Types and Chemical Structure and Properties of Siloxane

Apr 28, 2021

There are many types of polysiloxanes, which are mainly divided into three categories according to the chemical structure and properties of the products:
Siloxane
Siloxane (2 photos)
①Silicone oil (modified silicone oil) is a low molecular weight (generally less than 10,000) linear structure polymer. In order to achieve certain properties, the molecular structure will also be grafted and modified. Colorless or light yellow transparent liquid, water-repellent and oil-repellent, with high boiling point and low freezing point, good heat resistance and chemical stability, and is used in various industries as chemical additives; the most common one is that it can be used as Defoamers in various industries, hydraulic oils, advanced lubricants, filler surface treatment agents and demulsifiers, latex coagulants, and can also be used as waterproofing/water reducing agents for building materials, textiles, paper and many other materials, plastics Industry lubricants, release agents, personal care hair moisturizers, foam stabilizers in foamed polyurethane, agricultural ink coatings industry can also be used as leveling agents, gold-letters, etc., and also a good electrical insulator.
②Silicone rubber is a linear structure polymer with a large molecular weight (one hundred thousand grade). After adding fillers and other additives, and vulcanizing, an elastomer, namely silicone rubber, can be obtained. Silicone rubber has the characteristics of electrical insulation, chemical stability, physiological inertia, and good elasticity in a wide temperature range; it is mainly used to manufacture rubber products used at high or low temperatures and artificial organs required in plastic surgery.
③Silicone resin is a linear structure polymer that contains active groups and can be further cured. It can be made of heat-resistant high-grade electrical insulating paint (silicone paint), heat-resistant plastic (silicone plastic), laminated glass cloth and protective coating, etc.

Siloxane oligomers have a series of unique and excellent properties. The thermal stability, impact strength, adhesive strength, lubricity, flame retardancy, solvent resistance, air permeability and leveling property of ordinary polymer materials modified by siloxane oligomers can be improved

Leveling agent is a kind of commonly used coating additives. After coating construction, after flowing and drying, a flat, smooth and uniform coating film is formed gradually. The leveling property of coating film refers to the characteristics of smooth film. There are many factors affecting the leveling property of coating, including the volatility and solubility of solvent, surface tension of coating, wet film thickness and surface tension gradient, and coating The most important factors are the surface tension of the coating, the surface tension gradient produced by the wet film in the film forming process and the ability of the surface tension homogenization of the wet film surface layer. To improve the leveling property of the coating, it is necessary to adjust the formulation and add appropriate additives to make the coating have the appropriate surface tension and the ability to reduce the surface tension gradient

There are many kinds of leveling agents, and the types of leveling agents used in different coatings are also different. The most commonly used leveling agents in oil-based coatings are acrylate polymers, while the most commonly used leveling agents in waterborne coatings are polyurethane. Organosilicon leveling agents can be used in both oil-based coatings and waterborne coatings. Silicone leveling agents have good wettability and anti shrinkage porosity, which can improve the flow rate The results show that polydimethylsiloxane can improve the wettability of the substrate, control the surface flow and improve the leveling effect. The introduction of organic groups helps to improve the compatibility of polysiloxane and coating resin, even if the concentration is increased, it will not produce insoluble side effects The modified polysiloxane can reduce the interfacial tension between the coating and the substrate, improve the wettability to the substrate, improve the adhesion, prevent brush marks, orange peel, reduce shrinkage, pinhole and other film surface defects
Preparation of leveling agent

Add a quantitative amount of D4, MM and acid clay into the three round bottom flask equipped with stirring device, condenser and thermometer, start magnetic stirring, heat to the set temperature, keep the reaction under reflux, and the system viscosity gradually increases in the reaction process. After the reaction, a transparent organosilicon leveling agent can be obtained by filtration, separation and purification. Characterization method
The conversion of leveling agent was determined by drying weight loss method
The leveling property of leveling agent was determined according to the standard coating leveling property scraping test method
The product structure was characterized by FT-IR and KBr smear
The surface tension was measured by the surface tension tester
BZY type automatic surface tension is adopted