The VMQ code is a chemistry description, not a brand name: each letter tells the specifier which organic groups hang off the siloxane backbone, which directly drives temperature range, fluid behaviour, and cure system [S1][S3].
ASTM D1418 covers the general nomenclature for rubber and rubber lattices; for silicone elastomers, the "Q" denotes the polysiloxane (silicon-oxygen) chain, and the prefix letters denote pendant substituents, with M = methyl, V = vinyl, P = phenyl, and F = fluorine on the fluorosilicone branch [S1][S3].
The D1418 Letter Code: V + M + Q Decoded
Under ASTM D1418, the polymer classification is set by the organic side chains attached to the silicon-oxygen chain; if other groups are present, their initials are listed prior to the MQ designation, with MQ indicating methyl groups and V indicating phenyl groups in some references, while more standard references use V for vinyl substitution [S1][S3][S4].
VMQ (Vinyl Methyl Silicone) is the standard general-purpose designation, and the silicone family also includes PVMQ for extreme low-temperature service and FVMQ for fuel, oil, and solvent-resistant stocks [S3][S4].
The hard rule: the Q is the family, the prefix letters are the modifiers, so MQ, VMQ, PMQ, and PVMQ are all "silicones" distinguished only by the pendant groups, and that is the entire reason four sub-codes exist inside one letter family [S1][S3][S9].
Cross-Reference Across Three Standards: D1418, ISO/DIN 1629, and D2000
ASTM D1418 lists Q, MQ, VMQ, and PVMQ for the silicone family; ISO/DIN 1629 carries the identical Q, MQ, VMQ, and PVMQ designations, so a European datasheet and a US datasheet name the same polymer identically [S5][S8][S9].
For line-item call-outs in parts drawings and O-ring specifications, ASTM D2000/SAE J200 uses a different code set: FC, FE, and GE, where FC, FE, and GE are the D2000 "type/class" line call-outs used to drive hardness, tensile, and ageing requirements on a finished part [S2][S5].
In practice this means a buyer who needs a silicone O-ring specifies by D2000 line (for example, GE or FC) plus durometer and tensile, but references D1418/ISO 1629 to lock the polymer family to silicone, not to nitrile rubber or EPDM rubber [S2][S5].
What VMQ Tells You About the Compound
VMQ's main weakness is low tensile strength, poor tear and wear resistance; its strengths are excellent heat, ozone and corona resistance, dielectric stability, and resistance to many oils, chemicals, and solvents [S5].
Standard silicone compounds are usually peroxide-cured; platinum-cured compounds offer better flexibility and very low volatile matter, which is why platinum-cured grades are specified for medical systems requiring compliance to USP Class VI [S4][S5][S8].
Typical physical ranges for VMQ: durometer 20 to 90 Shore A, tensile strength 200 to 1,500 PSI, elongation 100% to 900%, hardness range 25 to 90 Shore A in published datasheets, and compression set rated good to excellent [S2][S5].
Sub-Family Comparison: MQ vs VMQ vs PMQ vs PVMQ vs FVMQ
MQ is general-purpose methyl silicone; VMQ adds vinyl substitution and is the standard general-purpose grade; PMQ adds phenyl for improved low-temperature flexibility; PVMQ is the extreme low-temperature stock; and FVMQ is the fluorosilicone branch used for fuel, oil, and solvent resistance [S3][S4].
On four decision criteria the sub-families line up as follows: low-temperature limit runs roughly -60°C standard for VMQ versus -100°C for special phenyl-modified PVMQ compounds, with brittle point down to -178°F (-115°C) in published VMQ data; high-temperature continuous service sits at +225°C standard, +300°C for special compounds, with +550°F (+288°C) as the published static maximum; fluid resistance to aliphatic and aromatic hydrocarbons is poor across the MQ family but good to excellent in FVMQ; and relative cost is medium-high for VMQ versus a further premium for FVMQ and medical-grade platinum-cured VMQ [S2][S3][S5].
The trade-off the letter code forces on a specifier is clear: pick the side-chain chemistry first, then pick the D2000 line, because the side chain drives temperature and fluid behaviour while the D2000 line drives the mechanical property envelope [S2][S3].
VMQ Thermal Envelope in Numbers
The published low-temperature range for VMQ is -178°F to -90°F (-115°C to -68°C) brittle point, with -170°F (-112°C) as the minimum for continuous static use, and -60°C (-76°F) as the standard low service temperature [S2][S5].
The high-temperature range is +400°F to +550°F (+204°C to +288°C) with +550°F (+288°C) as the maximum for continuous static use, and 225°C (437°F) standard / 300°C (572°F) special-compound high service temperatures per published datasheets [S2][S5].
That envelope, roughly -60°C to +225°C standard and down to -100°C or up to +300°C for special compounds, is the headline reason a specifier asks for VMQ by name rather than for silicone rubber as a generic industrial rubber class [S2][S5].
Failure Modes and Mis-Spec Traps
VMQ performs poorly in concentrated acids and alkalis, in ketones, in petroleum oils and fuels, in halogenated solvents, in ethers, and in steam above 120°C; it also has poor to fair gas permeability and poor to good radiation resistance [S2][S5].
VMQ performs well in engine and transmission oils (limited), diluted salt solutions, dry heat, ozone, weather, animal and vegetable oils, refrigerant ammonia (rated excellent), and at low temperatures where other elastomers embrittle [S2][S5].
The common mis-spec trap is treating VMQ as a fuel- or oil-resistant elastomer: for any hydrocarbon-rich service above ambient, FVMQ (fluorosilicone) is the D1418-coded answer, and nitrile rubber or hydrogenated nitrile usually wins on cost when the temperature envelope allows it [S2][S3].
Applications and Regulatory Pathways
VMQ is often used in automotive systems such as boots, oil-filter valves, and lighting gaskets; it can be formulated from "white list" ingredients per 21 CFR 177.2600 for food and beverage contact; it can be submitted to NSF for drinking-water service; and it can be used in medical systems requiring USP Class VI compliance [S5].
Platinum-cured VMQ is the grade of choice for medical and low-volatile-matter service, requires clean-room production, and carries a higher cost than standard peroxide-cured VMQ because of the platinum catalyst [S4][S5].
For an engineer cross-referencing a part on a drawing, the path is: D1418/ISO 1629 letter code (Q family, VMQ or PVMQ) to fix the polymer, D2000/SAE J200 line call-out (FC, FE, or GE) to fix the property envelope, and the cure system (peroxide vs platinum) to fix the regulatory and cleanliness tier [S2][S5][S8].
Trackable next node: confirm whether the silicone grade on a current drawing specifies a D2000 line call-out (FC, FE, GE) or only a D1418 letter code, because the D2000 call-out is what locks tensile, elongation, and heat-ageing requirements at the part level rather than at the polymer level [S2][S5]. A second signal worth watching is any internal change from peroxide-cured VMQ to platinum-cured VMQ on medical or food-contact drawings, since the cure-system line on a datasheet is the only place that cost and cleanliness tier are visible [S4][S5].
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