I. Structure and Properties: Si-H bonds are located on the side chains (not at the ends), with the general chemical formula: (CH₃)₃SiO[Si(CH₃)(H)O]ₙ[Si(CH₃)₂O]ₘSi(CH₃)₃. Active hydrogen is evenly distributed, enabling three-dimensional network crosslinking.
Hydrogen content is adjustable (0.02%~1.5%), customizable, and directly affects crosslinking density.
Physicochemical Properties: Appearance: Colorless, transparent, oily liquid; Viscosity range: 10~1000 mPa·s (customizable); Temperature resistance: -50℃~250℃; Stable reactivity: Si-H bonds readily react with vinyl (Vi) and hydroxyl (-OH) groups.
Key Advantages: High crosslinking efficiency: Multiple Si-H bonds on the side chains, suitable for deep curing. Strong mechanical properties: Tear-resistant and compression set resistant after crosslinking. Excellent weather resistance: UV-resistant and ozone-resistant, suitable for outdoor applications.
II. Specific Application Areas and Cases
1. Addition-Cure Silicone Rubber (Electronics/Medical/Industrial) LED Encapsulation Adhesive: Crosslinks with vinyl silicone oil to form a highly transparent, high-temperature resistant elastomer. Formulation Key Points: Hydrogen content 0.2%~0.5%, platinum catalyst 1~10 ppm. Medical Silicone Products (Catheters, Prostheses) Advantages: Non-toxic, good biocompatibility, FDA certified. High-Temperature Sealing Gasket Performance Requirements: Hydrogen content 0.8%~1.2%, resistant to long-term aging at 250℃.
2. Adhesives and Sealants Electronic Potting Compound Functions: Insulation, moisture resistance, shock resistance, hydrogen content 0.5%~1.0%. Building Curtain Wall Adhesive Features: High elastic modulus, weather resistance for over 20 years.
3. Waterproof and Anti-Stick Coating Baking Mold Anti-Stick Coating Process: Hydrogen-containing silicone oil + vinyl resin, contact angle >110° after curing. Textile Waterproof Finishing Effect: Reacts with fiber hydroxyl groups to achieve long-lasting waterproofing (effective after 50 washes). 4. Toughening Mechanism of Engineering Plastics (e.g., PC, ABS) in Plastic and Rubber Modification: The side-chain Si-H reacts with the polar groups of the plastic, improving impact resistance. Example of hydrophobic treatment for rubber surfaces: Coating the surface of automotive rubber parts to reduce the coefficient of friction.
5. Defoamer (Industrial Grade): Defoaming formulation for oil extraction: Hydrogen-containing silicone oil + hydrophobic SiO₂, resistant to high temperature and pressure.
III. Selection of Hydrogen-Containing Silicone Oil
Platinum Catalyst Matching Dosage: 1~50 ppm (Excess may lead to side reactions or toxicity). Inhibitor: Add ethynyl alcohols (e.g., 1-ethynyl-1-cyclohexanol) to delay curing and adapt to operating time requirements.
Process Control Curing Temperature: 80℃~150℃ (High temperature accelerates the reaction, low temperature reduces bubbles). Vacuum Degassing: Avoids the release of trace amounts of hydrogen gas from the Si-H reaction, which can cause bubbles.
IV. Precautions for Use
Storage Conditions: Must be sealed and protected from light to prevent hydrolysis of Si-H bonds (generating hydrogen gas). Catalyst Matching: Platinum catalyst dosage 1~50 ppm to avoid sulfur and amine poisoning. Process Control: Curing temperature: 80℃~150℃ (high temperature accelerates the reaction). Vacuum Degassing: Avoids Si-H side reactions that generate bubbles. VI. Future Technology Directions: Low Volatility: Reduces curing shrinkage and improves the reliability of electronic devices. Photocuring Modification: Develop UV-triggered crosslinking hydrogen-containing silicone oils for precision coating. Nanocomposites: Simultaneously enhance thermal conductivity and mechanical properties through SiO₂/graphene modification.
Summary: Side-chain hydrogen-containing silicone oils, with their multiple active sites and high crosslinking density, have become core materials for electronic adhesives, medical silicone, and high-end coatings. The key to their application lies in: precisely controlling the hydrogen content (0.1%~1.5%) to match performance requirements; optimizing the catalyst system (platinum/inhibitor) to balance curing speed and operability; and combining filler technology (such as thermally conductive/conductive fillers) to expand functional applications.
