Silicon prepolymers are a class of silicon oligomers with specific functional groups (such as hydroxyl, acrylate, epoxy, etc.), combining the excellent properties of silicones (e.g., low surface tension, weather resistance, flexibility) and reactivity. They are widely used in the modification of polymer materials. Below is a systematic overview of their core content:

I. Definition and Core Concepts

Organosilicon prepolymers are intermediates with molecular weights between monomers and polymers. Through functional group design, they achieve chemical bonding with resins (e.g., polyurethane, epoxy resin, acrylates), endowing materials with the following characteristics:

Low Surface Tension: Improves leveling and anti-adhesion properties.

High Reactivity: For example, dihydroxy prepolymers copolymerize with isocyanate (-NCO) to synthesize silicone-modified polyurethane.

Thermal Stability and Flexibility: Reduces resin brittleness and enhances heat resistance (e.g., improved high-temperature resistance in modified epoxy resins).

II. Chemical Structure and Types

Based on functional group differences, they are mainly classified into the following types:

1.Dihydroxy-Terminated Type

Structure: Polysiloxane with hydroxyl groups at both ends, molecular weight 4,000–30,000.

Application: Copolymerizes with polyurethane to provide coatings with wear resistance, smoothness, and anti-fouling properties.

2.Acrylate-Functionalized Type

Structure: Contains acrylate groups.

Application: Used in UV-curing systems to enhance the smoothness and scratch resistance of plastics and coatings.

3.Epoxy-Terminated Type

Structure: Contains epoxy groups at both ends (e.g., epoxy-terminated silicone oil) for synthesizing modified epoxy resins.

Application: Prepares high-temperature-resistant adhesives for electronic device bonding.

4.High Refractive Index Functional Type

Synthesis: Introduces carbazole groups via hydrosilylation, achieving a refractive index of 1.577 for LED encapsulation materials.

III. Characteristics and Advantages

Surface Performance Optimization: Reduces coating surface tension, promotes leveling, and minimizes cratering.

Enhanced Mechanical Properties: Improves wear resistance, flexibility, and impact strength of resins.

Customizable Functionality: Achieves specific requirements like hydrophilicity or refractive index through functional group design.

IV. Development Trends and Challenges

Research Directions:

Developing water-based prepolymers to align with environmental trends.

Designing multi-functional prepolymers to increase crosslinking density (e.g., elastic emulsions for textiles).

Technical Challenges:

Compatibility issues between amino silicone oils and platinum catalysts.

Stability control of prepolymers under high temperatures.

Organosilicon prepolymers serve as a "performance bridge," enabling complementary advantages between silicones and organic polymers through molecular design. They show significant potential in high-end coatings, electronic encapsulation, biomaterials, and other fields.