Lexicon of Elastomer Technology

(A-Z)

Lexicon of Elastomer Technology

Bonding of elastomers to substrates like glass, metal, or plastic. Important for co-extrusion and overmoulding. Adhesion promoters or plasma treatment improve bonding.

Tests simulating long-term stress (hot air, ozone, UV, media immersion). Used to predict seal lifetime.

Additives that protect elastomers from UV, ozone, and thermal degradation. Especially important for EPDM, CR, and Silicone in outdoor use.

Mixture of different polymers. Common blends: PVC/NBR, TPE/PP – to combine elasticity, temperature resistance, and processability.

Used to ensure adhesion between NBR, FKM, EPDM and metal or plastic in multi-material parts.

Evaluation of material behaviour after exposure to various media (oils, fuels, water/steam, acids/alkalis, cleaning/disinfection agents).

Key standards

  • ISO 1817:2024 – Effect of liquids on vulcanized or thermoplastic rubber (changes in mass/volume/hardness/strength after immersion in specified liquids).

  • ASTM D471 – US equivalent (often correlated with ISO 1817; specification alignment required). 

  • Note: chemical resistance must always be reported as temperature- and time-dependent (e.g. 70 h/23 °C, 168 h/100 °C) with swelling and pre-strain documented.

Typical material behaviour (indicative)

  • EPDM: excellent in hot water/steam and alkalis; poor in mineral oils/fuels.

  • NBR/HNBR: excellent in oils/fuels; HNBR more heat-resistant.

  • FKM/FFKM: very high chemical resistance incl. fuels/aromatics.

  • Silicone: good against water/alcohols/cleaners; sensitive to mineral oils/hydrocarbons.

  • TPE: strongly type-dependent (TPE-S, -V, -E, -U, etc.); always check media and temperature.

Extended tests

  • Abrasion: ISO 4649:2024 (rotating drum volume loss, methods A/B).

  • Gas/vapour permeability: ISO 2782-1:2022 (differential pressure methods), ISO 2782-2:2018 (gas transmission).

  • Ozone cracking resistance: ISO 1431-1:2022 (visual/image analysis, standard climate, defined ozone concentration).

A mix of base rubber, fillers, curing agents, and additives. Each material (NBR, HNBR, FKM, etc.) has tai-lored compounds for specific uses.

Used to produce foam rubber, EPDM, FKM, Silicone, or TPE components, especially seals and gaskets.eee/c

Measurement of permanent deformation after compression. Critical for long-lasting sealing materials like foam rubber, FKM, and Silicone.

Chemical (for EPDM, FKM, NBR) or physical (for TPE). Determines final mechanical properties.

Chemical process (e.g., vulcanization) that gives rubber its elastic properties. TPE achieves elasticity through physical properties and does not require curing.

Typical values:
PTFE: very high (~2.2g/cm³)
Foam rubber: very low (due to cellular structure)
TPE, NBR, EPDM: around 1.1–1.3g/cm³

Elastomers such as CR, HNBR, and TPE perform well under vibration and impact—used in mounts or shock-absorbing components.

Excellent weather, ozone, and steam resistance. Not oil-resistant—NBR, HNBR, or FKM are preferred for oil applications.

Examples: carbon black increases strength (common in NBR, CR); chalk reduces cost (e.g., in basic PVC compounds).

The fire performance of elastomers is assessed using international standards covering flammability, smoke density and toxicity.

  • Key standards:

    • EN 45545 (railway, Europe): assesses materials in rolling stock against fire safety requirements (Hazard Levels HL1–HL3). Tests: flammability, smoke density, smoke toxicity.

    • DIN 4102 (Germany): building material classes B1 (hardly flammable), B2 (normally flammable), B3 (easily flammable).

    • EN 13501-1 (Europe, construction): classification A1–F with smoke (s1–s3) and burning droplets (d0–d2).

    • UL 94 (USA, plastics): horizontal/vertical flame classifications (HB, V-2, V-1, V-0, 5VA/5VB).

    • FMVSS 302 (automotive, USA): horizontal burning rate of materials.

  • Material behaviour:

    • Silicone: inherently flame-retardant, often UL 94 V-0, typically compliant with EN 45545 HL1–HL3.

    • TPE: variable flammability; halogen-free flame retardants required to achieve EN 13501-1 (e.g. B-s2,d0) or EN 45545 classification.

    • EPDM: with flame retardants, widely used in building and railway applications.

    • FKM / FFKM: excellent self-extinguishing properties, high cost.

  • Relevance:

    • Construction: EN 13501-1 applies for façades, doors, windows.

    • Railway: EN 45545 mandatory (e.g. R22/R23 for seals).

    • Automotive: FMVSS 302 standard.

Resistance to repeated bending and flexing. Silicone, EPDM, and TPE perform well in this area—important for dynamic seals and flexible connectors.

Typical ranges:
TPE: 30–90 Shore A
Foam rubber: very soft (~10–30 Shore 00)
PTFE: hard (Shore D)
FKM, HNBR, CR: medium to high hardness (60–90 Shore A)

Efficient method for complex parts made from TPE, FKM, Silicone, CR, etc. Fast, repeatable, automated.

Ideal for TPE, Silicone, PVC, FKM parts. Ensures high precision and fast cycle times.

Main component of natural rubber (NR). Also found in synthetic IR rubber, less common in technical seal-ing.

Measures impact resilience – less common for rubber, more relevant for TPE or PVC under sudden loads.

German term for elastomers. Covers materials like NBR, EPDM, Silicone, CR, FKM, HNBR, etc.

Rubber compounds (EPDM, NBR) are processed in internal mixers. TPE and PVC are processed thermo-plastically (extrusion, injection).

Excellent elasticity but poor oil and ozone resistance. Often replaced by EPDM, Silicone, or FKM in de-manding environments.

Great oil resistance, moderate weather resistance. HNBR offers better heat stability; FKM offers superior chemical resistance.

Unwanted excessive vulcanization. A concern with EPDM, NBR – not applicable to TPE, which does not cure chemically.

TPE is ideal for 2K molding (e.g., soft-touch).
Can be combined with metal, PP, PA, etc.

High: EPDM, FKM, Silicone, CR
Low: NBR, foam rubber (unless stabilized)

Alternative to sulfur curing – used for FKM, EPDM, Silicone. Enhances heat resistance and lowers emis-sions.

Used for foam rubber, EPDM, FKM, Silicone parts.
TPE is generally injection molded.

From compound mixing to final product – varies by application (e.g., aerospace-grade FKM vs. basic foam rubber).

Uncured base elastomer. TPEs are already processable thermoplastics—no raw rubber phase.

Excellent in Silicone, TPE, natural rubber
Low in PTFE, which behaves more plastically.

Generic term for elastic polymers. Includes NBR, EPDM, FKM, Silicone, CR, HNBR, etc.

EPDM, FKM, and PTFE are highly stable. Natural rubber and soft TPE can degrade over time.

Examples:
TPE: wide range
PTFE: ~60 Shore D
FKM: 70–90 Shore A
Foam rubber: very soft (Shore 00)

High-performance elastomer with outstanding resistance to temperature and ageing.

  • Types:

    • HTV (solid rubber, High Temperature Vulcanizing) → suitable for extrusion (profiles, hoses) and injection moulding (moulded parts).

    • LSR (Liquid Silicone Rubber) → liquid, for precision injection-moulded parts, also in 2K technology.

    • RTV (Room Temperature Vulcanizing) → one- or two-component, curing at room temperature, e.g. for sealing and bonding.

  • Properties:

    • Temperature range: −50 to +250 °C (up to +300 °C for special grades).

    • Excellent resistance to weather, ozone and UV.

    • Remains flexible even at very low temperatures (down to −60 °C).

    • Electrically insulating or semi-conductive.

    • Odourless and tasteless, suitable for drinking water and food applications.

  • Mechanical data:

    • Density: 1.05–1.35 g/cm³

    • Hardness: 5–90 Shore A

    • Tensile strength: 5–11 N/mm²

    • Elongation at break: 100–900 %

    • Tear resistance: 5–50 N/mm

    • Compression set (175 °C, 22h): 20–25 %

  • Processing:

    • Extrusion: continuous profiles for doors, windows, façades, hoses.

    • Injection moulding: HTV or LSR parts, e.g. seals, grommets, membranes.

    • RTV: sealing and bonding applied directly during installation.

  • Typical applications:

    • Door and window seals, façade profiles.

    • Sanitary seals and moulded parts.

    • Automotive and mobile applications.

Best materials: FKM, FFKM, PTFE
Poor resistance: EPDM, TPE, foam rubber (open cell types)

Current core standards for elastomers (selection; “EN ISO” = EU adoption of ISO texts).

Mechanical

  • Tensile: ISO 37:2024 (tensile strength, elongation, stress-strain behaviour).

  • Tear strength: ISO 34-1:2022 (trouser/angle/crescent test pieces).

  • Rebound resilience: ISO 4662:2017 (pendulum/tripsometer).

  • Hardness: ISO 48-2:2018 (IRHD hardness), Shore hardness: defined in ISO 48-4 (replaces ISO 7619-1).

  • Density: ISO 2781:2018 (2 methods; quality control/mass calculation).

  • Compression set: ISO 815-1:2019 (ambient/elevated temperatures, methods A–C).

Fire behaviour (construction/rail/automotive)

  • EN 13501-1 (construction products: Euroclasses A1–F, smoke s1–s3, droplets d0–d2).

  • DIN 4102 (national legacy system: B1/B2/B3; now largely replaced by EN 13501-1).

  • EN 45545-2 (railway: material requirements by HL1–HL3 and R categories, e.g. R22/R23 for seals and hoses).

  • UL 94, FMVSS 302 (plastics/automotive; additional, informative).

NBR swells in fuels, EPDM in oils.
PTFE, FKM, FFKM resist most aggressive media.

Top performers:
FFKM: up to 300°C
PTFE: up to 260°C
Silicone: up to 230°C
TPE, NBR: ~100–120°C max

Elastomers expand more than glass or metal. Profiles must compensate movement.

Material family combining rubber-like properties with thermoplastic processability.

  • Properties:

    • Elastic without chemical crosslinking, reprocessable

    • Hardness: 30–90 Shore A

    • Heat resistance up to 100–120 °C

    • Good recovery behaviour, recyclable

  • Processing: extrusion, 2K injection moulding, overmoulding with rigid plastics

  • Typical applications: door and window seals, frame gaskets, façade profiles, seals in mobile applications

High: EPDM, FKM, Silicone, PTFE
Low: NBR, PVC, TPE-S → needs stabilizers

Essential for classic rubbers, not needed for TPE, PVC.

EPDM/Silicone → very low. TPE/Foam → higher depending on structure. Important for outdoor applications.

Important for TPE, PVC (more plastic-like). Classic elastomers don’t have a clear yield point.