Selection of sealing materials for waterproof connectors!

Waterproof connectors match O-rings of different materials according to the use environment (temperature, medium, weather resistance, etc.). The core material selection principles are: medium resistance, suitable temperature range, elasticity retention, and anti-aging. ‌‌

‌Nitrile rubber (NBR)‌: Common industrial/automotive waterproof connectors (such as IP67) suitable for normal temperature (-40~120℃), water or weakly polar media, ‌oil-resistant and wear-resistant but not ozone/UV-resistant‌, low cost, the most common.
‌Ethylene-propylene diene rubber (EPDM)‌: Specially used in ‌water, steam, humid or outdoor environments‌ (-50~150℃), ‌excellent in weather resistance, ozone resistance, and polar solvent resistance, but not resistant to oil‌. It is commonly used in bathrooms, water services, and outdoor electrical connectors.
‌Silicone Rubber (VMQ)‌: Used for ‌wide temperature range (-60~200℃) and food/medical/electronic connectors‌, ‌high and low temperature resistance, non-toxic insulation, but poor oil resistance and low mechanical strength‌, suitable for clean or extreme temperature scenarios.
‌Fluorine rubber (FKM)‌: used in ‌high temperature (-20~250℃), oil/chemical medium harsh environment‌(such as military industry, stone Chemical, engine compartment connector), oil-resistant and chemical corrosion-resistant, but brittle at low temperatures and high cost.
‌Hydrogenated nitrile (HNBR)‌: Based on NBR, it improves heat resistance/ozone resistance (-40~150℃). It is used in ‌automobile high-pressure oil circuits or high-dynamic waterproof connectors‌, with low performance and cost.
‌Polytetrafluoroethylene (PTFE) or fluorosilicone (FVMQ)‌: In special occasions (such as strong solvents, ultra-high temperatures or low friction), ‌PTFE has strong chemical resistance but poor elasticity and is often used as a supplement; FVMQ takes into account both fluorocarbon oil resistance and silicone temperature resistance‌. ‌‌
The selection must match the connector’s protection level (such as IP67/IP68), working medium (water, oil, coolant, etc.), temperature range and UV/ozone exposure. Wrong materials will cause expansion, hardening, cracking and failure. Standard waterproof connectors (such as M12, M8, D-sub waterproof models) usually default to NBR or EPDM; high-temperature/chemical environments prefer FKM; food electronics prefer VMQ. ‌‌