What is the carbon content of SemiSIL R620?

SemiSIL R620 features a precision-controlled carbon content of 1.5% - 2.1%. This HMDS treatment ensures excellent hydrophobicity and superior optical clarity in liquid silicone rubber (LSR) applications.

Is R620 suitable for transparent silicone rubber?

Yes, SemiSIL R620 is specifically designed for high-transparency systems. The HMDS surface modification provides a high refractive index compatibility, making it the gold standard for clear LSR and HTV parts.

SemiSIL R620: Hydrophobic Fumed Silica (HMDS Treated)

SemiSIL R620 is a HMDS treated Hydrophobic fumed silica (Hexamethyldisilazane treated)based on a high-surface-area 200 m2/g. Engineered for high-end elastomers, R620 provides high hydrophobicity and superior mechanical reinforcement, making it the preferred choice for transparent LSR and HTV silicone rubber systems.

Quick Profile

Surface Treatment: HMDS (Hexamethyldisilazane)
Surface Area (BET): 200 ± 20 m²/g
CAS Number: 112945-52-5
Carbon Content: 1.5% - 2.1%
Key Advantage:Exceptional clarity in LSR, high tear strength, and excellent moisture resistance.

Strategic Applications & Solutions

LSR & HTV Rubber Acts as a powerful reinforcing filler for HTV silicone rubber and LSR. It boosts tear strength and tensile properties while maintaining the highest optical clarity.

High-End Coatings The ideal anti-settling agent in coatings. It prevents pigment sedimentation in clear coats and high-gloss finishes without affecting the final transparency.

Technical Powders Serves as an advanced anti-caking aid for sensitive powders. It provides superior fluidization and protects high-value powder formulations from moisture-induced clumping.

Adhesives & Inks Ensures stable thixotropy for printing inks and structural adhesives. It allows for high-build applications with zero sagging, even under high shear conditions.

Key Functional Properties of SemiSIL R620

Ultimate Optical Clarity As a specialized high hydrophobicity silica for LSR, the HMDS treatment ensures the highest transparency in liquid silicone rubber, providing invisible reinforcement without compromising optical quality or color stability.

Superior Mechanical Strength Based on a hydrophobic silica with 200 BET carrier, it delivers exceptional tear strength and tensile modulus in HTV elastomers, making it the gold standard for high-durability and high-precision silicone parts.

Permanent Hydrophobic Barrier This HMDS surface modified silica features an impenetrable moisture shield that protects moisture-sensitive electronic coatings and high-value powder formulations.

Advanced Thixotropy & Anti-Settling SemiSIL R620 acts as a precision anti-sagging agent in coatings and printing ink, building a temperature-stable 3D network that ensures perfect pigment suspension and zero vertical slump in high-gloss clear coats.

Technical Data (TDS)

Property	Standard Value	Unit	Method
Specific Surface Area (BET)	200 ± 20	m²/g	GB/T 20020
pH Value (in 4% dispersion)	5.5 ~ 8.0	-	GB/T 20020
Carbon Content	1.5 ~ 2.1	Wt%	GB/T 20020
Loss on Drying (2h @ 105°C)	≤ 0.7	Wt%	GB/T 20020
Loss on Ignition (2h @ 1000°C)	≤ 4.0	Wt%	GB/T 20020
Tamped Density	40 ~ 60	g/L	GB/T 20020
Silica Content (SiO₂)	≥ 99.8	%	GB/T 20020

Note: All parameters of our HMDS treated fumed silica R620 meet international industrial standards.

Packaging & Logistics

Non-DG Compliance: Fully safe for Railway, Sea (Shipping), and Truck transportation.

20'FCL Loading • 180kg / pallet (18 bags)
• 10 pallets / 1600kg total

40'HQ Loading • 220kg / pallet (22 bags)
• 20 pallets / 4400kg total

Common Questions about HMDS Treated Fumed Silica R620

Is SemiSIL R620 a direct alternative to Aerosil® R812 or HDK® H20?

Yes. SemiSIL R620 is a 1:1 technical equivalent to industry-standard HMDS grades like Aerosil R812. It is based on a 200 BET carrier and features the same HMDS surface modified silica chemistry, making it a reliable drop-in replacement for high-performance elastomers and coatings.

Why is R620 preferred for LSR (Liquid Silicone Rubber) applications?

SemiSIL R620 is the premier high hydrophobicity silica for LSR because the HMDS treatment creates a highly compatible interface with silicone polymers. It provides superior mechanical reinforcement (tear and tensile strength) while maintaining ultimate optical clarity, which is essential for medical-grade and high-transparency silicone parts.

How does the 200 BET surface area impact coating performance?

As a hydrophobic silica with 200 BET, R620 builds a much denser thixotropic network compared to lower surface area grades. This makes it an elite anti-sagging agent in coatings, ensuring that even high-build clear coats remain uniform on vertical surfaces without settling or cloudiness.

How does R620 perform in high-humidity environments?

SEMISIL R620 offers extreme water repellency. It acts as a permanent moisture barrier, preventing micro-clumping in technical powders and ensuring that sensitive printing inks maintain stable rheology even in tropical climates.

When should I choose R620 (HMDS) over R202 (PDMS)?

Choose SemiSIL R620 when optical clarity and maximum reinforcement are your top priorities, particularly in LSR and HTV. Choose R202 when you need the "silicone oil" effect to prevent crepe hardening in HCR or require maximum stability in polar resins like epoxy.

Factory-Direct hydrophobic fumed silica R620

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