| HS Code | 435890 |
| Chemical Composition | Polysiloxane with Si-O backbone and organic groups |
| Thermal Stability | Stable up to 250°C |
| Water Repellency | Hydrophobic with excellent water resistance |
| Electrical Insulation | High dielectric strength and low conductivity |
| Chemical Resistance | Resistant to acids, alkalis, and common solvents |
| Weather Resistance | Excellent resistance to UV radiation and weathering |
| Hardness | Ranges from soft to hard with high scratch resistance |
| Flexibility | Maintains flexibility at low temperatures |
| Adhesion | Good adhesion to metals, glass, and plastics |
| Transparency | High optical clarity in cured film |
As an accredited Silicone Resin factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Silicone Resin packed in 25 kg net fiber drums with inner polyethylene liner, sealed and labeled for safe handling and storage. |
| Container Loading (20′ FCL) | Silicone Resin loaded as 20′ FCL in drums/IBCs, securely palletized and braced, ensuring safe transport and product integrity. |
| Shipping | Silicone resin ships in sealed drums or totes, protected from moisture and contamination. Non-hazardous in most forms, but avoid extreme heat or direct sunlight. Ensure secure palletization, upright orientation, and clear labeling. Standard freight, rail, or sea transport is suitable, with storage below 30°C to maintain stability. |
| Storage | Store silicone resin in a cool, dry, well-ventilated area away from direct sunlight, heat sources, and open flames. Keep containers tightly sealed to prevent moisture contamination, as humidity can affect stability. Avoid exposure to incompatible materials like strong oxidizers. Follow manufacturer guidelines for shelf life and handling. Use proper personal protective equipment when transferring. |
| Shelf Life | Silicone resin has a shelf life of 12 months when stored in sealed containers, away from moisture and heat. |
Occupational exposure to exhaust gas temperatures above 500 °C removes acrylic, alkyd, and epoxy-phenolic binders from consideration in the stack, muffler, and furnace coating segment. The binder system is a silanol-functional methyl phenyl silicone resin with a phenyl-to-methyl ratio between 0.8:1 and 1.2:1. A production-scale spray formulation is compounded at 55–70 wt% methyl phenyl silicone resin solids, 10–20 wt% leafing aluminium flake, 5–12 wt% ceramic microspheres, 1–3 wt% fumed silica, and 2–5 wt% anti-settling wax. Thinning to 18–22 s DIN 4 mm cup at 20 °C is performed with xylene or aromatic 100. The coating is applied with conventional air-atomized spray equipment at 0.35–0.45 MPa. Wet film is laid down in two passes to achieve 25–40 μm dry film thickness. Ambient flash-off is 15 min, followed by forced cure at 230 °C for 30 min. For service above 650 °C, a second coat is applied and cured under identical conditions. VOC content is measured by ASTM D3960. High-temperature resistance is evaluated by ASTM D2485-18. Salt spray resistance is tested under ASTM B117-19 for 500 h with scribe creep typically below 2.5 mm. Adhesion is rated by ASTM D3359-17 after thermal cycling from ambient to 650 °C. Terminal parts include automotive exhaust headers, industrial oven burner tubes, furnace dampers, and chimney caps. Batch-to-batch viscosity variation of the resin intermediate is controlled within ±10% to prevent sagging on vertical rounds.
Vacuum pressure impregnation lines for traction motor stators require a low-viscosity resin that withstands thermal class 200 or 220 operation. A methyl phenyl silicone impregnating resin is supplied at 50–55 wt% solids in xylene or at 40–45 wt% solids in 1,2,4-trimethylbenzene. Viscosity at 25 °C is held between 200 mPa·s and 400 mPa·s with a cone-and-plate viscometer per ISO 2884-2. Zinc octoate catalyst is metered at 0.3–1.0 wt% on resin solids. The process sequence begins with preheating wound stators at 100–105 °C for 4 h until insulation resistance stabilizes above 500 MΩ. The vessel is evacuated to 2.0–5.0 kPa for 30 min before resin is introduced. Dry nitrogen at 0.4–0.6 MPa is applied for 60 min. After drain, stators are rotated for 10 min to remove excess resin. Cure is 180 °C for 2 h, then 220 °C for 4 h. The cured resin must qualify under IEC 60085 as class 200 or class 220 depending on the powertrain duty cycle. Electrical breakdown after 240 h at 250 °C is tested by ASTM D149; supplier reports exceed 12 kV/mm. UL 1446 system sealing is required when the varnish is combined with magnet wire and slot liner materials. Terminal products are elevator traction motors, rail traction alternators, and high-speed spindle motors. Published data for salt spray performance of unpainted VPI windings in direct coastal exposure is limited.
Accelerated weathering data from coil coating lines show that silicone resin modification above 40 wt% cracks after 1000 h in ASTM G154 Cycle 1. The coil coating topcoat is therefore formulated with a hydroxyl-functional saturated polyester, a methyl phenyl silicone resin at 20–35 phr on polyester solids, and hexamethoxymethyl melamine at 5–10 phr. Blocked p-toluenesulfonic acid catalyst is added at 0.5–1.5 wt%. The liquid coating is applied by reverse roll coater at 20–25 μm dry film thickness on 0.5 mm chromated aluminium. Peak metal temperature is held at 216–232 °C for 20–30 s. Line speed is 30–80 m/min depending on oven length. Low PMT leaves unreacted methoxy groups that cause water sensitivity; PMT above 243 °C causes intercoat adhesion loss. The cured film is evaluated for T-bend flexibility per ASTM D4145. Specification requires no cracking at 2T after 24 h ambient cure. Gloss retention is measured by ISO 2813 and QUV weathering by ASTM G154. Pencil hardness is H–2H per ASTM D3363. Terminal product is pre-painted aluminium for roofing, facade panels, and outdoor signs. Compliance for coil coating facilities includes VOC determination by ASTM D3960 and hazardous air pollutant reporting under 40 CFR Part 63 Subpart SSSS.
Pre-mixing a methyl phenyl silicone resin flake at 90–110 °C into a carboxyl-terminated polyester produces the binder system for high-heat powder coatings. The premix is fed to a co-rotating twin-screw extruder with an L/D ratio between 20:1 and 28:1 at 300–400 rpm. Barrel zones are set from 90 °C to 120 °C. Silicone resin content is 20–50 phr on total binder. The extruded sheet is cooled, broken into chips, and ground with a classifier mill to a D50 of 30–35 μm. Electrostatic spray application applies 40–60 μm dry film. Cure is 230 °C for 15 min or 240 °C for 10 min. High-temperature adhesion is tested by ASTM D2485-18. Salt spray resistance per ASTM B117-19 is typically 500 h with less than 2.5 mm scribe creep on shot-blasted steel. Pencil hardness after thermal aging is 2H–4H per ASTM D3363. The system contains no VOC and complies with RoHS Directive 2011/65/EU for lead, cadmium, mercury, and hexavalent chromium. Avoid combining with amine-functional flow modifiers because amine groups accelerate premature crosslinking in the extruder. Terminal parts are barbecue burners, fireplace surrounds, oven racks, and exhaust manifolds. Particle size distribution is measured by laser diffraction per ISO 13320.
Release coatings for bakery and confectionery moulds are formulated from 100% solids methyl phenyl silicone resin. The resin is thinned to 35–45 s DIN 4 mm cup at 20 °C with aromatic 100 before application. The substrate is grit-blasted carbon steel or degreased aluminium. Spray application applies 20–35 μm dry film in one or two passes. Cure is 250 °C for 30 min in a forced-air oven. Full crosslinking is verified by solvent rub test. The cured film must meet the extractive limits of FDA 21 CFR 175.300 for resinous and polymeric coatings intended for food contact. Repeated contact with lard, butter, and sugar is simulated by thermal cycling between 20 °C and 230 °C. Release force for bread dough is measured on a tensile tester with a 25 mm probe at 230 °C. The coating remains effective for 500 to 1000 bake cycles depending on abrasive dough and alkaline cleaning agents. Alkaline cleaners above pH 11 reduce service life. Terminal products are bread pans, cake moulds, roasting trays, and pizza screens. REACH compliance is required for the aromatic solvent. The resin itself is not classified as a substance of very high concern under the REACH candidate list.
Liquid silicone resin formulations for SMD LED packages use siloxane resins with phenyl content above 50 mol% to raise refractive index and thermal stability. The resin is supplied as two parts mixed at 1:1 by mass. Viscosity at 25 °C is 2000–5000 mPa·s measured by ISO 3219. The catalyst is a platinum complex. Dispensing is performed with a positive-displacement dispenser onto lead-frame reflectors. Vacuum degassing at 2.0 kPa for 10 min removes entrapped air. Cure is 100 °C for 1 h, then 150 °C for 2 h. Hardness after cure is Shore D 40–60 per ASTM D2240. Optical transmittance at 400 nm for a 2.0 mm coupon is above 95% in supplier technical data. Thermal resistance is evaluated by IEC 60068-2-14 thermal shock from -40 °C to 125 °C. The encapsulant must comply with RoHS Directive 2011/65/EU and China RoHS. Terminal products are SMD LED packages for automotive interior lighting, backlight units, and general illumination. Avoid contact with amine-containing surface contaminants because platinum catalyst inhibition causes soft cure. Published data for long-term lumen maintenance above 10,000 h is limited to OEM qualification reports.
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Silicone resin denotes a highly crosslinked polysiloxane network composed primarily of trifunctional CH3SiO1.5 (T) and quadrifunctional SiO2 (Q) units, with methyl and phenyl substituents controlling hydrophobicity, compatibility, and thermal stability. Representative methyl-phenyl silicone resin solutions are supplied at 50–60 wt% solids in xylene under designations such as SILRES® REN 60, while methyl silicone resin solutions are offered at 40–50 wt% solids for low-organic masonry treatments. Manufacturer-documented specification limits for the methyl-phenyl grade include dynamic viscosity 40–80 mPa·s at 25 °C by ISO 3219, non-volatile content controlled by ISO 3251, flash point 23–28 °C by ISO 1523, and hydroxyl content 0.2–0.6 wt%. The product is therefore a thermosetting binder rather than a thermoplastic acrylic or a linear silicone oil; film formation requires condensation cure at 180–250 °C, producing a siloxane network that cannot be re-melted by heat alone.
Table 1 lists typical specification ranges for two resin architectures.
| Property | Test method | Methyl-phenyl silicone resin solution | Methyl silicone resin solution |
|---|---|---|---|
| Non-volatile content | ISO 3251 | 50–60 wt% | 40–50 wt% |
| Dynamic viscosity at 25 °C | ISO 3219 | 40–80 mPa·s | 15–30 mPa·s |
| Flash point | ISO 1523 | 23–28 °C | 25–31 °C |
| Hydroxyl content | titration | 0.2–0.6 wt% | 0.5–1.0 wt% |
| Primary solvent | — | xylene | butyl acetate/xylene |
In electrical insulation applications, a methyl-phenyl silicone resin maintains volume resistivity between 10¹⁴ Ω·cm and 10¹⁵ Ω·cm at 25 °C when measured by ASTM D257. The dielectric strength of a 25–30 µm cured film is typically reported above 20 kV/mm at room temperature and remains above 12 kV/mm after 1000 h at 250 °C in a circulating-air oven. This retention is attributable to the 452 kJ/mol Si–O bond energy in the resin backbone, compared with approximately 348 kJ/mol for the carbon–carbon bond in epoxy and polyester systems. On a production-scale trickle-impregnation line for random-wound stator cores, the resin bath is held at 22–26 s by ISO 2431 cup 5 mm; when solvent loss raises viscosity above 35 s, slot penetration becomes incomplete and cured layer thickness varies by more than ±8 µm across a 1200 mm stack height. The thermal cure schedule consists of 30 min at 180 °C followed by 60 min at 250 °C. An epoxy-phenolic varnish can develop similar initial dielectric strength but typically shows greater thermogravimetric mass loss after 1000 h at 250 °C under ISO 11358-1; published data for identical stack configurations is limited.
For concrete and masonry facades, a low-viscosity methyl silicone resin is diluted to 7–10 wt% active content in white spirit and spray-applied at 8–10 MPa through a reversible tip with 0.28 mm orifice. Capillary penetration depth on C20/25 concrete at equilibrium moisture content reaches 3–6 mm; water absorption after 24 h immersion is reduced to 1–3 wt% when tested by ISO 15148, while water-vapour transmission remains above 60% of the untreated reference. Because the resin cures as a pore-lining monolayer rather than a continuous surface film, it differs from an acrylic sealer; freeze-thaw resistance is retained for 100 cycles from –20 °C to +20 °C under EN 13581. Application on fresh concrete with pH above 12.5 is excluded because alkaline hydrolysis of the siloxane network reduces water repellency within 6 months; substrate pH is therefore checked by ASTM F710 and should be below 10 at application.
Aluminium-pigmented silicone resin topcoats for exhaust stacks are mixed in a sawtooth high-speed disperser at tip speeds between 5000 s⁻¹ and 8000 s⁻¹. At lower tip speeds, leafing aluminium flakes remain agglomerated above 50 µm when screened by ISO 1524; at higher tip speeds, flake deformation reduces specular reflectance below 60% of the initial value. In a 200 L production batch, premature addition of the full xylene charge before the paste phase increased the 50 µm agglomerate count from 12 to 63 particles per 100 mL. The finished coating is applied at 25–30 µm dry film thickness with conventional air spray at 0.4–0.5 MPa, flashed for 15 min at 23 °C, and baked for 30 min at 200 °C. Before any aliphatic solvent exposure, a post-cure of 60 min at 250 °C is required; otherwise the uncured siloxane network fails methylethylketone double-rub testing after fewer than 20 rubs by ASTM D5402.
On coil coating lines operating at 18 m/min through a 22 m gas-fired oven, methyl-phenyl silicone resin formulations are controlled at 50–60 mPa·s application viscosity and 18–22 µm dry film thickness. The peak metal temperature must reach 204–232 °C for 25–35 s; below this range, blocked-polymer adhesion remains weak and the film fails reverse-impact testing at 20 J under ASTM D2794. Silicone resin releases from polyolefin-based and acrylate-based coil primers because of lower surface energy, so an epoxy-silane primer is used in tandem. Compared with a polyester topcoat on identical substrate, the silicone resin system retains higher gloss and colour stability after 2000 h of ASTM G154 cycle 1 exposure, but exhibits lower flexibility at 0T bend; published data for full coil-line correlation is limited.
An under-cured silicone resin film is attacked by aromatic solvents because residual silanol groups allow solvent swelling and chain reorganisation. At 200 °C for 30 min, the network reaches only 40–60% of ultimate crosslink density; methylethylketone double-rubs fail below 20 by ASTM D5402. Post-curing at 250 °C for 60–90 min raises the double-rub count above 100 and reduces swelling in xylene to 10–15% linear film expansion. This behaviour differs from a two-component epoxy, which develops solvent resistance at 23 °C within 7 days but loses flexibility above 150 °C. The silicone resin therefore imposes a thermal cure requirement that is incompatible with heat-sensitive substrates such as polyethylene and polypropylene unless a catalytic silanol condensation package is employed.
Blending a methyl-phenyl silicone resin with bisphenol A epoxy at 20 wt% modification creates a hybrid that improves dry heat resistance from 180 °C to 230 °C but introduces a processing conflict: the silanol condensation reaction accelerates at the epoxy cure temperature of 150–180 °C and can cause viscosity to double within 5 min if a tin catalyst is present above 0.1 wt%. On a twin-screw extruder with L/D 40:1, the processing window narrows to ±5 °C around 160 °C; below this range grafting is incomplete, above this range the mixture gels at the die. Unlike a polydimethylsiloxane oil, the resin contributes crosslink density and raises melt strength, but incompatible phenyl-rich domains can appear as haze when phenyl content exceeds 25 mole% of siloxane units.
| Property after cure | Test method | Methyl-phenyl silicone resin | Epoxy-phenolic | Polyester |
|---|---|---|---|---|
| Continuous dry heat limit | ASTM D2485 | 250–300 °C | 180–200 °C | 120–150 °C |
| Volume resistivity at 25 °C | ASTM D257 | 10¹⁴–10¹⁵ Ω·cm | 10¹²–10¹³ Ω·cm | 10¹¹–10¹² Ω·cm |
| MEK double rubs after 200 °C/30 min | ASTM D5402 | 20–40 | 80–120 | 100–200 |
| Flexibility after ageing | ISO 1519 | 10–15% elongation | 3–5% elongation | 5–10% elongation |
Substitution of an acrylic topcoat with a methyl-phenyl silicone resin on exterior aluminium cladding requires rebalancing the cure window and surface treatment. The silicone resin film cures at 230–250 °C for 20–30 min, whereas the acrylic bake is typically 150–170 °C for 15 min. Adhesion to chromate-free conversion-coated aluminium reaches class 0–1 in cross-cut testing by ISO 2409 only when the substrate pre-treatment layer is fully cured; residual moisture above 0.3 g/m² reduces adhesion to class 3 and causes microblistering after 500 h of ASTM B117 salt spray. In terms of exterior durability, the silicone resin demonstrates less chalking and higher 60° gloss retention after 3000 h of ASTM G154 cycle 2 exposure than the acrylic control, but it has lower initial hardness. Pencil hardness is typically HB–F by ISO 15184 after the first bake, compared with H–2H for a crosslinked acrylic; the silicone resin reaches H–2H only after supplemental post-cure.
For release papers and high-temperature non-stick surfaces, a methyl silicone resin with low phenyl content is applied at 0.5–1.5 g/m² dry coat weight from a solvent solution. Cure is carried out at 150–180 °C for 30 s in a through-air oven; the resulting release force against a standard acrylic adhesive tape is controlled to 20–50 cN/25 mm when measured by FINAT FTM 3. Unlike fluoropolymer coatings, the silicone resin does not require the same primer intensity on metal, but it is not suitable for continuous exposure to boiling water or strong mineral acids because siloxane bond hydrolysis becomes significant below pH 2 and above pH 12.
Compared with a high-molecular-weight polydimethylsiloxane gum, the silicone resin is a low-molecular-weight, highly branched oligomer with T/Q unit functionality. The gum is processed as a thixotropic paste with Mooney viscosity 20–50 MU and cures by platinum-catalysed addition or peroxide initiation, while the resin cures by condensation of silanol groups. The resin therefore has higher hardness and better high-temperature dielectric properties but lower elongation at break; elongation of a cured silicone resin film is typically 5–15%, whereas a 40 Shore A silicone rubber exceeds 300% by ISO 37. This distinction defines the application boundary: the resin is selected where stiffness, overcoatability, and high-temperature adhesion are required; the rubber is selected where cyclic mechanical deformation dominates.
