SEMITECH supplies 11 silicone intermediate grades spanning the midstream of the organosilicon value chain — cyclic siloxanes (DMC / D4 / D5), tetra-functional crosslinkers (TEOS), silylation reagents (HMDS), and polymer building blocks (hydrogen silicone, vinyl endblocker, OH-PDMS) — the inputs every downstream silicone manufacturer specifies as critical raw materials.
| 11 | 200 kg | 25 t |
|---|---|---|
| Intermediate grades stocked | Min. order (Tier 1) | Bulk container quantity |
Where Silicone Intermediates Sit in the Industry Chain
SEMITECH operates in the midstream: post-hydrolysis intermediates (DMC, D4, D5), alkoxide derivatives (TEOS), silylation reagents (HMDS), and functional-polymer building blocks that downstream manufacturers buy in tonnage to make silicone fluids, rubber, and silane coupling agents. Three buyer segments:
- Silicone manufacturers needing DMC / D4 / OH-PDMS / vinyl-endblocker at tonne scale
- Coatings and ceramics compounders needing TEOS as crosslinker or sol-gel binder
- Semiconductor and specialty-chemical buyers needing high-purity HMDS
Tier 1: Cyclic Siloxanes (DMC / D4 / D5) — The Silicone Polymer Source
DMC — Dimethylcyclosiloxane Mixture (CAS 69430-24-6)
The largest-volume silicone intermediate by tonnage — hydrolysed from dimethyldichlorosilane to start every silicone fluid, gum, and resin polymerisation.
DMC is the hydrolysis product of dimethyldichlorosilane. Every silicone fluid, rubber gum, and resin starts from DMC via ring-opening polymerisation. Industrial purity ≥99%. SEMITECH supplies in 200 kg drums and 25 t ISO-tanks.
D4 — Octamethylcyclotetrasiloxane (CAS 556-67-2)
Purified four-ring monomer separated from DMC by distillation — workhorse for cosmetic-grade PDMS fluids, HCR silicone gum, and dimethicone.
D4 is the purified monomer for high-quality PDMS (cosmetic-grade, dimethicone, textile softener). EU REACH classifies D4 as SVHC (vPvB) for cosmetic leave-on applications. Cosmetic-grade CoA (28-parameter) on request.
D5 — Decamethylcyclopentasiloxane (CAS 541-02-6)
Five-ring volatile cyclic — the most important carrier and skin-feel modifier in personal care, with sustained 5–8% annual demand growth in Asia.
D5 is the most important volatile silicone in cosmetics — antiperspirant, sunscreen, hair conditioner, colour cosmetics. Cosmetic-grade (≥99%) and technical grade available.
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Tier 1: TEOS and HMDS — Tetra-Functional and Silylation Workhorses
TEOS — Tetraethyl Orthosilicate, Si(OC₂H₅)₄ (CAS 78-10-4)
The most widely traded alkoxysilane on a tonnage basis — used as precision-casting binder, sol-gel coating precursor, and zinc-silicate paint binder.
Three dominant applications: (1) precision-casting binder for lost-wax ceramic shell moulds; (2) sol-gel and anti-graffiti coatings; (3) zinc-silicate primers for marine steel (ASTM D520). SEMITECH supplies industrial TEOS (≥98%) and pre-hydrolysed Ethyl Silicate-32/40.
HMDS — Hexamethyldisilazane, (CH₃)₃SiNHSi(CH₃)₃ (CAS 999-97-3)
High-margin silylation reagent for fumed silica surface treatment, semiconductor wafer photoresist primer, and analytical-chemistry silylation.
Three applications: (1) fumed silica hydrophobic surface treatment; (2) semiconductor wafer HMDS primer; (3) analytical GC-MS silylation. Industrial (≥98%) and electronic-grade (≥99.9%, 4–6x premium) available.
Tier 2: Hydrogen, Vinyl, and OH-Functional Silicone Polymer Building Blocks
Methyl Hydrogen Silicone Oil (CAS 63148-57-2)
Si-H functional at 0.18%, 0.36% or 0.75% H content — textile water-repellent through addition-cure crosslinkers.
Vinyl-Terminated PDMS (CAS 68083-19-2)
A-side polymer for addition-cure at 1k / 10k / 50k cSt — for LSR, RTV-2 medical, and HCR addition-cure rubber.
OH-Terminated PDMS / 107 Silicone Glue (CAS 70131-67-8)
Foundation polymer for RTV-1 and RTV-2 condensation-cure sealants — "107 silicone glue" across 25 to 20,000 cSt.
Tier 3: Phenyl, Fluoro, and MQ Resin Specialties
Phenyl Silicone Oil (CAS 63148-58-3)
Methylphenyl polysiloxane with 250°C continuous thermal stability — LED encapsulation, hot-fluid insulation, transformer cooling.
Fluorosilicone (CAS 63148-56-1)
Trifluoropropyl-methyl polysiloxane — silicone heat stability + fluoropolymer chemical resistance for fuel-system O-rings and long-wear cosmetics.
MQ Silicone Resin (CAS 68988-89-6)
Trimethylsilyl tackifier for silicone PSA — medical tape, transdermal patches, electronic attachment at M:Q ratios 0.6 / 0.8 / 1.0.
SEMITECH Intermediates Grade Reference: Key Specifications
| Tier | Grade | CAS No. | Spec | Primary Application | Pack Size |
|---|---|---|---|---|---|
| 1 | DMC | 69430-24-6 | ≥99% (D3+D4+D5+D6) | Silicone polymer source for fluid/rubber | 200 kg drum / 25 t ISO-tank |
| 1 | D4 (industrial) | 556-67-2 | ≥99.5% | High-quality PDMS fluid, HCR gum | 200 kg drum / ISO-tank |
| 1 | D5 (cosmetic / industrial) | 541-02-6 | ≥99% / ≥99.9% (cosmetic) | Cosmetics, hair-care, release fluid | 200 kg drum |
| 1 | TEOS / Ethyl Silicate-40 | 78-10-4 | ≥98% TEOS / 40% SiO₂ | Casting binder, zinc-silicate primer | 25 kg / 200 kg drum |
| 1 | HMDS (industrial / electronic) | 999-97-3 | ≥98% / ≥99.9% | Fumed silica surface treatment, semicon photoresist primer | 25 kg drum / 5 kg SS canister |
| 2 | Methyl Hydrogen Si Oil | 63148-57-2 | 0.18% / 0.36% / 0.75% H | Textile water-repellent / addition-cure crosslinker | 200 kg drum |
| 2 | Vinyl-PDMS | 68083-19-2 | 1k / 10k / 50k cSt | Addition-cure silicone A-side polymer | 200 kg drum |
| 2 | OH-PDMS / 107 | 70131-67-8 | 25 / 100 / 1k / 5k / 20k cSt | RTV-1 / RTV-2 condensation-cure base polymer | 200 kg drum / 1 t IBC |
| 3 | Phenyl Si Oil | 63148-58-3 | 5–25% phenyl content | LED encapsulation, hot-fluid insulation | 25 kg / 200 kg drum |
| 3 | Fluorosilicone | 63148-56-1 | 3,3,3-trifluoropropyl methyl Si | Fuel system O-rings, premium cosmetics | 25 kg drum |
| 3 | MQ Silicone Resin | 68988-89-6 | M:Q = 0.6 / 0.8 / 1.0 | Silicone PSA tackifier, release modifier | 25 kg drum (solid / 60% solution) |
FAQ
+DMC or D4 — which should a silicone polymer manufacturer specify?
DMC is the lower-cost feedstock — appropriate when polymerisation handles mixed ring sizes (most industrial PDMS). D4 is specified when polymer MW distribution must be tightly controlled (cosmetic dimethicone, semiconductor-grade, medical HCR gum). Cost differential 15–25%.
+Is SEMITECH D4 / D5 compliant with EU REACH for cosmetics?
D4 restricted in wash-off cosmetics above 0.1%; D5 restrictions evolving. SEMITECH issues per-batch CoA with regulatory disclosure; finished-product compliance is the formulator's responsibility.
+TEOS vs Ethyl Silicate-32 / Ethyl Silicate-40?
TEOS is the pure monomer (28% theoretical SiO₂). ES-32/40 are pre-hydrolysed forms (32/40% SiO₂) ready for direct use in zinc-silicate primers and inorganic-zinc paints. Use TEOS for sol-gel research and fresh hydrolysis control.
+Why is electronic-grade HMDS so much more expensive?
Ultra-low chloride (<1 ppm), ultra-low metals (<100 ppb), filtered particulate, stainless-steel canister packaging. The 4–6x premium is purification and packaging; specify electronic-grade only for semiconductor lithography.
+What are typical MOQ and lead times?
Tier 1 cyclics: 200 kg drum minimum, 25 t ISO-tank for bulk pricing. TEOS/HMDS/functional polymers: 25 kg minimum. Lead time 1–2 weeks Asia, 3–5 weeks Europe/North America. Air freight for screening samples on 5-day turnaround.
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