| HS Code | 885440 |
| Product Name | Phenyl Hydrogen Silicone Resin SH305 |
| Chemical Type | Phenyl hydrogen polysiloxane resin |
| Appearance | Colorless to pale yellow transparent liquid |
| Solid Content | ≥98% |
| Viscosity At 25 C | 100-500 mPa·s |
| Density At 25 C | 1.05-1.10 g/cm³ |
| Refractive Index At 25 C | 1.53-1.55 |
| Hydrogen Content | 0.3-0.5 wt% |
| Volatile Content At 150 C For 3 H | ≤2% |
| Flash Point | >100°C |
| Solubility | Soluble in toluene, xylene, and other aromatic solvents |
| Catalytic Curing | Platinum-catalyzed hydrosilylation addition cure |
| Thermal Stability | High thermal stability after curing |
As an accredited Phenyl Hydrogen Silicone Resin SH305 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Phenyl Hydrogen Silicone Resin SH305 is supplied in 25 kg net steel drums with protective inner liners. |
| Container Loading (20′ FCL) | Phenyl Hydrogen Silicone Resin SH305 loaded in a 20′ FCL container, packed in drums and securely stowed for ocean transport. |
| Shipping | SH305 Phenyl Hydrogen Silicone Resin is typically shipped in sealed, labeled drums or containers under cool, dry, ventilated conditions, protected from moisture, heat, and ignition sources. Confirm the current SDS for UN classification, packaging, labels, and transport documentation with the supplier and carrier before shipment. |
| Storage | Store Phenyl Hydrogen Silicone Resin SH305 in tightly closed containers in a cool, dry, well-ventilated area away from heat, sparks, open flames, and direct sunlight. Keep away from moisture, water, acids, bases, and oxidizing agents to prevent reaction and hydrogen evolution. Use inert gas blanketing if recommended; maintain clear labels and inspect containers regularly for leaks or damage. |
| Shelf Life | Typical shelf life is 12 months from manufacture when kept unopened in original packaging under cool, dry, well-ventilated storage conditions. |
High-brightness white LED assemblies operating above 150 lm/W place the encapsulant directly in the blue radiation path, with die junction temperatures often exceeding 125°C during long-duration lumen maintenance testing. Phenyl hydrogen silicone resin SH305 is used in such systems as a hydrosilylation crosslinker for vinyl-functional phenylmethyl silicone gum because the phenyl content raises the refractive index to 1.53–1.56, which reduces total internal reflection loss at the silicone–die interface. In a platinum-catalysed formulation, SH305 is added at an Si-H:Si-vinyl molar ratio between 1.0:1 and 1.4:1; ratios below 0.9:1 leave residual vinyl groups that act as oxidation sites and reduce durometer stability, while ratios above 1.5:1 risk post-cure hydrogen evolution and bubble formation at cast thicknesses above 3 mm. A Karstedt or platinum-alkynyl catalyst concentration of 1 ppm to 5 ppm Pt is used with a volatile methylvinylcyclosiloxane inhibitor to maintain pot life longer than 8 h at 25°C. The mixed resin is degassed in a planetary centrifugal mixer at 2000 rpm under 200 Pa vacuum until bubble-free, then injected into preheated moulds at 70°C to 80°C and cured in nitrogen at 150°C for 1 h, then 180°C for 2 h. The main process conflict is premature gelation in thick sections: hydrosilylation exotherm can raise the internal temperature above the inhibitor’s active window, causing centre gel before mould filling completes. This is controlled by holding mould temperature below 85°C during injection and limiting shot volume to 150 mL on a litre-scale dispense line. Transmission of 2 mm plaques per ASTM D1003 typically exceeds 97% at 450 nm after initial cure; after 1000 h at 150°C in air, transmission loss remains below 5% and Shore durometer shift per ASTM D2240 remains below 5 points. Thermal cycling per JESD22-A104 from -45°C to 125°C for 500 cycles does not produce delamination at the silicone–silver leadframe interface when the leadframe is pre-treated with a vinyl and trimethoxy adhesion promoter. Sulfur-containing die attach residues and amine-based mold release agents are excluded from the line because they poison the platinum catalyst at concentrations above 10 ppm in mixed resin.
Selective spray valve application of a solventborne SH305-based conformal coating at wet film thicknesses of 25 µm to 75 µm produces a tack-free outer layer after jet air at 60°C for 15 min; however, the interior under ball-grid array packages cures more slowly because the hydrosilylation catalyst requires uniform heat and because solvent must escape through the outer skin. For this reason, the resin is formulated with a phenylmethyl vinyl silicone having viscosity of 500 mPa·s to 1500 mPa·s and applied in two passes rather than one, with an interpass interval of 20 min at 70°C. Cure is completed at 80°C for 30 min, not by air drying alone, because the Si-H/vinyl network does not crosslink reliably at ambient temperature without platinum catalyst and heat. Coated test coupons must meet IPC-CC-830B insulation resistance after 85°C/85% RH aging, with surface insulation resistance stable above 100 MΩ when tested per IPC-TM-650 method 2.6.3.3. Crosshatch adhesion on FR-4 is measured per ASTM D3359-23, with 5B adhesion retained after thermal shock; pencil hardness is 2H to 3H per ASTM D3363. The principal failure mode is edge cracking when dry film thickness exceeds 100 µm, because the phenyl groups increase rigidity and the coating cannot accommodate thermal expansion mismatch with the substrate. Automated spray programs are therefore written to keep line speed at 60 mm/s to 120 mm/s and overlap at 50%, with air cap pressure limited to 0.2 MPa, to avoid ribbing that creates high-thickness channels. The coating is not used on assemblies carrying exposed polycarbonate lenses, because residual xylene or toluene in the phenyl hydrogen resin will craze polycarbonate at solvent loading above 1 wt% in the cured film.
A grit-blasted carbon steel duct in a biomass flue gas line reaches surface temperatures of 240°C to 280°C during soot-blowing cycles. Standard methyl silicone binders in aluminium-pigmented heat-resistant paints degrade through methyl group oxidation, causing film shrinkage and adhesion loss after roughly 500 h. SH305 is used as a co-binder in a phenylmethyl silicone anticorrosion system because phenyl groups increase oxidative stability and the Si-H groups provide additional crosslinking with vinyl-functional phenyl silicone resins. The coating is prepared with 30 phr to 50 phr aluminium flake, 10 phr mica, 5 phr glass frit, and 55–65 parts of silicone binder blend at 50% solids in xylene. Application proceeds after surface preparation to Sa 2.5 per ISO 8501-1; a zinc ethyl silicate shop primer is not used directly beneath this formulation because zinc ions poison the platinum catalyst during cure and reduce insolubility. Instead, an inert phenyl silicone barrier coat is applied at 25 µm dry film thickness and flash baked at 150°C for 10 min before the topcoat. The full system is cured at 200°C for 30 min in forced air, not at ambient temperature; below 180°C the hydrosilylation reaction is too slow and the film remains soft for more than 48 h. Salt spray resistance is tested per ISO 9227:2022; on scribed 75 µm dry film panels, creep from the scribe is below 2 mm after 3000 h. Thermal shock resistance is verified by cycling from 280°C to 25°C for 50 cycles without mud cracking. A process bottleneck is that the coating reservoir must be purged with dry nitrogen, because ambient moisture reacts with Si-H groups to release hydrogen, causing pot viscosity to drift upward by 20% to 30% over 8 h and producing microfoam in the wet film. Published data for SH305-specific exposure beyond 3000 h in biomass flue gas condensate is limited; qualification is normally extended through plant trial coupons rather than extrapolation from conventional silicone esters.
Hydrophobization of precipitated silica and glass microspheres with SH305 is performed in a vertical Henschel mixer at 1200 rpm. The resin is diluted to 5 wt% solids in xylene and sprayed through a peristaltic pump at 20 g/min onto filler pre-dried to 0.3% moisture at 120°C for 4 h. Mixing continues for 20 min after liquid addition; the treated filler is then spread on trays and cured at 150°C for 2 h under forced air. The treated powder is evaluated by pressing a compact and measuring water contact angle per ASTM D7334; a value above 120° is required for release into moisture-resistant silicone rubber compounds. Residual volatiles are quantified by headspace GC at 180°C for 30 min, and the release criterion is below 0.1 wt%. A production failure mode occurs when the resin spray is added too quickly, exceeding 30 g/min on a 50 L mixer, because local overwetting forms agglomerates that survive subsequent compounding and appear as undispersed gel particles in extruded silicone profiles. The hydrophobic layer is stable under neutral water at 25°C, but sodium hydroxide solution at pH 12 causes contact angle to fall below 90° within 24 h, so treated filler is not specified for alkaline aqueous dispersions.
Silicone pressure-sensitive adhesives based on MQ silicate resin and phenylmethyl siloxane gum are formulated with SH305 to adjust peel force and cohesive strength. The adhesive is compounded on a three-roll mill with water-cooled rolls at 20°C, using 40 wt% to 60 wt% MQ resin solids in toluene, 35 wt% to 55 wt% siloxane gum, and 0.5 wt% to 2.0 wt% SH305 as crosslinker. A platinum catalyst at 50 ppm Pt based on solids is added last, and the mixture is passed through the rolls three times at nip pressures of 0.3 MPa to 0.5 MPa. The adhesive is coated onto 25 µm polyimide film with a comma coater, dried at 120°C for 2 min, and cured at 170°C for 3 min in an inert atmosphere with residual oxygen below 100 ppm. The Si-H:Si-vinyl molar ratio is controlled between 1.2:1 and 1.8:1; at 1.2:1 the 180° peel force on stainless steel per ASTM D3330/D3330M-04(2018) is in the range 8 N/25 mm to 12 N/25 mm and loop tack is high, while at 1.8:1 peel force drops by roughly 30% and the shear adhesion failure temperature exceeds 200°C. Over-curing above 180°C or for longer than 5 min embrittles the adhesive and causes debonding at the polyimide interface, whereas under-cure produces adhesive transfer to the release liner and fogging in enclosed electronics when total volatiles exceed 0.5 wt% by headspace GC. The coated roll is conditioned at 25°C/50% RH for 24 h before slitting; the primary specification is ASTM D3330/D3330M for peel, ASTM D3654/D3654M for shear, and ASTM D4496 for insulation resistance. Addition of SH305 above 3 wt% produces excessive gel content and coating streaks, so the formulation window is narrow and requires gravimetric metering rather than volumetric splash blending.
Vacuum pressure impregnation of high-voltage motor windings uses a phenyl hydrogen silicone resin formulation to fill stator voids and bond conductors without introducing free radical initiators that degrade at class H operating temperatures. The stator is preheated at 105°C for 6 h under 100 Pa to remove moisture, then flooded with a resin mixture containing SH305 and a vinyl-functional phenylmethyl silicone at 60% solids in low-odour aromatic solvent. Impregnation is carried out in a pressure vessel at 0.4 MPa for 2 h, followed by a drain period of 45 min to reduce pooling in end windings. Final cure is staged at 120°C for 2 h, 150°C for 2 h, and 175°C for 4 h under nitrogen. Bond strength on a coil stack is tested by the ASTM D2519 method; a minimum shear strength of 5 MPa at 25°C is used as the pass criterion. Thermal endurance is assessed according to IEC 60216 with a class H reference temperature of 180°C, but long-term ageing data for SH305-based varnish beyond 2000 h at 180°C is limited and must be generated from the specific stator insulation system. Process control excludes moisture and copper carboxylate accelerators because Si-H groups react with water to release hydrogen and increase tank pressure; viscosity is monitored with a rotational viscometer at 25°C, and the bath is rejected if viscosity increases by more than 25% of initial value. The main failure mode is under-cured varnish in deep slots, caused by insufficient heat transfer through the copper mass; therefore, winding temperature is mapped with embedded thermocouples during cure, and the time at 175°C is extended by 1 h if the core temperature lags the oven set point by more than 15°C.
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Phenyl Hydrogen Silicone Resin SH305 is supplied as a phenyl-functional polysiloxane bearing pendent silicon hydride groups. The molecular architecture combines aryl substitution for elevated refractive index and hydride sites for platinum-catalysed hydrosilylation crosslinking. In optical encapsulant compounding, the resin is blended with phenyl vinyl silicone resins, a Karstedt platinum catalyst, and an addition inhibitor such as 1-ethynylcyclohexanol. The free hydride function is located on the resin rather than on a separate low-molecular-weight linear crosslinker, which alters the distribution of crosslink junctions and the fraction of mobile extractable siloxane after cure. Typical binder incorporation levels range from 10 % to 60 % by mass, depending on target hardness, optical clarity, and long-term thermal aging performance. The product is not used as a standalone film former; it functions as the hydride donor in a two-part addition-cure formulation.
Product applications include LED encapsulation, transparent protective coatings, and high-temperature optoelectronic potting. In these processes, viscosity and refractive index control are critical because the resin must flow into fine cavities without trapping air and must maintain optical transmission after thermal and photochemical aging. Lot-specific certificates should be consulted for exact nonvolatile content, Si-H activity, and phenyl distribution. Published data for this specific configuration is limited; where values are given in this document, they represent manufacturer target ranges or analogous phenyl hydrogen resin behaviour rather than certified lot data.
The target specification matrix summarises the principal incoming inspection parameters. The ranges are not statistical process-control limits and should not be used for release acceptance without verification against the certificate of analysis. Dynamic viscosity is measured by rotational viscometry after solvent removal, because residual xylene or toluene depresses apparent viscosity. A cone-plate rheometer equipped with a 25 mm, 1 ° cone is operated at 10 s⁻¹ and 25 °C under ISO 3219:1994. Refractive index is determined by Abbe refractometry under ISO 489:1999; representative phenyl methyl siloxane resins show an increase of roughly 0.02–0.04 per 10 % incremental phenyl substitution. Volatile content is measured by gravimetric loss under ISO 3251:2019 at 105 °C for 3 h. Si-H content is commonly determined by gasometric titration after alkaline hydrolysis; the 0.20–0.50 wt% range is typical for this resin class.
| Parameter | Test method | Target range / representative value |
|---|---|---|
| Appearance | Visual inspection | Colourless to pale amber clear liquid |
| Dynamic viscosity at 25 °C | ISO 3219:1994 | 2000–6000 mPa·s |
| Refractive index at 25 °C | ISO 489:1999 | 1.50–1.56 |
| Density at 25 °C | ISO 2811-1:2016 | 1.05–1.15 g/cm³ |
| Volatile content | ISO 3251:2019 | ≤2.0 wt% |
| Si-H content | Gasometric titration / internal method | 0.20–0.50 wt% |
Incoming viscosity outside the target range does not automatically require rejection; it can indicate incomplete solvent removal, moisture contamination, or batch-to-batch variation in phenyl substitution. If viscosity exceeds 6000 mPa·s, the resin may still be usable after controlled thinning with xylene or a reactive diluent, but the diluent type must be selected to avoid shifting the Si-H:vinyl molar ratio outside the formulation window.
The presence of both aryl and hydride functions on the same siloxane scaffold changes the steric environment of the hydrosilylation reaction. The addition of silicon hydride to vinyl siloxane proceeds through a platinum-olefin-hydride intermediate, and the rate is sensitive to olefin substitution and siloxane steric bulk. Phenyl rings adjacent to hydride-bearing D or T units reduce apparent reactivity compared with dimethyl methyl hydrogen siloxane fluids at equivalent molar Si-H concentration. In non-isothermal differential scanning calorimetry at 10 K/min under ISO 11357-1:2018, analogous phenyl hydrogen resin–vinyl resin mixtures exhibit an addition exotherm with an onset near 85–95 °C and a peak maximum near 105–130 °C. The exact peak shifts with platinum concentration in the 2–10 ppm range and with inhibitor loading.
The structural benefit is a lower concentration of unreacted low-molecular-weight crosslinker after cure. In solvent-extraction checks using refluxing xylene, addition-cured networks formed with SH305-type phenyl hydrogen resin show reduced extractable siloxane compared with linear methyl hydrogen crosslinker controls. The difference is most pronounced when the formulation is cured for less than 30 min at 100 °C, because unreacted linear crosslinker remains mobile and can migrate to the encapsulant surface. Migration kinetics in polymer matrices depend on molecular weight and glass transition temperature; high-T branched resin segments are less mobile than short-chain dimethyl fluids.
On production-scale twin-screw or planetary mixers, SH305 is typically preheated to 30–40 °C before addition to phenyl vinyl resin because aryl substitution raises low-shear viscosity and mixing torque. Vacuum degassing is performed at −0.098 MPa or lower until bubble release ceases. Filtration through 5–10 µm absolute-rated glass-fibre or polypropylene cartridges is specified before dispensing. High shear above 5000 s⁻¹ should be avoided when volatile solvent content is below 1 wt%, because local viscous heating can initiate premature hydrosilylation in uninhibited masterbatches. Work life is controlled by inhibitor concentration, catalyst concentration, and temperature; moving-die rheometer gel times at 25 °C can be adjusted from 30 min to 120 min using 1-ethynylcyclohexanol at 50–300 ppm.
Premature gelation has been observed in continuous dispensing lines when mixed material is forced through fine-mesh filter media with unswept dead zones. If the filter housing temperature exceeds 60 °C, gel particles can form, block the element, and create pressure excursions beyond 0.6 MPa. This is a processing bottleneck in LED encapsulant lines using progressive-cavity pumps; filter elements must be cooled or replaced frequently during long runs. The temperature limit is particularly relevant for heated supply lines and solenoid valves located close to the dispense head.
In high-refractive-index LED encapsulants, SH305 is blended with a phenyl vinyl resin or silicone oligomer to produce a mixed hydride–vinyl system. The total hydride-to-vinyl molar ratio is usually maintained between 1.0:1 and 1.8:1. At lower ratios, incomplete cure leaves a tacky surface and elevated extractables; at ratios above 2.0:1, excess Si-H can undergo secondary oxidation and increase hardness drift after thermal aging. The cure profile is frequently staged: 80 °C for 30 min, then 120 °C for 60 min, followed by 150 °C for 120 min in a forced-air oven. This staged schedule limits bubble formation and reduces thermal stress at the die surface.
The processing window near the fast-cure threshold is narrow. For formulations containing 300 ppm inhibitor and 5 ppm platinum, gelation at 100 °C may occur within 5–10 min; an oven overshoot to 120 °C before cavity fill is complete shortens gel time to less than 2 min in some configurations. As a result, vacuum-assisted dispensing equipment with heated reservoirs should maintain reservoir temperature at 25 ± 2 °C and line temperature below 35 °C until the material enters the mould. The ±5 °C thermal limit is especially relevant for high-speed automated encapsulation lines, where residence time in heated gates can initiate gelation and cause wire sweep or incomplete dome formation.
Table 2 compares the target profile of SH305 with a linear dimethyl methyl hydrogen crosslinker of similar Si-H content. The data are representative, not lot-specific.
| Property | SH305 target profile | Linear methyl hydrogen crosslinker | Test method |
|---|---|---|---|
| Dynamic viscosity at 25 °C | 2000–6000 mPa·s | 20–80 mPa·s | ISO 3219:1994 |
| Refractive index at 25 °C | 1.50–1.56 | 1.40–1.41 | ISO 489:1999 |
| Si-H species | Pendent on phenyl-functional resin | Pendent on linear dimethyl chain | ¹H NMR / FTIR |
| Effect on cured extractables | Lower mobile crosslinker content | Higher free low-molecular-weight fraction unless volatilised | Reflux extraction, internal method |
| High-refractive-index encapsulant suitability | Maintains RI above 1.50 | Reduces RI; not suitable above 1.50 | ISO 489:1999 |
A linear methyl hydrogen crosslinker is not automatically inferior. In low-refractive-index release coatings, foam-control agents, or hydrophilic treatments, lower viscosity and simpler structural distribution are advantageous. However, when optical clarity and thermal yellowing resistance are specified, SH305 reduces the number of formulation variables by delivering phenyl optical properties and hydride crosslink density in one resin.
SH305 is neither a phenyl vinyl resin nor a phenyl silanol condensation resin. Phenyl vinyl resins supply unsaturated crosslink sites but require an external hydride source; SH305 supplies the hydride source without introducing a low-refractive-index dimethyl hydrogen fluid. Phenyl silanol resins cure by condensation with alkoxy or silanol species and release water or alcohol, whereas SH305-based addition cure releases no volatile condensation by-product. That distinction reduces void formation in thick-section encapsulants and simplifies post-cure degassing. Comparative tensile testing under ISO 527-2:2012 and hardness measurement under ISO 868:2003 should be performed after formulation changes because network architecture is different from condensation-cure phenyl resin matrices. SH305 is not a direct drop-in replacement for phenyl vinyl resin; its use level is governed by the required Si-H:vinyl molar ratio and the desired Shore hardness.
Selecting SH305 also changes the storage and mixing strategy. Phenyl silanol resins may require moisture-sensitive organometallic catalysts, whereas SH305 requires platinum catalyst and hydrosilylation inhibitor control. The absence of condensation by-products supports lower total mass loss after cure when measured by thermogravimetric analysis under ISO 11358-1:2022, but the exact value depends on the total formulation.
Long-term optical stability in SH305-cured phenyl silicone encapsulants is constrained by thermal oxidation of the phenyl substituents and residual platinum-catalysed redistribution of the siloxane network. In thermogravimetric analysis under nitrogen at 10 °C/min according to ISO 11358-1:2022, phenyl silicone systems typically show a higher 5 % mass-loss temperature than dimethyl analogues because aryl groups resist chain depolymerisation. Under air, oxidative degradation begins at lower temperatures; high-phenyl resins may show 1 % mass loss after 1000 h at 150 °C in environmental ovens, but SH305-specific values require lot-specific confirmation. Colour stability is screened by yellowness index under ASTM E313-20 after thermal aging. A shift of less than 2.0 after 1000 h at 150 °C is a commonly used internal threshold for LED encapsulant formulations, but the acceptance limit is application-specific.
For UV environments, QUV testing under ASTM G154-23 cycle 1 for 500 h is used to screen the onset of yellowing and surface haze. Phenyl content improves refractive index but can increase conjugated oxidation by-products under high-intensity blue or UV LED flux. Formulators therefore evaluate photometric transmission after 500 h at 85 °C and 85 % relative humidity under IEC 60068-2-78 for damp-heat stability. If transmission loss at 450 nm exceeds 5 %, the formulation requires adjustment of phenyl content, catalyst residues, or antioxidant package.
SH305 should be stored in closed stainless steel or glass-lined vessels under dry nitrogen or argon. Free silicon hydride groups are sensitive to alkaline condensation catalysts, strong acids, and organotin compounds; exposure to these materials can generate hydrogen and alter Si-H content. Storage at 5–30 °C is standard. Freeze-thaw exposure below 0 °C may cause temporary viscosity stratification; rehomogenisation by gentle heating at 35 °C for 24 h under inert gas is advised before sampling. Iron residues from carbon steel equipment can accelerate siloxane redistribution and should be avoided. Cleaning before cure is performed with anhydrous toluene, xylene, or isopropanol; after cure, addition-cured silicone residues resist solvent dissolution and require mechanical removal or hot alkaline cleaning.
Operational boundaries include exclusion of amine-based additives, sulfur-containing adhesion promoters, and organotin condensation catalysts from SH305-containing masterbatches. These species can poison the platinum catalyst or induce non-selective Si-H side reactions. If an adhesion promoter is required, vinyltrimethoxysilane or vinyl-functional silicone oligomers are typically screened at levels below 1.5 wt%; compatibility must be confirmed by differential scanning calorimetry for cure exotherm retention and by cross-cut adhesion testing under ISO 2409:2020. Use with solvent-borne systems at high relative humidity should be accompanied by substrate pre-drying when RH exceeds 60 %, because residual surface moisture can contribute to microvoiding and adhesion loss at the encapsulant–substrate interface.
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