1. Emerson & CumingPage 1 TRFA Oct 3-4, 2004 Adhesives and Potting Compounds for High Service Temperature in Automotive Applications Liz Walker liz.walker@nstarch.com Michel Ruyters michel.ruyters@nstarch.com The Thermoset Resin Formulators Association Meeting Boston, MA October 3-4, 2004 Presented at

2. Emerson & CumingPage 2 TRFA Oct 3-4, 2004 Presentation Outline Introduction –Automotive Electronics Evolution - New Demands on Adhesives & Protective Materials –New Materials Development Program -Target Properties & Test Matrix Epoxy Materials –Anhydride Cured –Improved Resin & Compounds –Imidazole Cured –Summary of Material Properties Alternative High Performance Thermoset Technology –Possible Candidate Materials Cyanate Ester Adhesive Next Generation – Improve Thermal Shock Performance –Combine Toughening with Thermal Stability Summary

3. Emerson & CumingPage 3 TRFA Oct 3-4, 2004 Harsh Environments for Automotive Electronics Motor Management -40°C to +180°C High service temperature (180°C) Fuels, Oils, Vibration On Transmission -40°C to +180°C ATF, Vibration

4. Emerson & CumingPage 4 TRFA Oct 3-4, 2004 Conseqences for Polymeric Materials Polymeric materials used for the assembly and protection of electronics must survive higher service temperatures, temperature extremes, fluid exposure and vibration. –Critical Properties High Temperature Resistance – 150°C - 200°C Adhesion to Metals and Engineered Plastics Adhesion Retention at High Temperature Chemical Resistance Operate in Wide Temperature Range

5. Emerson & CumingPage 5 TRFA Oct 3-4, 2004 New Product Development - Target Properties Thermal Stability –High crosslink density – High Tg above use temperature –Low thermal degradation – Low weight loss Adhesion –High values at 180°C to aluminum and plastics (PBT, PPS,...) –Minimal decrease during service life @ -40°C to + 180°C Easy to Process –1 Component Compound, no mixing required –Low temperature, minimal cure time post cure in operation only –Long working time, shelf life –Low viscosity for potting, easy air release

6. Emerson & CumingPage 6 TRFA Oct 3-4, 2004 New Product Development - Testing Thermal Stability – –TMA - Glass Transition & Coefficient of thermal expansion –TGA - Report Temperature at 1% weight loss –Fluid Immersion – weight change at temperature Oil SAE 10W-40- 24 hr @ 150°C, Water 1 hr @ 100°C Adhesion – Maximize values, minimize loss –Tensile Lap Shear Strength (TLSS) ASTM D-1002 –Test at room temperature (RT) and 180°C Initial and after exposure to 180°C –Aluminum ( acid etch), untreated PPS, 30%GF PBT Easy to Process –Viscosity over time for pot life/working time and shelf life 3 days minimum at RT with no increase in viscosity 25°C and 40°C conditions

7. Emerson & CumingPage 7 TRFA Oct 3-4, 2004 High Temperature Performance Epoxies 1 st Generation Epoxy materials - multifunctional resins cured with anhydrides Advantage High adhesion Thermally stable Good chemical resistance Low exotherm Disadvantage Two component Moisture sensitive Slow to react, long multi-step cure schedules

8. Emerson & CumingPage 8 TRFA Oct 3-4, 2004 High Temperature Performance Epoxies 2 nd Generation novel multifunctional epoxy resin blend High crosslink density possible Low viscosity : fillers can be used Good reactivity at high temperature Low reactivity at room temperature Novel accelerated anhydride Good latency at room temperature Highly efficient cure at 120-150°C 1 Component formulated products Example - Compound 1

9. Emerson & CumingPage 9 TRFA Oct 3-4, 2004 Long Cure/ Post Cure – Maximize Tg, Minimize CTE Example - Compound 1

10. Emerson & CumingPage 10 TRFA Oct 3-4, 2004 Thermal Stability – Low Weight Loss (TGA) 1 % weight loss @ 297 °C TGA Test atmosphere : 20% O 2, 80% N 2 50 ml/min Example – Compound 1

11. Emerson & CumingPage 11 TRFA Oct 3-4, 2004 Adhesion – Aluminum to Aluminum 84% retention tested@ 25°C 93% retention tested @ 180°C Compare Testing Temperature and Aging Effects Tensile Lap Shear Strength - Example Compound 1

12. Emerson & CumingPage 12 TRFA Oct 3-4, 2004 Adhesion PPS to PPS 81% retention tested @ 25°C 88% retention tested @ 180°C Compare Testing Temperature and Aging Effects Tensile Lap Shear Strength Example - Compound 1

13. Emerson & CumingPage 13 TRFA Oct 3-4, 2004 High Temperature Performance Epoxies Proprietary solid imidazole hardener –Moderate Tg, still maintains good chemical resistance –Faster Cure, higher reactivity than Compound 1 Various cure temps./ times full cure at 150°C/30min –Improved stability as a 1 Component Product Long potlife 1 wk at RT Longer Shelf Life 3 mos@ 6°C (2 X Compound 1) –Much Improved adhesion 2X to 3X TLLS vs. Compound 1 at 25°C and 180°C Increased polarity, resulting in better wetting of substrate Example - Compound 2

14. Emerson & CumingPage 14 TRFA Oct 3-4, 2004 Thermal Stability – Low Weight Loss (TGA) 1% Weight Loss @ 322°C Example - Compound 2

15. Emerson & CumingPage 15 TRFA Oct 3-4, 2004 Adhesion - Aluminum to Aluminum 60% retention tested @ 25°C 46% retention tested @ 180°C Compare Testing Temperature & Aging Effects Tensile Lap Shear Strength Example – Compound 2

16. Emerson & CumingPage 16 TRFA Oct 3-4, 2004 Adhesion PPS to PPS 88% retention tested @ 25°C 84.5% retention tested @ 180°C Compare Testing Temperature & Aging Effects Tensile Lap Shear Strength Example – Compound 2

17. Emerson & CumingPage 17 TRFA Oct 3-4, 2004 Compare Properties - Compounds 1 & 2 Compound 1Compound 2 Hardness, Shore D9390 Volumetric cure shrinkage, %- 1.5 E modulus at 25°C, MPa63008000 Tg by TMA>200°C * post cured 145°C Water absorption, % after 1 hr / 100°C+ 0.05+0.08 Oil absorption, % SAE 10W-40 24 hr/150°C + 0.050.05 Volume Resistivity, Ohm.cm1.97 x 10 15 2.0 x 10 15 Surface Resistance Ohm1.9 x 10 12 1.4 x 10 12 Dielectric Constant / Dissipation Factor 50 Hz 1 kHz 1 MHz 4.6 0.010 4.1 0.007 3.9 0.012 4.8 0.021 4.5 0.015 4.3 0.011

18. Emerson & CumingPage 18 TRFA Oct 3-4, 2004 Performance of Anhydride & Imidazole Cured Epoxy Materials Summary Anhydride Cured Epoxy Stable 1-Part with -40°C Storage Low Viscosity, Low Exotherm –Good for potting Very High Tg, Low CTE possible –With post cure Moisture sensitive, respiratory sensitizer Lower than desired adhesive strength on plastics Both can be brittle at -40°C limiting thermal shock performance Imidazole Cured Epoxy Stable 1-Part with +25°C Storage Higher Reactivity, Higher Exotherm –Good for adhesive bonds Moderate Tg, high thermal stability – Maintains good chemical resistance Higher initial Adhesive strength – Higher loss after aging on Al

19. Emerson & CumingPage 19 TRFA Oct 3-4, 2004 Alternative High Performance Thermoset Materials Chemisties Considered –Polyimid Mainly solids, two-step imidisation, water by-product, voids –Bismaleimide Mainly solids, high processing temperatures Chemistry Tested –Cyanate Ester Liquid monomer available Possibility to blend for improved properties

20. Emerson & CumingPage 20 TRFA Oct 3-4, 2004 Cyanate Ester Epoxy Blend Adhesion Al to Al- TLSS 89.7% retention tested @ 25°C 76.4% retention tested @ 180°C Compare Testing Temperature and Aging Effects

21. Emerson & CumingPage 21 TRFA Oct 3-4, 2004 Cyanate Ester Epoxy Blend Adhesion PPS to PPS - TLSS 85.7% retention tested @ 25°C 79.4% retention tested @ 180°C Compare Testing Temperature and Aging Effects

22. Emerson & CumingPage 22 TRFA Oct 3-4, 2004 Cyanate Ester Epoxy Blend - Thermal Stability 0.5 % weight loss at 300°C TGA – Thermal Stability

23. Emerson & CumingPage 23 TRFA Oct 3-4, 2004 Cyanate Ester Advantages –1 Component, low viscosity possible –Very high thermal stability, high Tg –High initial adhesion like epoxy imidazole on Al and PPS retention @ 180°C better on aluminum –Less susceptible to moisture after cure –Can be modified/blended to improve performance or cure –Limitations –Current formulas require very high temperature cure or multi-step cure at lower temperatures –Uncured liquid is moisture sensitive

24. Emerson & CumingPage 24 TRFA Oct 3-4, 2004 Challenge to Improve Polymeric Materials Combine Low and High Temperature Performance Poor Performance in thermal shock Eliminating micro-cracking Toughened thermosets can control micro-cracking, but cause –reduced Tg & thermal stability High Temperature Resistance High Chemical Resistance Temperature Shock Resistant High crosslink density Reduced modulus

25. Emerson & CumingPage 25 TRFA Oct 3-4, 2004 Improve Thermal Shock Performance -40°C to 180°C Micro-cracking –Understand micro-cracking physics Model changes during thermal shock –Improve Testing Perform fatigue and fracture analysis Develop optical methods to verify modeling Reduce micro-cracking while retaining high temperature performance Toughening that does not compromise thermal stability

26. Emerson & CumingPage 26 TRFA Oct 3-4, 2004 Toughening Thermosets Improve Thermal Shock Performance Co-Reaction with Elastomers - –Low Tg, soft segments chemically bound to high Tg hard segments Co-Polymer blend with phase separation - during cure –Large low Tg soft domain clusters form between high Tg rigid segments, driven by polarity differences Elastomeric particles –Hard rigid high Tg matrix with low Tg cushions throughout –absorb impact and stress

27. Emerson & CumingPage 27 TRFA Oct 3-4, 2004 Co-polymer Blend with Phase Separation Compound 3Compound 4 Cure, Time and Temperature 30” @ 150°C or 60” @ 120°C 150” @ 121°C or 30” @ 160°C Hardness, Shore D87D85D E modulus at 25°C, MPa80006500 Tg by TMA100°C117.5°C Oil absorption, SAE 10W-40 @ 120°C <0.25% in 400 hrs Currently under test Volume Resistivity, Ohm.cm1.97 x 10 15 >2.5 x 10 15 Example Compounds 3 & 4

28. Emerson & CumingPage 28 TRFA Oct 3-4, 2004 Summary - High Service Temperature Adhesives and Potting Compounds Demonstrated – 1 Component Epoxies –High Tg, low viscosity, low CTE Potting Compound, high service temperature (when post cured) –Moderate Tg Adhesive for 180°C - maintains adhesion after heat exposure –Cyanate ester blend with High Adhesion –Slightly higher thermal stability than Epoxies –Adhesion equal to imidizole/ epoxy, better high-adhesion retention on Al Future Goals for New Product Development –Maintain high temperature stability & adhesion AND –Improve Adhesion to Engineering Plastics –Improve Thermal Shock Performance

29. Emerson & CumingPage 29 TRFA Oct 3-4, 2004 Appreciation, Acknowledgements & References Industry –Robert Bosch GmbH –Epcos –Wabash Emerson & Cuming –G. Van Wuytswinkel –C. Bosmans –C. Van Der Borght ICI –G. Smyth –R. Bailey –P. Dooling References –High Performance Thermosets Lin/Pearce –Polymer Toughening C. Arends –Cyanate Ester Technology I. Hamerton