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Synthesis of Silicone Resin and Its Application in Hair Cosmetics

Mar 23, 2021

Hair structure
Hair grows in simple hair follicles, and the part above the skin surface is called the hair shaft, and the part inside the hair follicle is the hair root. There are hair bulbs connected to the lower part of the hair follicle at the lower end of the hair root. The concave part of the lower end of the hair bulb is called the hair papilla. There are connective tissues, nerve endings and capillaries in the dermal papilla, which play a vital role in the growth of hair. The upper part of the hair follicle is followed by the sebaceous glands, the sebum it secretes has a nourishing effect on the hair and scalp. Most of the hair is hair shaft. The hair is then composed of three parts, from the outside to the inside are the hairy skin, the fur quality and the hair medulla.

The small fur is the outer surface of the hair, its function is to protect the fur quality, give the hair luster and elasticity, and to a certain extent determine the color of the hair. The hairy skin is generally composed of 6-10 layers of squamous cells overlapping and arranged. The total thickness of the hair cortex is generally 3-4um, and the area accounts for about 15% of the total cross-section of the hair. The healthy and undamaged hair cuticles are smooth and orderly arranged under the scanning electron microscope. Fur quality is the most important component of hair, which determines the elasticity, strength, tone and thickness of the hair. The area of ​​the fur-like part accounts for about 82% of the total cross-section of the hair. The hair medulla is the central part of the hair, and its area only accounts for about 3% of the total cross-section of the scalp. The hair medulla has little effect on the properties of the hair.

The chemical composition of hair
The main chemical component of hair is keratin, which accounts for 65%-95% of the hair (varies according to the moisture content of the hair). In addition, the hair also contains lipids (1%-9%), pigments and some trace elements such as silicon, iron, copper, manganese and so on. The trace elements are combined with the branched chains of keratin or fatty acids, not in the free state. Keratin is a polymer of amino acids, which is connected by dozens of amino acids through amide bonds or polypeptide bonds, disulfide bonds, ionic bonds or salt bonds, and hydrogen bonds.

Nature of hair
The tensile strength of hair is also strong, and its breaking stress can reach 150 grams. It can resist the external force in the helical conformation of keratin a in the front yield zone and maintain the hair shape without changing the length. The friction coefficient of hair is higher than that of synthetic fiber, which is caused by the special structure of the scaly arrangement of hair cuticles on the surface of the hair. The friction coefficient of hair increases with age and hair damage. In addition, hair wet friction is higher than dry friction and increases with the increase of relative humidity. It has a directionality, that is, the friction from hair root to hair tip is smaller than the direction from hair tip to hair root28]. Hair has the function of triboelectricity. When the surface of the hair is covered with sufficient hair care ingredients such as cationic surfactants, triboelectricity generally does not occur. When the hair is moist or the temperature is high, static electricity generally does not occur. The luster of the hair plays an important role in beauty. When the surface of the hair becomes rough due to damage, it will lose its luster due to light scattering [291.

Combability of hair
The combability of the hair is an important indicator to test the hair care effect of shampoo. It refers to the amount of resistance encountered when the comb passes through the hair. It is not only related to factors such as the diameter, rigidity, degree of curl, length, humidity, material, density and size of the comb, but also to the fluttering, smoothness and moisturizing properties of the hair after shampooing. Under the premise of determining the hair and comb, the influencing factors of combability are mainly the deposition of cationic polymers and silicone oil on the hair cutin surface in the shampoo, and the amount of silicone oil deposited on the hair plays an important role. According to the literature: the greater the amount of silicone oil deposited on the hair, the better the combability of the hair.

The deposition of silicone oil from the shampoo on the keratinous surface of the hair is mainly affected by these factors: 1) the amount of silicone oil added; 2) the size of the silicone oil emulsion particles; 3) the viscosity of the silicone oil itself; 4) the presence or absence of cationic polymers.

Verification of wet hair combing
In this experiment, the friction resistance curve of the hair to the comb was recorded by a self-made comb tester. The quality of combing is measured by the friction resistance curve. In addition, the overall average combing force of the hair bundle can be used to characterize the combability. The average combing force is small and the combing ability is good. The combability tester uses a mass method to measure frictional resistance, and uses advanced balance measurement (multiple sets of data can be output in 1 second) to simulate a real person combing hair, that is, the combing process can be completed in about 1 second.

With the improvement of people's living standards and people's higher and higher requirements for cosmetics, silicone has become indispensable in the field of cosmetics production. At present, the silicone used in cosmetics is usually based on silicone oil. The application of silicone resin in cosmetics has not emerged until recent years. Its many excellent properties: lubricity, hydrophobicity, physiological inertness, resistance to ultraviolet radiation and compatibility, etc., provide the possibility to improve the performance of cosmetics. Some of the new silicone resin products can also provide special functions that ordinary silicone resins do not have, and become new stars in cosmetic applications.

The production technology of this kind of silicone resin is only in the hands of a few major international silicone production giants. my country's silicone industry has relatively little research in this area, and due to its high price, this also limits the application range of silicone resin. Only in cosmetics and high-end skin care products-some applications. Therefore, it is particularly necessary to continuously research and develop new silicone resins with independent intellectual property rights and low cost to expand its application range. This subject is carried out in this context.

In this paper, it is planned to use methyltrimethylsilane as the raw material to synthesize silicone resin microspheres by the hydrolysis-condensation method to investigate the influence of the microspheres under different polymerization conditions; at the same time, the silicone resin emulsion is synthesized by the emulsion polymerization method. , Hope to further improve the performance of silicone resin. The silicone resin synthesized according to different methods was applied to the formula of hair conditioner, and its influence on the dry and wet combability of the hair was investigated. In the future, if the experimental conditions permit, it can be added to other personal care products, such as skin care products, color cosmetics, etc., and it will have broad application prospects.

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