Quantifying Water Vapor Diffusion across Elastomer Pressure Sensor Seals
Water vapor diffusion across elastomer seals causes reference cavity pressurization and dielectric drift, requiring coulometric ISO 15105-2 verification.
Ethylene Propylene Diene
Elastomer Formulation
Synthetic rubber polymer compounding defines ethylene propylene diene monomer as a terpolymer network built from saturated hydrocarbon backbones crosslinked via targeted unsaturation. Elastomeric sealing elements require this chemical architecture to resist oxidative degradation under sustained thermal stress. Molecular chains consist of ethylene and propylene units copolymerized with a non-conjugated diene comonomer.
That third monomer introduces pendant double bonds that remain outside the main polymer chain to provide sites for sulfur or peroxide vulcanization.
Polymer Rheology
Viscosity testing under standardized shear conditions determines the processing behaviour of raw polymer batches before compound cure. Mooney viscosity values quantify resistance to flow at elevated temperatures during internal mixing operations. Polymer chain length distribution affects extrusion rates and calender shrinkage during component manufacturing.
Molecular weight averages dictate green strength properties prior to crosslinking reactions in closed molds.
Degradation Thresholds
Ozone attack targets residual unsaturation sites within improperly cured elastomeric matrices, causing microcrack formation under mechanical tension. Weathering resistance protocols measure surface degradation rates following prolonged ultraviolet exposure in artificial accelerated weathering chambers. Crosslink density optimization restricts chain scission processes, thereby maintaining elongation at break values after thermal aging cycles.
Compression set testing evaluates recovery performance after constant deflection at specified temperatures over extended durations.
Thermal Boundaries
Service temperature limits depend heavily on the specific cure system selected during compound formulation and reactor grade specifications. Peroxide crosslinking networks deliver superior heat aging stability compared to conventional sulfur vulcanizates by eliminating polysulfidic bonds prone to thermal cleavage. Continuous operational exposure above maximum rated thresholds promotes crosslink reversion and subsequent hardening of the rubber matrix.
Volume swell measurements in designated hydrocarbon fluids establish chemical compatibility limits for industrial sealing applications.