Fluorine Rubber Sheet Datasheet Interpretation Guide

2025-12-17 16:23:43

　　Fluorine rubber (often called FKM or Viton®) is a premium elastomer known for exceptional chemical and temperature resistance. Understanding its datasheet is critical for proper material selection. Here's how to interpret key parameters.

　　1. Base Polymer Type & Composition

　　What to look for: The specific FKM grade (e.g., Type A, B, F, etc. per ASTM D1418) or copolymer composition.

　　Interpretation:

　　Type A (Dipolymers): Vinylidene fluoride (VDF) and hexafluoropropylene (HFP). Good general chemical resistance.

　　Type B (Terpolymers): VDF, HFP, and tetrafluoroethylene (TFE). Enhanced chemical and solvent resistance.

　　Type F (Specialty): Perfluoroelastomers (FFKM) with highest resistance but highest cost.

　　Why it matters: Determines the fundamental resistance profile. Increasing fluorine content (65-71%) generally improves chemical/thermal resistance but can reduce low-temperature flexibility.

　　2. Physical Properties

　　A. Hardness (Shore A)

　　Typical Range: 50 to 90 Shore A.

　　Interpretation: Softer (lower number) = better sealing/conformability. Harder = better extrusion resistance and dimensional stability.

　　Check: Ensure it matches your gland design specifications.

　　B. Tensile Strength & Elongation at Break

　　Typical: 10-25 MPa (Tensile), 100-300% (Elongation).

　　Interpretation:

　　Tensile Strength: Resistance to tearing/rupture under tension. Higher is generally better for dynamic applications.

　　Elongation: Flexibility and ability to stretch without breaking. Critical for seals undergoing installation stretch or compression.

　　C. Compression Set (ASTM D395, Method B)

　　Typical: 10-30% after 70 hours at 200°C or 275°C.

　　Interpretation: The most critical property for sealing. Lower percentage = better elastic recovery = longer-lasting seal.<20% is excellent. Always note test temperature and duration.

　　3. Thermal Properties

　　A. Continuous Service Temperature

　　Typical Range: -20°C to +230°C (some grades up to 300°C short-term).

　　Interpretation: The sustained temperature range where key properties are retained. Do not confuse with peak/short-term exposure ratings.

　　Critical Check: Verify both upper and lower limits suit your application.

　　B. Glass Transition Temperature (Tg)

　　Typical: -15°C to -5°C for standard FKMs.

　　Interpretation: The temperature at which rubber becomes brittle. For low-temp flexibility, you need a Tg significantly below your minimum operating temperature.

　　4. Fluid & Chemical Resistance

　　The Core of FKM Selection

　　A. Chemical Compatibility Charts

　　Interpretation: Look for volume swell % and property retention % after immersion in specific fluids at a given temperature and time.

　　<10% swell: Excellent compatibility.

　　10-20% swell: Acceptable for many static seals.

　　>20% swell: Likely unsuitable; check tensile/elongation retention.

　　Key Resistances (FKM's strengths):

　　Excellent: Aromatic hydrocarbons, oils, fuels, acids, many oils.

　　Poor/Potentially Damaging: Ketones (acetone), esters, some amines, hot water/steam, and anhydrous ammonia.

　　B. ASTM Fluid Immersion Tests (ASTM D471)

　　Standard Reference Fuels: IRM 901, 902, 903. Shows performance in fuel.

　　Interpretation: Check volume, hardness, and tensile changes. Significant hardening or cracking indicates incompatibility.

　　5. Permeation & Gas Sealing

　　Look for: Gas permeability coefficients (e.g., for N₂, CO₂, He).

　　Interpretation: FKM has relatively low gas permeability. Critical for sealing fuels, refrigerants (HFO/HFC), or vacuum applications.

　　6. Flame & Smoke Ratings

　　Look for: UL 94, ASTM E162, or similar certifications.

　　Interpretation: FKM is inherently flame retardant. Specific ratings may be required for aerospace, mass transit, or oil/gas applications.

　　7. Processability & Form

　　Sheet Size: Thickness, width, and length tolerances.

　　Cure System: Peroxide vs. Bisphenol. Affects chemical resistance and processing.

　　Peroxide-cured: Better acid/steam resistance, higher compression set resistance.

　　Bisphenol-cured: Standard for most applications.

　　Mold Release: May affect surface energy for bonding if required.

　　8. Agency Approvals & Compliance

　　Common Standards: FDA CFR 177.2600 (for incidental food contact), USP Class VI (medical), NSF/ANSI 61 (drinking water), ASTM D2000 line callouts.

　　Interpretation: Verify the exact grade listed has the approval; approvals are not generic to all FKM.

　　Step-by-Step Selection Workflow

　　Define the Environment:

　　Chemicals/Fluids: List ALL, including concentrations and temperatures.

　　Temperature: Steady-state operating, peak, and minimum.

　　Pressure: Dynamic vs. static.

　　Match to Datasheet:

　　Cross-reference your chemical list with the manufacturer's compatibility guide.

　　Ensure operating temperature is within the continuous service range.

　　Prioritize Critical Properties:

　　Static Seal? Focus on Compression Set and chemical swell.

　　Dynamic Seal? Focus on Tensile Strength, Abrasion Resistance, and compression set.

　　Low-Temp Application? Verify Tg and TR10 (brittle point) ratings.

　　Verify Process & Regulatory Needs:

　　Can it be bonded/molded as needed?

　　Does it have required agency approvals?

　　Request Real-World Validation:

　　For critical applications, request application-specific test data from the supplier or conduct a pilot test.

　　Common Pitfalls to Avoid

　　Assuming all FKM is the same: A Type A and a Type B can behave very differently in the same fluid.

　　Ignoring low-temperature requirements: FKM gets stiff and brittle below its Tg.

　　Overlooking compression set at temperature: A 25% set at room temp can be 50%+ at 200°C.

　　Missing minor fluid components: A 1% additive can degrade the seal even if the base fluid is compatible.

　　Key Datasheet Abbreviations

　　FKM / FPM: Standard designation for fluoroelastomers (ISO/ASTM).

　　MTR: Material Test Report (batch-specific certification).

　　TR10: Temperature at which elastomer is 10x less flexible than at room temp (indicator of low-temp capability).

　　ML, MH: Minimum and maximum torque from a rheometer curve (indicate cure characteristics).

　　By systematically comparing these datasheet parameters against your application's specific demands, you can reliably select the correct FKM Sheet grade, ensuring optimal performance, safety, and service life. When in doubt, consult directly with the rubber manufacturer's technical team.