When choosing alkali resistant rubber, polarity is a key consideration factor. Due to the strong polarity of alkali (such as sodium hydroxide and potassium hydroxide), polar rubber is usually more resistant to alkali erosion than non-polar rubber. The following are several common and alkali resistant rubber types and their characteristics:

1. Nitrile rubber (NBR)

Advantages: Excellent oil resistance, good tolerance to non-polar solvents, as well as outstanding alkali resistance and wear resistance. High cost-effectiveness and wide range of applications.

Alkali resistance: Under medium and low temperature conditions (usually below 100 ° C), it exhibits excellent resistance to medium concentrations (such as 10% -30%) of alkaline solution (NaOH/KOH) and is the preferred material for alkali and oil resistant conditions.

Typical applications: chemical equipment seals (O-rings, gaskets), alkali hose liners, oil and alkali resistant gloves, roller covers, etc.

2. chloroprene rubber (CR)

Advantages: Excellent weather resistance, ozone resistance, and flame resistance, with good tolerance to medium strength acids and bases (including alkalis), and balanced overall performance.

Alkali resistance: It exhibits good resistance to dilute alkali solution (concentration below 30%) and medium concentration alkali solution at room temperature. Alkali resistance is usually better than natural rubber and styrene butadiene rubber, but may be slightly inferior to nitrile rubber (depending on the formula and usage conditions).

Typical applications: weather resistant sealing strips, rubber hose outer adhesive, conveyor belt covering adhesive, acid and alkali resistant rubber boots, adhesives, etc.

3. Ethylene propylene diene monomer (EPDM) rubber

Advantages: Weather resistance, ozone resistance, heat resistance (up to 150 ° C or above), excellent steam resistance, excellent resistance to polar chemicals (including alkali), and good electrical insulation.

Alkali resistance: Even under high temperature (100-130 ° C) conditions, it can withstand high concentrations (over 50%) of strong alkalis (such as NaOH, KOH)

Still possessing excellent resistance, it is the preferred universal rubber for high-temperature alkali resistance.

Typical applications: hot alkali sealing components, steam hoses, automotive cooling system components, chemical resistant linings, roof waterproofing membranes, heat-resistant conveyor belts, etc.

4. Fluororubber (FKM)

Advantages: Excellent high temperature resistance (up to 200 ° C or above) and chemical resistance (including strong acids, alkalis, organic solvents, and oils), making it the "aristocrat" of rubber.

Alkali resistance: Even under high temperature conditions, it exhibits excellent resistance to the vast majority of strong alkalis (such as concentrated NaOH, KOH), making it the preferred material for harsh alkaline and high-temperature environments.

Disadvantages: Expensive price, poor low-temperature elasticity, slightly poor processability.

Typical applications: aerospace seals, chemical reactor seals, high reliability valve liners, oil well equipment seals, semiconductors

Industry resistant chemical components, etc.

5. Chlorosulfonated polyethylene rubber (CSM)

Advantages: Excellent weather resistance, ozone resistance, heat resistance, chemical resistance (including acid and alkali), and good color stability.

Alkali resistance: exhibiting good resistance to strong oxidizing acids and strong bases, especially suitable for chlorine containing bleaching agents (such as sodium hypochlorite)

Waiting for an oxidizing alkaline environment.

Typical applications: tank lining (especially suitable for chlorinated chemicals), acid and alkali resistant adhesive tape, wire and cable sheaths, corrosion-resistant rubber rollers, equipment sealing in the paper industry, etc.

6. Hydrogenated Nitrile Rubber (HNBR)

Advantages: While retaining the excellent oil and alkali resistance of nitrile rubber, it significantly improves heat resistance, ozone resistance, and chemical resistance.

Alkali resistance: Alkali resistance is better than ordinary nitrile rubber, especially in higher temperatures and more demanding chemical environments.

Typical applications: automotive engine oil seals, oilfield drilling equipment seals, high-performance industrial seals, etc., suitable for occasions that require higher performance than NBR.

7. Perfluoroether rubber (FFKM)

Advantages: Currently, the most chemically resistant material in commercial rubber can resist almost all chemicals (including the strongest oxidizing acids, strong bases, and organic solvents), and has excellent high temperature resistance (up to 300 ° C or above).

Alkali resistance: It has absolutely excellent tolerance to strong alkalis of any concentration and temperature.

Disadvantage: Extremely expensive price.

Typical applications: semiconductor manufacturing, sealing and components in extreme chemical environments (such as high-purity PFA valve diaphragms, pump seals), aerospace critical seals, etc.

Key selection considerations

Concentration and temperature: The alkali resistance of rubber heavily depends on the concentration and temperature of the alkaline solution. Rubber that is resistant to high concentrations of alkali at room temperature may experience a sharp decline in performance at high temperatures. When selecting, it is necessary to specify the specific working conditions (alkali type, concentration, temperature, whether it contains oxidants, etc.).

Rubber formula: The design of different vulcanization systems, reinforcement systems, plasticizers, anti-aging agents, and other formula designs for the same rubber based rubber will significantly affect its final chemical resistance (including alkali resistance). The specific brand data sheet provided by the manufacturer is the most important reference basis.

Non polar rubber has poor alkali resistance: Non polar rubber such as natural rubber, styrene butadiene rubber, and butadiene rubber have poor alkali resistance, especially not resistant to high-temperature alkaline solutions, and are prone to swelling and degradation.

Silicone rubber: has a certain tolerance to dilute alkali solution, but has poor resistance to strong alkali (especially high-temperature strong alkali) and is easily corroded and damaged.

Selection suggestions

General alkali resistant preferred (cost-effective): Nitrile rubber (suitable for medium and low temperature, medium concentration alkaline solution), EPDM rubber (suitable for high temperature, high concentration alkaline solution).

Requires oil and alkali resistance: nitrile rubber (preferred), hydrogenated nitrile rubber (higher requirements).

High temperature resistance and strong alkali resistance are required: fluororubber (with good comprehensive performance), perfluoroether rubber (with extremely high prices in extreme environments).

Requires alkali resistance to oxidation (such as sodium hypochlorite): chlorosulfonated polyethylene rubber.

Require excellent comprehensive performance (weather resistance, ozone resistance, moderate alkali resistance): chloroprene rubber.