Surface modification of silica (silica) is a key technology that alters its surface properties through chemical or physical methods to improve its dispersibility and compatibility in composite materials. The following provides a comprehensive analysis of modification methods, modifier types, process parameters, performance improvements, and application cases.

I. Main Modification Methods
1. Silane Coupling Agent Modification
Utilizing the dual-reactive nature of silane coupling agents, one end of the organic group reacts with hydroxyl groups on the silica surface, while the other end reacts with polymer chains such as rubber. Silane coupling agents commonly used in the rubber industry are divided into sulfur-containing silane coupling agents (such as Si69 and Si75) and sulfur-free silane coupling agents (such as KH550, KH560, and KH570).

2. Alcohol Ester Modification
On the silica surface, fatty alcohols react with silanol groups, removing water molecules and replacing them with alkoxy groups. This method requires high temperature and high pressure. The modifier, fatty alcohol, is relatively inexpensive, but the modification effect is affected by the length of the alkyl chain.

3. Polymer Grafting: Polymers are grafted onto the silica surface to enhance the interaction between the particle and the matrix and change the particle surface polarity. This is suitable for grafting polymers with lower molecular weights; grafting polymers with higher molecular weights requires more stringent conditions.

4. Polymer Coating: A coating with a different chemical composition is applied to the silica surface to reduce interactions between hydroxyl groups, lower surface energy, and improve dispersibility. This is a commonly used surface modification technique.

5. Other Modification Methods: These include ionic liquid modification, macromolecular interface modification, and combined modification. Ionic liquid modification offers advantages such as being liquid at room temperature, non-volatile, and less likely to cause contamination, but the modification effect is less effective.

II. Common Modifier Types: Silica surface modifiers are generally chemical substances that react readily with silica surface hydroxyl groups. Organic modifiers are more effective. Main types include:

Modifier Type Representative Substances Characteristics
Organosilicon Halides: Dimethyldichlorosilane, Trimethylchlorosilane Highly reactive but highly corrosive
Siloxanes: Polydimethylsiloxane (PDM), Hexamethyldisiloxane (M2) Mildly reactive, stable modification results
Alcohols: Butanol, Pentanol, Linear Heptanol Low-cost, but require high temperature and high pressure conditions
Silazanes: Hexamethyldisilazane High modification efficiency, but relatively high cost
Silane Coupling Agents: KH550, KH560, KH570 Excellent modification results, most widely used

III. Key Parameters of Modification Process
1. Temperature Control
Silane Coupling Agent Modification: 75-250°C
Alcohol Ester Modification: High temperature and high pressure conditions
Drying: 150-200°C

2. Time Setting
Silane Coupling Agent Modification: 5 hours
Drying Time: 2-4 hours
Calcination Time: Adjusted according to product requirements

3. Other Parameters
Pressure: 0.1-0.3 MPa (for certain processes)
Modifier Dosage: 0.5%-2% (silane coupling agent)
Atmosphere: Hot air flow rate 0.5-1.5 m/s

IV. Improved Performance After Modification
1. Improved Physical Properties
Dispersion: Modified silica is more evenly dispersed in the matrix
Compatibility: Strengthens the interfacial bond with the matrix
Mechanical Strength: Tensile strength increased by 30%-50%
Temperature Resistance: Expands the operating temperature range

2. Improved Chemical Properties
Weather Resistance: Enhanced UV and oxidation resistance
Media Resistance: Improved oil, acid, and alkali resistance
Stability: Reduced performance degradation over long-term use

3. Practical Application Results
In tires: Rolling resistance reduced by 3.7%, fatigue temperature rise reduced by 15%
In rubber products: Abrasion and tear resistance significantly improved
In coatings: Anti-fouling and self-cleaning properties enhanced

V. Typical Application Cases
1. Rubber Industry
Tire Manufacturing: Adding modified silica can reduce rolling resistance by 15%-30% and improve wet grip
Seals: Improve heat resistance and mechanical strength
2. Plastics Industry
As a filler: Increases the hardness, strength, and impact resistance of plastic products
Electronic packaging: High-purity spherical nano-SiO₂ is used in integrated circuit packaging
3. Coatings Industry
Architectural coatings: Improve can opening and anti-fouling properties
Specialty coatings: Provide UV protection and improve weather resistance
4. Other Applications
Inks: Improving printing performance and durability
Cosmetics: As a thickener and stabilizer
Pharmaceuticals: As a drug carrier

VI. Technological Development Trends
Green Modification Technology: Developing low-pollution, low-energy modification processes
Multifunctional Modification: Imparting silica with additional functionalities (such as conductivity and magnetism)
Nanocomposite Modification: Composite modification with other nanomaterials
Intelligent Control: Achieving precise control and automation of the modification process
Silica surface modification technology significantly expands its application in various industrial fields by altering its surface properties, and is a key research direction in materials science.