Liquid silicone rubber (LSR) is widely used in medical devices, electronic packaging, and baby products due to its excellent physiological inertness, heat resistance, and electrical properties. In the addition-cure system of LSR, hydrogen-containing silicone oil serves as the core crosslinking agent, and the precision of its molecular structure directly determines the physical and mechanical properties and processing stability of the final product.
One. Crosslinking Mechanism in Addition Curing Vulcanization Systems
The curing of liquid silicone is based on a platinum-catalyzed hydrosilylation reaction. In this process, vinyl-terminated polydimethylsiloxane (the base adhesive) and hydrogen-containing silicone oil (the crosslinking agent) undergo an addition reaction under the action of a catalyst, forming a three-dimensional network structure.
Low-hydrogen silicone oil (typically referring to silicone oil with a side chain hydrogen content between 0.18% and 1.0%) plays the role of "network nodes" in this system. Its Si-H bonds serve as reactive sites, binding with vinyl groups and connecting the linear polymer chains.
The logic behind controlling crosslinking density and hardness:
Hydrogen content directly corresponds to crosslinking density. At the same addition level, using silicone oil with higher hydrogen content (such as WTS-202 V100-0.75) means more reaction sites per unit volume, increased crosslinking density, higher hardness after curing, improved modulus, and enhanced resistance to compression deformation. Conversely, using a low-hydrogen-content model (such as WTS-202 V100-0.18) helps reduce crosslinking density, giving the product a softer feel and higher elongation at break.
Two. The Influence of Low-Hydrogen Silicone Oil on Product Performance
Suppressing Side Reactions and Improving Product Yield
During liquid silicone molding, Si-H bonds are prone to side reactions that generate hydrogen gas, leading to pores inside the product or a sticky surface. Using low-hydrogen-content silicone oil as a crosslinking agent, or as an active diluent and regulator for high-hydrogen-content crosslinking agents, can effectively control the reaction rate and exothermic peak, suppress hydrogen gas generation, and ensure product density and surface smoothness.
Low volatility ensures product purity
Liquid silicone products (especially food-grade and medical-grade) have strict limits on volatile residues. Low-hydrogen silicone oils, with their low volatility, can significantly reduce the precipitation of small molecules during injection molding, preventing mold contamination (scaling) and reducing the risk of odor and aging in the finished product.
Advantages of Reactivity in Side-Chain Structures
Compared to terminal hydrogen structures, hydrogen-containing side-chain structures offer superior steric hindrance regulation capabilities. In complex formulations, low-hydrogen-content silicone oils with side chains provide a wider processing window, ensuring material stability during storage after mixing, while also enabling rapid cross-linking under heating conditions.
Three. Baite Silicon Industry's Low-Hydrogen Silicone Oil Series: Preferred Raw Materials for Precise Crosslinking
In the fields of liquid silicone and organosilicon deep processing, the stability of raw materials is key to successful formulation. Baiter silicone's hydrogen-containing silicone oil series is specifically designed for high-quality synthesis and applications.
Core Product Advantages:
Excellent Reactivity:The rationally designed side-chain structure boasts high Si-H bond activity, matching mainstream platinum catalysis systems for high vulcanization efficiency.
Stable Hydrogen Content: Minimal batch-to-batch fluctuations in hydrogen content ensure consistent hardness and physical properties of liquid silicone products.
Low Volatility:Strict control of small molecule content effectively reduces molding porosity, improving product appearance and aging resistance.
As a fundamental raw material for the synthesis of hydrophilic polyether silicone oils, alkyl-modified silicone oils, and silicone rubber crosslinking agents, Baite silicone's low-hydrogen silicone oil series provides a solid material guarantee for the organosilicon industry chain due to its excellent quality and stability. For detailed technical parameters and application guidance, please contact the Veechem Chemicals technical team.
