Adhesives and Potting Compounds for High Service Temperature in

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
liz.walker@nstarch.com
michel.ruyters@nstarch.com
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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