In the modern silicone industry, low-hydrogen silicone oil is playing an increasingly important role as a key crosslinking agent and modification intermediate. With the increasing integration of the electronics industry and the growing demand for high-performance elastomers, how to precisely control the activity and distribution of silicon-hydrogen bonds (Si-H) has become a core issue in improving product performance.
Jiujiang Deep Sea Technology will provide an in-depth analysis of the professional applications of low-hydrogen silicone oil in the fields of liquid silicone (LSR) and electronic potting compounds from four dimensions: chemical mechanism, application scenarios, performance impact, and selection recommendations.
I. Chemical nature and reaction mechanism of low-hydrogen silicone oil
Low-hydrogen silicone oils typically refer to side-chain hydrogen-containing polymethylsiloxanes or end-chain co-hydrogen-containing silicone oils with a hydrogen content between 0.1% and 0.5% (w/w). Their molecular chains contain a certain proportion of active Si-H bonds, which, under the action of a platinum catalyst, can undergo an addition reaction (hydrosilylation) with vinyl-containing base silicones.
Compared to high-hydrogen silicone oils (typically >1.0%), low-hydrogen silicone oils offer a gentler and more controllable crosslinking mechanism.
Reduce cross-linking density: Prevent materials from becoming brittle due to excessively rapid or dense cross-linking.
Enhanced flexibility: The introduction of long chain segments increases the elasticity of the mesh structure and improves tear resistance.
Suppressing side reactions: reducing hydrogen bubbles generated during the reaction of excess Si-H with moisture, ensuring the compactness of the product.
II. In-depth application in liquid silica gel (LSR)
Liquid silicone, a highly transparent and tear-resistant addition elastomer, is widely used in baby products, medical devices, and smart wearables. Low-hydrogen silicone oils primarily function as auxiliary crosslinking agents or toughening agents in these applications.
2.1 Adjusting Hardness and Modulus The hardness of LSRs is typically between Shore A 10-80 degrees. The modulus of the elastomer can be precisely adjusted by changing the proportion of low-hydrogen silicone oil. Due to its relatively long molecular chains, it retains some of the mobility of the molecular chains while providing crosslinking points, allowing the finished product to maintain high hardness without sacrificing its elongation at break.
2.2 Enhancing Transparency and Inhibiting Yellowing High-quality low-hydrogen silicone oils are deeply refined, resulting in extremely low volatile matter (D4-D10) content. In medical-grade LSRs, using low-hydrogen silicone oils effectively avoids impurity precipitation caused by low purity crosslinking agents, ensuring long-term optical transparency of the product and significantly inhibiting yellowing during high-temperature vulcanization.
2.3 Typical Data Reference According to industry literature and experimental data, in a typical Shore A 40 degree LSR formulation, by using a low-hydrogen silicone oil with a hydrogen content of 0.18%, the tensile strength can be increased by about 15%-20% and the tear strength can be increased by about 25% compared to using a high-hydrogen silicone oil alone.
III. Technological Advantages in the Field of Electronic Encapsulation
Electronic potting compounds are mainly used for sealing components such as LED drivers, sensors, and transformers. Their core requirements are low viscosity, high insulation, flame retardancy, and thermal stability.
3.1 Excellent Penetration and Leveling Properties: Low-hydrogen-content silicone oils have low viscosity (typically 50-300 mm²/s), which gives the potting compound excellent flowability before curing. This allows it to penetrate into the tiny gaps of precision electronic components, achieving omnidirectional encapsulation and avoiding pores or dead zones.
3.2 Excellent Dielectric Properties: The non-polar molecular structure of low-hydrogen-content silicone oils endows them with extremely high dielectric strength (≥ 20 kV/mm) and extremely low dielectric constant. During crosslinking, low-hydrogen-content silicone oils can form a highly symmetrical three-dimensional network with the base adhesive, reducing the presence of polar groups and thus ensuring the insulation stability of electronic components under high-frequency currents.
3.3 Temperature Resistance and Stress Buffering: Electronic products undergo cyclic thermal cycling during operation. The crosslinked network formed with the participation of low-hydrogen-content silicone oils has a lower glass transition temperature. This means that within a temperature range of -50°C to 200°C, the potting compound remains elastic, absorbing internal stress caused by thermal expansion and contraction, and protecting fragile solder joints and chips from mechanical damage.
Low-hydrogen silicone oil, as the "skeleton support" for liquid silicone (LSR) and electronic potting compounds, is developing towards ultra-low volatility, high purification, and functionalization.
