ELASTOMER MATERIAL / SILICONE (VMQ)
Silicone, or VMQ, is screened for excellent low-temperature flexibility, heat resistance, weathering and electrical properties. Mechanics, media, permeation, cure system, post-curing and regulatory status remain compound-specific.
Upload a drawingVMQ is a sensible family to screen when an elastomer must stay flexible across a broad temperature range, withstand weathering and ozone, or deliver electrical properties. Typical parts include seals, diaphragms, grommets, protective caps and custom mouldings. The material name does not prove food-contact, medical, flame, tear or fluid performance. Each requirement needs evidence for the specific compound and finished part.
Wacker gives specific ELASTOSIL LSR and HCR grades a service range of about −55 °C to +210 °C and recommends additional heat stabilisation above +180 °C. This is a product example, not approval for every VMQ moulding. Duration, oxygen exposure, fluid, mechanical load, wall thickness and post-curing affect ageing. Do not use a data-sheet maximum as a component limit without life and functional testing.
LSR is a liquid, usually addition-cured two-component silicone used in automated injection moulding and complex small geometries. HCR or HTV is a high-consistency silicone processed by compression, transfer or injection moulding depending on the part. The route changes the tool, feed system, flash, cavity count, post-curing, surface and economical batch. LSR and HCR are not merely interchangeable commercial options; the supplier should identify and justify the proposed process.
Silicone compounds cover a broad Shore A range. Wacker, for example, publishes LSR grades around 41 ±3 Shore A and 60 ±3 Shore A, with other families covering further hardnesses. Those values do not promise universal availability. Specify nominal hardness, tolerance and a method such as ISO 48-4. Thin or curved parts can make direct measurement unreliable, so a reference test slab or another agreed method may be needed.
Compression set is a central compound comparison for static seals. Wacker describes low or improved compression set for selected LSR grades, but that performance belongs to the exact formulation and test condition. ISO 815-1 defines the method. Compare suppliers only at the same temperature, duration, compression, specimen geometry and recovery condition. For long-term heat, extended ageing may be more informative than one short test.
Silicone is not approved by temperature range alone. Oils, fuels, steam, cleaning fluids, gases and alternating media can affect swelling, strength or permeation. FKM or fluorosilicone may be assessed for fuel and oil, while a suitable EPDM compound may be assessed for water and steam depending on temperature. The RFQ must identify the actual media, concentration, contact time and permitted property change.
No. Colour and transparency do not prove regulatory suitability. Food contact, potable water, medical, pharmaceutical or biocompatibility duties require a specific compound with current evidence for the intended market and application. Processing, post-curing, pigment, cleaning and part geometry can also matter. State the exact regulation, document version, migration or test requirement and delivery evidence in the RFQ. COMET never infers compliance from the word silicone.
ISO 3302-1 is a basis for dimensions on solid moulded rubber products and ISO 3302-2 for selected geometrical tolerances. Depending on process, hardness and geometry, silicone is highly flexible; measuring force, conditioning and datums can change the result. Concentrate tight tolerances on functional characteristics. LSR micro-parts, thin lips and precision O-rings may need more specific drawing and inspection rules. Agree the measurement method before tooling release.
Silicone often offers better low-temperature flexibility and good dry-heat performance, while FKM is commonly preferred for many oils and fuels. Do not choose on maximum temperature alone. Mechanical duty, fluid, gas permeation, compression set, cleaning cycle and evidence determine the compound. Give both sourcing routes the same duty profile and test conditions for a reliable comparison.
For silicone, LSR or HCR process, hot- or cold-runner design, cavity count, venting, vacuum, flash limit, automatic demoulding, pigmentation and post-curing all influence cost. A universal MOQ or LSR break-even quantity is unreliable without the part and tool concept. Require separate figures for tooling, sampling, unit price, minimum batch, post-curing, inspection, cleanliness, packaging and freight. This exposes process costs hidden behind a low piece price.
Provide the drawing and revision, function, temperature-time profile, fluid, pressure or vacuum, motion, target hardness, colour or transparency, surface requirement, annual and batch demand, permitted flash and evidence. Clarify LSR or HCR preference, post-curing, cleanliness, product contact, packaging and test conditions. If the process is open, ask each supplier to justify its route and state the technical and commercial effects separately.
VMQ is a strong first choice for low-temperature flexibility, heat, weathering and electrical duties, but it is not automatically suitable for oil, fuel, steam or regulated product contact. LSR or HCR, hardness, cure and post-curing belong to the actual compound and process offer. Comparable quotations need the same drawing, tolerance, test and evidence basis.
The ranges and properties support initial screening. The offered compound, complete specification and customer approval remain decisive.
TECHNICAL ENQUIRY
Send the drawing, temperature, media, hardness and evidence needs. We will structure LSR or HCR, tolerances, tooling and validation.
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