EPDM Sulfur vs. Peroxide Cure: Comparing Heat Aging and Compression Set.

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.