There is a close correlation between the molecular structure of phenyl silicone oil and its high temperature resistance mechanism. Its structural characteristics work synergistically in multiple dimensions to give it excellent thermal stability. The following is an analysis of the relationship between molecular structural characteristics and high temperature resistance mechanisms:

1. Changes in molecular structure caused by the introduction of phenyl substituents
Phenyl silicone oil is a modified product formed by replacing part of the methyl groups with phenyl groups on the basis of methyl silicone oil. The introduction of phenyl groups directly changes the molecular structure of the siloxane main chain, which is specifically manifested as follows:

Enhanced steric effect
As a rigid group, phenyl groups are large in size and have a planar structure. After replacing methyl groups, the rigidity of the molecular chain is significantly increased. This steric hindrance effect effectively inhibits the free rotation and sliding of the molecular chain at high temperatures, reducing the risk of thermal degradation caused by intensified molecular motion.
Conjugated system formation
There are delocalized π electrons in the aromatic ring structure of phenyl groups, forming a conjugated system with the siloxane main chain. The delocalization of this electron cloud reduces the electron density fluctuations inside the molecule, thereby slowing down the rate of oxidation reactions at high temperatures and delaying the oxidative degradation process.

2. The correlation between molecular structure and high temperature resistance mechanism
The high temperature resistance of phenyl silicone oil is not the result of a single mechanism, but a comprehensive manifestation of the combined action of its molecular structure characteristics:

Inhibition of thermal oxidative degradation
The free radical quenching effect of phenyl: phenyl can capture free radicals generated at high temperatures, block free radical chain reactions, and thus inhibit oxidative degradation.
The conjugated system reduces oxidation activity: the aromatic ring structure of phenyl reduces the oxidation activity of the siloxane main chain, making it less susceptible to oxygen attack at high temperatures.
Improved thermal oxidative stability: the introduction of phenyl significantly prolongs the oxidation induction period of phenyl silicone oil at high temperatures, reduces the rate of oxidation product generation, and significantly improves thermal oxidative stability over ordinary silicone oil.
Increasing thermal decomposition temperature
The energy absorption effect of phenyl: the high bond energy of phenyl (about 498 kJ/mol) enables it to absorb more heat energy at high temperatures without breaking, thereby delaying the decomposition of the molecular chain.
Enhanced main chain stability: the presence of phenyl reduces the depolymerization tendency of the siloxane main chain, making it more inclined to crosslink rather than decompose at high temperatures, thereby maintaining the integrity of the molecular structure.
Significantly improved thermal decomposition temperature: The thermal decomposition temperature of phenyl silicone oil is usually 50-100℃ higher than that of ordinary silicone oil, and it can still maintain a stable chemical structure in a high temperature environment.
Enhanced molecular chain rigidity
Steric hindrance limits molecular movement: The rigid structure of phenyl limits the flexibility of the molecular chain, reduces the sliding and entanglement of the molecular chain at high temperature, and thus reduces the risk of thermal degradation caused by increased molecular movement.
Reduced thermal expansion coefficient: Phenyl silicone oil has a small thermal expansion coefficient and a small volume change at high temperature, which reduces the risk of molecular chain breakage caused by thermal expansion.
Improved viscosity stability at high temperature: The viscosity change rate of phenyl silicone oil at high temperature is significantly lower than that of ordinary silicone oil, and it can maintain stable lubrication performance in a high temperature environment.
Promote the formation of cross-linked network
Phenyl promotes cross-linking reaction: Under high temperature conditions, the presence of phenyl promotes the cross-linking reaction between siloxane molecular chains, forming a denser three-dimensional network structure.
Cross-linked network improves thermal stability: The formation of the cross-linked network further enhances the rigidity and thermal stability of the molecular chain, making phenyl silicone oil less likely to decompose or volatilize at high temperatures.
Performance retention at high temperature: The presence of the cross-linked network enables phenyl silicone oil to maintain excellent mechanical properties and chemical stability at high temperatures, and is suitable for extreme high temperature environments.

3. The influence of molecular structure parameters on high temperature resistance
The high temperature resistance of phenyl silicone oil is closely related to its molecular structure parameters, which is specifically manifested as follows:


The relationship between phenyl content and high temperature resistance
Low phenyl content (5-10%): significantly improves low-temperature fluidity, while moderately improving high temperature resistance, suitable for occasions that require both high and low temperature performance.
Medium phenyl content (25%): significantly enhances high temperature resistance and radiation resistance, suitable for high temperature lubrication, electrical insulation and other fields.
High phenyl content (above 45%): further improves high temperature resistance, radiation resistance and chemical stability, but reduces low temperature fluidity, suitable for extreme high temperature environments.
Relationship between molecular weight and high temperature resistance
High molecular weight phenyl silicone oil: longer molecular chain, higher cross-linking density, better thermal stability, but higher viscosity and poorer fluidity.
Low molecular weight phenyl silicone oil: lower viscosity, good fluidity, but relatively poor thermal stability, suitable for high temperature lubrication occasions requiring low viscosity.
Relationship between molecular chain branching degree and high temperature resistance
Straight-chain phenyl silicone oil: molecular chain arrangement is regular, crystallinity is high, thermal stability is good, but low-temperature fluidity is poor.
Branched phenyl silicone oil: molecular chain branching degree increases, crystallinity is reduced, low-temperature fluidity is improved, but thermal stability is slightly reduced.