How to select the material for rubber joints

EPDM (Ethylene Propylene Diene Monomer), NBR (Nitrile Butadiene Rubber), and Neoprene (Chloroprene Rubber, or CR) are the three most widely used synthetic rubbers in industry. Their core differences lie in their resistance to various media, which is determined by their chemical structures.Below is a comparison of their key characteristics and a selection guide:1. Comparison of Key CharacteristicsCharacteristic EPDM NBR Neoprene/CRKey Advantage Weather, ozone, and hot water resistance Oil and fuel resistance Weather resistance, flame retardancy, moderate oil resistanceOil Resistance Poor (swells in contact with oil) Excellent (material of choice) Moderate (better than EPDM, weaker than NBR)Weather/Ozone Resistance Excellent (top choice for outdoors) Poor (prone to aging/cracking) Good (better than NBR)Temperature Range -50°C to +150°C -30°C to +120°C -40°C to +120°CElectrical Insulation Excellent Poor AverageTypical Hardness Shore A 55–65 (commonly soft) Shore A 65–75 (commonly medium-hard) Shore A 60–702. Detailed Application Scenarios and Selection RecommendationsEPDM (Ethylene Propylene Diene Monomer) Application Scenarios:o Outdoor Environments: Automotive weatherstripping, construction waterproofing membranes, door and window seals (due to superior UV and ozone resistance).o Water/Steam Systems: Hot water pipe seals, cooling tower linings, sanitary equipment (excellent resistance to hot water and steam).o Electrical Insulation: Cable sheathing, transformer insulation pads.o Alkaline Media: Resistant to alkaline solutions, alcohols, and ketones. ‌Contraindications‌: Strictly prohibited for use in environments involving contact with mineral oil, gasoline, diesel, or aromatic hydrocarbon solvents; otherwise, rapid swelling and failure will occur.‌NBR (Nitrile Rubber)‌Applications‌:o‌Fuel/Lubrication Systems‌: Oil pump seals, fuel hoses, hydraulic system O-rings, machine tool pads.o‌Oily Environments‌: Flooring in oily workshop areas, vibration-dampening pads for oily mechanical components.o‌Acrylonitrile Content Selection‌: High acrylonitrile content offers better oil resistance but poorer low-temperature performance; low acrylonitrile content offers good low-temperature elasticity but slightly weaker oil resistance.‌Contraindications‌: Not suitable for long-term outdoor exposure (susceptible to ozone and UV aging) or for use with polar solvents (e.g., ketones, esters).‌Neoprene / CR (Chloroprene Rubber)‌Applications‌:o‌Balanced Performance Needs‌: Applications requiring a balance of oil resistance, weather resistance, and aging resistance (e.g., outdoor oil hoses, air conditioning hoses).o‌Flame Retardancy‌: Due to chlorine in its molecular structure, it is self-extinguishing; commonly used for fire-resistant cable sheathing and conveyor belts.o‌Adhesives and Wetsuits‌: Widely used in all-purpose adhesives (neoprene cement) and wetsuit materials (closed-cell foam structure provides good thermal insulation).o‌Moderate Chemical Exposure‌: Resistant to weak acids, weak alkalis, and saltwater.‌Characteristics‌: Performance falls between EPDM and NBR; an "all-rounder" material, though not specialized for extreme conditions.3. Quick Selection Decision Tree1.‌Does it come into contact with oils (engine oil, gasoline, hydraulic fluid)?‌oYes → Choose ‌NBR‌ (best) or ‌CR‌ (if weather resistance is also required).oNo → Proceed to the next step.2.‌Is it for long-term outdoor use (exposure to sun and rain) or contact with hot water/steam?‌oYes → Choose ‌EPDM‌.oNo → Proceed to the next step. 3. Is flame retardancy or a balance of moderate weather/oil resistance required?o Yes → Choose Neoprene (CR).o No → Consider lower-cost SBR (Styrene-Butadiene Rubber) or NR (Natural Rubber).Summary: For oil resistance → Use NBR. For resistance to sunlight/hot water → Use EPDM. For a combination of some oil resistance and weather/flame resistance → Use Neoprene (CR).