Elastomer Developments for Sealing Automotive Climate Control Systems Using Carbon Dioxide Dale M. Ashby & Gerhard Buch O-Ring Division Parker Hannifin

Topics to be Discussed l Introduction l Design Theory l Elastomer Development Theory l CO2 Testing Programs l Application Field Trials l Conclusions and Future Work

Introduction l Most Work has been Proprietary l Huge Variety of Lubricants Available l Many Hardware Challenges in Addition to the Elastomer Issues l Research Performed in US and Europe with Specific Customers

Seal Design l Design factors include:  Pressure Range of Operation  Temperature Envelope  Connector Geometry  Surface Finish of Mating Parts  Lubricant Used (type AND mfg)  Elastomeric recipe  Environmental Factors (vibration,safety,etc)

Seal Design l Typical Design example:  CO2 Pressure of 2200 psig  Upper Temperature of 300 F  Lubricating Oils of PAG, PAO or POE  Seal Configurations include Bonded seals, O-rings, Square-cuts, and Custom Molded Shapes

 Ethylene Propylene (EPDM)-45 to 150C  Ethylene Acrylate (AEM)-35 to 150C  Ethylvinyl Acetate (EVM)-30 to 150C  Neoprene (Polychloroprene) (CR)-35 to 110C  Fluorocarbon (FKM)-30 to 200C  Hydrogenated Nitrile (HNBR)-35 to 150C Useful Temperature Range of Candidates

Candidate Refrigeration Oils for CO2  Mineral Oil  POE (PolyolEster)  AB(Alkyl Benzene)  PVE(Polyvinyl Ether)  PAG (Polyalkylene Glycol)  PAO(Polyalpha Olefin)

Relative Resistance of Various Polymers C AEMFKMHNBREPDMEVM POE A Hardness Chg, pts Volume Chg, % POE B Hardness Chg, pts Volume Chg, %

Relative Resistance of Various Polymers C AEMFKMHNBREPDMEVM PAG A Hardness Chg, pts Volume Chg, % PAG B Hardness Chg, pts Volume Chg, %

Effect of Compounding on PAG A Oil Resistance after C EPDM AEPDM B Hardness Change, pts (Shore A)-1-7 Volume Change, % Surface DeteriorationNoneModerate

Effect of Compounding on PAG A Oil Resistance after C FKM AFKM B Hardness Change, pts (Shore A)-2-8 Volume Change, % Surface DeteriorationNoneModerate

Effect of Compounding on PAG A Oil Resistance after C HNBR AHNBR B Hardness Change, pts (Shore A)-9-18 Volume Change, % Surface DeteriorationModerateSevere

CO2 Testing Program Project Partners Fahrzeug Hydraulik

Low and High Temperature Properties Requirements (Compressor): -40 to 150°C (suction) and -40°C to 180°C (discharge + shaft seal) Important: gas tightness required and dynamics (temperature cycles & vibrations) Testing Program

Low Temperatures: Test: Storage of elastomer specimen at below -40°C under air and CO 2 atmosphere Result: Significantly higher flexibility of samples being under CO 2 atmosphere compared to those being under air. Testing Program

High Temperatures: Test: Heat aging of O-Rings 2 200°C under air and CO 2 atmosphere Result: Cracks, hardness increase & high com- pression set on EPDM under air atmosphere.Significantly better results under CO 2 Testing Program

High Temperatures: Test: Heat aging of O-Rings 2 200°C under air and CO 2 atmosphere Testing Program AirCO 2

Explosive Decompression (ED) Test: Rapid decompression within seconds after CO 2 saturation at -42°C and 150°C. 5 repeated cycles at 150°C. Result: HNBR C best (no damages), followed by FKM C and EPDM C. All other elastomers tested suffered partially heavy damages. Testing Program

Explosive Decompression (ED) Examples for typical damages: Testing Program

Lubricant Compatibility Test: Immersion of slabs in different lubricants 2 150°C Result: Excellent compatibility of FKM C with Lubricants tested. EPDM C showed limitations with experimental POE & PAG formulations. Testing Program

Lubricant Compatibility Results 2 150°C Lubricant A = Conventional Lubricant, used for 134a Lubricant B =Experimental High Performance Lubricant designed for CO 2 Testing Program Volume Change [% ] Hardness Change [IRHD] FKM Lub. A FKM Lub. B EPDM Lub. A EPDM Lub. B HNBR Lub. A HNBR Lub. B FKM Lub. A FKM Lub. B EPDM Lub. A EPDM Lub. B HNBR Lub. A HNBR Lub. B

Permeation Effects Test: Permeation measurement on slabs Result: In line with the results already published [1]. At high temperatures FKM, EPDM, FKM have similar performance. At temperatures near CO 2 critical point permeation coefficient of FKM strongly increasing with pressure. Testing Program

Permeation Effects Testing Program

Compressor using O-Ring materials: FKM C & EPDM C, tests done by Tests: High temperature aging, system bench tests, vehicle system tests. Results: No system failure due to seals. No damage found on seals which are related to temperature or lubricant exposure. Low compression set values even for EPDM Fluid compatibility major factor Application Field Trials Fahrzeug Hydraulik

Leakage measurement on different connector designs using FKM C & EPDM C O-Rings, tests done by Germany Schematic connector sealing design example: Application Field Trials Installation guidance device FKM O-Ring EPDM O-Ring

Conclusions l Lubricating Oil Compositions Vary Widely l Specific Elastomer Formulations must be Evaluated l Explosive Decompression Issues Continue l Design approach Must be Included in the Overall Solution

Future Work l Evaluate Additional Lubricants l Develop Additional Tailored Recipes l Continue to Investigate Permeation Resistant Compounds l Investigate the ED Issue through Seal Designs and Novel Compounding l Evaluate Additional Design Concepts

LuK-Sanden, Bad Homburg, Germany Eaton Fluid Power GmbH, Muggensturm, Germany Fuchs Europe, Hamburg, Germany We thank these companies for the kind permission to use the test data shown in the presentation Acknowledgements

[ 1]Leisenheimer, Fritz, Oellrich: Untersuchungen zum Permeabilitätsverhalten von CO2 in Elastomeren für die Automobilklimatisierung, KI Luft- und Kältetechnik 12/2000, Germany References