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Fluorosilicone rubber for sealing higher temperature transmission fluids.

Regulatory requirements and key market drivers are shaping design trends for smarter, safer, quieter and more energy-efficient vehicle technologies with steadily less environmental impact. Among vehicle powertrain enhancements to increase fuel economy as well as to enhance vehicle performance and quality, significant advances have been made in transmission design and automatic transmission fluid (ATF) technology.

Fluorosilicone elastomers, such as Silastic brand fluorosilicone rubber from Dow Corning, were used for years in sealing applications on earlier-generation transmission systems. Their selection was primarily due to their ATF resistance, their ability to maintain sealing performance over a broad temperature range, and specifically their ability to seal at very low temperatures. The fluorosilicone rubber material family has a glass transition temperature of around -68[degrees]C to help maintain sealing effectiveness in extreme cold better than many organic elastomers that have much higher glass transition temperatures.

However, the combination of advancements in ATF fluids and increasing operating temperatures has resulted in traditional fluorosilicone materials experiencing performance and durability issues in these new environments. These issues typically have arisen in the material's ability to adequately seal over the service life of the vehicle and in long-term degradation, as measured by retention of mechanical properties after long-term ATF exposure. As a result, fluoroelastomer materials such as fluorocarbon rubber (FKM) have found increased use for sealing newer-generation ATFs and transmissions operating at higher temperatures. Even so, FKMs still have performance limitations when it comes to low-temperature sealing performance down to -40[degrees]C, and meeting lower modulus requirements necessary for many of the sealing applications.

Recent advancements in fluorosilicone technology now offer solutions that can meet both long-term mechanical property retention requirements and effective sealability in these new environments. This article details the process and validation testing that Dow Corning conducted to develop next-generation fluorosilicone rubber (FSR) for effective sealing of current ATFs used in advanced transmission designs. With typical fluid operating temperatures as high as 150[degrees]C, the newest FSR elastomers can maintain key performance properties such as tensile strength and elongation, and provide certain advantages over FKM sealing materials due to their lower-temperature performance and lower modulus.

Changes in transmission design and ATF technology

Conventional three- or four-speed automatic transmissions are being replaced with multiple-speed stepped transmissions, dual-clutch transmissions (DCT) and continuously variable transmissions (CVT). New torque converter clutch technologies, more stable friction materials and lower fluid viscosities to reduce shudder are among other refinements being introduced. While most automatic transmission fluids have changed incrementally over the years, the newer transmission designs required substantially upgraded formulations. Today's typical OEM factory-fill ATFs are designed to provide improved performance in terms of friction durability, viscosity stability, aeration and foam control, and oxidation resistance in transmission designs that operate at much higher temperatures.

Dow Coming's FSR development process involved formulating fluorosilicone rubber compound to provide an effective sealing solution for these widely used automatic transmission fluids:

* Mercon LV ATF for most vehicles from Ford Motor

* ATF+4 ATF for Dodge, Jeep and Chrysler

* Dexron VI ATF used on General Motors vehicles

* Pentosin ATF1 used on VW and Audi vehicles (Mercon is a registered trademark of Ford Motor; ATF+4 is a trademark of FCAUS LLC; Dexron is a registered trademark and brand of General Motors LLC; and Pentosin is a trade name of Deutsche Pentosin-Werke.)

Innovating with fluorosilicone rubber technology

Dow Corning is a recognized global leader in specialty fluorosilicone engineered elastomers, with the market's broadest range of fluorosilicone bases, custom compounds and fluoro-liquid silicone rubbers. Yet, with key advancements in vehicle design and systems technology, the performance capabilities of fluorosilicone rubber must continue to increase to keep pace with today's challenging mobility needs.

Fluorosilicone rubber is formulated from fluorosilicone polymers that contain a (-Si-O-) repeating group on the polymer backbone. One unique difference, compared to their dimethylsiloxane (silicone) counterparts, is the incorporation of a fluorine component attached to the base polymer backbone. Fluorosilicone polymers replace one methyl side group on each silicon molecule with a trifluoropropyl side group (figure 1).

The resulting polymer retains dimethylsilicone's durability in very hot and very cold temperatures, while adding high resistance to non-polar solvents and aggressive fluids. A vinyl side group allows the polymer to be crosslinked. As such, fluorosilicone rubber is commonly referred to as FVMQ: Silicone rubber having fluorine, vinyl and methyl substitute groups on the polymer chain per ASTM Standard D1418-10a Standard Practice for Rubber and Rubber Latices--Nomenclature.

During its FSR technology development process to meet current transmission sealing needs, Dow Corning utilized its historical knowledge and in-depth expertise regarding fluorosilicone bases to identify the necessary polymer and base technology, which has improved resistance to newer, more aggressive ATFs. Selecting the right base technology along with identifying and incorporating the necessary additives and modifiers helped to unlock the solution needed.

Fluorosilicone (FSR) vs. fluorocarbon (FKM)

While FKM rubber has long held an advantage over fluorosilicone in terms of having higher-temperature capabilities, Dow Corning is steadily closing the gap with new developments. In one recent example, Dow Coming's new FSR compounding technology delivered fluorosilicones for turbocharger hose liners that are capable of withstanding temperatures up to 250[degrees]C, while maintaining excellent peel strength and adhesion to methylvinylsiloxane (VMQ) hose coverings. The compounding technology also offers high-temperature stability, compression set resistance and high resilience for applications such as engine seals, gaskets, diaphragms and valves.

Developing a more effective sealing solution for today's advanced transmission designs and ATF fluid technologies can add to several notable advantages that fluorosilicone already has over FKM materials:

* Better low-temperature performance, with flexibility maintained at temperatures down to -68[degrees]C. This may prove advantageous for preventing possible leakage with lower-viscosity ATFs under extreme cold conditions.

* Easier processing and faster curing to enhance seal fabrication productivity and gain potential cost savings.

* Softer materials with lower durometer and modulus to enhance sealing effectiveness and durability.

* Lower density for improved weight savings and reduced material usage.

Making the case for change

Current OEM factory-fill ATFs are specifically formulated for advanced transmission designs that require sealing elastomers to withstand much higher operating temperatures. Previous-generation transmission fluids, such as Dexron III ATF, were designed for handling limited gear shifts and lower operating temperatures. Development of such fluids did not consider the need to withstand temperatures above 125[degrees]C. In contrast, current, more viscosity-stable ATFs such as Dexron VI are being specified for multiple-speed transmissions operating at higher temperatures of 125[degrees]C and beyond.

As these newer ATFs were being developed to optimize the performance of advanced transmission designs, traditional FKM sealing technologies required reformulation to provide better property retention when exposed to the different ATF chemistries and increased operating temperatures. At this time, fluorosilicone compounds were only qualified for sealing traditional fluids at lower temperatures.

As a first step, a team of Dow Corning scientists compared the effects of both Dexron III and Dexron VI on established generations (Gen 1, Gen 2) of FVMQ (fluorosilicone, FSR) elastomers. This established a baseline for beginning the development of new fluorosilicone rubber options to handle the updated ATF formulations and higher transmission operating temperatures,

Initial tests conducted with FSR exposure of six weeks (1,008 hours) at 125[degrees]C showed Gen 2 outperforming Gen 1, although changes in tensile strength and elongation were still significant. The negative effects on FSR samples were more severe with Dexron VI exposure. Subsequent tests with Dexron VI ATF at 150[degrees]C identified higher losses after FSR exposure of just two weeks (336 hours), and property degradation increased with four weeks (672 hours) of exposure. Older-generation FSRs were limited in their ability to provide for long-term sealing of the reformulated ATFs used in current transmission designs at higher operating temperatures (table 1).

These findings confirmed the need to develop a new-generation FSR that would maintain its key performance properties at acceptable levels with long-term exposure to reformulated ATFs operating at higher transmission temperatures (table 1).

* Dexron III was less aggressive than Dexron VI.

* Gen 2 FSR generally outperformed Gen 1 FSR, regardless of fluid temperature.

* Aging exposure to Dexron VI at 150[degrees]C caused unacceptable losses in both tensile strength and elongation, as well as excessive gains in hardness and modulus.

Evaluating different FVMQ rubber base technologies

Utilizing a one- and two-week screening process, the project team performed benchmark testing of different FVMQ rubber base technologies to understand the impact on performance properties after exposure to Dexron VI ATF at 150[degrees]C. All of the selected bases showed significant reduction in performance properties after just two weeks (336 hours) of exposure. Yet, some bases performed better than others. An analysis of how each base was designed and what impacts ATF exposure had on material performance led to a better understanding of how to design and develop an optimized rubber base for ATF resistance. The exposure testing of different fluorosilicone rubber bases led to some preliminary observations using the data in table 2:

* Bases 1, 2 and 3 tend to harden, while bases 4 and 5 soften.

* Bases 3 and 5 exhibit the lowest loss of tensile strength.

* Bases 4 and 5 have the least change in elongation and 100% modulus.

Starting with the correct type of FVMQ base is critical for meeting specified property-retention and sealing-performance requirements when exposed to current ATFs at high operating temperatures. From its screening of different FSR bases, the Dow Corning team was able to identify the right base technology needed to initiate development of a workable Gen 3 fluorosilicone rubber solution.

Optimizing selected FSR compounds

With potential ATF resistance improvements gained through rubber base modifications and proper compounding, a limited two-week exposure testing proved to be insufficient to determine differences in projected compound performance and sealing service life. Six weeks (1,008 hours) of exposure testing was carried out to identify any major differences in compound options.

DoE (design of experiment) methodology was employed by the Dow Corning team to determine compound design factors that can significantly impact mechanical property retention for fluorosilicone rubber exposed to newer-generation automatic transmission fluids. This involved executing a 17run, central-composite, three-factor response surface model design. Compound property retention was evaluated after two-week and six-week ATF exposures. Various DoE test runs are shown to highlight the range of properties achieved within the design space of the DoE. The data highlight the range of properties and retention performance possible based on the correct selection of additives, modifiers and fluorosilicone bases. Proper selection of all three of these variables is necessary to achieve optimum retention performance (table 3)

* Of the 17 runs, the best, worst and two in between were selected for comparison.

* After just two weeks of exposure, the differences between compounds were minimal; the real differences appeared after six weeks (1,008 hours) of exposure.

The comparative data indicated which compound technology worked best and aided FVMQ compound optimization to help achieve acceptable property retention with long-term exposure to ATFs at 150[degrees]C.

Gen 3 performance versus previous FSR options

Based on the results seen in Dow Coming's DoE testing, a new Gen 3 fluorosilicone compound was formulated to provide long-term property retention when exposed to today's most widely used ATFs: Mercon LV, ATF+4, Dexron VI and Pentosin ATF1. To illustrate the significant gains made, the performance of the optimized Gen 3 FSR formulation was compared with that of previous Gen 2 and Gen 1 fluorosilicone rubber compounds. A side-by-side comparison of exposure testing results with the same ATFs at 150[degrees]C clearly shows far better property retention for the newly developed FSR option in all ATFs and all exposure times. Referring to table 4, some conclusions include:

* Gen 3 FSR maintains good property retention, regardless of exposure testing duration. Initial losses seen after two weeks (336 hours) do not markedly accelerate as exposure time increases.

* Gen 1 FSR showed unacceptable losses in tensile strength and elongation after only two weeks (336 hours) of ATF exposure, and these losses escalated after four weeks (672 hours) of testing.

* Gen 2 FSR generally fared better than Gen 1 FSR in ATF exposure testing at 150[degrees]C, even though its elongation loss and modulus gain were comparatively worse after only two weeks (336 hours). Yet, after four weeks (672 hours) of exposure, the Gen 2 FSR material showed lower losses than Gen 1 FSR in both tensile strength and elongation.

* Gen 2 and Gen 1 FSR data at only four weeks, even when exposed to the less-aggressive fluids, show retention properties at or over generally allowed limits required for six-week exposure.

Validating Gen 3 FSR performance in various ATFs

The Gen 3 FSR formulation was further optimized to withstand long-term fluid exposure at 150[degrees]C, and property retention was validated with 1,008 hours (six weeks) of testing; such extended testing was not possible with Gen 1 and Gen 2 materials due to severe degradation. As shown in table 5, the new FSR material demonstrates excellent property retention in all of the most common ATFs used in today's advanced transmission designs. This indicates good potential for meeting OEM material specifications and performance requirements for transmission sealing; these typically target tensile strength and elongation losses of no more than 50% each. Table 5 demonstrates the following:

* The new Gen 3 FSR formulation offers low durometer hardness, along with good mechanical strength, high elongation and low 100% modulus.

* Regardless of the specific type of ATF, both tensile strength and elongation are maintained at acceptable levels with minimized softening, modulus gain or volume swell.

* Fluids such as Pentosin and Dexron VI are more aggressive than ATF+4 and Mercon LV as far as impacting property retention, yet the optimized Gen 3 fluorosilicone formulation is suited to work well with all of these transmission fluids.

Gen 3 FSR sealing CSR tests

CSR, or compression stress relaxation, is useful for understanding the ability of a material to maintain adequate sealing force over an extended period of time and exposure to different fluids. CSR tests can measure the stress decay of an elastomer under constant compressive strain, and this decay can provide an indication of the material service life. The Dow Corning team conducted CSR testing on the updated Gen 3 FSR material at 125[degrees]C and 150[degrees]C in Dexron VI, and at 150[degrees]C in Mercon LV. The test data showed reasonable retained sealing force (RSF) throughout 1,008 hours (six weeks) of testing at the specified temperatures for both fluids. As expected, fluid exposure at 125[degrees]C had less impact than exposure at the higher temperature of 150[degrees]C (table 6).

Impact on ATF foam control

When designing materials that will be exposed to automatic transmission fluids, the potential impact of a reformulated material on the foaming characteristics of the ATF must be evaluated. Excessive fluid foaming can negatively affect transmission lubrication, increase component friction and cause premature transmission failure. Typical ATFs are formulated with antifoam additives, and the additives in rubber compounds should not hinder transmission fluid foam control.

Following exposure testing of the new Gen 3 FSR material in four current ATFs, the potential effect of the Gen 3 FSR on ATF foam control characteristics was examined. Testing was performed per ASTM D892 procedures, with a fluid temperature of 24[degrees]C. The foam control capability of unaged Dexron VI ATF was compared with aged Dexron VI exposed to Gen 3 fluorosilicone material. As shown in figure 2, the aged ATF met specified foam control requirements of less than 50 mm of foam height after blowing for five minutes, and 0 mm of foam height within 10 minutes after blowing has stopped.

Meeting challenges for the road ahead

With deep industry experience, materials creativity and problem-solving innovation, Dow Corning has successfully developed next-generation fluorosilicone elastomers to meet the challenges of increased operating temperatures for an expanding range of vehicle applications. New formulations for handling higher temperatures previously have been introduced to meet application needs for turbocharger hose liner applications, engine seals and gaskets, diaphragms and flexible valves.

Now, in the latest example of upgrading its fluoroelastomer capabilities, Dow Corning has developed, tested and optimized fluorosilicone rubber compounds to provide effective, long-term sealing integrity with excellent property retention in current and emerging transmission designs. The new technology was especially developed to withstand exposure to aggressive synthetic transmission fluids at temperatures up to 150[degrees]C, meeting the high-temperature capabilities of FKM rubber, while also offering better low-temperature performance, low modulus and lower hardness options.

Ongoing work aims to optimize fluorosilicone rubber for the best combination of fluid resistance, high-temperature performance and cost-effective processing. At Dow Corning, fluorosilicone rubber (FVMQ) development continues to evolve.

Caption: Figure 1--structure of dimethylsilicone and fluorosilicone rubber

Caption: Figure 2--effect of Gen 3 FSR on foam control characteristics of Dexron VI ATF (tested to ASTM D892)
Table 1 - baseline performance data for Gen 1 and
Gen 2 FSRs in Dexron III and Dexron VI ATFs

ATF            FSR        Durometer          Tensile    Elongation (1)
                      hardness (a),    strength (1),
                        durometer A              MPa

FSR exposure to ATF for 1,008 hours (six weeks) at 125[degrees]C

Dexron III   Gen 1               56             7.30               250
             Gen 2               68             7.36               134
Dexron VI    Gen 1               54             6.18               264
             Gen 2               65             6.04               138

FSR exposure to ATF for 336 hours (two weeks) at 150[degrees]C

Dexron VI    Gen 1               52             4.52               236
             Gen 2               65             5.19               132

FSR exposure to ATF for 672 hours (four weeks) at 150 [degrees]C

Dexron VI    Gen 1               54             1.99               110
             Gen 2               66             4.20               113

ATF            FSR            100%        [DELTA]      [DELTA]
                      modulus (1),      durometer      tensile
                               MPa      hardness,    strength,
                                      pts. change     % change

FSR exposure to ATF for 1,008 hours (six weeks) at 125 [degrees]C

Dexron III   Gen 1            2.66             +2        -33.5
             Gen 2            5.63            +13         -7.8
Dexron VI    Gen 1            2.38              0        -43.7
             Gen 2            4.56            +10        -24.3

FSR exposure to ATF for 336 hours (two weeks) at 150 [degrees]C

Dexron VI    Gen 1            2.14             -2        -58.8
             Gen 2            4.03            +10        -35.0

FSR exposure to ATF for 672 hours (four weeks) at 150 [degrees]C

Dexron VI    Gen 1            1.88              0        -81.9
             Gen 2            3.88            +11        -47.4

ATF            FSR        [DELTA]     [DELTA]        Volume
                      elongation,        100%    swell (1),
                         % change    modulus,             %
                                     % change

FSR exposure to ATF for 1,008 hours (six weeks) at 125 [degrees]C

Dexron III   Gen 1          -47.4       +30.4           8.4
             Gen 2          -52.8       +98.9           1.1
Dexron VI    Gen 1          -44.4       +16.7           8.1
             Gen 2          -51.4       +61.1           1.9

FSR exposure to ATF for 336 hours (two weeks) at 150 [degrees]C

Dexron VI    Gen 1          -50.3        +4.9           8.8
             Gen 2          -53.5       +42.4           2.2

FSR exposure to ATF for 672 hours (four weeks) at 150 [degrees]C

Dexron VI    Gen 1          -76.8        -7.8           5.8
             Gen 2          -60.2       +37.1           1.5

(1) ATF exposure and volume swell tested to ASTM D471

Table 2 - comparative data for evaluating different
types of FVMQ rubber bases

Properties, A changes

FVMQ base rubber evaluation profiles

                                               Base    Base    Base
                                                 #1      #2      #3

Control data: Base properties as supplied

Durometer hardness (2), durometer A              60      57      48
Tensile strength (5 bars) (3), MPa             9.61    8.51    8.41
Elongation (5 bars) (3), %                      347     440     392
100% modulus (5 bars) (3), MPa                 2.31    1.95    1.57

Properties after exposure to Dexron VI ATF
for 168 hours (one week) at 150 [degrees]C

Durometer hardness (1), durometer A              64      65      56
[DELTA] durometer hardness change, points        +4      +8      +8
Tensile strength (1), MPa                      6.62    5.45    6.86
[DELTA] tensile strength, % change              -31     -36     -18
Elongation (1), %                               182     214     240
[DELTA] elongation, % change                    -48     -51     -39
100% modulus (1), MPa                           3.3    2.79    2.47
[DELTA] 100% modulus, % change                  +43     +43     +57
Average volume swell (1), %                     0.8     1.3     1.5

Properties after exposure to Dexron VI ATF
for 336 hours (two weeks) at 150 [degrees]C

Durometer hardness (1), durometer A              64      65      55
[DELTA] durometer hardness change, points        +4      +8      +7
Tensile strength (1), MPa                      5.55    4.46    5.63
[DELTA] tensile strength, % change              -42     -48     -33
Elongation (1), %                               159     180     221
[DELTA] elongation, % change                    -54     -59     -44
100% modulus (1), MPa                          3.41    2.80    2.43
[DELTA] 100% modulus, % change                  +48     +44     +55
Average volume swell (1), %                     0.4     1.1     1.1

Properties, A changes

FVMQ base rubber evaluation profiles

                                               Base    Base
                                                 #4      #5

Control data: Base properties as supplied

Durometer hardness (2), durometer A              55      41
Tensile strength (5 bars) (3), MPa            11.03    8.97
Elongation (5 bars) (3), %                      360     343
100% modulus (5 bars) (3), MPa                 2.06    1.20

Properties after exposure to Dexron VI ATF
for 168 hours (one week) at 150 [degrees]C

Durometer hardness (1), durometer A              54      37
[DELTA] durometer hardness change, points        -1      -4
Tensile strength (1), MPa                      6.57    6.51
[DELTA] tensile strength, % change              -40     -27
Elongation (1), %                               266     291
[DELTA] elongation, % change                    -26     -15
100% modulus (1), MPa                          2.10    1.26
[DELTA] 100% modulus, % change                   +2      +5
Average volume swell (1), %                     1.8     1.6

Properties after exposure to Dexron VI ATF
for 336 hours (two weeks) at 150 [degrees]C

Durometer hardness (1), durometer A              50      37
[DELTA] durometer hardness change, points        -5      -4
Tensile strength (1), MPa                      4.81    5.21
[DELTA] tensile strength, % change              -56     -42
Elongation (1), %                               243     278
[DELTA] elongation, % change                    -33     -19
100% modulus (1), MPa                          1.83    1.17
[DELTA] 100% modulus, % change                  -11      -3
Average volume swell (1), %                     1.4     1.3

(1) ATF exposure and volume swell tested to ASTM D471

(2) Durometer tested per ASTM D2240

(3) Tensile strength, elongation and modulus tested to ASTM D412

Table 3 - comparative data for FVMQ compound
optimization

Properties, A changes

FVMQ compound evaluation factors

                                              Run #13    Run #2

Control data: Compound properties

Durometer hardness (2), durometer A                39        40
Tensile strength (3), MPa                        8.84      9.21
Elongation (3), %                                 360       353
100% modulus (3), MPa                            1.11      1.17

Properties after exposure to Dexron VI
ATF for 336 hours (two weeks) at 150 [degrees]C

Durometer hardness (1), durometer A                34        34
[DELTA] durometer hardness, points change          -5        -6
Tensile strength (1), MPa                        4.76      5.34
[DELTA] tensile strength, % change              -46.2     -42.0
Elongation (1), %                                 293       297
[DELTA] elongation, % change                    -18.6     -15.9
100% modulus (1), MPa                            0.96      1.03
[DELTA] 100% modulus, % change                  -13.5     -12.0
Volume swell (1), %                               2.2       2.3

Properties after exposure to Dexron VI
ATF for  (1),008 hours (six weeks) at 150 [degrees]C

Durometer hardness (1), durometer A                32        36
[DELTA] durometer hardness, points change          -7        -4
Tensile strength (1), MPa                        1.13      3.28
[DELTA] tensile strength, % change              -87.2     -64.4
Elongation (1), %                                 155       243
[DELTA] elongation, % change                    -56.9     -31.2
100% modulus (1), MPa                            0.82      1.01
[DELTA] 100% modulus, % change                  -26.1     -13.7
Volume swell (1), %                              -5.0      -0.3

Properties, A changes

FVMQ compound evaluation factors

                                              Run #9    Run #7

Control data: Compound properties

Durometer hardness (2), durometer A               40        40
Tensile strength (3), MPa                       8.62      7.99
Elongation (3), %                                361       337
100% modulus (3), MPa                           1.13      1.35

Properties after exposure to Dexron VI
ATF for 336 hours (two weeks) at 150 [degrees]C

Durometer hardness (1), durometer A               35        37
[DELTA] durometer hardness, points change         -5        -3
Tensile strength (1), MPa                       5.63      5.32
[DELTA] tensile strength, % change             -34.7     -33.4
Elongation (1), %                                294       291
[DELTA] elongation, % change                   -18.6     -13.6
100% modulus (1), MPa                           1.14      1.14
[DELTA] 100% modulus, % change                  +0.9     -15.6
Volume swell (1), %                              2.6       2.7

Properties after exposure to Dexron VI
ATF for  (1),008 hours (six weeks) at 150 [degrees]C

Durometer hardness (1), durometer A               36        40
[DELTA] durometer hardness, points change         -4         0
Tensile strength (1), MPa                       3.31      4.03
[DELTA] tensile strength, % change             -61.6     -49.6
Elongation (1), %                                235       247
[DELTA] elongation, % change                   -34.9     -26.7
100% modulus (1), MPa                           1.14      1.21
[DELTA] 100% modulus, % change                  +0.9     -10.4
Volume swell (1), %                              0.3       0.4

(1) ATF exposure and volume swell tested to ASTM D471

(2) Durometer tested per ASTM D2240

(3) Tensile strength, elongation and modulus tested to ASTM D412

Table 4 - comparative test data for Gen 1, Gen 2 and
Gen 3 FSRs exposed to ATFs at 150[degrees]C

                                         Gen 1 FSR in ATFs

Properties, A changes           Mercon    ATF+4    Dexron    Pentosin
                                    LV                 VI        ATF1

Control data: FSR compound properties

Durometer hardness (2),
durometer A                         54       54        54          54
Tensile strength3, MPa              11       11        11          11
Elongation (3), %                  475      475       475         475
100% modulus (3), MPa             2.04     2.04      2.04        2.04

Properties after exposure to ATF for 336
hours (two weeks) at 150 [degrees]C

Durometer hardness (1),
  durometer A                       55       48        52          56
[DELTA] durometer hardness,
points change                       +1       -6        -2          +2
Tensile strength (1), MPa         8.23     6.37      4.52        4.64
[DELTA] tensile strength, %
change                             -25    -41.9     -58.8       -57.7
Elongation (1), %                  315      345       236         213
[DELTA] elongation, % change     -33.7    -27.4     -50.3       -55.2
100% modulus (1), MPa             2.37     1.79      2.14        2.25
[DELTA] 100% modulus, %
change                           +16.2    -12.3      +4.9       +10.3
Volume swell (1), %                7.9     13.4       8.8         7.2

Properties after exposure to ATF for 672
hours (four weeks) at 150 [degrees]C

Durometer hardness (1),
durometer A                       56.5       53        54          56
[DELTA] durometer hardness,
points change                     +2.5       -1         0          +2
Tensile strength (1), MPa         4.91     2.50      1.99        2.31
[DELTA] tensile strength, %
change                           -55.2    -77.2     -81.9       -78.9
Elongation (1), %                  247      200       110         144
[DELTA] elongation, % change     -48.0    -57.9     -76.8       -69.7
100% modulus (1), MPa             2.13     1.78      1.88        1.91
[DELTA] 100% modulus, %
change                            +4.4    -12.7      -7.8        -6.4
Volume swell (1), %                7.3      5.7       5.8         5.5

                                         Gen 2 FSR in ATFs

Properties, A changes           Mercon    ATF+4    Dexron    Pentosin
                                    LV                 VI        ATF1

Control data: FSR compound properties

Durometer hardness (2),
durometer A                         55       55        55          55
Tensile strength3, MPa               8        8         8           8
Elongation (3), %                  284      284       284         284
100% modulus (3), MPa             2.83     2.83      2.83        2.83

Properties after exposure to ATF for 336
hours (two weeks) at 150 [degrees]C

Durometer hardness (1),
  durometer A                       67       64        65          68
[DELTA] durometer hardness,
points change                      +12       +9       +10         +13
Tensile strength (1), MPa         7.98     7.86      5.19        5.06
[DELTA] tensile strength, %
change                               0     -1.5       -35       -36.6
Elongation (1), %                  168      177       132         111
[DELTA] elongation, % change     -40.8    -37.7     -53.5       -60.9
100% modulus (1), MPa             4.92     4.56      4.03        4.67
[DELTA] 100% modulus, %
change                           +73.9    +61.1     +42.4         +65
Volume swell (1), %                1.3      2.5       2.3         1.1

Properties after exposure to ATF for 672
hours (four weeks) at 150 [degrees]C

Durometer hardness (1),
durometer A                         67       62        66          68
[DELTA] durometer hardness,
points change                      +12       +7       +11         +13
Tensile strength (1), MPa         7.21     6.39      4.20        4.04
[DELTA] tensile strength, %
change                           -9.60    -19.9     -47.4       -49.4
Elongation (1), %                  149      176       113         104
[DELTA] elongation, % change     -47.5    -38.0     -60.2       -63.4
100% modulus (1), MPa             5.03     3.92      3.88        3.97
[DELTA] 100% modulus, %
change                           +77.7    +38.5     +37.1       +40.3
Volume swell (1), %                1.0      3.0       1.5         0.6

                                Gen 3 FSR in ATFs

Properties, A changes           Mercon    ATF+4    Dexron    Pentosin
                                    LV                 VI        ATF1

Control data: FSR compound properties

Durometer hardness (2),
durometer A                         41       41        41          41
Tensile strength3, MPa             7.6      7.6       7.6         7.6
Elongation (3), %                  328      328       328         328
100% modulus (3), MPa             1.65     1.65      1.65        1.65

Properties after exposure to ATF for 336
hours (two weeks) at 150 [degrees]C

Durometer hardness (1),
  durometer A                       43       40        41          42
[DELTA] durometer hardness,
points change                       +2       -1         0          +1
Tensile strength (1), MPa         6.69     5.29      5.62        5.24
[DELTA] tensile strength, %
change                           -12.0    -30.4     -26.1       -31.1
Elongation (1), %                  269      240       269         245
[DELTA] elongation, % change     -18.0    -26.8     -18.0       -25.3
100% modulus (1), MPa              1.9     1.75       1.7         1.8
[DELTA] 100% modulus, %
change                           +15.2     +6.1      +3.0        +9.1
Volume swell (1), %                3.7      5.9       4.3         3.2

Properties after exposure to ATF for 672
hours (four weeks) at 150 [degrees]C

Durometer hardness (1),
durometer A                         43     40.5        40          42
[DELTA] durometer hardness,
points change                       +2     -0.5        -1          +1
Tensile strength (1), MPa         6.04     5.89      4.93        4.96
[DELTA] tensile strength, %
change                           -20.5    -14.6     -35.1       -34.7
Elongation (1), %                  260      289       267         254
[DELTA] elongation, % change     -20.7    -14.0     -18.6       -22.6
100% modulus (1), MPa             1.86     1.48      1.59        1.73
[DELTA] 100% modulus, %
change                           +12.7     -7.5      -3.6        +4.8
Volume swell (1), %                4.1      6.6       4.5         3.4

(1) ATF exposure and volume swell tested to ASTM D471

(2) Durometer tested per ASTM D2240

(3) Tensile strength, elongation and modulus tested to ASTM D412

Table 5 - long-term Gen 3 FSR performance
testing in various ATFs at 150[degrees]C

Automatic transmission fluid (ATF)

Properties, A changes           Mercon    ATF+4    Dexron   Pentosin
                                    LV                VI       ATF1

Control data: Gen 3 FSR compound
properties for testing (six weeks)

Durometer hardness (2),
durometer A                       43.2     44.9     44.9       44.9
Tensile strength (3), MPa         7.83      6.9      6.9        6.9
Elongation (3), %                  367      336      336        336
100% modulus (3), MPa             1.45      1.6      1.6        1.6

Properties after exposure to ATF for
 (1),008 hours (six weeks) at 150 [degrees]C

Durometer hardness (1),
durometer A                         43       39     42.5         43
[DELTA] durometer hardness,
points change                     -0.2     -5.9     -2.4       -1.9
Tensile strength (1), MPa         5.76     5.34     4.25       4.16
[DELTA] tensile strength, %
change                           -26.4    -22.6    -38.4      -39.7
Elongation (1), %                  285      294      252        251
[DELTA] elongation, % change     -22.2    -12.5    -25.0      -25.3
100% modulus (1), MPa             1.68     1.41     1.47       1.45
[DELTA] 100% modulus, %
change                           +16.0    -11.9     -8.1       -9.4
Volume swell (1), %                3.3      7.4      3.4        2.7

(1) ATF exposure and volume swell tested to ASTM D471

(2) Durometer tested per ASTM D2240

(3) Tensile strength, elongation and modulus tested to ASTM D412

Table 6 - compression stress relaxation
(CSR) data (tested to SAE J2979)

                                    Gen 3 FSR exposure to:

CSR aging                       Dexron VI            Dexron VI
measurements                at 125 [degrees]C    at 150 [degrees]C

Sealing force
  (initial), N                     66.8                 59.0
Sealing force
  (after 336 hours), N             36.0                 20.1
Sealing force
  retention, %                     53.9                 34.1
Sealing force
  (after 672 hours), N             29.6                 12.8
Sealing force
  retention, %                     44.3                 21.6
Sealing force
  (after 1,008 hours), N           28.3                 9.2
Sealing force
  retention, %                     42.3                 15.6

                                Gen 3 FSR
                               exposure to:

CSR aging                       Mercon LV
measurements                at 150 [degrees]C

Sealing force
  (initial), N                     67.0
Sealing force
  (after 336 hours), N             31.8
Sealing force
  retention, %                     47.5
Sealing force
  (after 672 hours), N            21.88
Sealing force
  retention, %                     32.7
Sealing force
  (after 1,008 hours), N           14.1
Sealing force
  retention, %                     21.0
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Author:Armstrong, Dave, II; Griffith, Phil; Gross, Craig; Tonge, Lauren
Publication:Rubber World
Date:Apr 1, 2017
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