Dr Robert Drake

“Pushing the Boundaries of
Fluorosilicone Rubber”
Dr. R. A. Drake, Dr. L. M. Tonge, P. J. Griffith, Dr. K. B. King
Topics
• Overview of Fluorosilicone Rubber (FVMQ)
• Dow Corning Innovation in FVMQ
– High Resilience & Low Compression technology
• New Bases
– High Temperature & Fluid Resistance technology
•
•
•
•
Acid Acceptors
Peroxide Effects
Redox Stabilisers
Adhesion
2
FVMQ Definitions and benefits:
Fluorosilicone Chemistry
VMQ
CH=CH2
CH3
Si
Si
O
O
Si
m
n
CH3
CH2 CH2 CF3 CH=CH2 FVMQ
CH3
Si
O
O
n
m
CH3
CH3
Replacing one CH3 with CH2CH2CF3 gives:
•
•
•
•
•
•
Improved resistance to non-polar hydrocarbon fuels,
oils, and solvents
Increased specific gravity
Improved solubility in polar fluids such as esters and
ketones
Improved lubricity
Lower use temperature by eliminating polymer Tm
crystallization
A 10x increase in viscosity at the same molecular
weight
very
cold
very
hot

  
aggressive
fluids
We are improving
FVMQ here
3
Typical Automotive FVMQ applications
Some examples
• Fuel line safety seals
• Oil system seals
• Turbocharger hoses
• Membranes
• O-rings
• Gaskets
• ...
4
Dow Corning Innovation in FVMQ
• Global Development Team
• Multi-generational approach making improvements across our
fluorosilicone supply chain
• Focus on material performance and durability in application
–
–
–
–
Resilience
Compression Set
Thermal Stability
Fluid Stability
• Oil, Acid Gas Condensate…
– Fatigue Life
– FVMQ adhesion to VMQ
5
HIGH RESILIENCE & LOW
COMPRESSION SET
6
High Resilience & Low Compression Set Developments
• New bases have been launched meeting the following needs:
–
–
–
–
–
–
High resilience/rebound
Low compression set
High fuel resistance
Reduced stickiness when unwrapping and mill handling
Globally available as U-stock bases or in compounds
Blending can cover 40 to 70 durometer range
• Designed for molding applications such as o-rings,
diaphragms, and other fuel contact applications
7
Silastic LS-2940 U / LS-2970 U Blends
Formulation, Parts
Silastic LS-2940 U Fluorosil Rubber..................................................
Silastic LS-2970 U Fluorosil Rubber..................................................
DBPH-502............................................................................................
Test1
Physical Properties2
Unit
ASTM D2240
ASTM D412 Die C
ASTM D412 Die C
ASTM D412 Die C
ASTM D2632
ASTM D624B
ASTM D395
Hardness
Tensile strength
Elongation at break
Modulus 100%
Bashore Resiliency
Tear Strength
Compression Set3
Shore A
MPa
%
MPa
% Rebound
kN/m
%
100
0
1
42
8.8
360
1.2
31
15
6
70
30
1
50
50
1
30
70
1
49
9.5
320
1.8
56
10.0
300
2.3
62
10.8
289
3.0
28
26
26
17
10
20
6
19
7
0
100
1
71
10.4
241
4.2
25
19
8
1
ASTM: American Society for Testing and Materials.
Properties obtained using 1.0 phr DBPH-50 (DHBP) (2,5-bis (tert-butylperoxy) 2,5 dimethyl
hexane) on 1.91mm (0.075 inch thick) slabs; as molded 10 minutes at 171°C (340°F); postcured
4 hours at 200°C (392° F).
3
Tested according to method B, type II (6mm), plied disks, 22hrs 177°C.
2
8
Fluid Resistance Data
Formulation, Parts
LS-2940 U…………………………………
LS-2970 U…………………………………
DBPH-50…………………………………..
100
0
1
0
100
1
Fluid Resistance, Volume Swell per ASTM D471
Reference Fuel B, 24 hrs @23°C
Reference Fuel C, 70 hrs at 23°C
Reference Fuel C, 168hrs at 60°C
FAM B Fuel, 168 hrs at 60°C
19
21
24
34
19
19
22
29
Properties obtained using 1.0 phr DBPH-50 (DHBP) (2,5-bis (tert-butylperoxy) 2,5 dimethyl hexane) on 1.91mm (0.075 inch thick) slabs; as molded 10
minutes at 171°C (340°F); post cured 4 hours at 200°C (392° F).
9
Mill Handling Performance
10
10
THERMAL STABILITY
11
FVMQ Degradation
•
Various degradation mechanisms occur in FVMQ on heating
–
–
–
–
•
F- promoted chain cleavage and depolymerisation
Oxidative cleavage of cross-links and side groups
Changes to filler / polymer interactions
…
CF3
Range of environments
– Dry heat
• 70h to 14 days @ 250-275 °C
• 700 hours @ 220 °C plus 70 hours @ 240 °C
–
–
–
–
–
*
Si
*
n
O
Me
Oil – Dexron VI used as an aggressive test oil, 7 days @ 150 °C
Compression set 3 & 7 days @ 200 °C
Fuel
Acid Gas Condensate
…
12
Analysis of Heat Age Conditions – 40 & 60 Duro
13
Effects of Temperature and Time
14
Tensile Strength MPa
• HF can form during heat
aging and this leads to
siloxane depolymerisation
• Addition of the correct
type and amount of an
acid acceptor can
significantly improve
thermal performance
• Can have conflicting
impacts on stability in
fluids and interactions
with other components
that need to be managed
9.0
8.0
7.0
6.0
AA 1
5.0
AA 2
4.0
AA 3
3.0
AA 4
2.0
1.0
0.0
0
5
10
Days at 250 °C
15
10.0
9.0
Tensile Strength MPa
Acid Acceptors
10.0
8.0
7.0
6.0
5.0
No AA 4
4.0
Level 1 AA4
3.0
Level 2 AA4
2.0
1.0
0.0
0
5
10
Days at 250 °C
15
15
• Choice of peroxide
influences the cured
network and thus the
thermal stability
• Also has an effect on oil
stability and compression
set
• Dialkyl or Diacyl
peroxides are preferred
for FVMQ cure and
thermal stability
10.0
8.0
Peroxide 1
6.0
Peroxide 2
Peroxide 3
4.0
Peroxide 4
2.0
0.0
0
5
10
Days at 250 °C
15
500
450
Elongation at Break %
Peroxide Choice
Tensile Strength MPa
12.0
400
350
300
Peroxide 1
250
Peroxide 2
200
Peroxide 3
150
Peroxide 4
100
50
0
0
5
10
Days at 250 °C
15
16
Redox Stabilisers
• FVMQ is typically stabilised with Cerium complexes
• The use of other redox active metals is known for stabilisation
of siloxanes against thermal decomposition
• Redox stabilisers thought to work by decomposition of
peroxides formed from O2 oxidation thus preventing branching
chain reactions, though much debate in literature
– R• + Mx+1+ → R+ + Mx+
– 4 Mx+ + O2 → 4 Mx+1+ + 2 O2-
• Oxygen diffusion and sample thickness are important
parameters in thermal stability
• In the absence of any added redox stabiliser will get rapid
decomposition at elevated temperature
17
Metal Oxide Redox Stabilisers
• A wide range of redox active
oxides are available
• These show variable
performance for stabilisation of
FVMQ
• The initial oxidation state,
particle size and shape all play
a role in obtaining good redox
stabilisation
• Variable interactions between
combinations of redox
stabilisers
Stabiliser
Number of samples
14d @ 250 °C
Hardness
50% Modulus, MPa
100% Modulus, MPa
Tensile Strength, MPa
Elongation, %
Redox 1
Δ Hardness (Shore A)
Δ Weight (%)
Δ 50% Modulus (%)
Δ 100% Modulus (%)
Δ Tensile Strength (%)
Δ Elongation (%)
700h @ 220 plus 70h @ 240 °C
Hardness
50% Modulus, MPa
100% Modulus, MPa
Tensile Strength, MPa
Elongation, %
Δ Hardness (Shore A)
Δ Weight (%)
Δ 50% Modulus (%)
Δ 100% Modulus (%)
Δ Tensile Strength (%)
Δ Elongation (%)
12
Redox 2 Significant Difference
12 Student's t-test
61.8
1.79
2.91
4.5
181
64
1.81
2.99
4
152
Yes
No
No
Yes
Yes
10.3
-4.80%
82%
65%
-50%
-50%
12.4
-5.10%
87%
74%
-55%
-58%
Yes
No
No
No
Yes
Yes
61
1.56
2.62
5
212
62.3
1.64
2.85
5.3
201
No
Yes
Yes
Yes
Yes
8.8
-3.90%
60%
51%
-44%
-41%
10.5
-3.30%
69%
64%
-40%
-45%
Yes
No
No
Yes
Yes
No
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Design-Expert® Software
Factor Coding: Coded
EB, 14d @ 250 C
Design Points
100
EB, 14d @ 250 C
2
1.00
270
0.50
• Design of Experiment
methodology used to
study redox stabiliser
interactions
• See variable
interactions depending
on stabilisers used
and properties studied
A: Redox 3
X1 = B: Redox 1
X2 = A: Redox 3
160
180
0.00
200
220
240
240
220
-0.50
-1.00
-1.00
-0.50
0.00
0.50
1.00
B: Redox 1
19
Expanded Boundaries - 60Shore FVMQ
12
Tensile MPa
10
8
6
Old FSR
4
New FSR
2
0
Initial
7d at 225
°C
3d @ 250
°C
3d @ 260
°C
3d @ 275
°C
Elongation at Break %
400
350
300
250
200
Old FSR
150
New FSR
100
50
• Graphs show
performance of a new
FVMQ material using
the technology
discussed vs. an
older FVMQ
• Available for
evaluation
• Further development
of new heat stabilised
bases ongoing
0
Initial
7d at 225
°C
3d @ 250
°C
3d @ 260
°C
3d @ 275
°C
20
21
18
Tensile Strength Mpa
Heat Aging
Benchmark Tensile
15
Hose Grade FKM
12
Higher Fluorine FKM
9
LS-2860
Dev FSR 1 - 60 Shore
6
Dev FSR 2 - 60 Shore
3
0
0
5
10
Days at 250 °C
15
• Standard Dow Corning FSR bases such as LS-2860 do not
heat age well at 250 °C
• Development FSR materials show considerable improved
heat stability with good tensile strength retention on aging
• FKM shows higher initial tensile but worse heat aging
performance in the case of the higher fluorine grade
21
VMQ – FVMQ ADHESION
22
Turbocharger Hoses
• Turbocharger hoses can be
multilayer construction using
fluoro-polymers and VMQ
• Similarity between FVMQ and
VMQ, chemical nature of
siloxane backbone, cure
chemistry, and cure speed
make an ideal combination
• Strong and durable adhesion
between the layers is required
• Dow Corning has a patented
solution for chemical adhesion
between MVQ and FVMQ
23
FVMQ-VMQ adhesion
• Adhesion is obtained via interfacial reaction
• FVMQ / VMQ combinations with improved initial and
aged adhesion are available
6
180° Peel Adhesion kN/m
5
4
Hose grade FKM/VMQ
Higher Fluorine
FKM/VMQ
Current FSR/VMQ
3
2
Development FSR/VMQ
1
FSR breaks
0
0
5
10
Days at 225 °C
15
24
Summary
• The boundaries of FVMQ performance have been extended
across a range of properties
–
–
–
–
Resilience
Compression Set
Thermal Stability
Fluid Stability
• Oil, Acid Gas Condensate…
– Fatigue Life
– Adhesion to VMQ
very
cold
very
hot

  
aggressive
fluids
• FVMQ ready to help address your needs
We have improved
FVMQ here
25
Thank You!
The information provided in this presentation does not constitute a contractual commitment by Dow Corning. While Dow Corning
does its best to assure that information contained in this presentation is accurate and fully up-to-date, Dow Corning does not
guarantee or warranty the accuracy or completeness of information provided in this presentation. Dow Corning reserves the right
to make improvements, corrections and/or changes to this presentation in the future.
26