Transcript Elastomer Developments for Sealing Automotive Climate Control Systems Using Carbon Dioxide

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
Introduction
 Design Theory
 Elastomer Development Theory
 CO2 Testing Programs
 Application Field Trials
 Conclusions and Future Work

Introduction
Most Work has been Proprietary
 Huge Variety of Lubricants Available
 Many Hardware Challenges in
Addition to the Elastomer Issues
 Research Performed in US and
Europe with Specific Customers

Seal Design

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

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
Useful Temperature Range of
Candidates
 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)
 Hydrogenated
Nitrile (HNBR)
-30 to 200C
-35 to 150C
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
168 Hrs @ 100C
AEM
FKM
HNBR EPDM EVM
POE A
Hardness Chg, pts
Volume Chg, %
-5
+1
+21.5 +8
POE B
Hardness Chg, pts
Volume Chg, %
-6
+1
-9
+24.5 +15.5 +28
-6
+14
-2
+9.8
-7
+26
-3
-7
+17.1 +21
Relative Resistance of Various Polymers
168 Hrs @ 100C
AEM
FKM
HNBR EPDM EVM
PAG A
Hardness Chg, pts
Volume Chg, %
-5
+23
-2
+9.8
-9
+12
PAG B
Hardness Chg, pts
Volume Chg, %
-5
+31
-3
-13
+14.5 +27
-1
+8.5
-9
+26.5
-9
+18
-10
+39
Effect of Compounding on PAG A Oil
Resistance after 168 hrs @ 100C
Hardness Change, pts (Shore A)
Volume Change, %
Surface Deterioration
EPDM A
EPDM B
-1
+8.5
None
-7
+17.9
Moderate
Effect of Compounding on PAG A Oil
Resistance after 168 hrs @ 100C
Hardness Change, pts (Shore A)
Volume Change, %
Surface Deterioration
FKM A
FKM B
-2
+9.8
None
-8
+18.1
Moderate
Effect of Compounding on PAG A Oil
Resistance after 168 hrs @ 100C
Hardness Change, pts (Shore A)
Volume Change, %
Surface Deterioration
HNBR A
HNBR B
-9
+12.0
Moderate
-18
+38.5
Severe
CO2 Testing Program
Project Partners
Fahrzeug
Hydraulik
Testing Program
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 CO2 atmosphere
Result:
Significantly higher flexibility of samples
being under CO2 atmosphere compared to
those being under air.
Testing Program
High Temperatures:
Test:
Heat aging of O-Rings 2 weeks @ 200°C
under air and CO2 atmosphere
Result:
Cracks, hardness increase & high compression set on EPDM under air
atmosphere.Significantly better results
under CO2
Testing Program
High Temperatures:
Test:
Heat aging of O-Rings 2 weeks @ 200°C
under air and CO2 atmosphere
Air
CO2
Testing Program
Explosive Decompression (ED)
Test:
Rapid decompression within seconds after
CO2 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 weeks @ 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 weeks @ 150°C
Lubricant A = Conventional Lubricant, used for 134a
Lubricant B = Experimental High Performance Lubricant
designed for CO2
Volume Change [% ]
Hardness Change [IRHD]
25
0
20
-2
15
-4
10
-6
5
-8
0 FKM
Lub. A
FKM
EPDM EPDM HNBR
Lub. B Lub. A Lub. B Lub. A
HNBR -10 FKM
Lub. B
Lub. A
FKM
EPDM EPDM HNBR
Lub. B Lub. A Lub. B Lub. A
HNBR
Lub. B
Testing Program
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 CO2 critical point permeation
coefficient of FKM strongly increasing with
pressure.
Testing Program
Permeation Effects
FKM
500
20°C
Q [cm 2/s/bar]x10-8
450
400
180°C
350
300
40°C
250
200
120°C
80°C
150
100
50
0
0
20
40
60
80
100
120
pv [bar]
Application Field Trials
Compressor using O-Ring materials: FKM C &
Fahrzeug
EPDM C, tests done by
Hydraulik
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
Leakage measurement on different connector designs
using FKM C & EPDM C O-Rings, tests done by
Germany
Schematic connector sealing design example:
Installation
guidance
device
FKM O-Ring
EPDM O-Ring
Conclusions
Lubricating Oil Compositions Vary
Widely
 Specific Elastomer Formulations must
be Evaluated
 Explosive Decompression Issues
Continue
 Design approach Must be Included in
the Overall Solution

Future Work
Evaluate Additional Lubricants
 Develop Additional Tailored Recipes
 Continue to Investigate Permeation
Resistant Compounds
 Investigate the ED Issue through
Seal Designs and Novel Compounding
 Evaluate Additional Design Concepts
