VMQ HCR (HCR/HTV)
Grade
ASTM PVMQ, PMQ
Standard millable gum stock for extruded profiles, cable jackets and compression-molded parts.
Values for the HCR condition
Other VMQ grades and fills
VMQ is listed in 17 conditions; see the grade overview at VMQ.
Compare all 17 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Closed-cell silicone sponge / foam | Use for low-force compressible gasketing, weather sealing and insulation strips. | — | 1 | 180 | 30 Shore A |
Thermally conductive | Choose for thermal interface pads and gap fillers between heat sources and heat sinks. | — | 4 | 120 | 20 Shore D |
two-part room-temperature-vulcanizing silicone | Use for mold making, potting/encapsulation and low-volume cast parts where no press is available. | — | 5 | 400 | 30 Shore A |
Shore A 30 | Pick for soft seals, damping pads, wearable/skin-contact parts needing low compression force. | — | 6 | 550 | 30 Shore A |
Electrically conductive / ESD | For EMI gaskets, ESD-safe seals, conductive keypad pills and roller coverings. | — | 6 | 250 | 22 Shore D |
Shore A 40 | Use for low-closure-force gaskets, keypads and flexible tubing. | — | 7 | 480 | 40 Shore A |
Flame-retardant UL 94 V-0 compound | Use for cable jackets, rail and e-mobility parts requiring self-extinguishing performance. | — | 7 | 300 | 22 Shore D |
Phenyl-modified low-temperature silicone | Choose when service below -60 °C or improved radiation resistance is required. | — | 8 | 350 | 60 Shore A |
SHA60Default Shore A 60 | Default all-round compound for O-rings, gaskets and extruded profiles. | — | 8 | 350 | 20 Shore D |
Shore A 50 | Balanced sealing force and flexibility for static gaskets and medical tubing. | — | 8 | 420 | 50 Shore A |
Shore A 80 | For rollers, back-up rings and parts requiring stiffness over elasticity. | — | 8 | 180 | 30 Shore D |
HCRThis page HCR/HTV | Standard millable gum stock for extruded profiles, cable jackets and compression-molded parts. | — | 8 | 350 | 20 Shore D |
Low compression-set / heat-stabilized compound | Post-cured, iron-oxide heat-stabilized compound for long-term static seals up to 230 °C. | — | 8 | 250 | 25 Shore D |
Oil / steam-resistant modified silicone | Specify where contact with hot engine oil, ATF or pressurized steam is unavoidable (still far below FVMQ for fuels). | — | 8 | 250 | 20 Shore D |
Shore A 70 | Choose for pressure seals and O-rings needing extrusion resistance. | — | 9 | 280 | 25 Shore D |
Platinum-cured liquid silicone rubber | Pick for high-volume injection-molded precision parts, thin walls and clean/medical applications. | — | 10 | 550 | 50 Shore A |
High-tear / high-strength compound | Select for thin-wall parts, keypads and demolding-critical geometries needing tear resistance. | — | 11 | 650 | 50 Shore A |
What is VMQ HCR?
VMQ HCR is VMQ in the HCR grade — standard millable gum stock for extruded profiles, cable jackets and compression-molded parts. VMQ HCR has a tensile strength of 8 MPa (1.16 ksi), stronger than 50% of silicone grades. Elongation at break is 350% and the elastic modulus is 0.01 GPa (7.25×10⁻⁴ Msi). VMQ HCR has a density of 1.2 g/cm³ (0.0434 lb/in³), heavier than 50% of silicone grades. Its glass-transition temperature is -123°C (-189 °F). SHA60 is the default condition FabDigit quotes; HCR is available on request or by drawing note.
Limitations
- Needs corrosion protection — 68/100, worse than 100% of silicone grades
VMQ HCR properties
Typical room-temperature values for VMQ HCR; 17 are specific to this condition. Other listed values are VMQ reference data and may not represent this condition. Bars are the position among silicone grades.
Physical6
VMQ HCR has a density of 1.2 g/cm³ (0.0434 lb/in³), heavier than 50% of silicone grades. Its glass-transition temperature is -123°C (-189 °F).
Mechanical9
VMQ HCR has a tensile strength of 8 MPa (1.16 ksi), stronger than 50% of silicone grades. Elongation at break is 350% and the elastic modulus is 0.01 GPa (7.25×10⁻⁴ Msi).
Thermal8
VMQ HCR is rated for continuous service to 200°C (392 °F). It conducts heat at 0.22 W/m·K (0.127 BTU/hr·ft·°F), better than 100% of silicone grades. Thermal expansion is 250 µm/m·K (138.9 µin/in·°F).
Electrical7
VMQ HCR is an electrical insulator with a dielectric strength of 22 kV/mm (558.8 V/mil) and a resistivity of 1×10¹³ Ω·m.
Chemical & Environmental3
Corrosion resistance is good (68/100), worse than 100% of silicone grades. UV resistance is excellent.
Sustainability4
Producing a kilogram of VMQ HCR takes about 135 MJ of energy and emits 7 kg of CO₂ — more than 50% of silicone grades. Typical recycled content is 0%.
Manufacturability7
VMQ HCR's machinability is poor (25/100, better than 50% of silicone grades); weldability poor (15/100); formability excellent (85/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with VMQ HCR
Is VMQ easy to machine?
Cured silicone is best die-cut, water-jet or laser-cut; conventional machining requires freezing/support or very sharp tools since the part deflects under cutter load.
Can VMQ be welded?
Not weldable; join by adhesive bonding with primer, self-fusing (uncured-to-cured) overmolding, or RTV silicone adhesive — untreated surfaces need plasma/primer for good bond strength.
Can VMQ be formed, bent or molded?
HCR is compression/transfer-molded or extruded and cured at 150–190 °C followed by 4 h post-cure at ~200 °C; LSR is injection-molded from 1:1 A/B pumps at 160–210 °C mold with cold runners; allow 2–3 % shrink.
What surface finishes work on VMQ?
Deflash by cryogenic tumbling; post-cure removes volatiles for low compression set and odor; apply plasma/corona or fluoro/parylene coatings for low-friction, low-tack surfaces — silicone cannot be painted without special primers.
VMQ chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| vinyl-methyl siloxane unitscure sites for peroxide or Pt addition cure | 0.05 – 0.5 | 0.2 |
| fumed silica (reinforcing filler)surface-treated pyrogenic SiO2 | 20 – 40 | 30 |
| process aid / structure-control fluidshort-chain silanol-terminated siloxane | 1 – 6 | 3 |
| curing agent (organic peroxide or Pt cat | 0.3 – 2 | 1 |
| heat stabilizer (Fe2O3 / Ce compounds) | 0 – 2 | 0.5 |
| pigment | 0 – 2 | 0.5 |
| polydimethylsiloxane (PDMS) base polymerlinear siloxane backbone, high molecular weight gum | ≥ 55 (balance) | — |
VMQ HCR — frequently asked
What is VMQ HCR used for?
VMQ HCR is typically used for medical seals, food-grade gaskets, keypads, high-temp gaskets and baby products. In short: widest service temperature elastomer; standard for medical-grade rubber; low strength, high flexibility.
What is the tensile strength of VMQ HCR?
VMQ HCR has a typical tensile strength of 8 MPa (1.16 ksi) — stronger than 50% of silicone grades. Strength varies by condition: see the 17 listed tempers.
Is VMQ HCR easy to machine?
Not especially — machinability is rated poor (25/100, better than 50% of silicone grades). Cured silicone is best die-cut, water-jet or laser-cut; conventional machining requires freezing/support or very sharp tools since the part deflects under cutter load.
Can VMQ HCR be welded?
Not readily — weldability is rated poor (15/100). Not weldable; join by adhesive bonding with primer, self-fusing (uncured-to-cured) overmolding, or RTV silicone adhesive — untreated surfaces need plasma/primer for good bond strength.
What surface finishes work on VMQ HCR?
Deflash by cryogenic tumbling; post-cure removes volatiles for low compression set and odor; apply plasma/corona or fluoro/parylene coatings for low-friction, low-tack surfaces — silicone cannot be painted without special primers.
Can VMQ HCR be formed, bent or molded?
HCR is compression/transfer-molded or extruded and cured at 150–190 °C followed by 4 h post-cure at ~200 °C; LSR is injection-molded from 1:1 A/B pumps at 160–210 °C mold with cold runners; allow 2–3 % shrink.
What is the maximum service temperature of VMQ HCR?
VMQ HCR is rated for continuous use to about 200°C (392 °F), and briefly to 280°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM D2000 (SAE J200) — Rubber Classification System, type F/G class VMQ — ASTM International (2023)
- ISO 1629 — Rubber and latices, nomenclature (Q group) — ISO (2013)
- ELASTOSIL R / ELASTOSIL LR series technical data — Wacker Chemie (2023)
- SILASTIC HCR / LSR product selection guide — Dow (2022)
- KE series silicone rubber compounds — Shin-Etsu Chemical (2022)
- Engineered Materials Handbook Vol. 2 — Engineering Plastics / Elastomers — ASM International (1988)
- O-Ring Handbook ORD 5700 (elastomer compatibility) — Parker Hannifin (2021)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.