Get a Quote

Silicone Intermediates: SEMITECH Portfolio — DMC, D4, D5, TEOS, HMDS and Functional Polymer Building Blocks for the Silicone Value Chain

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.
Contents
Key Numbers
11
Intermediate grades stocked
200 kg
Min. order (Tier 1)
25 t
Bulk container quantity

Where Silicone Intermediates Sit in the Industry Chain

The organosilicon industry begins with metallurgical-grade silicon (Si) reduced from quartz, advances through chlorosilanes (HSiCl₃ / SiCl₄ / methylchlorosilanes from the Müller-Rochow direct synthesis) into hydrolysis intermediates, and terminates in the end-product silicone polymers — fluids, gums, rubbers, resins, and silane coupling agents. SEMITECH operates squarely in the midstream: we supply the hydrolysis intermediates (DMC, D4, D5), the alkoxide derivatives (TEOS), the silylation reagents (HMDS), and the functional-polymer building blocks (hydrogen-, vinyl-, OH-terminated PDMS) that downstream manufacturers buy in tonnage volumes to make silicone fluids, silicone rubber, and silane coupling agents.

Silicone intermediates are commodity-priced compared with finished products but carry multi-thousand-tonne global trade flow because every silicone manufacturer — from major rubber compounders to small specialty-fluid blenders — needs a continuous supply. SEMITECH’s eleven-grade portfolio is structured to serve three buyer segments:

  1. Silicone manufacturers producing finished fluids, gums, or rubber needing tonne-scale DMC / D4 / OH-PDMS / vinyl-endblocker.
  2. Coatings, ceramics and precision-casting compounders needing TEOS as a tetra-functional crosslinker or sol-gel binder.
  3. Semiconductor and specialty-chemical buyers needing high-purity HMDS for photoresist surface preparation, fumed-silica surface treatment, or silylation reactions.

MOQ scales accordingly: 25 kg samples for screening, 200 kg drums for trial batches, 25-tonne bulk-tank containers for production-scale supply.

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 (dimethylcyclosiloxane mixture, predominantly D3 / D4 / D5 / D6) is the hydrolysis product of dimethyldichlorosilane and the single largest-volume silicone intermediate by tonnage. Every silicone fluid, every silicone rubber gum, every silicone resin starts from DMC via base- or acid-catalysed ring-opening polymerisation. Industrial purity is ≥99% with controlled D4:D5 ratio for downstream polymer molecular-weight control. SEMITECH supplies DMC in 200 kg drums for laboratory and pilot-plant work and in 25-tonne ISO-tank containers for production-scale silicone manufacturers; lead time ex-Zhejiang is 1–2 weeks.

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 four-ring monomer separated from the DMC mixture by fractional distillation. D4 is the workhorse for high-quality PDMS fluid manufacture (cosmetic-grade silicone oil, dimethicone fluids), for HCR silicone gum (where stoichiometric D4 polymerisation produces the cleanest molecular-weight distribution), and for textile softener finishes. Cosmetic-grade D4 must meet stringent low-impurity specifications including residual chloride, water, and trace metals; SEMITECH issues a comprehensive cosmetic-grade CoA (28-parameter) on request. Note that EU REACH classifies D4 as a substance of very high concern (PBT) for cosmetic leave-on applications under specific exposure scenarios — buyers must confirm regulatory compliance for their finished application.

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 five-ring cyclic — by far the most important volatile silicone in cosmetics and personal care, used as a carrier and skin-feel modifier in antiperspirants, sunscreens, hair conditioners, and colour cosmetics. SEMITECH supplies a cosmetic-grade D5 (≥99% purity with low-D4 and low-D6 specifications) and a separate technical grade for industrial release-fluid and dry-cleaning applications. Cosmetic-grade D5 sees a sustained 5–8% annual demand growth driven by personal-care formulators in Asia substituting cyclomethicone-derivatives for hydrocarbon volatile carriers.

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.

TEOS is the most widely traded alkoxysilane on a tonnage basis. Three downstream applications dominate:

  1. Precision-casting binder — TEOS hydrolysed in ethanol with a small acid catalyst forms a colloidal silica binder for ceramic shell-mould slurry in lost-wax (investment) casting of turbine blades, jewellery, and complex metal parts.
  2. Sol-gel and anti-graffiti coating — partial hydrolysis produces silica networks used in protective coatings for natural-stone facades, glass anti-fogging treatment, and automotive headlamp UV-resistance.
  3. Ethyl silicate paint binder (Zinc Silicate primers) — TEOS-based zinc-rich primers for marine and offshore steel structures meeting ASTM D520 specifications.

SEMITECH supplies industrial TEOS (≥98% purity) and pre-hydrolysed Ethyl Silicate-32 / Ethyl Silicate-40 (28% / 40% SiO₂ content respectively) — the latter being the standard format for paint-formulation buyers who want to skip the on-site hydrolysis step.

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.

HMDS is a high-margin silylation reagent. Three signature applications:

  1. Fumed silica surface treatment — HMDS reacts with surface silanols on hydrophilic fumed silica to produce hydrophobic grades (SEMITECH’s own Semisil R-series uses HMDS as the surface treatment).
  2. Semiconductor wafer pre-baking (HMDS Primer) — applied to silicon wafers before photoresist coating to improve adhesion of organic photoresist to the silicon dioxide surface.
  3. Analytical chemistry silylation — HMDS converts polar OH and NH groups to TMS (trimethylsilyl) ethers/amines for GC-MS volatility, used in pharmaceutical impurity analysis and steroid metabolite quantitation.

SEMITECH supplies industrial-grade HMDS (≥98%) for fumed silica processing and electronic-grade HMDS (≥99.9%) for semiconductor lithography. The semiconductor-grade carries a 4–6× price premium and is delivered in stainless-steel canisters with PTFE-lined valves and certified low-particulate, low-metal specification.

Tier 2: Hydrogen, Vinyl, and OH-Functional Silicone Polymer Building Blocks

Methyl Hydrogen Silicone Oil (CAS 63148-57-2)

Si-H functional siloxane copolymer supplied at 0.18%, 0.36% or 0.75% H content — textile water-repellent finishes through addition-cure crosslinkers.

Methyl hydrogen silicone oil (MD′ₓM, methyl hydrogen siloxane copolymer) is supplied at three hydrogen contents — 0.18%, 0.36%, and 0.75% — covering the application spectrum from low-reactivity textile water-repellent finishes (0.18%) through standard release coatings (0.36%) to highly reactive crosslinkers for addition-cure silicone rubber (0.75%). The Si-H bond reacts with vinyl-PDMS in the presence of platinum catalyst (Karstedt or Speier from SEMITECH’s catalyst portfolio) to form the addition-cure network.

Vinyl-Terminated PDMS (CAS 68083-19-2)

A-side polymer for addition-cure silicone systems at 1k / 10k / 50k cSt — for LSR, RTV-2 medical, and HCR addition-cure rubber.

Vinyl-terminated PDMS (vinyl-MM endblocker for short chains; vinyl-functional siloxane for higher MW) is the matched A-side for addition-cure silicone systems. SEMITECH supplies three viscosities: 1000 cSt for thin-section LSR, 10,000 cSt for medium RTV-2, and 50,000 cSt for high-strength HCR addition cure.

OH-Terminated PDMS / 107 Silicone Glue (CAS 70131-67-8)

Foundation polymer for RTV-1 and RTV-2 condensation-cure sealants — known in the Chinese silicone industry as “107 silicone glue” across viscosity grades 25 to 20,000 cSt.

OH-terminated PDMS (commonly known in the Chinese silicone industry as “107 胶 / 107 silicone glue”) is the foundation polymer for RTV-1 and RTV-2 condensation-cure silicone sealants. SEMITECH supplies it across the standard viscosity grades — 25 cSt and 100 cSt for one-component low-modulus sealants, 1,000 cSt and 5,000 cSt for high-modulus structural silicones, and 20,000 cSt for tooling-grade RTV-2.

Tier 3: Phenyl, Fluoro, and MQ Resin Specialties

Phenyl Silicone Oil (CAS 63148-58-3)

Methylphenyl polysiloxane with 250°C continuous thermal stability — for LED encapsulation, hot-fluid insulation, and transformer cooling.

Phenyl silicone oil (methylphenyl polysiloxane) replaces some methyl groups with phenyl, raising thermal stability to 250°C continuous and 300°C short-term — useful in LED encapsulation (where thermal cycling demands cure stability), high-temperature electrical insulating fluids, and specialty fluid for transformer cooling under elevated ambient.

Fluorosilicone (CAS 63148-56-1)

Trifluoropropyl-methyl polysiloxane combining silicone heat stability with fluoropolymer chemical resistance — premium for fuel-system O-rings and long-wear cosmetics.

Fluorosilicone (trifluoropropyl-methyl polysiloxane) carries the unique combination of silicone temperature stability and fluoropolymer chemical resistance — the premium specification for fuel-system O-rings, cosmetic specialty applications (long-wear lipstick, mascara), and certain release-coating substrates.

MQ Silicone Resin (CAS 68988-89-6)

Trimethylsilyl tackifier for silicone pressure-sensitive adhesives — used in medical tape, transdermal patches, and electronic component attachment, supplied at three M:Q ratios (0.6 / 0.8 / 1.0).

MQ silicone resin (trimethylsilyl-functional resin / silicone resin solid) is the tackifier for silicone pressure-sensitive adhesives (used in medical tape, transdermal patches, electronic component attachment). SEMITECH supplies MQ resin at three M:Q ratios (0.6, 0.8, 1.0) covering the application spectrum.

Scope Discipline: Why SEMITECH Does Not Trade Chlorosilanes or Polysilicon

SEMITECH’s portfolio deliberately stops at the post-hydrolysis intermediates. We do not supply the upstream chlorosilanes — trichlorosilane (TCS, HSiCl₃), silicon tetrachloride (STC, SiCl₄), or methylchlorosilanes (M1 / M2 / M3). These materials react violently with atmospheric moisture, releasing hydrogen chloride and (for TCS) hydrogen gas, and require integrated production-to-consumption pipelines that are economically unworkable for an intermediate-trading model. They also fall under UN Class 8 corrosive transport regulations (UN 1295 for TCS, UN 1818 for STC) creating a logistics burden no end-user benefits from.

We similarly do not supply polysilicon or metallurgical-grade silicon — these are subject to US export-control regimes (EAR, UFLPA forced-labour traceability) that introduce structural compliance risk into a trade flow. SEMITECH’s positioning is the post-chlorosilane midstream where chemistry is stable, transport is straightforward, and downstream demand is wide and persistent. This discipline keeps our supply chain simple and our customer base broad.

SEMITECH Intermediates Grade Reference: Key Specifications

TierGradeCAS No.SpecPrimary ApplicationPack Size
1DMC69430-24-6≥99% (D3+D4+D5+D6)Silicone polymer source for fluid/rubber200 kg drum / 25 t ISO-tank
1D4 (industrial)556-67-2≥99.5%High-quality PDMS fluid, HCR gum200 kg drum / ISO-tank
1D5 (cosmetic / industrial)541-02-6≥99% / ≥99.9% (cosmetic)Cosmetics, hair-care, release fluid200 kg drum
1TEOS / Ethyl Silicate-4078-10-4≥98% TEOS / 40% SiO₂Casting binder, zinc-silicate primer25 kg / 200 kg drum
1HMDS (industrial / electronic)999-97-3≥98% / ≥99.9%Fumed silica surface treatment, semicon photoresist primer25 kg drum / 5 kg SS canister
2Methyl Hydrogen Si Oil63148-57-20.18% / 0.36% / 0.75% HTextile water-repellent / addition-cure crosslinker200 kg drum
2Vinyl-PDMS68083-19-21k / 10k / 50k cStAddition-cure silicone A-side polymer200 kg drum
2OH-PDMS / 10770131-67-825 / 100 / 1k / 5k / 20k cStRTV-1 / RTV-2 condensation-cure base polymer200 kg drum / 1 t IBC
3Phenyl Si Oil63148-58-35–25% phenyl contentLED encapsulation, hot-fluid insulation25 kg / 200 kg drum
3Fluorosilicone63148-56-13,3,3-trifluoropropyl methyl SiFuel system O-rings, premium cosmetics25 kg drum
3MQ Silicone Resin68988-89-6M:Q = 0.6 / 0.8 / 1.0Silicone PSA tackifier, release modifier25 kg drum (solid / 60% solution)
SEMITECH’s eleven-grade silicone-intermediates portfolio is the structural complement to our finished-product lines. Customers buying our silicone fluids, RTV silicones, silane coupling agents, or fumed silica increasingly buy the upstream intermediates from the same SEMITECH supply chain — single-source dual-stream sourcing reduces qualification overhead and allows volumetric pricing across the basket.

FAQ

DMC or D4 — which should a silicone polymer manufacturer specify?
DMC is the lower-cost feedstock with controlled D3:D4:D5:D6 ratio — appropriate when the downstream polymerisation is engineered to handle a mix of ring sizes (most industrial PDMS production). D4 (purified four-ring) is the higher-purity feedstock specified when the polymer molecular-weight distribution must be tightly controlled — high-quality cosmetic dimethicone, semiconductor-grade silicone fluids, and HCR gum for medical implant applications. Cost differential is 15–25%; choose by downstream specification, not by default.
Is SEMITECH D4 / D5 compliant with EU REACH for cosmetic applications?
EU REACH classifies D4 (CAS 556-67-2) as PBT/vPvB substance of very high concern and restricts its use in wash-off cosmetics above 0.1%. D5 (CAS 541-02-6) restrictions are evolving — currently restricted in wash-off products with potential extension to leave-on. SEMITECH issues per-batch CoA with regulatory disclosure; the burden of compliance for the finished cosmetic application rests with the formulator. For ASEAN, North American, and most Asia markets, D4 / D5 cosmetic use remains permitted within established guidelines. Consult your regulatory team before specifying.
What is the difference between TEOS and Ethyl Silicate-32 / Ethyl Silicate-40?
TEOS (Si(OC₂H₅)₄) is the pure tetraethyl orthosilicate monomer at 28% theoretical SiO₂. Ethyl Silicate-32 and Ethyl Silicate-40 are partially hydrolysed and condensed forms with 32% and 40% SiO₂ content respectively — they have already undergone the controlled condensation step that paint formulators would otherwise need to perform on-site. Use ES-32 and ES-40 directly in zinc-silicate primer and inorganic-zinc paint formulations; use TEOS for sol-gel research, ceramic binder development, and applications requiring fresh hydrolysis control.
Why is the price of electronic-grade HMDS so much higher than industrial HMDS?
Electronic-grade HMDS (≥99.9% purity, used in semiconductor wafer photoresist primer) requires ultra-low chloride (<1 ppm), ultra-low metal contamination (<100 ppb total Fe + Cu + Cr + Na + K), ultra-low particulate (≥0.2 μm filtered), and delivery in stainless-steel canisters with PTFE-lined valves. The purification step (multiple distillations under inert atmosphere) and the packaging (stainless steel vs HDPE drums) account for most of the 4–6× premium versus industrial HMDS. Specifying electronic-grade for non-semiconductor applications is wasted spend; industrial HMDS at ≥98% serves all fumed-silica processing, analytical silylation, and most chemical synthesis use cases.
Why does SEMITECH not supply trichlorosilane or silicon tetrachloride?
Three reasons:
  1. Safety — TCS and STC react violently with moisture, releasing HCl and (for TCS) hydrogen, requiring sealed pipeline-to-pipeline transfer that intermediate trading does not provide.
  2. Logistics — UN Class 8 corrosive transport classification creates significant freight, insurance, and incident-response burden.
  3. Economics — TCS / STC supply is captive to integrated polysilicon and silane producers (Wacker, Hemlock, GCL, Tongwei) selling pipeline volumes; intermediate traders cannot match their pricing.
Customers needing TCS / STC should source directly from the integrated producers; for the post-chlorosilane intermediates (DMC, D4, D5, TEOS, HMDS, etc.), SEMITECH is the cost-rational alternative.
What are typical MOQ and lead times for production-scale orders?
Tier 1 cyclic siloxanes (DMC, D4, D5): 200 kg drum minimum, with bulk pricing tier at 25-tonne ISO-tank container. TEOS / HMDS / functional polymers: 25 kg drum minimum for samples and trial, 200 kg drum standard production. Lead time ex-Zhejiang for stocked grades is 1–2 weeks to Asia, 3–5 weeks to Europe and North America. Bulk-tank ISO-container shipments require 4-week production scheduling notice. Air freight available for screening samples (1–25 kg) on 5-working-day turnaround.