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Comparison of Ethylene Propylene and Saturated Nitrile Compounds for use in the Refrigerant HFO 1234yf

Presented by Don Bowman

Composite Sealing Systems Division (CSS) San Diego, CA

September 20, 20011

Basic Questions

· · · · Why this testing was initiated? What testing was performed? How was the testing executed? How does this apply to air conditioning systems?

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Outline

· · · · · Selection of a Seal Material by the Lab Permeation Methods Testing Conditions Results Application

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Selection of Seal Material

· As with most sealing systems, the material choice is a compromise between the various sealing characteristics of the material.

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Typical Laboratory Testing

· Rubber Physical Properties on Dumbbells and O-Rings ­

· · · · Hardness Tensile Elongation Modulus

· Compression Set

· Buttons, plies, o-rings, parts

Typical Laboratory Testing

· Rubber and Fluid Compatibility

Test Tube, Beaker, Bomb

· Physicals · Volume change

Laboratory

· Material properties at elevated or sub-ambient temperature · Others

Bond, Corrosion, Small amount of test fluid Various PAG oils

· Low Temperature Material Properties

Brittleness, Tg, TR10, Gehman

Low Temperature Testing

· Temperature Retraction TR10 or Tg ­

· CR · EPDM #1 · HNBR #2 -31C (-35F) -51C (-60F) -17C (+2F)

· Effects of fluid

· Volume swell improves low temperature · Increases permeation and aging

Must Seal Two (2) Types of Leakage

Flange

Permeation Seal Tangential

Flange

· Tangential: leakage between the seal and the mating hardware

· Permeation: leakage through the rubber material

Permeation

· Developed fixture for diaphragm

· Increased rate · Compared materials

· Multiple parts

· Increased rate

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R-134a

Permeation rate (grams/day) 10 9 8 7 6 5 4 3 2

1

0 V720 FKM N1206HNBR 175F N1922HNBR 150F N674 NBR Y1038ECO E1197EPDM RT E692 EPDM C873 CR

225F 200F

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Comparison for R-134a

Property Polymer C873-70 CR E1197-80 EPDM N1173-75 HNBR N1206-70 HNBR

Permeation

Compatibility R-134a PAG oil/ R-134a Mineral Oil Compression set

A

A A C C

AAAD B+ -55 +150

C

C C B B -30 +150

D

C C B B-40 +150

Temp Low

Temp High

-40 +125

Rating scale from A to F.

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Market Trends for Seal Materials

· Ethylene Propylene EPDM · Saturated Nitrile HNBR · Chloroprene CR (limited)

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HFO 1234yf Testing

· · · ·

· · · ·

EPDM #1- Black 75 duro ethylene propylene material EPDM #2 - Black 70 duro ethylene propylene material EPDM #3 - Black 70 duro ethylene propylene material EPDM #4 - Black 75 duro ethylene propylene material

HNBR #1 ­ Black 70 duro saturated nitrile material HNBR #2 - Black 80 duro saturated nitrile material HNBR #3 ­ Red color 70 duro saturated nitrile material HNBR #4 - Red color 70 duro saturated nitrile

Permeation HFO 1234yf

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HFO 1234yf Testing Cycle

· · · · Filling fixtures at -60C Weight equilibration at 75C (158F) Weight equilibration at room temperature Weight equilibration at 100C (212F) (Selected) · Weight equilibration at room temperature

Permeation

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Permeation

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Permeation

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Permeation

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Permeation

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Conclusions

· Permeation rates are only one factor in the choice of a seal material. All design parameters must be evaluated. · Permeation rates increase dramatically with increasing temperature. This, in part, could be due to the increased vapor pressure of the system. · The high temperature results display variation again probably due to the high pressure.

Conclusions - continued

· The HNBR compounds as a polymer family have a lower permeation rate of pure HFO 1234yf than the EPDM polymer family. · The addition of the lubricating oil appears to improve the permeation rate for the elastomers which more closely represent the actual application. The EPDM materials appear to be improved more than the HNBR. Confirmation testing is needed.

Application:

Selection of the Proper Seal Compound requires:

· Permeation resistance of the HFO 1234yf. · Resistance to degrading by the HFO 1234yf and the lubricant. · High temperature resistance for the operating system and surrounding environment. · Low temperature seal ability · Compression set resistance in the system due to fluid and temperature exposure.

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Application:

Both EPDM and HNBR are viable candidates for use in HFO 1234yf systems.

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Questions?

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Information

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