VMQ Silicone O-Rings
Food-grade, medical-grade and extreme-temperature sealing from -60°C to +200°C
Overview
VMQ (Vinyl Methyl Silicone), commonly called silicone rubber, is the material of choice for applications requiring wide temperature flexibility, food safety compliance, or biocompatibility. Unlike NBR and FKM, VMQ is not intended for petroleum oil sealing, but it excels in dry heat, moderate steam, polar solvents, and clean-environment applications.
VMQ O-rings maintain elastomeric properties from -60°C to +200°C, with specialty grades extending to +230°C for short-term service. The saturated siloxane backbone resists UV, ozone, and oxidation without surface cracking — key for outdoor, lighting, and UV-exposed applications.
Curing system matters for VMQ. Peroxide-cured silicone is the standard industrial grade. Platinum-cured silicone produces a cleaner compound: minimal extractables, no peroxide byproduct residues, and better biocompatibility — required for medical implant contact, direct food contact in sensitive applications, and semiconductor use. Request the curing system specification when ordering for regulated applications.
FDA 21 CFR §177.2600 compliant grades are available for repeated food contact. USP Class VI certified grades are available for pharmaceutical and medical equipment. Both may require compound-specific certification — specify at order time.
Critical limitation: tensile strength of 5–10 MPa is the lowest of common elastomers. VMQ is unsuitable for dynamic sealing under significant pressure. Design for static service; use backup rings in any application above 10–15 bar.
Lead time: 7–15 days standard; 3–5 days for stocked sizes. MOQ: 1 piece. ISO 9001 certified.
The molecular structure of VMQ is fundamentally different from carbon-based elastomers: it consists of a backbone of alternating silicon and oxygen atoms (siloxane, -Si-O-Si-O-) with methyl (-CH₃) and vinyl (-CH=CH₂) side groups attached to silicon. The Si-O bond energy is approximately 452 kJ/mol, significantly higher than the C-C bond energy of 348 kJ/mol in organic elastomers — this is the origin of silicone's exceptional thermal stability and oxidation resistance. The vinyl content, typically 0.1–1.0 mol%, provides crosslinking sites for peroxide or platinum curing. Peroxide curing (typically dicumyl peroxide) generates C-C crosslinks and leaves small amounts of volatile byproducts (acetophenone, cumyl alcohol). Platinum curing (addition cure using hydrosilane crosslinkers and platinum catalysts) forms Si-C and Si-O-Si crosslinks with zero byproduct generation, producing the cleanest compounds. The free volume in silicone polymers is unusually high, which explains both the excellent low-temperature flexibility (glass transition temperature of -120°C) and the high gas permeability (10–100× higher than NBR).
Quantified comparisons with other elastomers clarify VMQ's position in the material selection hierarchy. In low-temperature flexibility, VMQ achieves TR10 of -55°C to -60°C (ASTM D1329), versus EPDM's -45°C to -50°C and NBR's -35°C to -40°C — a 10–20°C advantage that makes VMQ essential for cryogenic-adjacent and aerospace cold-start applications. In tensile strength, VMQ's 5–10 MPa is 40–70% lower than EPDM's 10–18 MPa and 50–75% lower than NBR's 10–20 MPa — this mechanical weakness is the primary reason VMQ is limited to static and low-pressure service. In compression set at 175°C (ASTM D395 Method B, 70 h), VMQ achieves ≤ 30%, while NBR would exceed 60% and fail — but EPDM achieves ≤ 20% at 150°C, and when temperature-normalized, EPDM outperforms VMQ in hot static sealing. In ozone resistance (ASTM D1171, 50 pphm, 20% strain), VMQ shows no cracking after 1000+ hours, matching EPDM and vastly outperforming NBR. In gas permeability, VMQ is 10–30× more permeable than NBR to oxygen and 50–100× more permeable to water vapor — a disadvantage for pressure containment but an advantage for breathable medical devices.
A practical selection and design decision tree: if your application is a food processing valve seal in direct contact with dairy or beverage at temperatures below +100°C and pressures below 5 bar, specify platinum-cured FDA VMQ at 50–60 Shore A for maximum conformability and compliance. If your application is a medical device seal requiring USP Class VI and minimal extractables, specify platinum-cured VMQ with cytotoxicity testing and batch-specific extractables documentation — never use peroxide-cured VMQ for implant or blood-contact applications. If your application is an outdoor electrical enclosure gasket in a hot climate (Arizona, Dubai) with daily temperature cycling from 20°C to 80°C, specify 60 Shore A peroxide-cured VMQ with UV stabilizer — the wide temperature range prevents hardening in winter and softening in summer. If your application is an aircraft fuel system static seal at -40°C, specify FVMQ (fluorosilicone) rather than VMQ, as VMQ swells excessively in jet fuel. If your application involves any petroleum oil, hydraulic fluid, or fuel contact, do not use VMQ — specify NBR, FKM, or FVMQ. If pressure exceeds 15 bar in any VMQ application, design PTFE backup rings into the groove to prevent extrusion.
Storage of VMQ requires attention to its unique vulnerabilities. VMQ is not susceptible to ozone cracking due to its saturated siloxane backbone, but it is sensitive to certain contaminants: silicone polymers can be swollen by silicone-based greases and oils (a compatibility advantage within silicone systems but a contamination risk if mixed with other elastomers). Store VMQ O-rings in opaque packaging below 25°C, away from plasticizers, solvents, and silicone fluid sources that could cause surface tackiness. Platinum-cured VMQ has a recommended shelf life of 5–7 years; peroxide-cured grades are stable for 7–10 years, though peroxide residues may slowly advance the cure state, causing a minor hardness increase (2–4 Shore A) over very long storage. A common error is storing VMQ in PVC bags or near PVC materials — plasticizer migration from PVC can soften VMQ surfaces and cause tackiness. Another frequent mistake is using VMQ in high-pressure pneumatic systems without backup rings: at 20 bar air pressure, a 70 Shore A VMQ O-ring will extrude through a 0.15 mm clearance gap within hours, causing immediate failure.
Material Properties
| Temperature Range | -60°C to +200°C (-76°F to +392°F); short-term to +230°C |
| Hardness Range | 30–80 Shore A (ASTM D2240) |
| Tensile Strength | 5–10 MPa (ASTM D412) — lowest of common elastomers |
| Elongation at Break | 200–800% (ASTM D412) |
| Compression Set (70 h/175°C) | ≤ 30% (ASTM D395 Method B) |
| Low-Temperature Flexibility (TR10) | -55°C to -60°C (ASTM D1329) |
| Specific Gravity | 1.10–1.50 |
| Color (standard) | Translucent or red |
| Compliance | FDA 21 CFR §177.2600, USP Class VI, RoHS |
Typical Applications
Food & Beverage
Processing equipment seals, filling machine O-rings, and dairy handling systems requiring FDA 21 CFR §177.2600 compliance in low-pressure static service.
Medical Devices
Respiratory equipment, drug delivery systems, and surgical instrument seals requiring USP Class VI biocompatibility and platinum cure certification.
Aerospace
Low-temperature fuel system static seals, cabin pressure seals, and cryogenic equipment requiring reliable flexibility to -60°C.
Electronics
Connector seals, enclosure gaskets, and thermal management systems requiring UV stability and wide temperature cycling.
Lighting & Outdoor
Weatherproof lighting fixture seals, outdoor electrical enclosures, and solar panel junction box gaskets with multi-decade UV and ozone resistance.
Chemical Compatibility Summary
Compatible With
- - Water and steam
- - Dilute acids and alkalis
- - Animal and vegetable oils
- - Ozone and weathering
- - Some petroleum oils (special grades)
Incompatible With
- - Concentrated acids and alkalis
- - Aromatic hydrocarbons
- - Chlorinated solvents
- - Petroleum oils (general purpose)
- - Superheated steam
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Read articleKey Advantages
Extreme Temperature Range
VMQ maintains elastomeric properties from -60°C cryogenic conditions to +200°C dry heat — no other standard elastomer matches this combination. TR10 low-temperature retraction (ASTM D1329) of -55°C to -60°C ensures cold-start sealing integrity in aerospace and outdoor equipment.
FDA and Medical Compliance
Standard grades meet FDA 21 CFR §177.2600 for repeated food contact. Platinum-cured USP Class VI grades are available with cytotoxicity testing documentation for pharmaceutical and healthcare applications.
Excellent UV and Ozone Resistance
The siloxane backbone is inherently resistant to oxidation, ozone, and UV radiation. Outdoor VMQ O-rings retain physical properties for 20+ years without surface cracking in ozone-rich environments.
Low Volatiles (Platinum Cure)
Platinum-cured silicone releases minimal volatile byproducts, making it suitable for sensitive applications in food, medical, and clean-room manufacturing environments where peroxide residues are unacceptable.
Lowest Glass Transition Temperature of Any Standard Elastomer
VMQ's glass transition temperature (Tg) is approximately -120°C, compared to -50°C for EPDM and -40°C for standard NBR. While the practical low-temperature limit is defined by TR10 (-55°C to -60°C) rather than Tg, this deep sub-ambient flexibility reserve ensures that VMQ does not embrittle during rapid temperature drops in aerospace altitude changes or cryogenic system cool-down. No other common O-ring material maintains elastomeric behavior across a 260°C span (-60°C to +200°C).
Broadest Color and Regulatory Option Range for Visual Identification
VMQ is available in more colors than any other O-ring material — translucent, red, blue, white, green, yellow, orange, and custom Pantone matching — because silicone pigments are inert and do not affect cure chemistry. This enables sophisticated color-coding systems in food plants (blue = water, red = CIP, white = product contact) and pharmaceutical facilities. Platinum-cured USP Class VI grades are available with comprehensive regulatory packages including cytotoxicity (ISO 10993-5), sensitization (ISO 10993-10), and irritation (ISO 10993-10) test reports per batch.
Frequently Asked Questions - VMQ
Can silicone O-rings be used with petroleum oils?
No. Standard VMQ silicone swells severely in petroleum-based oils, fuels, and most hydrocarbon solvents. ASTM D471 immersion in IRM 903 oil at 100°C shows volume changes exceeding 50% for many VMQ compounds — this causes complete loss of sealing force. For petroleum oil sealing, specify NBR (to +120°C) or FKM (to +200°C). VMQ's niche is temperature extremes, food/pharma compliance, and dry environments where oil is absent.
What is the difference between VMQ and FVMQ?
VMQ is standard vinyl methyl silicone. FVMQ (Fluorosilicone) adds fluorine groups to the silicone polymer backbone, giving it improved resistance to petroleum fuels, oils, and non-polar solvents — while retaining silicone's wide temperature range (-60°C to +175°C). FVMQ is used in aerospace fuel system seals where both low-temperature flexibility and fuel resistance are required. FVMQ costs 3–5× more than standard VMQ.
Are your silicone O-rings FDA compliant?
Yes. We supply FDA 21 CFR §177.2600 compliant VMQ O-rings for food and beverage applications. For pharmaceutical and medical applications, USP Class VI platinum-cured grades are available. Request a compound-specific compliance certificate when ordering — not all VMQ formulations meet both standards, and the certificate should identify the compound by designation, not just material family.
What is the difference between platinum-cured and peroxide-cured silicone?
Peroxide-cured silicone is the standard industrial grade — cost-effective and mechanically adequate for most applications. Platinum-cured silicone uses an addition-cure chemistry that produces no byproduct residues. The result is lower extractables, better biocompatibility, and cleaner behavior in sensitive food, pharmaceutical, and medical environments. Platinum cure is required by most USP Class VI certification protocols and by major food processing customers concerned about peroxide residues in direct-contact seals. Specify 'platinum cure' for food contact, medical, and bioprocess sealing.
What colors are available for silicone O-rings?
Standard colors are translucent and red. Blue, white, green, yellow, orange, and custom Pantone colors are available on request. Color coding is commonly used in food processing and pharmaceutical facilities to prevent material mix-up — for example, blue for water circuits, red for CIP circuits, white for product-contact seals. Custom colors typically add 1–2 weeks to lead time and minimum order quantities may apply.
Is VMQ suitable for steam applications?
VMQ has acceptable resistance to dry steam up to approximately 150°C for static, infrequent service. However, hydrolysis of the siloxane backbone under prolonged wet steam exposure causes progressive degradation — tensile strength and compression set worsen over time. For continuous saturated steam service, EPDM is the correct material (better hydrolysis resistance, ≤ 25% compression set at 150°C). FFKM pharmaceutical grades are used for steam above 180°C in autoclave and clean-steam systems.
Can VMQ O-rings handle high pressure?
VMQ's low tensile strength (5–10 MPa) and high elongation make it prone to extrusion through clearance gaps at moderate pressure. The practical pressure limit for static VMQ O-rings without backup rings is approximately 10–15 bar in a well-toleranced groove. Above 15 bar, use PTFE backup rings (one on each side for alternating pressure). For dynamic sealing above 5 bar, VMQ is generally not recommended — specify NBR or FKM for dynamic pressure applications. Design for static use only.
Do VMQ compounds meet IATF 16949, USP Class VI, or medical device regulations?
For automotive, VMQ compounds are available from IATF 16949-certified facilities with full PPAP documentation and material test reports. For medical devices, platinum-cured USP Class VI VMQ is supplied with comprehensive regulatory packages including cytotoxicity testing per ISO 10993-5, sensitization per ISO 10993-10, irritation per ISO 10993-10, and USP physicochemical tests (USP <661>, <87>, <88>). For EU medical device regulation (MDR 2017/745), we provide material biocompatibility summaries and supplier declarations. For semiconductor, ultra-low-outgassing VMQ grades with ASTM E595 TML ≤ 0.5% are available. Each medical batch includes a certificate of conformance referencing the specific USP Class VI test lot and cytotoxicity pass/fail result.
How do you ensure batch consistency for silicone O-rings, especially for medical and food grades?
VMQ batch consistency is controlled through: (1) Silicone gum testing — every polymer lot is tested for viscosity (Mooney or Brookfield), vinyl content (0.1–1.0 mol%), and volatile content (<0.5%). (2) Compounding — silica reinforcing filler (fumed silica, specific surface area 150–400 m²/g), heat stabilizer, and pigment are weighed to ±0.1%; platinum catalyst and hydrosilane crosslinker (for platinum-cure grades) are handled in clean-room conditions. (3) In-process testing — every batch is tested for rheometry (tack-free time, cure rate) and specific gravity. (4) Slab testing — hardness (±3 Shore A), tensile (±10%), elongation (±15%), tear strength, and compression set at 175°C (≤ 30%). (5) Regulatory testing — FDA compounds undergo extraction testing per 21 CFR §177.2600; USP Class VI compounds undergo physicochemical, cytotoxicity, and sensitization testing on a representative batch basis with retention samples. Lot-specific CoCs include all data and compound traceability.
Can VMQ O-rings from different suppliers be used interchangeably?
Dimensionally, AS568 and ISO 3601 VMQ O-rings are interchangeable across suppliers. Material equivalence requires verifying cure system (peroxide vs platinum — never interchange these in regulated applications), filler system (fumed silica type and loading affect mechanical properties), and regulatory status (FDA and USP Class VI certifications are supplier-specific and not transferable). Peroxide-cured VMQ from different suppliers is generally interchangeable for industrial applications. Platinum-cured medical grades vary more significantly in extractables levels and biocompatibility — switching suppliers for medical device seals requires comparative extractables testing and cytotoxicity verification. For food contact, ensure the new supplier's compound is listed on the appropriate FDA food contact notification or has a valid Letter of No Objection.
What color coding conventions are standard for silicone O-rings?
Translucent is the traditional color for platinum-cured medical and food-grade VMQ, signifying purity and absence of carbon black. Red is widely used for standard peroxide-cured industrial VMQ. Blue is common for FDA food-contact grades as a visual differentiator from industrial red. White is used in dairy and pharmaceutical applications where pigment contamination must be minimized. Green, yellow, and orange are often used for custom color-coding systems in multi-fluid facilities — for example, green = water, yellow = steam, orange = CIP chemical. Because VMQ is available in virtually any color, many facilities implement comprehensive color-coding SOPs. Always document your color code system and train maintenance staff, as color conventions are facility-specific rather than industry-standard.
What is the sustainability and recyclability profile of VMQ silicone?
VMQ has several sustainability advantages. The siloxane backbone is derived from silicon (sand, SiO₂), one of Earth's most abundant elements, rather than petroleum-derived monomers. Silicone's extreme durability in outdoor and high-temperature applications (20+ year service life) reduces replacement frequency and waste. VMQ is chemically inert and does not release toxic substances during use or disposal. Post-industrial silicone scrap (flash, rejected parts) can be recycled into lower-grade silicone products or used as filler in silicone rubber compounds. VMQ is REACH and RoHS compliant and free of phthalates, bisphenol A, and heavy metals. Bio-based silicone grades using plant-derived methanol in the silicone synthesis pathway are commercially available and offer 20–40% renewable carbon content. For customers with circular economy targets, we offer silicone recycling programs for post-industrial scrap from high-volume users.