I. Overview of silica gel

1. Silica gel (SiO₂)

 Definition: Silica gel is an ultrafine silica powder with high specific surface area, high porosity and good dispersibility.

Application: As a reinforcing agent, thickener and anti-settling agent, it is widely used in rubber, coatings, inks, cosmetics and medicine.

2. Silica gel

Definition: Silica gel is a high molecular polymer with siloxane (Si-O-Si) as the main chain, which has excellent high and low temperature resistance, elasticity and chemical stability.

Application: Used as sealing material, adsorbent, catalyst carrier and insulating material.

3. Silica gel

Composition: A composite material of silica gel and silica gel, in which silica gel is dispersed in a silica gel matrix by physical or chemical methods.

Performance characteristics:

Mechanical properties: The addition of silica gel significantly improves the tensile strength, tear strength and wear resistance of silica gel.

Chemical corrosion resistance: The high specific surface area and chemical inertness of silica gel enhance the corrosion resistance of silica gel.

II. Analysis of chemical corrosion resistance of silica gel

1. Acid and alkali resistance

Acidic medium:

Performance: Silica gel has excellent tolerance to dilute acid (such as dilute sulfuric acid, dilute hydrochloric acid), and the siloxane bond (Si-O-Si) has high chemical stability and is not easily hydrolyzed by acid.

Influence:

Concentration effect: High concentration of strong acid (such as concentrated sulfuric acid, concentrated nitric acid) may cause slow hydrolysis of siloxane bonds, reducing material performance.

Temperature effect: High temperature accelerates the attack of acid on siloxane bonds and shortens the service life of the material.

Alkaline medium:

Performance: Poor tolerance to strong alkali (such as sodium hydroxide, potassium hydroxide), siloxane bonds are easily hydrolyzed under alkaline conditions to form silicates.

Influence:

Concentration effect: High concentration of strong alkali will accelerate the hydrolysis reaction, resulting in rapid degradation of silica gel.

Temperature effect: High temperature significantly accelerates the alkaline hydrolysis process.

2. Organic solvent resistance

Performance: Silica gel has good tolerance to most organic solvents (such as alcohols, ketones, and esters), and the hydrophobicity of siloxane bonds prevents solvent penetration.

Impact:

Solvent polarity: Polar solvents (such as acetone and ethyl acetate) have little swelling effect on silica gel, while non-polar solvents (such as benzene and toluene) may cause slight swelling.

Temperature effect: At high temperatures, the permeability of solvents increases, which may cause silica gel to swell or dissolve.

3. Oxidation resistance

Performance: At room temperature, silica gel has good tolerance to oxidants (such as hydrogen peroxide and potassium permanganate).

Impact:

High temperature effect: At high temperatures, oxidants may accelerate the oxidation and breakage of siloxane bonds, resulting in a decrease in material performance.

4. Salt spray resistance

Performance: In a salt spray environment, silica gel exhibits excellent corrosion resistance, and siloxane bonds are resistant to erosion by salt ions.

Impact: Humidity impact: High humidity environment may promote the penetration of salt ions and accelerate material aging.

3. Factors affecting the chemical corrosion resistance of silica gel

1. Content and dispersibility of silica gel

Content: An appropriate amount of silica gel (usually 10-30%) can significantly improve the corrosion resistance of silica gel, but excessive amount may lead to uneven dispersion and defects.

Dispersibility: Good dispersibility ensures that silica gel is evenly distributed in the silica gel matrix to form an effective protective barrier.

2. Crosslinking density of silica gel

Crosslinking density: The network structure of silica gel with high crosslinking density is denser, which hinders the penetration of chemical media and improves corrosion resistance.

Crosslinking agent selection: Suitable crosslinking agents (such as peroxides, silane coupling agents) can optimize the crosslinking structure and enhance corrosion resistance.

3. Surface treatment of silica gel

Treatment method: Surface treatment of silica gel with silane coupling agents, stearic acid, etc. can improve its compatibility with the silica gel matrix and improve dispersibility.

Effect: The surface treated silica forms a stronger interface with silica gel, enhancing the corrosion resistance of the material.

4. Environmental conditions

Temperature: High temperature accelerates chemical corrosion reaction and reduces the service life of the material.

Humidity: High humidity environment promotes the penetration of chemical media and accelerates material aging.

Medium concentration: High concentration chemical media has a stronger corrosive effect on materials.

4. Methods to improve the chemical corrosion resistance of silica gel

1. Optimize the addition amount and dispersibility of silica

 Addition amount: Determine the optimal silica content through experiments to balance corrosion resistance and mechanical properties.

Dispersion process: Use high shear mixing, ultrasonic dispersion and other technologies to ensure uniform dispersion of silica.

2. Select suitable cross-linking agent and cross-linking process

Cross-linking agent: Select a cross-linking agent with good compatibility with the silica matrix to optimize the cross-linking density.

Cross-linking process: Control the cross-linking temperature and time to form a dense cross-linking network structure.

3. Surface modification of silica

Modifier: Use silane coupling agent, stearic acid, etc. to treat silica surface to improve its compatibility with silica gel.

Modification effect: Enhance the interface bonding between silica and silica gel and improve the corrosion resistance of the material.

4. Add corrosion-resistant fillers

Filler selection: Add corrosion-resistant fillers such as alumina and zirconium oxide to synergize with silica to improve the corrosion resistance of the material.

Filler treatment: Surface treatment of fillers to improve their compatibility with silica gel.

5. Optimize preparation process

Mixing process: Use appropriate mixing temperature and time to avoid degradation of silica gel and agglomeration of silica gel.

Vulcanization process: Control the vulcanization temperature and time to ensure that the silica gel is fully vulcanized to form a dense network structure.

V. Application areas of chemical corrosion resistance of silica gel

1. Chemical equipment seals

Application: Seals for pumps, valves, pipelines and other equipment to prevent leakage of chemical media.

Advantages: Excellent chemical corrosion resistance and sealing performance, extending the service life of equipment.

2. Automobile industry

Application: Used in engine gaskets, oil seals, fuel pipes and other components to resist corrosion from fuel, lubricating oil and coolant.

Advantages: Maintain good corrosion resistance and mechanical properties at high temperatures.

3. Medical field

 Application: Used in seals for drug delivery systems and medical devices to resist corrosion from liquid medicine.

Advantages: Good biocompatibility and strong chemical corrosion resistance.

4. Electronic industry

Application: Used as packaging materials for electronic components to resist corrosion from acids, alkalis and organic solvents.

Advantages: Excellent insulation performance and chemical corrosion resistance to ensure the reliability of electronic components.

5. Construction field

Application: Used in building sealants and waterproof materials to resist environmental corrosion such as acid rain and salt spray.

Advantages: Good weather resistance, strong chemical corrosion resistance, and extended building service life.

VI. Conclusion

Since its excellent chemical corrosion resistance, silica gel has broad application prospects in the fields of chemical industry, automobile, medicine, electronics and construction. By optimizing the content, dispersibility, surface treatment and cross-linking structure of silica gel, its chemical corrosion resistance can be further improved to meet the needs of different application fields. Future research should focus on the development of new corrosion-resistant fillers, the innovation of surface modification technology and the exploration of environmentally friendly preparation processes to promote the development and application of silica gel materials.