Choosing between silicone and rubber is the first engineering decision in any custom parts project — and the most common mistake is choosing by price alone.
Temperature: silicone works from -70°C to 232°C and keeps elasticity at both extremes. NBR tops out near 120°C; EPDM reaches 150°C; FKM handles 250°C but costs several times more.
Chemical resistance: for mineral oils and fuels, NBR and FKM are the right answers — silicone swells in oil. For water, steam, ozone and UV, EPDM and silicone lead. For weak acids and alkalis, both silicone and EPDM perform well.
Compliance: food-contact (FDA 21 CFR 177.2600, LFGB) and medical (USP Class VI, ISO 10993) applications usually force silicone; automotive and industrial parts rarely need it.
Cost: NBR and EPDM are the economical workhorses; silicone sits mid-range; FKM is premium. A smart approach is to let the environment — not the catalog — pick the material, then optimize grade and hardness. Send us your operating conditions and we will propose 2-3 compound options with cost implications.