| HS Code | 558537 |
| Product Name | Phenyl Silicone Fluid RH-C226A |
| Chemical Type | Phenyl polysiloxane |
| Appearance | Colorless to pale yellow transparent liquid |
| Viscosity At 25 C | 200–500 mPa·s |
| Density At 25 C | 1.05–1.10 g/cm³ |
| Refractive Index At 25 C | 1.53–1.54 |
| Phenyl Content | 25–30% |
| Flash Point | >300°C |
| Volatile Content | ≤1% |
| Thermal Stability | High-temperature resistant |
| Dielectric Strength | ≥20 kV/mm |
| Volume Resistivity | ≥1×10^14 Ω·cm |
| Acid Value | ≤0.05 mg KOH/g |
| Pour Point | ≤-30°C |
As an accredited Phenyl Silicone Fluid RH-C226A factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Phenyl Silicone Fluid RH-C226A is packaged in 200 kg iron drums, suitable for industrial storage and transport. |
| Container Loading (20′ FCL) | One 20′ FCL container loaded with Phenyl Silicone Fluid RH-C226A in sealed drums, securely stowed and properly labeled for shipment. |
| Shipping | Phenyl Silicone Fluid RH-C226A is shipped in securely sealed steel drums or IBCs under clean, dry conditions. Containers are labeled and handled according to the SDS and applicable transport regulations. Store away from moisture, heat, and contamination; classify and document per supplier SDS and local requirements. |
| Storage | Store Phenyl Silicone Fluid RH-C226A in a cool, dry, well-ventilated area away from heat, ignition sources, strong oxidizers, and direct sunlight. Keep containers tightly closed and properly labeled to prevent moisture and contamination. Store only in original containers. Use secondary containment and avoid freezing or excessive temperatures. Follow local regulations and the product SDS for specific storage limits and incompatibilities. |
| Shelf Life | Typically 24 months from manufacture when stored in original, unopened containers in a cool, dry, well-ventilated area. |
In high-brightness LED package assembly, the need for a high-refractive-index coupling layer between the emitting die and encapsulation resin creates a measurable sensitivity to phenyl content and moisture absorption in phenylmethylpolysiloxane fluids. When phenyl silicone fluid RH-C226A is incorporated as a co-fluid into addition-cure phenyl silicone resins at 5–25 phr, the mixed refractive index shifts from approximately 1.47 to 1.54 depending on the methyl-to-phenyl siloxane ratio; this shift is verified by ASTM D1747-09 at 25 °C. In LED chip-scale packages, the optical coupling gel is deposited by precision meter-mix dispensing equipment with a dispense volume tolerance of ±2%, followed by vacuum degassing at 0.5–1.0 kPa for 10–15 min to remove entrapped air before thermal cure. The cure schedule commonly used is 80 °C for 1 h, then 150 °C for 2 h in a convection oven. Ambient humidity above 60% RH during dispensing is known to cause void formation and reduced adhesion to silver-plated lead frames, so humidity control is not optional on a production line. Long-term reliability is conditioned to JEDEC JESD22-A101 temperature-humidity bias at 85 °C/85% RH, JEDEC JESD22-A102 autoclave exposure at 121 °C/100% RH, and JEDEC JESD22-A104 thermal cycling from -40 °C to +125 °C. Outgassing acceptance under ASTM E595-15 must remain below 1.0% total mass loss and below 0.1% collected volatile condensable material for space-sensitive optoelectronics. Terminal components produced from this route include chip-on-board LED modules, high-CRI lighting engines, silicone-lensed UV-LED packages, and optical coupling gels in automotive forward lighting. Published data for RH-C226A-specific thermal aging kinetics in high-brightness LED packages is limited, so incoming batch refractive index and residual catalyst activity require screening before formulation scale-up.
| Phenyl silicone fluid addition (phr) | Mixed refractive index at 25 °C (ASTM D1747-09) | Mixed viscosity at 25 °C (mPa·s) | Shore A hardness | Total mass loss (ASTM E595-15) |
|---|---|---|---|---|
| 5 | 1.47 | 1,200 | 45 | 0.2% |
| 15 | 1.50 | 1,850 | 50 | 0.3% |
| 25 | 1.52 | 2,500 | 56 | 0.4% |
| 35 | 1.54 | 3,000 | 62 | 0.5% |
| 45 | 1.55 | 3,400 | 66 | 0.6% |
Representative values for phenylmethylpolysiloxane co-fluids at 25 °C; not grade-specific production control values.
Closed-loop thermal oil systems operating above 260 °C impose different oxidation and viscosity-stability requirements than ordinary dimethyl silicone heat carriers. Phenyl substitution along the siloxane chain raises the continuous service ceiling of RH-C226A relative to polydimethylsiloxane by reducing oxidation-prone methyl-rich domains and restricting chain depolymerization to low-molecular-weight cyclic siloxanes. The actual maximum bulk fluid temperature must nevertheless be confirmed by ASTM D6743 thermal stability testing in the presence of nitrogen. In practice, RH-C226A is used as the primary heat transfer base fluid or blended with dimethyl silicone at 20–50 wt% to adjust low-temperature viscosity. A hindered phenol antioxidant is added at 0.5–1.5 wt% to extend oxidation life, and a metal deactivator at 0.05–0.2 wt% protects against copper-catalysed degradation from heat exchanger tubes. The production process for a closed-loop charge involves drying the system to less than 200 ppm water content, charging the fluid under nitrogen pressure to 2–3 bar, and circulating through a 10 µm strainer before heating at a ramp rate not exceeding 5 °C/min above 200 °C. System components must include an expansion tank blanketed with nitrogen, a centrifugal pump with a mechanical seal rated for 300 °C, and a bypass valve sized for thermal expansion. Failure to maintain nitrogen blanketing exposes the fluid to oxidation at temperatures above 180 °C, leading to viscosity increase and acid number rise. Data from comparable phenylmethylpolysiloxane fluids indicate that viscosity at 40 °C by ASTM D445-21 may increase by 10–20% after 1,000 h at 280 °C under nitrogen, while open contact with air at the same temperature can double the acid number within 48–72 h. The base fluid is classified under ISO 6743-12 family Q. Terminals using this fluid class include hot-oil units for plastic blow-molding and injection tooling, jacketed glass-lined reactors, and thermal test benches for automotive electric-vehicle battery cooling plates.
Rotary vane vacuum pumps used in process vacuum service require base oils that maintain low vapour pressure and do not form carbonaceous deposits in high-temperature zones. RH-C226A can function as the main base stock at 70–90 wt% in vacuum pump oils when compounded with an ashless antiwear package at 1–2 wt%, a defoamer at 0.1 wt%, and a rust inhibitor at 0.2 wt%. The lower volatility of phenylmethylpolysiloxane compared with dimethyl silicone at 150 °C reduces backstreaming in pumps handling aggressive chemical vapours, provided the pump is not exposed to strong acidic or alkaline streams that catalyse siloxane rearrangements. For high-temperature grease production, the fluid is added at 15–25 wt% into a lithium complex thickener system through a pressure reactor heated to 190–210 °C, then milled in a three-roll mill to a worked penetration of 265–295 mm/10 according to ASTM D217. The downstream production test sequence includes viscosity measurement by ASTM D445-21, viscosity index by ASTM D2270-10, corrosion testing by ASTM D130-19 for copper strip, and four-ball wear testing by ASTM D2266-19. Acceptable values for high-temperature silicone grease typically remain below 0.6 mm wear scar at 60 kg load. The fluid should not be combined with amine-based antioxidant packages at concentrations above 0.5 wt%, because amine-silicone incompatibility can produce haze and accelerate gelation in closed reservoirs. Terminals produced include high-temperature oven chain oils for textile stenter frames, rotary vane pump oils for freeze-drying and vacuum packaging lines, and lithium complex greases for bakery conveyor bearings under 180 °C continuous exposure.
Airless spray deposition of semi-permanent release films on hot rubber molds is used where high flash point and low surface tension reduce mold fouling and simplify part surface finish control. In this use, RH-C226A is pre-diluted with a low-viscosity dimethyl silicone fluid at 1:1–1:3 before loading into an airless spray system at 0.6–1.2 MPa atomizing pressure. The effective phenyl silicone content on the mold surface is built up in three successive passes to a dry film thickness of 5–10 µm, measured by a dry-film thickness gauge. For internal release addition in peroxide-cured rubber compounds, the fluid is added at 0.5–2.0 wt% during the second-stage open mill mixing cycle at 50–60 °C, after carbon black and before the peroxide cure system. Addition above 2.0 wt% is known to reduce tensile strength by interfering with filler-polymer interaction, visible as a 5–10% drop in modulus at 100% elongation when tested by ASTM D412-16. Compliance requirements depend on the end article: rubber articles in repeated food contact are evaluated under FDA 21 CFR 177.2600, and incidental-contact release agents under FDA 21 CFR 178.3570. In the European Union, the preparation must be registered under REACH (EC) No 1907/2006 and may require food-contact listing via national measures. Terminals manufactured with this release route include EPDM gaskets, molded rubber air intake ducts, cured silicone rubber keypads, and compression-molded elastomer vibration mounts. The major operational limitation is that residues on the part surface reduce adhesion for post-molding painting or bonding; to remove them, plasma treatment or solvent wiping with isopropyl alcohol after demolding is required.
The loose-tube cable filling operation begins with a soft gel prepared from RH-C226A as the primary liquid phase at 80–95 wt%, thickened with hydrophobic fumed silica at 5–15 wt% and stabilized with a redox buffer at 0.2–0.5 wt% to limit hydrogen evolution. The gel must show stable viscosity under shear and low oil separation after aging. Production equipment is a vacuum planetary mixer at -0.095 MPa and 60–80 °C, followed by tube filling through a gear pump at a line speed of 200–600 m/min and a gel temperature of 70–90 °C. Compliance for optical cable is assessed under IEC 60794-1-22 mechanical testing and Telcordia GR-20-CORE environmental reliability, with oil separation governed by internal procedures such as a 24 h/80 °C separation test requiring less than 3% syneresis and hydrogen generation below 0.02 mL/g after 48 h/150 °C. Phenyl silicone fluid in this application is selected over dimethyl silicone because aromatic substitution increases hydrophobicity and reduces moisture penetration into the fiber core. Its somewhat higher viscosity at low temperature requires a pour point modifier when cables are specified for -40 °C installation. Published data for this specific grade in optical cable filling compounds is limited, so qualification must be performed by the cable compounder using their own filler system and extrusion line. Terminal products include loose-tube outdoor fiber optic cables, water-blocked indoor/outdoor distribution cables, and microduct drop cables with high fiber count.
| Standard / test condition | Measured property | Acceptance basis |
|---|---|---|
| IEC 60794-1-22 tensile, -40 °C to +70 °C | Attenuation change | ≤ 0.05 dB/km |
| Telcordia GR-20-CORE environmental cycling | Gel separation | ≤ 3% |
| ASTM D445-21 at 25 °C | Base oil kinematic viscosity | 100–500 mm²/s |
| ASTM E595-15, 125 °C/24 h | Outgassing total mass loss | ≤ 1.0% |
Measurements on sealed damper hardware show that the damping fluid’s viscosity-temperature slope governs shear torque transmission across a wide clutch speed range. RH-C226A is blended with high-molecular-weight dimethyl silicone at 10–30 wt% to target a kinematic viscosity of 100–500 mm²/s at 25 °C, and the finished fill is degassed at 80 °C and 0.5 kPa before injection into the viscous coupling under vacuum. The fill volume is set to 85–95% of the internal coupling volume to allow thermal expansion. Excess fill beyond 95% leads to overpressure at 120 °C and seal extrusion, while underfill below 80% reduces torque transfer and creates cavitation noise. Validation testing on an engine dynamometer uses a repeated sweep from 500 rpm to 1,500 rpm, with a fluid temperature rise from 40 °C to 110 °C; torque decay across the sweep must remain below 15% to ensure consistent damping. The fluid is evaluated by ASTM D445-21 for kinematic viscosity, ASTM D341-20 for viscosity-temperature slope, and ASTM D2270-10 for viscosity index. Long-term oxidation resistance is assessed with ASTM D4636-17 corrosion-oxidation testing on aluminum and steel coupons. Limitations include incompatibility with ethylene-propylene diene monomer seals if the phenyl silicone fluid is contaminated with mineral oils, and the need to avoid open-air processing above 180 °C to prevent oxidative gel formation. Terminals using this damping fluid class include automotive fan viscous couplings, engine crankshaft torsional vibration dampers, and instrument dashpots in avionics indicators.
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Phenyl Silicone Fluid RH-C226A is identified as a linear phenylmethylpolysiloxane belonging to the aryl-modified silicone fluid class. In this class, a controlled fraction of the Si–CH3 groups of a polydimethylsiloxane backbone is replaced by Si–C6H5 functionality. The substitution alters refractive index, thermal stability, oxidative resistance, density, and compatibility with aromatic resins. Publicly available product-specific documentation for the RH-C226A designation remains limited; consequently, the data discussed below are class-typical for phenylmethylsiloxane fluids with optical and thermal service requirements, and lot-specific values must be obtained from the supplier’s certificate of analysis.
The product is normally characterized by kinematic viscosity at 25 °C according to ASTM D445 or ISO 3104, refractive index at 25 °C using ASTM D1218, flash point by ISO 2592 or ASTM D92, and volatile content by gravimetric methods such as ISO 3251 or an agreed supplier procedure. Incoming inspection on production lines typically also records moisture content by Karl Fischer titration according to ASTM D6304 or ISO 15512, because water contamination above class thresholds can produce haze or hydrolysis-induced viscosity shifts in aryl-modified siloxanes.
The fluid is evaluated for use in closed-loop heat transfer, optical encapsulant formulations, high-temperature damping, and release-agent modification. Its operational differentiation from dimethyl silicone fluids arises from the phenyl substituent, which increases refractive index, density, and thermal stability while reducing low-molecular-weight cyclic evolution during sustained thermal service.
In polydimethylsiloxane, thermal degradation under inert conditions proceeds via cyclic oligomer formation through chain-folding and siloxane bond cleavage. In phenylmethylsiloxane fluids, the aryl substituent contributes π-electron density that can stabilize adjacent siloxane bonds and reduce the rate of low-molecular-weight cyclic evolution. Published thermogravimetric data for phenylmethylsiloxane fluids with refractive indices from 1.500 to 1.550 show weight-loss onset temperatures commonly reported in the range of 350 °C to 400 °C under nitrogen at a heating rate of 10 °C/min, whereas dimethyl fluids of comparable kinematic viscosity typically display onset temperatures in the range of 300 °C to 350 °C under identical conditions. These figures are class-reported and are not a lot-specific guarantee for RH-C226A.
Oxidative stability also differs. Phenyl substituents are more resistant to radical abstraction than methyl substituents; oxidation of a dimethyl fluid at sustained temperatures above 150 °C in air can produce carbonyl species and eventually silica-like gels, whereas phenyl-modified fluids often show lower acid-number rise and lower viscosity increase over the same exposure interval. The comparative measurement is usually performed in forced-air ovens with 50 g samples in borosilicate vessels, with viscosity drift measured by ASTM D445 and acid number by ASTM D974. Inhibited phenylmethylsiloxane grades are often specified with total acidity below 0.01 mg KOH/g after 1,000 h at 150 °C, whereas uninhibited dimethyl fluids may exceed 0.05 mg KOH/g under similar conditions. Gel time is commonly recorded when kinematic viscosity reaches 200% of initial; this endpoint is more reproducible than visual gelation for process control. For RH-C226A, an oxidative-stability protocol should be agreed before long-duration use above 150 °C.
Closed-loop heat transfer systems that operate between 200 °C and 280 °C are sometimes charged with a phenylmethylsiloxane fluid of the RH-C226A class because its lower volatility and higher aromatic content can reduce vapor lock and coking compared with mineral oils. Transfer-line viscosity is measured with capillary viscometers per ASTM D445, while in-situ process viscosity under shear may be monitored with a cone-and-plate rheometer at 1 s-1 to 100 s-1. Production-scale experience indicates that batch-to-batch variation in phenyl distribution can shift viscosity at 25 °C by several percent even when refractive index stays within specification; therefore incoming lots are temperature-adjusted to 25.0 °C ± 0.1 °C before parallel viscosity and refractive index verification.
When the fluid is used as a damping medium in automotive sensor applications, air bubbles entrained during drum filling can produce inconsistent damping response. Vacuum deaeration at 10–50 mbar for 30–60 min is commonly applied before filling. The product class exhibits lower surface tension than comparable polyalkylene glycols, but the exact surface tension for RH-C226A should be confirmed by du Noüy ring or Wilhelmy plate measurement according to ASTM D1331 or DIN 53914. Avoid uncontrolled exposure to relative humidity above 60%; moisture uptake can increase the Karl Fischer water content above 100 ppm, which is a common rejection threshold for optical or hot-cure applications. Storage in carbon steel containers without epoxy phenolic linings at temperatures above 40 °C should be avoided; trace iron from unlined vessels can catalyze siloxane condensation and gradual viscosity build.
Materials of construction for storage and processing include 316L stainless steel, borosilicate glass, and epoxy-phenolic lined carbon steel. Copper alloys should be excluded at temperatures above 150 °C because copper species catalyze oxidative gelation and can produce color bodies. Nitrile and natural rubber gaskets are unsuitable at elevated temperature; fluorocarbon or polytetrafluoroethylene gaskets are preferred for transfer lines. These limitations are based on silicone fluid compatibility practice and should be confirmed against the supplier safety data sheet for RH-C226A.
Because public supplier documentation for the exact RH-C226A designation is limited, the following matrix defines the analytical framework against which a supplier certificate of analysis is read. Acceptance windows are contractual and vary by end-use. Phenyl molar fraction is normally calculated from UV absorption or 1H NMR integration; UV methods can overestimate phenyl content when residual benzene or toluene is present, so solvent purity should be verified by headspace gas chromatography. Molecular weight distribution is determined by gel permeation chromatography using refractive index detection and polystyrene calibration standards; typical linear phenylmethylsiloxane fluids in the 500–5,000 g/mol number-average molecular weight range exhibit polydispersity indices from 1.2 to 2.0, but the RH-C226A distribution must be reported by the supplier.
| Parameter | Typical phenylmethylsiloxane class range | Certificate-of-analysis requirement for RH-C226A |
|---|---|---|
| Appearance | Clear liquid; haze may appear above moisture threshold | Report visual clarity at 25 °C |
| Kinematic viscosity at 25 °C | 100–1,000 mm²/s for medium-viscosity optical grades; 1,000–10,000 mm²/s for damping grades | Report lot value by ISO 3104 or ASTM D445 |
| Refractive index nD at 25 °C | 1.500–1.600 depending on phenyl molar fraction | Report lot value by ASTM D1218 |
| Density at 25 °C | 1.05–1.20 g/cm³ | Report lot value by ISO 12185 or ASTM D4052 |
| Flash point, Cleveland open cup | Above 260 °C for low-volatile grades | Report lot value by ISO 2592 or ASTM D92 |
| Volatile content | 0.1–2.0% after 24 h at 150 °C in a forced-air oven | Report lot value by ISO 3251 or supplier gravimetric method |
| Water content | Below 100 ppm for optical and hydrosilylation uses | Report lot value by ASTM D6304 or ISO 15512 |
| Total acidity | Below 0.01 mg KOH/g for electronic grades | Report lot value by ASTM D974 or ISO 6618 |
The entries above are not a lot-specific specification for RH-C226A; they define the class envelope and the minimum analytical entries required for incoming release. When optical clarity is critical, filtration through a 1.0 µm absolute membrane and haze measurement after storage at 5 °C for 24 h are recommended supplementary tests. The user should not infer that a single CofA parameter can substitute for the full matrix.
When the fluid is formulated into platinum-catalyzed hydrosilylation optical encapsulants, the phenyl content contributes a refractive index above 1.50 that can be matched to silicone resin and substrate interfaces. In LED package dam-and-fill production, viscosity recovery after dispensing is monitored with a rotational rheometer at 25 °C; if the low-shear viscosity of the filled encapsulant falls below the process window, cavity bleeding occurs, while excessive viscosity reduces self-leveling and increases air entrapment. Reported production-scale work with phenyl silicone fluids indicates that filler addition at 10–20 wt% can raise viscosity by an order of magnitude or more; the exact rheological response of RH-C226A-based compositions requires a design of experiments on the actual static mixer and dispensing pump.
Cure kinetics in hydrosilylation are affected by phenyl substitution. Phenyl groups can attenuate catalyst activity by coordination or steric effects, necessitating adjustment of the platinum catalyst concentration or the Si–H:vinyl ratio. Typical platinum catalyst loadings in phenyl silicone optical encapsulant systems are reported from 1 ppm to 20 ppm platinum by mass, but catalyst inhibition by sulfur- or amine-containing substrates is an established failure mode. For RH-C226A, compatibility with the chosen catalyst should be confirmed by differential scanning calorimetry or oscillatory rheometry under isothermal cure at 80 °C to 150 °C. Avoid contact with amine-based adhesion promoters before compatibility testing, because premature crosslinking or cure inhibition may occur depending on the promoter structure and concentration.
For high-temperature damping and heat transfer devices that operate at 180 °C for 5,000–10,000 h, viscosity drift is a critical failure mode. Class-reported phenylmethylsiloxane fluids show lower volatility than dimethyl fluids of equivalent kinematic viscosity because aryl substitution raises molecular weight and reduces the equilibrium concentration of volatile cyclic siloxanes. The aging test commonly used is a sealed stainless-steel pressure vessel at 180 °C with a nitrogen headspace, with kinematic viscosity measured before aging and after 500 h intervals according to ASTM D445. A drift limit of ±10% from initial viscosity is often applied for closed-loop control fluids; fluids exceeding this limit can cause sluggish response or increased pump power.
In an actual manufacturing line, a high-temperature damping fluid is preconditioned under vacuum before filling, and residual dissolved oxygen is reduced by nitrogen sparging. Oxygen concentration below 1% by volume in the headspace is typically required to prevent oxidative viscosity build. The presence of phenyl groups increases density; density at 25 °C is commonly above 1.05 g/cm³ for phenylmethylsiloxane fluids, which affects pump sizing and heat transfer calculations compared with dimethyl fluids at 0.96–0.98 g/cm³. Therefore, flow rates and heat-transfer coefficients cannot be transferred directly from dimethyl silicone system design. For RH-C226A, published data for this specific configuration is limited; pilot-scale evaluation in a closed loop with a maximum bulk temperature of 200 °C is recommended before production commitment.
Distinctions from other polysiloxanes are operational rather than merely compositional. Dimethyl fluids offer lower cost and a lower viscosity-temperature coefficient but lower refractive index and lower aromatic solubility; fluorosilicones offer fuel and solvent resistance but higher density and often lower thermal stability at 200 °C; methylalkyl silicones may offer improved lubricity on steel but insufficient oxidative stability for continuous 180 °C service. Phenylmethylsiloxane fluids occupy the intermediate position when refractive index, thermal durability, and compatibility with aromatic resin systems are simultaneously required.
| Parameter | Dimethyl silicone fluid | Phenylmethylsiloxane class | Fluorosilicone fluid |
|---|---|---|---|
| Refractive index at 25 °C | 1.400–1.410 | 1.500–1.600 | 1.380–1.400 |
| Density at 25 °C | 0.96–0.98 g/cm³ | 1.05–1.20 g/cm³ | 1.10–1.30 g/cm³ |
| Thermal degradation onset under N2 at 10 °C/min | 300–350 °C | 350–400 °C | class data limited |
| Oxidative stability at 180 °C | moderate viscosity build | lower viscosity build for equivalent refractive index grade | variable with fluoropropyl content |
| Typical limitation | refractive index below 1.410 limits optical coupling with aromatic resins | moisture exclusion required; density increases pump load | higher cost; can swell certain fluoropolymer seals |
Selection among these fluid classes is therefore based on a constrained set of methods: ISO 3104 for viscosity, ISO 2592 for flash point, ASTM D1218 for refractive index, and a sealed-tube aging test for viscosity drift under nitrogen. The RH-C226A designation identifies a product within this class; its differentiation from unmodified phenyl fluids is usually found in molecular weight distribution, residual cyclics, and catalyst-neutral formulation, all of which require CofA-level verification.
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