EPDM Sulfur vs. Peroxide Cure: Comparing Heat Aging and Compression Set
Problem Statement
EPDM seals in automotive cooling systems fail under prolonged heat exposure (150°C+). Sulfur-cured EPDM shows excessive compression set (>40%) after 1,000 hours, causing leakage in radiator hose applications.
Material Science Analysis
- Sulfur-Cured EPDM: Forms polysulfide crosslinks. These bonds break under thermal stress, leading to permanent deformation. Sulfur accelerates oxidation at high temperatures.
- Peroxide-Cured EPDM: Creates stable carbon-carbon crosslinks. Resists thermal degradation due to higher bond energy (348 kJ/mol vs. 268 kJ/mol for S-S bonds). No sulfur means slower oxidation.
Technical Specs
| Parameter | Sulfur-Cured EPDM | Peroxide-Cured EPDM |
|---|---|---|
| Shore A Hardness | 70 ±5 | 70 ±3 |
| Tensile Strength (MPa) | 12.5 | 14.2 |
| Elongation at Break (%) | 350 | 320 |
| Continuous Temp. Range (°C) | -40 to +125 | -50 to +150 |
| Compression Set (22h @ 150°C, %) | 45 | 18 |
| Heat Aging (1,000h @ 150°C, ΔTensile) | -35% | -12% |
Standard Compliance
RubberQ’s IATF 16949 process controls:
- Peroxide dispersion (±0.1% tolerance)
- Cure time (±5 seconds at 180°C)
- Batch traceability via ASTM D2000 AA-703 callouts
For custom material compound development or IATF 16949 documentation, consult RubberQ’s engineering department.
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