I. The Role of Silicone Oil in Cosmetics 
Advantages of silicone oil 
Sensory experience: Enhances comfort and gives the product a glossy finish. 
Safety: Colorless and odorless, non-irritating to the skin, highly safe. 
Chemical stability: Does not react with other cosmetic raw materials. 
Appearance and aroma: The appearance and aroma of the product are not affected. 
Usage experience: Provides a light and refreshing feeling, and is easy to unfold. 
Hydrophobicity and smoothness: Enhance the hydrophobicity and smoothness of the product. 
Air permeability: Good gas permeability, without affecting the skin's breathing. 
The application forms of silicone oil 
Direct translation: Silicone oil, liquid-like polydimethylsiloxane, cyclic siloxane, etc. 
Formulation: Emulsion, dispersion solution, solution and composite silicone oil, etc. 
The Application of Silicone Oil in Various Cosmetics 
Skin care products: Low and medium viscosity silicone oil enhances the spreading property on the skin and protects it. 
Makeup products: Improve pigment dispersion, enhance spreadability and usability. 
Shampoo and mousse: Stabilize foam and improve the hair combing effect. 
Shaving cream: Enhances lubrication, reduces friction between the skin and the blade. 
The Application and Limitations of Volatile Silicone Oil 
Volatile silicone oil: Used in skin cosmetics, antiperspirants and body washes, serving as a volatile carrier. 
Environmental impact: The environmental effects of certain volatile silicone oils are subject to debate, and their use is restricted in some countries. 
Development of substitutes 
New type of volatile silicone oil: For instance, methyl tri-(trimethylsiloxy) silane (TMF-1.5), has superior volatility compared to traditional silicone oils. 
Performance comparison: The new silicone oil outperforms the traditional silicone oil in terms of expandability and touch feel. 

II. Silicone Oil Emulsions for Cosmetics 
Silicone emulsion offers various benefits to cosmetics, such as improving skin affinity, enhancing moisturizing effect, providing a good feel of use and stability. 
Types and Applications of Silicone Emulsions 
Water-in-oil (O/W) type: Various types have been developed and are widely used in various cosmetics. 
Oil-in-water (W/O) type: It has better affinity for the skin and is mainly used in skin care cosmetics and pharmaceutical products. 
Preparation of silicone oil emulsion 
Emulsifier selection: Select a polyether-modified silicone oil that is soluble in silicone oil. 
Stability improvement: These can be combined with thickeners or gelling agents to enhance the stability of the emulsion. 
The characteristics of polyether-modified silicone oil 
Molecular chain structure: The ends and side chains contain polyether chains, and the polymerization degree m + n affects the stability of the emulsion. 
Quality percentage: The quality percentage in the emulsion should be between 0.5% and 10%. 
Case Analysis 
Example 1: Using a specific formula and process, an O/W type silicone oil emulsion for hand cream was prepared. The emulsion was subjected to thermal cycling tests, and showed excellent stability. 
Example 2: Using simple formulas and processes, an optically transparent O/W type silicone oil microemulsion was prepared, which is suitable for use in skin care creams, antiperspirants, etc. 

The stability and efficacy of silicone oil emulsion 
Temperature stability: The structure of the polyether-modified silicone oil has a significant impact on the stability of the emulsion at different temperatures. 
Safety and Comfort: Highly safe for the skin, providing a pleasant user experience. 
The formula of W/O type silicone oil emulsion 
Ingredients Formula 1/Quality Percentage Formula 2/Quality Percentage
Viscosity (25℃) 10 cs dimethyl silicone oil 43.5 43.5
Polyether modified silicone oil (A) 5.0
Polyether modified silicone oil (B) 5.0
Dehydrated sorbitol monolaurate acid ester 1.5 1.5
Methyl p-hydroxybenzoate 0.1 0.1
Propyl p-hydroxybenzoate 0.1 0.1
1,3-Butanediol 10.0 10.0
Water 39.8 39.8 

III. Application of Composite Silicone Oil in Cosmetics 
The Definition and Preparation of Composite Silicone Oil 
Definition: A silicone oil solution formed by dissolving polydimethylsiloxane with a viscosity higher than 5×10°mPa·s in volatile dimethylcyclosiloxane or low-viscosity dimethylsilicone oil is called a composite silicone oil or silicone oil dispersion. 
Preparation: The mixture is prepared by dissolving high molecular weight polydimethylsiloxane and volatile or low-viscosity dimethylsiloxane through stirring. 
The Application of Composite Silicone Oil in Cosmetics 
Main application: Used in hair care products to prevent hair from frizzing and to enhance the ease of combing the hair. 
Formula selection: The silicone oil used in cosmetics should be of a higher grade than industrial grade. Careful selection is necessary to meet quality and safety standards. 
The typical formula of composite silicone oil 
High viscosity polydimethylsiloxane  Low viscosity dimethylsilicone oil  Composite silicone oil viscosity mm²/s
Viscosity mm²/s  Usage/portion  Viscosity mm²/s  Usage/portion
13,000,000  40  200  60  500,000
13,000,000  50  200  50  1,000,000
20,000,000  40  200  60  800,00 10 000 000 20 D5 80 10000
5 000 000 10 D5 90 1600
Note: Measured at 25 ℃ 

IV. Applications of Silicone Oil in the Medical and Food Industries 
Standard: In many countries, there are specific standards for silicone oil used in the medical field. China has also included it in its pharmacopoeia. 
External medication: As an additive for external medications, it improves the physical properties of the medication. 
Defoamer: Used for eliminating foam in the stomach, it helps alleviate stomach discomfort. 
Food-grade silicone oil: Mainly uses food-grade dimethyl silicone oil. 
Bean product processing: As a defoaming agent in the process of bean product manufacturing, it enhances production efficiency and product quality.