This paper deeply explores the influence of phenyl content on the performance of phenyl raw rubber. Through multi-faceted performance tests on phenyl raw rubber with different phenyl contents, the changes in physical properties, chemical properties and processing properties are analyzed. The study found that the change of phenyl content significantly affects the cold resistance, molecular rigidity, radiation resistance, flame resistance, etc. of phenyl raw rubber, and also has a certain effect on its processing process. This provides an important theoretical basis for the precise application and formulation optimization of phenyl raw rubber in different fields.
1. Introduction
As an important organosilicon material, phenyl raw rubber is widely used in many fields. Its unique properties are derived from the phenyl introduced into the molecular structure, and the different phenyl content has a crucial influence on its performance. In-depth study of the relationship between phenyl content and the performance of phenyl raw rubber will help to better understand and utilize this material and develop high-performance products that meet different needs.
2. Overview of phenyl raw rubber
Phenyl raw rubber, chemical name α, ω dihydroxy polydimethyl diphenylsiloxane, usually appears as a colorless and transparent oily liquid, which can be dissolved in organic solvents such as toluene, xylene, and chlorinated hydrocarbons. In its molecular structure, the presence of phenyl destroys the regularity of the siloxane molecular structure, thus giving the material special properties that are different from ordinary silicone rubber. According to the different phenyl content, it can be divided into three types: low phenyl, medium phenyl and high phenyl.
3. The influence of phenyl content on physical properties
3.1 Cold resistance
As the phenyl content increases, the rigidity of the silicone rubber molecular chain gradually increases, which limits the mobility of the molecular chain. In a low temperature environment, it is difficult for the molecular chain to arrange freely as when the phenyl content is low, resulting in a decrease in the cold resistance of the material. Studies have shown that when the phenyl content is low, such as when the ratio of phenyl to silicon atoms is 5-10% (low phenyl silicone rubber), its crystallization temperature is greatly reduced, and the working temperature of the resulting silicone can be extended to -100℃, with good cold resistance. However, when the phenyl content continues to increase, the rigidity of the molecular chain increases, and the cold resistance gradually deteriorates. This is because the introduction of phenyl destroys the regularity of the dimethylsiloxane structure, which helps to reduce the crystallization temperature within a certain range, but if the content is too high, the molecular chain rigidity will affect the activity of the molecular chain at low temperatures.
3.2 Molecular rigidity
The increase in phenyl content directly leads to an increase in the molecular rigidity of phenyl rubber. As a larger side group, phenyl increases the steric hindrance between molecular chains, making the internal rotation of the molecular chain difficult, thereby increasing the rigidity of the molecular chain. This change in molecular rigidity has an important influence on the mechanical properties of the material. For example, the hardness and modulus of the material will increase with the increase of phenyl content. In practical applications, high-rigidity phenyl rubber is suitable for some occasions that need to withstand large external forces and maintain stable shape, such as sealing materials for some mechanical parts.
3.3 Density
The relative atomic mass of phenyl is large. As the phenyl content increases, the density of phenyl rubber will also increase accordingly. This is because more phenyl groups with larger mass are introduced per unit volume. The change in density needs to be considered in some application scenarios that have strict requirements on the weight of the material. For example, in the aerospace field, too high density may increase the weight of the aircraft and affect its performance. Therefore, it is necessary to reasonably control the phenyl content to balance the density while meeting other performance requirements.
IV. The influence of phenyl content on chemical properties
4.1 Radiation resistance
As the phenyl content increases, the radiation resistance of phenyl rubber is significantly improved. When exposed to radiation, phenyl can absorb part of the radiation energy and dissipate the energy through its own structural changes, thereby protecting the main chain of silicone rubber molecules from being destroyed. Studies have shown that high phenyl silicone rubber (phenyl content of 40-50%) has excellent radiation resistance and can withstand radiation doses of up to 1x10^8 roentgen. This excellent radiation resistance makes phenyl raw rubber with high phenyl content have important applications in fields with more radiation environments such as nuclear power and aerospace, such as radiation-proof coating materials in nuclear power plants.
4.2 Flame resistance
The increase in phenyl content helps to improve the flame resistance of phenyl raw rubber. The presence of phenyl allows the material to form a more stable carbonized layer during the combustion process, which can effectively prevent heat and oxygen from transferring to the inside of the material, thereby slowing down the combustion rate. Compared with raw rubber with low phenyl content, raw rubber with high phenyl content is more difficult to ignite during combustion, and the flame propagation speed during combustion is slower, which has better flame retardant effect. This feature gives it an application advantage in some fields with high fire safety requirements, such as building fireproof sealing materials, flame retardant packaging materials for electronic equipment, etc.
4.3 Chemical stability
The introduction of phenyl enhances the chemical stability of phenyl rubber to a certain extent. Due to the electron cloud structure of phenyl, the electron cloud density around the silicon atoms on the molecular chain changes, and it has a certain resistance to the corrosion of some chemical substances. For example, in some corrosive environments, phenyl rubber with high phenyl content can maintain better performance stability than raw rubber with low phenyl content, and is not prone to chemical reactions and performance degradation. However, it should be noted that excessive phenyl content may affect the chemical stability of the material under certain special chemical environments due to the reaction of phenyl with specific chemicals. Therefore, in practical applications, it is necessary to select raw rubber with appropriate phenyl content according to the specific chemical environment.
V. Effect of phenyl content on processing performance
5.1 Mixing performance
Phenyl raw rubber with different phenyl content exhibits different mixing performance when mixed with other compounding agents (such as white carbon black, organic peroxide structure control agent, etc.). With the increase of phenyl content, the viscosity of the raw rubber increases, and the interaction between molecular chains increases, which increases the resistance during mixing and the difficulty of mixing. For example, high molecular weight phenyl silicone rubber is a very viscous material, and its room temperature viscosity may exceed 10 million centipoise, which is more viscous than methyl silicone rubber of the same molecular weight. When stirred by a paddle stirrer, due to the climbing characteristics of the polymer material, the rubber will hold the shaft as a whole and then rotate with the stirring shaft, while the part that the stirring paddle cannot reach will adhere to the kettle wall, and be completely separated from the rubber holding the shaft on the stirring paddle, and will not stick to each other, causing stirring failure. This requires the selection of appropriate stirring equipment and process parameters for raw rubber with different phenyl contents in the mixing process to ensure mixing uniformity.
5.2 Vulcanization performance
The phenyl content also affects the vulcanization performance of phenyl raw rubber. The vulcanization process is the process of transforming the raw rubber from a linear structure to a three-dimensional structure. Different phenyl contents will affect the rate and degree of the vulcanization reaction. Generally speaking, a higher phenyl content will slow down the vulcanization reaction rate to a certain extent, because the steric hindrance effect of phenyl may hinder the contact between the vulcanizer and the reactive active points of the rubber molecular chain. In the vulcanization process control, it is necessary to adjust the vulcanization temperature, time and other parameters according to the phenyl content to obtain the ideal vulcanized rubber performance. For example, for raw rubber with high phenyl content, it may be necessary to appropriately increase the vulcanization temperature or extend the vulcanization time to ensure that the vulcanization reaction is fully carried out.
VI. Conclusion
In summary, the phenyl content has a significant impact on the performance of phenyl raw rubber in many aspects. In terms of physical properties, as the phenyl content increases, the cold resistance decreases, and the molecular rigidity and density increase; in terms of chemical properties, the radiation resistance, flame retardancy and chemical stability are improved, but there may be differences under specific chemical environments; in terms of processing performance, the mixing difficulty increases and the vulcanization performance is affected. In practical applications, the phenyl content should be precisely controlled according to specific needs to give full play to the performance advantages of phenyl raw rubber and provide high-performance material solutions for various fields. In the future, with the continuous deepening of research on phenyl raw rubber, it is expected to further expand its application areas and develop more high-performance and multifunctional material products.