As a high-performance polymer material, silicone resin's high-temperature resistance characteristics are derived from its unique molecular structure and chemical bond energy advantages, and it has shown irreplaceable application value in aerospace, electrical and electronic, industrial coatings and other fields.


The following detailed analysis is carried out from the four dimensions of thermal stability, molecular structure, high temperature performance and practical application scenarios：


1. The basis of thermal stability: the chemical advantages of Si-O bonds
The main chain of silicone resin is composed of silicon (Si) and oxygen (O) atoms alternately, forming a Si-O-Si bond, the bond energy is as high as 422.5 kJ/mol, far surpassing the C-C bond (347 kJ/mol) and the C-O bond (358 kJ/mol).This high bond can give silicone resin the following characteristics：


Stable structure at high temperature: In an environment above 300℃, the Si-O bond is not easy to break, the molecular chain remains intact, and the material decomposition or carbonization is avoided.
Low coefficient of thermal expansion: The coefficient of thermal expansion of silicone resin is close to that of inorganic materials, and the size changes are small at high temperatures, which is suitable for the protection of precision components.
Strong oxidation resistance: The Si-O bond has excellent tolerance to oxygen and ozone, and it is not easy to age in a high temperature oxidation environment.


2. The relationship between molecular structure and temperature resistance mechanism
The high temperature resistance of silicone resin is closely related to its molecular structure, which is manifested as：


Influence of side chain substituent：
Methyl substitution group: It gives the resin good flexibility and low temperature compliance, but side chain oxidation is prone to occur at high temperatures, and it is suitable for environments of 200-300℃.


Phenyl substitution group: Improves the rigidity of the molecular chain and enhances the thermal stability of high temperature through the conjugated effect. It is suitable for environments of 300-400℃.
Vinyl substitution group: A three-dimensional mesh structure can be formed by crosslinking reaction, which significantly improves the high-temperature mechanical strength and heat resistance.


Crosslinking density and thermal stability：
The molecular chain movement of silicone resins with high crosslinking density is limited at high temperatures, and the thermal decomposition temperature can be increased to more than 400℃.
For example, the additive silicone resin prepared by the silicon-hydrogen addition reaction has a dense crosslinking network and a thermal decomposition temperature of up to 450℃.


3. High temperature performance: multi-dimensional data support
Thermal decomposition temperature：
The thermal decomposition temperature of ordinary silicone resins is 350-400℃, while the thermal decomposition temperature of modified products (such as adding inorganic fillers or nano particles) can be increased to more than 500℃.
The thermal decomposition temperature of some special silicone resins (such as modified resins containing boron, aluminum and other elements) can even reach 600℃.


Thermal weightlessness analysis (TGA)：
In a nitrogen atmosphere, the mass loss of silicone resin at 300℃ is usually less than 5%, and the mass loss at 400℃ is about 10-15%.
The mass loss of the modified resin at the same temperature can be further reduced to less than 5%.


High temperature mechanical properties：
At 250℃, the tensile strength of silicone resin can be maintained at 70-80% of the normal temperature value, while the tensile strength of ordinary organic resin may drop below 50%.
At 300℃, the hardness change rate of silicone resin is less than 15%, while the hardness change rate of epoxy resin may exceed 30%.


4. Application scenario and performance matching
Aerospace field：
Used in engine compartments, thermal protective coatings, etc., the material is required to maintain structural integrity at a high temperature above 400℃.For example, the turbine blade coating of a certain type of aviation engine uses modified silicone resin, which can be used for a long time at 450℃.


Electrical and electronic field：
As an H-class insulating material, silicone resin can still maintain excellent electrical insulation properties at high temperatures above 180℃.For example, the insulating paint in high-voltage transformers uses silicone resin, which can work for a long time at 200℃.


Industrial coating field：
It is used for anticorrosive coating of high-temperature pipelines, chimneys and other equipment, and the material is required to be chemically resistant to corrosion at 300-400℃.For example, the exhaust pipe coating of a petrochemical plant uses silicone resin, which is resistant to acid and alkali corrosion at 350℃.


Emerging areas：
In the fields of 3D printing high-temperature molds, thermal management of new energy vehicle batteries, etc., the high temperature resistance of silicone resins has been further applied.For example, a 3D printing high-temperature mold uses a silicone resin matrix composite material, which can work continuously at 280℃.


Five, the direction of performance optimization
Inorganic filler modification：
Adding inorganic fillers such as alumina and boron nitride can significantly improve the thermal conductivity and temperature resistance of silicone resins.For example, a silicone composite material with 20% alumina added can increase its thermal decomposition temperature to 450℃.


Nano particle doping：
The introduction of nano-silica, carbon nanotubes, etc. can enhance the crosslinking density and thermal stability of the resin.For example, the mass loss of nano-silica-doped silicone resin at 400℃ can be reduced to 8%.


Gradient structure design：
The gradient structure silicone resin is prepared through molecular design to achieve the synergistic optimization of the high temperature resistance of the surface layer and the flexibility of the inner layer.For example, a certain type of gradient structure silicone coating can still maintain adhesion at 500℃.