Fluoroelastomer Products With Improved Chemical Resistance
The chemical industry has been faced with the need for improvement in the production of basic commodities, such as gasoline, while at the same time being increasingly impacted by local and Federal environmental regulations. Leakage or spills due to gasket failure, involve expensive cleanup and time consuming paperwork. The development of new polymer bases has allowed rubber sheeting manufacturers to offer improved gasketing materials to the chemical industry, but cost is still a determining factor governing usage. For several years, Kalrez – a DuPont Dow elastomer, has been generally considered the most chemically resistant elastomer available. Cost was extremely high, and due to process difficulties, it was marketed only in finished goods form (molded O-rings or seals). Recently, polymers approaching Kalrez in resistance have been introduced and some of these Fluoroelastomers are described below.
1. Mosites #2924 – BRE (Base Resistant Elastomer)
2. Mosites #2902 – a polymer based on Aflas TFE/P (TetraFluoroEthylene / Propylene)
3. Mosites #10322 – Viton® ETP (Extreme Viton®)
4. Mosites #10327 – High Fluorine Content (73% Fluorine) Fluoroelastomer
5. Mosites #10328 – Perfluoroelastomer (3M / Dyneon equivalent to Kalrez)
6. Mosites #10314 – Viton® GF compound as a control
Original Physical Properties
Compound # | #2924 | #2902 | #10322 | #10327 | #10328 | #10314 |
---|---|---|---|---|---|---|
Hardness (Shore A) | 71 | 74 | 76 | 82 | 73 | 75 |
Tensile Strength (psi) | 2130 | 2789 | 1760 | 2971 | 2150 | 2760 |
Elongation at Break (%) | 366% | 243% | 284% | 364% | 128% | 276% |
Modulus at 100% Elongation (psi) | 467 | 881 | 774 | 635 | 1650 | 576 |
Modulus at 300% Elongation (psi) | 1872 | – | – | 2107 | – | – |
Tear Strength (ppi) | 121 | 117 | 124 | 207 | 126 | 142 |
Specific Gravity | 1.68 | 1.58 | 1.82 | 1.94 | 2.02 | 1.81 |
% Compression Set (22 hours at 350°F) | 52% | 15% | 61% | 12% | 53% | 9% |
Approximate Base Cost/pound | $20/lb | $21/lb | $200/lb | $25/lb | $2500/lb | $20/lb |
An immersion study was performed on these polymer choices in fluid compositions that involve a broad range of chemical resistance characteristics. Both high and low ph fluids were evaluated; as were aromatic and oxygenated solvents. Due to polymer cost, the perfluoroelastomer was not tested. Published data shows the fluid media chosen to have little or no effect on this polymer.
Acid Resistance – 72 Hours at 158° F in 37% Hydrochloric Acid
Compound # | #2924 | #2902 | #10322 | #10327 | #10328 | #10314 |
---|---|---|---|---|---|---|
Hardness (Shore A) | -6 pts | 0 pts | 0 pts | -3 pts | – | 0 pts |
Tensile Strength (psi) | -22% | -5% | -24% | -7% | – | +5% |
Elongation at Break (%) | -5% | -3% | -0% | +2% | – | -2% |
Modulus at 100% Elongation (psi) | +11% | +16% | -40% | +3% | – | +7% |
Modulus at 300% Elongation (psi) | +2% | – | – | -9% | – | – |
Tear Strength (ppi) | -15% | -12% | -18% | +1% | – | -7% |
% Volume Swell | +15% | +3% | +3% | +0% | +2% | +4% |
Base Resistance – 72 Hours at 250° F in 50% Sodium Hydroxide
Compound # | #2924 | #2902 | #10322 | #10327 | #10328 | #10314 |
---|---|---|---|---|---|---|
Hardness (Shore A) | 0 pts | 0 pts | +1 pts | -3 pts | – | -1 pts |
Tensile Strength (psi) | -30% | +12% | -7% | -13% | – | +0% |
Elongation at Break (%) | -13% | -8% | -12% | -6% | – | -4% |
Modulus at 100% Elongation (psi) | +9% | +3% | -13% | -1% | – | +5% |
Modulus at 300% Elongation (psi) | +2% | – | – | +2% | – | – |
Tear Strength (ppi) | -10% | -8% | -11% | +7% | – | -4% |
% Volume Swell | +1% | +1% | +1% | -5% | +1% | +1% |
Aromatic Solvent Resistance – 72 Hours at 75° F in Toluene
Compound # | #2924 | #2902 | #10322 | #10327 | #10328 | #10314 |
---|---|---|---|---|---|---|
Hardness (Shore A) | -24 pts | -19 pts | 0 pts | -1 pts | – | 0 pts |
Tensile Strength (psi) | -71% | -61% | -23% | -6% | – | -14% |
Elongation at Break (%) | -39% | -54% | -12% | +3% | – | -10% |
Modulus at 100% Elongation (psi) | -41% | -1% | -26% | +2% | – | -6% |
Modulus at 300% Elongation (psi) | – | – | – | -10% | – | – |
Tear Strength (ppi) | -57% | -67% | +2% | -4% | – | -0% |
% Volume Swell | +35% | +51% | +7% | +0% | +2% | +1% |
Oxygenated Solvent Resistance – 72 Hours at 75° F in Methyl Ethyl Ketone
Compound # | #2924 | #2902 | #10322 | #10327 | #10328 | #10314 |
---|---|---|---|---|---|---|
Hardness (Shore A) | -42 pts | -19 pts | -7 pts | -23 pts | – | -22 pts |
Tensile Strength (psi) | * | -79% | -25% | -59% | – | -87% |
Elongation at Break (%) | * | -66% | -16% | -46% | – | -81% |
Modulus at 100% Elongation (psi) | * | – | -30% | -55% | – | – |
Modulus at 300% Elongation (psi) | * | – | – | – | – | – |
Tear Strength (ppi) | * | -76% | -21% | -53% | – | -68% |
% Volume Swell | +267% | +73% | +19% | +37% | +9% | +186% |
*Sample was too swollen and distorted to test. |
The above tests show the importance of matching a seal material to the fluid environment it will see upon installation. Information about service conditions and temperatures must be considered before a compound can be recommended.