Silicone rubber, as a polymer material widely used in modern industry and daily life, the source of its excellent properties is deeply rooted in its unique microstructure. An in - depth exploration of the relationship between the microstructure and macro - properties of silicone rubber not only helps us understand its working mechanism but also provides a theoretical foundation for the optimization and innovation of materials.
From a microscopic perspective, the main chain of silicone rubber is composed of silicon - oxygen bonds (Si - O). The silicon - oxygen bonds have a relatively high bond energy, endowing silicone rubber with excellent thermal stability. Compared with ordinary carbon - carbon bonds, silicon - oxygen bonds have a longer bond length and a larger bond angle, making the molecular chain have good flexibility. This is the key factor for silicone rubber to exhibit high elasticity on a macroscopic scale. On the side groups of the molecular chain, organic groups such as methyl are usually connected. The presence of these side groups, on the one hand, increases the distance between molecular chains, reduces the intermolecular forces, and further enhances the mobility of the molecular chain. On the other hand, the steric hindrance effect of methyl groups, to a certain extent, hinders the close packing of molecular chains, enabling silicone rubber to maintain elasticity and also have good air permeability.
When a cross - linking reaction occurs in silicone rubber, the molecular chains are connected to each other through chemical bonds to form a three - dimensional network structure. The cross - linking density has a significant impact on the properties of silicone rubber. Appropriate cross - linking can limit the excessive slippage of molecular chains and enhance the tensile strength and wear resistance of the material. However, if the cross - linking degree is too high, the mobility of the molecular chain is overly restricted, and silicone rubber will become hard and brittle, losing some of its elasticity. By controlling the type and dosage of cross - linkers, researchers can accurately regulate the cross - linking density of silicone rubber, thereby achieving the directional optimization of its macro - properties.
In the microstructure, the presence of impurities or defects will have a negative impact on the properties of silicone rubber. Impurities may disrupt the regularity of the molecular chain, reduce the intermolecular forces, and lead to a decrease in the strength and stability of the material. Micro - defects such as voids and cracks, when subjected to external forces, will become stress - concentration points, accelerating the damage of the material. Therefore, in the production process of silicone rubber, strictly controlling the purity of raw materials and the processing technology to reduce the introduction of impurities and defects is an important part of ensuring product quality.
This close relationship between the microstructure and macro - properties is vividly reflected in practical applications. Seals working in high - temperature environments precisely utilize the thermal stability of the silicon - oxygen bonds in the main chain of silicone rubber and the stable network structure formed by appropriate cross - linking to ensure good sealing performance even at high temperatures. In application scenarios that require high elasticity and flexibility, such as the encapsulation of flexible electronic devices, the flexibility of the silicone rubber molecular chain and the high elasticity conferred by a low cross - linking density can adapt to the deformation requirements of the device, such as bending and stretching, while protecting the internal precision electronic components.
High Strength Precipitated Type Silicone Rubber
