Adhesives and Potting Compounds for High Service Temperature in Automotive Applications Presented at The Thermoset Resin Formulators Association Meeting Boston, MA October 3-4, 2004 Emerson & Cuming Liz Walker Michel Ruyters [email protected] [email protected] Page 1 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 Emerson & Cuming Page 2 TRFA Oct 3-4, 2004 Harsh Environments for Automotive Electronics Motor Management On Transmission -40°C to +180°C High service temperature (180°C) Fuels, Oils, Vibration -40°C to +180°C ATF, Vibration Emerson & Cuming Page 3 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 Emerson & Cuming Page 4 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 Emerson & Cuming Page 5 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 Emerson & Cuming Page 6 TRFA Oct 3-4, 2004 High Temperature Performance Epoxies • 1st Generation Epoxy materials - multifunctional resins cured with anhydrides • Advantage • High adhesion • Thermally stable • Good chemical resistance • Low exotherm O H3C O O O • Disadvantage • Two component • Moisture sensitive • Slow to react, long multi-step cure schedules Emerson & Cuming Page 7 TRFA Oct 3-4, 2004 O O O O O High Temperature Performance Epoxies Example - Compound 1 • 2nd 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 R O O H • Novel accelerated anhydride • Good latency at room temperature • Highly efficient cure at 120-150°C • 1 Component formulated products Emerson & Cuming Page 8 TRFA Oct 3-4, 2004 n O f Long Cure/ Post Cure – Maximize Tg, Minimize CTE Example - Compound 1 Cure Postcure 2h / 120°C Tg CTE (ppm ) 135 50 2h / 120°C 4h / 200°C 216 39 2h / 120°C 12h / 200°C 227 29 Emerson & Cuming Page 9 TRFA Oct 3-4, 2004 Thermal Stability – Low Weight Loss (TGA) Example – Compound 1 TGA Test atmosphere : 20% O2, 80% N2 50 ml/min 1 % weight loss @ 297 °C Emerson & Cuming Page 10 TRFA Oct 3-4, 2004 Adhesion – Aluminum to Aluminum Tensile Lap Shear Strength - Example Compound 1 8 7.6 6.8 6 MPa 5.7 5.6 6.5 6.4 5.3 5.2 84% retention tested@ 25°C at 25°C 4 at 180°C 2 0 0 1 6 12 93% retention tested @ 180°C Weeks Aged at 180°C Compare Testing Temperature and Aging Effects Emerson & Cuming Page 11 TRFA Oct 3-4, 2004 Adhesion PPS to PPS Tensile Lap Shear Strength Example - Compound 1 2.5 MPa 2 2.1 2 1.7 1.9 1.6 1.5 1.7 1.4 81% retention tested @ 25°C 1.5 at 25°C 1 at 180°C 0.5 0 0 1 6 12 88% retention tested @ 180°C Weeks Aged at 180°C Compare Testing Temperature and Aging Effects Emerson & Cuming Page 12 TRFA Oct 3-4, 2004 High Temperature Performance Epoxies Example - Compound 2 • 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 Emerson & Cuming Page 13 TRFA Oct 3-4, 2004 Thermal Stability – Low Weight Loss (TGA) Example - Compound 2 303°C 99.50% 100 322°C 99.00% 1% Weight Loss @ 322°C 341°C 98.00% Weight (%) XE 80207 80 60 40 0 100 200 300 400 Temperature (°C) Emerson & Cuming Page 14 TRFA Oct 3-4, 2004 500 600 700 Adhesion - Aluminum to Aluminum Tensile Lap Shear Strength Example – Compound 2 20 MPa 15 18.1 17 60% retention tested @ 25°C 13.6 10.8 10 12.7 10.9 6.7 at 25°C 6.3 at 180°C 5 46% retention tested @ 180°C 0 0 1 6 12 Weeks Aged at 180°C Compare Testing Temperature & Aging Effects Emerson & Cuming Page 15 TRFA Oct 3-4, 2004 Adhesion PPS to PPS Tensile Lap Shear Strength Example – Compound 2 88% retention tested @ 25°C 8 5.9 6 MPa 5.8 5.7 3.9 4 3.4 5.2 3.2 at 25°C 3.3 at 180°C 2 84.5% retention tested @ 180°C 0 0 1 6 12 Weeks Aged at 180°C Compare Testing Temperature & Aging Effects Emerson & Cuming Page 16 TRFA Oct 3-4, 2004 Compare Properties - Compounds 1 & 2 Compound 1 Compound 2 Hardness, Shore D 93 90 Volumetric cure shrinkage, % - 1.5 -1.0 E modulus at 25°C, MPa 6300 8000 Tg by TMA >200°C * post cured 145°C Water absorption, % after 1 hr / 100°C + 0.05 +0.08 + 0.05 0.05 Volume Resistivity, Ohm.cm 1.97 x 1015 2.0 x 1015 Surface Resistance Ohm 1.9 x 1012 1.4 x 1012 Dielectric Constant / Dissipation Factor 50 Hz 1 kHz 1 MHz 4.6 4.1 3.9 4.8 4.5 4.3 Oil absorption, % Emerson & Cuming SAE 10W-40 24 hr/150°C Page 17 TRFA Oct 3-4, 2004 0.010 0.007 0.012 0.021 0.015 0.011 Performance of Anhydride & Imidazole Cured Epoxy Materials Summary Anhydride Cured Epoxy Imidazole Cured Epoxy • Stable 1-Part with -40°C Storage •Stable 1-Part with +25°C Storage • Low Viscosity, Low Exotherm •Higher Reactivity, Higher Exotherm – Good for potting • Very High Tg, Low CTE possible – With post cure • –Good for adhesive bonds Moisture sensitive, respiratory sensitizer •Moderate Tg , high thermal stability – Maintains good chemical resistance •Higher initial Adhesive strength – Higher loss after aging on Al Lower than desired adhesive strength on plastics Both can be brittle at -40°C limiting thermal shock performance Emerson & Cuming Page 18 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 Emerson & Cuming Page 19 TRFA Oct 3-4, 2004 Cyanate Ester Epoxy Blend Adhesion Al to Al- TLSS 20 16.5 16.5 16.5 14.9 MPa 15 16.6 14.2 14.8 89.7% retention tested @ 25°C 12.6 at 25°C 10 at 180°C 5 0 0 1 6 12 76.4% retention tested @ 180°C Weeks Aged at 180°C Compare Testing Temperature and Aging Effects Emerson & Cuming Page 20 TRFA Oct 3-4, 2004 MPa Cyanate Ester Epoxy Blend Adhesion PPS to PPS - TLSS 6 5 4 85.7% retention tested @ 25°C 5 4.8 3.4 3.4 4.2 4 2.8 3 2 1 0 2.7 at 25°C at 180°C 79.4% retention tested @ 180°C 0 1 6 12 Weeks Aged at 180°C Compare Testing Temperature and Aging Effects Emerson & Cuming Page 21 TRFA Oct 3-4, 2004 Cyanate Ester Epoxy Blend - Thermal Stability ? Step 0,1329 % TGA – Thermal 13,2570e-03 mg Left Limit 33,96 °C Stability Right Limit 299,60 °C 35 Arocy L-10 0.5 %65weight loss at 300°C ZX1059 5 mg Method: TGA 30-700C,10Cmin/air 50 ml 30,0-700,0°C 10,00°C/min Air, 50,0 ml/min 50 0 100 5 150 10 200 15 250 20 300 25 350 30 400 35 450 40 45 550 50 600 55 650 60 °C min e Lab: METTLER Emerson & Cuming 500 METTL ER T OLEDO S TA R Syste m Page 22 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 Emerson & Cuming Page 23 TRFA Oct 3-4, 2004 Challenge to Improve Polymeric Materials Combine Low and High Temperature Performance High Temperature Resistance • Poor Performance in thermal shock High Chemical Resistance High crosslink density • Eliminating micro-cracking Reduced modulus • Toughened thermosets can control micro-cracking, but cause – reduced Tg & thermal stability Emerson & Cuming Temperature Shock Resistant Page 24 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 Emerson & Cuming Page 25 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 Emerson & Cuming Page 26 TRFA Oct 3-4, 2004 Co-polymer Blend with Phase Separation Example Compounds 3 & 4 Compound 3 Compound 4 Cure, Time and Temperature 30” @ 150°C or 60” @ 120°C 150” @ 121°C or 30” @ 160°C Hardness, Shore D 87D 85D E modulus at 25°C, MPa 8000 6500 Tg by TMA 100°C 117.5°C <0.25% in 400 hrs Currently under test 1.97 x 1015 >2.5 x 1015 Oil absorption, SAE 10W-40 @ 120°C Volume Resistivity, Ohm.cm Emerson & Cuming Page 27 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 Emerson & Cuming Page 28 TRFA Oct 3-4, 2004 Appreciation, Acknowledgements & References • Industry – Robert Bosch GmbH – Epcos – Wabash • ICI – G. Smyth – R. Bailey – P. Dooling • Emerson & Cuming – G. Van Wuytswinkel – C. Bosmans – C. Van Der Borght • References – High Performance Thermosets Lin/Pearce – Polymer Toughening C. Arends – Cyanate Ester Technology I. Hamerton Emerson & Cuming Page 29 TRFA Oct 3-4, 2004
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