Censil hydrophobic precipitated silica — surface treated with PDMS, HMDS, or alkylsilane. For coatings, adhesives, sealants, rubber & plastics. Anti-caking, reinforcement & rheology control. Free sample.
Sensilchem's hydrophobic silica is a specially surface-modified (silane treated) ultrafine white powder with exceptional water repellency and superior anti-caking properties. Dual-use for feed anti-caking and coating applications. BET >=160 m2/g, SiO2 >=95%, hydrophobicity >98%.
| Parameter | Specification |
|---|---|
| Model | Censil 17 |
| Appearance | White powder |
| Heating Loss (105C, 2h) % | <=10 |
| Ignition Loss (1000C, Dry Basis) % | <=8.5 |
| DBP Absorption (ml/100g) | >180 |
| pH (5% Suspension) | 6.5-8.5 |
| SiO2 Content % | >=95 |
| BET surface area (m2/g) | >=160 |
| Na2SO4 % | <=0.4 |
| Particle Size (um) | 1-45 |
| Heavy Metals (Pb) % | <=0.003 |
| Bulk Density (g/L) | 120-140 |
| Application | Feed anti-caking, coating additives, industrial applications |
| Parameter | Specification |
|---|---|
| Model | Censil D17 |
| Appearance | White powder |
| Heating Loss (105C, 2h) % | 3.0-5.0 |
| Ignition Loss (1000C, 2h) % | 4.0-7.0 |
| DBP Absorption (cm3/g) | 1.50-1.80 |
| pH (5% Suspension) | 6.5-7.5 |
| SiO2 Content (Dry Basis) % | >=98 |
| BET Surface Area (m2/g) | 170-220 |
| Na2SO4 % | <=4 |
| Particle Size (um) | 8-12 |
| Heavy Metals (Pb) % | <=0.003 |
| Arsenic (As) % | <=0.0003 |
| Bulk Density (g/L) | 130-180 |
| Application | Improves feed powder flowability, suitable for direct granulation |
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Censil hydrophobic silica is a range of surface treated silica products manufactured by Longyan Shenghe Chemical Co., Ltd. in Fujian, China. As a leading China hydrophobic silica manufacturer, Censil produces silane-modified precipitated silica with ≥98% hydrophobicity, serving formulators in coatings, adhesives, sealants, rubber, and plastic compounds who need moisture-resistant performance.
Censil hydrophobic precipitated silica is engineered as a cost-effective alternative to SIPERNAT® D17, Aerosil® R-series, and HDK® H-series — delivering equivalent moisture resistance and rheological performance at 30-50% lower cost. With multiple surface treatment options (PDMS, HMDS, alkylsilane) and custom surface treatment capabilities, Censil provides tailored hydrophobic silica solutions for every application.
Hydrophobic silica is produced by chemically modifying the surface of precipitated silica with silane coupling agents. The native silica surface contains abundant silanol groups (Si-OH) that are naturally hydrophilic — attracting water and limiting compatibility with organic matrices. By replacing these silanol groups with hydrophobic organic moieties, the silica becomes water-repellent while retaining its structural and functional properties.
| Treatment Agent | Chemical Type | Hydrophobicity Level | Best Applications | Censil Grade |
|---|---|---|---|---|
| PDMS (Polydimethylsiloxane) | Silicone-based treatment | Moderate-High (contact angle >140°) | Feed anti-caking, defoamers, general-purpose hydrophobic filler | Censil D17 |
| HMDS (Hexamethyldisilazane) | Trimethylsilyl treatment | High (contact angle >150°) | Coatings, powder coatings, cosmetics, free-flow agents | Censil D30 |
| Alkylsilane | Long-chain alkylsilane coupling | Very High (contact angle >160°) | Epoxy adhesives, PU sealants, polar reactive systems | Censil D50 |
| Octylsilane / Custom | Specialty silane coupling agents | Tailored to specification | Custom formulations, specialty rubber, niche applications | Custom on request |
The hydrophobic surface treatment process involves the following steps:
The choice of silane coupling agent determines the degree of hydrophobicity, compatibility with different matrices, and the rheological behavior of the treated silica in organic systems. Censil's technical team can recommend the optimal surface treatment for your specific formulation.
Hydrophobic silica for coatings provides dual functionality: moisture resistance and rheology modification. In solvent-based and high-solids coating systems, surface treated silica creates a thixotropic network that prevents pigment settling, controls sag resistance on vertical surfaces, and improves application properties — without absorbing atmospheric moisture that could cause coating defects.
| Coating Type | Recommended Grade | Dosage | Key Benefits |
|---|---|---|---|
| Anti-Corrosion Industrial Coatings | Censil D50 | 0.5-2.0% | Enhanced anti-corrosion, stable rheology, moisture barrier |
| Marine & Protective Coatings | Censil D50 | 1.0-3.0% | Superior water resistance, anti-settling for heavy pigments |
| Powder Coatings | Censil D30 | 0.5-1.5% | Flow control, anti-caking in powder, improved film properties |
| High-Solids Solvent Coatings | Censil D30 / D50 | 0.5-2.0% | Anti-sag, thixotropic control without moisture pickup |
| Defoamer Additives for Coatings | Censil D17 | 5-20% in carrier | Hydrophobic active carrier, efficient foam collapse |
In coating formulations, hydrophobic silica outperforms hydrophilic grades by maintaining consistent rheology in humid environments. While hydrophilic silica can absorb 5-10% atmospheric moisture over time (altering viscosity and potentially causing coating defects), hydrophobic silica remains dimensionally stable — ensuring reproducible coating performance from production to application.
Hydrophobic silica for adhesives and sealants is one of the most important applications of surface treated silica. In polar reactive systems — including epoxy adhesives, polyurethane sealants, and silane-terminated polymer (STP/SMP) formulations — hydrophobic silica provides stable, long-lasting rheology control that hydrophilic silica cannot achieve.
| System | Recommended Grade | Dosage | Key Benefits |
|---|---|---|---|
| Epoxy Adhesives (2-component) | Censil D50 | 1.0-4.0% | Stable thixotropy, anti-sag on vertical surfaces, no viscosity loss |
| Polyurethane (PU) Sealants | Censil D50 | 2.0-6.0% | Excellent moisture resistance, reinforcement, controlled flow |
| STP/SMP Adhesives & Sealants | Censil D30 / D50 | 3.0-8.0% | High transparency options, thixotropy, enhanced lap shear strength |
| Silicone Sealants (RTV/HTV) | Censil D30 | 5.0-15.0% | Reinforcing filler, tear resistance, transparency |
| Construction Adhesives | Censil D50 | 1.5-5.0% | Non-sag, high green strength, weather resistance |
| Hot-Melt Adhesives | Censil D17 | 1.0-5.0% | Heat resistance, viscosity control, open time adjustment |
The key advantage of hydrophobic silica in adhesives and sealants is its stability in high-pH and moisture-curing systems. Hydrophilic silica (like untreated precipitated silica or fumed silica) tends to lose rheological effectiveness in alkaline environments such as amine-cured epoxy, because polar groups in the curing agent interact with the silica's surface silanols. Hydrophobic silica's silane-treated surface protects against this interaction, maintaining consistent thixotropy throughout shelf life and after curing.
Surface treated hydrophobic silica serves as a high-performance reinforcing filler and processing aid in rubber and plastic compounds. The hydrophobic surface treatment improves dispersion in non-polar polymer matrices (SBR, BR, EPDM, natural rubber) and reduces filler-polymer interaction energy, leading to lower mixing viscosity and improved mechanical properties.
| Application | Recommended Grade | Function | Key Benefits |
|---|---|---|---|
| Tire Compounds (Green Tire) | Censil D50 | Reinforcing filler | Low rolling resistance, improved wet grip, better dispersion |
| Silicone Rubber (HTV/RTV) | Censil D30 | Reinforcing filler | High tensile strength, transparency, tear resistance |
| EPDM Rubber Profiles | Censil D17 / D50 | Semi-reinforcing filler | Improved extrusion, surface quality, weather resistance |
| Thermoplastic Compounds | Censil D17 | Processing aid, reinforcement | Improved stiffness, heat resistance, dimensional stability |
| Cable & Wire Compounds | Censil D50 | Reinforcing filler | Electrical insulation, flame retardancy synergy |
For rubber applications, hydrophobic silica's surface treatment reduces the filler's tendency to form hard agglomerates during mixing, enabling better dispersion at lower energy input. This translates to shorter mixing cycles, lower compound temperatures, and ultimately better mechanical properties in the finished rubber product.
Censil offers a comprehensive range of hydrophobic precipitated silica grades with different surface treatments and performance characteristics.
| Grade | Surface Treatment | BET (m²/g) | d50 (µm) | Carbon Content (%) | Hydrophobicity | Primary Application |
|---|---|---|---|---|---|---|
| Censil D17 | PDMS (silane-modified) | ≥160 | 8-12 | 1.5-3.0 | ≥98% | Feed anti-caking, defoamers, general hydrophobic filler |
| Censil D30 | HMDS (trimethylsilyl) | 200-250 | 5-10 | 2.0-4.0 | ≥98% | Coatings, powder coatings, silicone rubber, cosmetics |
| Censil D50 | Alkylsilane coupling | 250-300 | 3-8 | 2.5-5.0 | ≥98% | Epoxy adhesives, PU sealants, polar reactive systems |
| Censil 17 | Silane-modified (milled) | ≥160 | 5-8 | 1.5-3.0 | ≥98% | Feed anti-caking, coating additive, dual-use grade |
| Custom D-Series | Customer-specified silane | 50-300 | 3-15 | Custom | ≥95% | Tailored to specific formulations |
Formulators evaluating hydrophobic silica suppliers often compare Censil against leading international brands. Below is a specification-level comparison for key application segments.
| Property | Censil D17 | SIPERNAT® D 17 |
|---|---|---|
| SiO₂ Content | ≥95% | ≥96% |
| BET Surface Area | ≥160 m²/g | 150-200 m²/g |
| Particle Size (d50) | 8-12 µm | 8-12 µm |
| Hydrophobicity | ≥98% | ≥98% |
| Surface Treatment | PDMS (silane) | PDMS (silane) |
| Cost Index | 100 | 180-220 |
| Lead Time | 2-3 weeks | 6-10 weeks |
| Property | Censil D50 | Aerosil® R 202 | HDK® H20 |
|---|---|---|---|
| Silica Type | Precipitated (surface treated) | Fumed (PDMS treated) | Fumed (alkylsilane) |
| BET Surface Area | 250-300 m²/g | 80-120 m²/g | ~170 m²/g |
| Surface Treatment | Alkylsilane | PDMS (dimethicone) | Alkylsilane |
| Primary Particle Size | 10-30 nm (aggregate) | 12-16 nm | 12 nm |
| Rheology in Epoxy | Strong thixotropy | Strong thixotropy | Strong thixotropy |
| Best For | Polar systems (epoxy, PU) | Polar systems (epoxy, VE) | Polar systems (PU, STP) |
| Cost Index | 100 | 200-250 | 180-230 |
| Lead Time | 2-3 weeks | 4-8 weeks | 4-6 weeks |
Key Finding: Censil D50 hydrophobic precipitated silica delivers comparable rheological performance to fumed silica alternatives (Aerosil® R-series, HDK® H-series) in polar adhesive and coating systems at 40-60% lower cost. While fumed silica offers nano-scale primary particles for extreme thickening efficiency, Censil's surface-treated precipitated silica achieves effective rheology control at higher surface area (250-300 vs 80-170 m²/g) with significantly better cost efficiency. For formulators seeking a cost-effective alternative to Aerosil R202 or an HDK H20 replacement for epoxy adhesives, Censil D50 is the proven solution.
| Property | Typical Range | Test Method |
|---|---|---|
| SiO₂ Content (dry basis) | ≥95-99% (grade dependent) | GB/T 31586 |
| Loss on Drying (105°C, 2h) | ≤5% | GB/T 31586 |
| BET Surface Area | 50-300 m²/g (grade dependent) | BET/N₂ adsorption |
| DBP Absorption | 1.5-3.5 cm³/g (grade dependent) | GB/T 31586 |
| Carbon Content | 1.5-5.0% (treatment dependent) | Elemental analysis |
| Hydrophobicity Degree | ≥95-98% | Float test / contact angle |
| pH Value (5% suspension) | 4.0-8.5 (treatment dependent) | GB/T 31586 |
| Heavy Metals (Pb) | ≤0.001% | ICP-OES |
| Salt Content (Na₂SO₄) | ≤1.0% | GB/T 31586 |
Hydrophobic silica is precipitated or fumed silica that has been surface-treated with silane coupling agents to make it water-repellent. The silica's natural surface silanol groups (Si-OH) are chemically bonded with hydrophobic compounds — most commonly polydimethylsiloxane (PDMS), hexamethyldisilazane (HMDS), or alkylsilanes. This surface treatment converts the hydrophilic silica into a moisture-resistant material while preserving its porous structure, high surface area, and functional properties. Censil hydrophobic silica achieves ≥98% hydrophobicity, tested by float test and contact angle methods.
Hydrophilic silica has untreated silanol groups on its surface, making it water-wettable and highly polar. It disperses easily in water but absorbs moisture from air (up to 10% over time), which can cause problems in moisture-sensitive formulations. Hydrophobic silica has its surface silanol groups chemically modified with silane coupling agents, making it water-repellent. It does not absorb atmospheric moisture, provides better flowability in humid conditions, and is compatible with organic systems like epoxy, polyurethane, and silicone — making it the preferred choice for adhesives, sealants, and solvent-based coatings.
Yes. Censil D17 is a direct alternative to SIPERNAT® D17 for anti-caking and moisture-resistant applications, with matching hydrophobicity (≥98%), particle size (d50 8-12 µm), and surface treatment (PDMS). Censil D50 serves as a cost-effective alternative to Aerosil® R202 for rheology modification in epoxy adhesives and polar coating systems. Censil hydrophobic silica delivers equivalent performance at 30-50% lower cost, with shorter lead times (2-3 weeks vs 6-10 weeks) and custom surface treatment options.
Censil offers four main surface treatment options: (1) PDMS treatment — moderate hydrophobicity, ideal for feed anti-caking and defoamers (Censil D17); (2) HMDS treatment — high hydrophobicity for coatings and powder coatings (Censil D30); (3) Alkylsilane treatment — strong hydrophobicity for polar reactive systems like epoxy and PU sealants (Censil D50); (4) Custom silane coupling agents — tailored to specific customer requirements. The choice of treatment determines compatibility with your matrix system, degree of moisture resistance, and rheological performance.
In adhesives and sealants, hydrophobic silica serves as a rheology modifier and reinforcing filler. It creates a thixotropic network in polar systems (epoxy, polyurethane, STP/SMP) that prevents sagging during storage while breaking down under shear for easy application. Unlike hydrophilic silica, hydrophobic silica maintains stable rheology in alkaline environments (e.g., amine-cured epoxy) because its silane-treated surface is protected from interaction with polar groups. Censil D50 is recommended for hydrophobic silica in epoxy adhesives at 1-4% dosage, achieving strong thixotropy without viscosity loss during cure.
Censil hydrophobic precipitated silica offers 30-50% cost savings compared to equivalent products from Evonik (SIPERNAT® D17), Evonik (Aerosil® R-series), and Wacker (HDK® H-series). With a Cost Index of 100 versus 180-250 for international brands, Censil delivers the same moisture resistance, hydrophobicity, and rheological performance at significantly lower cost. As a China-based hydrophobic silica manufacturer with direct factory supply, Censil also offers 2-3 week lead times, custom surface treatment services, and technical support for formulation optimization.