How does white carbon black affect the properties of liquid silicone rubber?
Background and advantages of liquid silicone rubber
From traditional silicone to liquid silicone
The development of liquid silicone rubber is closely related to the study of silicon elements, and the discovery of silicon elements in the 19th century laid the chemical foundation for it; The application of silicone materials in the mid-20th century accumulated technical experience; In the 1970s, due to the limitations of solid silicone rubber technology (such as low molding efficiency), the industry began to develop liquid silicone rubber; In the late 1980s, its industrial production gradually realized; China entered the industrialization stage at the beginning of the 21st century.
Liquid silicone rubber (LSR for short) is a liquid elastomer material composed of high molecular weight polysiloxane as the basic polymer, reinforcing filler, cross-linking agent and other additives. It has the characteristics of high transparency, high and low temperature resistance (above -60 ℃~200 ℃), aging resistance, good biocompatibility, and no by-products during vulcanization. Through injection molding process, it can quickly produce various precision and complex shaped products.
At present, liquid silicone rubber is widely used in fields such as medical devices, food contact materials, automotive components, electronics and electronics, aerospace, etc.
Important parameters and their impact of Precipitated Silica
The specific surface area, oil absorption value, average particle size, and dispersibility of white carbon black have a significant impact on the mechanical properties, processability, and appearance of liquid silicone rubber.
(1) Specific surface area
Specific surface area is one of the key parameters affecting the performance of silicone rubber. A low specific surface area may result in insufficient reinforcement effect, while a high specific surface area may cause excessive viscosity of the system, affecting processing performance.
(2) Oil absorption value
The oil absorption value directly affects the mechanical properties and processing characteristics of silicone rubber. White carbon black with high oil absorption can provide stronger intermolecular forces, thereby enhancing tensile strength and tear strength.
(3) Average particle size
Excessive particle size can lead to severe light scattering and reduce product transparency; However, if the particle size is too small, it is easy to form agglomeration, which affects the uniformity of dispersion.
(4) Dispersibility
White carbon black with good dispersibility can be uniformly distributed in the system as a reinforcing filler for liquid silicone rubber. The hydroxyl groups on the surface of white carbon black form physical or chemical interactions with the molecular chains of silicone rubber, which can significantly enhance the tensile strength, tear strength, and hardness of the rubber material. At the same time, due to the high dispersibility of white carbon black, its structure can be easily destroyed during processing, mixing, and shearing, and it can be better dispersed in the rubber material, which can further improve its mechanical properties.
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