to balance 4. Rinse – Rinse panels in clear running tap water. 5. Dry – Air dry 15 minutes; force dry 10 minutes at 150°F ± 10°F (66°C ± 5°C). 6. If primer is to be used, it should be applied within four hours after surface preparation. B. Suggested Surface Preparation for Stainless Steel (17-7PH-TH [1050]) 1. Vapor Hone – #120 AI2O 3 grit. 2. Vapor Degrease – Perchloroethylene condensing vapors for 5-10 minutes.. 3. Acid Etch – Place panels in the following solution for two minutes at 145°F ± 5°F (62°C ± 2°C). 59.9 grams, M.F. Acid (Wyandotte) 170 mls Commercial Concentrated Nitric Acid. The balance of one liter of distilled or ion-free water. 4. Rinse – Rinse immediately in cold running tap water. Remove smut with distilled water-air spray under 90 psi pressure. 5. Acid Etch – Place panels in the following solution at 160°F ± 5°F (71°C ± 2°C). 30 parts by wt. Distilled or Ion-free Water 10 parts by wt. Concentrated Sulfuric Acid 4 parts by wt. Sodium Dichromate 6. Rinse – Rinse in cold tap water. Remove smut with a distilled water-air spray under 90 psi pressure. 7. Dry – Air dry 15 minutes; force dry 10 minutes at 150°F ± 10°F (66°C ± 5°C). 8. If primer is to be used, it should be applied within one hour after surface preparation. Product Application
  • 12 - C. Suggested Surface Preparation for Titanium 1. Use Scotch-Brite™ Hand Pad to remove all lettering. 2. Clean in Oakite 164 for 10 minutes at 190°F (88°C). Water break necessary. 3. Etch in acid solution for 5 to 7 minutes at 120-135°F (49-57°C). Acid make-up (to make approximately one gallon) Distilled Water 2.36 Liters HNO 3(70%) 1.29 Liters HF (48%) .13 Liters 4. Rinse in distilled water. 5. Soak in Phosphate-fluoride bath for 60-90 seconds at 90°F (32°C). Bath make-up (to make approximately one gallon) NA

3 PO 412H 2O 162 grams

Potassium Fluoride 41.7 grams Hydrofluoric Acid (48%) 0.113 liters Distilled Water 3.57 liters 6. Rinse in distilled water at 180°F (82°C) for 15 minutes. Rinse three times in solution. 7. Rinse in distilled water. 8. Air dry at 190°F (88°C) for 20 minutes. 2. Adhesive Layup A. Primer Application 1. Advantages Priming of bonding surfaces offers two distinct advantages: (1) ensures complete wetting of metal surfaces, which normally results in superior environmental properties and (2) simplifies production by protecting cleaned parts until bonding can be completed. 3M™ Scotch-Weld™ Structural Adhesive Primer EC-2174 is recommended to use with 3M™ Scotch-Weld™ Structural Adhesive Film AF 31. 2. Application Scotch-Weld EC-2174 primer may be applied by brushing or flow coating using one or two coats. A camel hair, horsehair or similar type brush is recommended. Dried primer thickness should be 0.0002-0.0006 inches. 3. Primer Dry a. Air dry for 60 minutes minimum at 75°F ± 5°F (24°C ± 2°C). b. Force dry in an air circulating oven for 60 minutes at 265°F (129°C). B. Film Application 1. Cut portion of film to be used from roll with protective liner in place. 2. Place film on metal using a separating liner as a protective cover. 3. Roll film into position with a rubber roller, ensuring that no air is trapped between primer and film. 4. Remove protective liner. 5. Assemble parts and cure. Excess primer and equipment may be cleaned prior to curing, with ketone* type solvent. *Note: When using solvents, extinguish all ignition sources and follow manufacturer’s precautions and directions for use. Product Application (continued)

  • 13 - 3. Cure Cycle A. General Cure Requirements The cure requirements for 3M™ Scotch-Weld™ Structural Adhesive Film AF 31 are a function of Scotch-Weld AF 31 film adhesive properties, specific application, equipment available, production limitations and bond properties required. General cure properties of Scotch-Weld AF 31 film adhesive are as follows: Tack, Flow, Cure Initiation Temperatures The tack, flow and cure initiation temperatures for Scotch-Weld film adhesive AF 31 are a time-temperature relationship and depend upon the rate of heat input. Normally, Scotch-Weld AF 31 film adhesive will have the following properties: Tack Temperature: 160°F-180°F (71°C-82°C) Flow Temperature: 180°F-220°F (82°C-103°C) Cure Initiation Temp.: 220°F-270°F (104°C-132°C) B. Cure Pressure Pressure is required during cure to form the part being bonded and contain any volatiles given off by the adhesive. Cure pressure may be applied in any manner which will insure uniform constant pressure throughout the bond area. Pressure must be uniformly applied before the curing reaction begins and maintained until a complete cure has been effected. The pressure required to contain volatiles is dependent on the rate at which bond line temperature is brought to the cure temperature. The bond line temperature rise rate for Scotch-Weld AF 31 film adhesive can be varied from 1°F to 300°F/minute. Rise rate (and cure pressure required) will depend on specific application, cure temperature, bonding equipment, method of heat application, production limitations and bond properties required. Figure I, Page 5, depicts typical pressures required for various bond-line temperature rise rates in platen presses. C. Cure Temperature The cure temperature may be varied from 250°F (121°C) to 450°F (232°C), depending upon the materials bonded, equipment available and bond properties desired. The desired pressure must be applied before the glue line reaches 160°F (71°C). The film will soften as temperature is increased to 180-210°F (82-99°C) and will wet the surface to which it has been applied. A chemical cure will be initiated between 220-270°F (104-132°C) and a low strength gel formed. Continued heating chemically converts the adhesive into a high strength, solvent-resistant bond. Scotch-Weld AF 31 film adhesive will change color only slightly upon application of heat. Edges of the bond that are exposed to air will change from yellow to rusty brown. D. Cure Time Cure time depends on the cure temperature used, methods of heat application, production limitations and bond properties required. Since no two bonding operations are exactly alike, it is suggested that a few simple experiments be conducted, varying both temperature and cure time to determine optimum conditions for the particular application. Figure 2, Page 14, is a guide from which an approximate cure cycle can be taken for various cure times or temperatures. Product Application (continued)
  • 14 - Storage at 40°F ± 5°F (4°C ± 2°C) is suggested for 3M™ Scotch-Weld™ Structural Adhesive Film AF 31 and 3M™ Scotch-Weld™ Structural Adhesive Primer EC-2174 to obtain maximum shelf life. Rotate stock on a “first in-first out” basis. Caution:Scotch-Weld AF 31 film adhesive and Scotch-Weld EC-2174 primer should be permitted to thoroughly warm to room temperature (75°F ± 5°F [24°C ± 2°C]) before being used to prevent moisture condensation. Storage and Handling E. Suggested Cure Cycle The following press cure cycle is suggested to obtain dense glue lines and maximum strengths: 1. Apply a pressure of 45 psi prior to reaching a bond-line temperature of 150°F (66°C) and maintain throughout the press cure cycle. 2. Raise the bond line temperature from ambient to 350°F (177°C) at a rate of 10°F per minute. 3. Cure for 60 minutes at 350°F (177°C). 4. Cool to below 200°F (93°C) bond-line temperature prior to release of pressure. (In lab tests, panels have been removed at 350°F (177°C), with no adverse effects). Product Application (continued) Shelf Life Standard shelf life of Scotch-Weld AF 31 film adhesive is 12 months from date of shipment in the original unopened container if stored at 40°F (4°C).
  • 15 - Scotch-W eld TM Structural Adhesive Film AF 31 Refer to Product Label and Material Safety Data Sheet for health and safety information before using this product. For additional health and safety information, call 1-800-364-3577 or (651) 737-6501. Precautionary Information Printed in U.S.A. ©3M 2006 78-6900-1326-9 (3/06) Recycled Paper 40% pre-consumer 10% post-consumer Aerospace and Aircraft Maintenance Division 3M Center, Building 223-1N-14 St. Paul, MN 55144-1000 www.3M.com/aerospace To request additional product information or to arrange for sales assistance, call toll free 1-800- 235-2376 or fax 1-800-435-3082 or 651-737-2171. For U.S. Military, call 1-866-556-5714 or fax 651-737-4380. If outside of the U.S., please contact your nearest 3M office. For Additional Information 3M MAKES NO W ARRANTIES, EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, ANY IMPLIED W ARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. User is responsible for determining whether the 3M product is fit for a particular purpose and suitable for user’s method of application. Please remember that many factors can affect the use and performance of a 3M product in a particular application. The materials to be bonded with the product, the surface preparation of those materials, the product selected for use, the conditions in which the product is used, and the time and environmental conditions in which the product is expected to perform are among the many factors that can affect the use and performance of a 3M product. Given the variety of factors that can affect the use and performance of a 3M product, some of which are uniquely within the user’s knowledge and control, it is essential that the user evaluate the 3M product to determine whether it is fit for a particular purpose and suitable for the user’s method of application. Important Notice If the 3M product is proved to be defective, THE EXCLUSIVE REMEDY , AT 3M’S OPTION, SHALL BE TO REFUND THE PURCHASE PRICE OF OR TO REPAIR OR REPLACE THE DEFECTIVE 3M PRODUCT. 3M shall not otherwise be liable for loss or damages, whether direct, indirect, special, incidental, or consequential, regardless of the legal theory asserted, including, but not limited to, contract, negligence, warranty, or strict liability. Limitation of Remedies and Liability This product was manufactured under a 3M quality standard registered under ISO9001 standards. ISO9001