2. Experimental results and discussion
2.1 Influence of sunscreen dosage on SPF value
At present, some of the companies in many countries have launched a variety of sunscreen, such as Switzerland roche PARSOL series, the ESCALOL series of international products companies in the United States, west Germany basf UVINOL series, west Germany's Merck RONA series of sunscreen, the sunscreen active ingredients are not equivalent, in ultraviolet light absorption and scattering are not the same.
The effect of the amount of sunscreen lotion on SPF number
In order to obtain a higher SPF, several sunscreen ingredients must be used in combination. The synergistic effect between sunscreen monomers can both increase the SPF of the formula and prevent skin allergies caused by excessive sunscreen dosage. In addition, nano-level Tioz and ZnO~D are added to the formula. As they are new broad-spectrum sunscreens, safe and non-irritating, and can greatly improve the SPF value of the product, the use of composite sunscreens has become the mainstream direction of manufacturers at present.
2.2 The influence of choice of broadband sunscreen lotion on SPF value
UvB and UvA are the ultraviolet rays that affect human skin. UVB rays are a direct cause of sunburn, while UvA rays can damage the skin. Long-term exposure can cause blackening, damage the collagen and elastic fibers of the skin, and promote skin aging and wrinkles. Therefore, it is important to prevent UVA radiation from UVA. Alleged wide band is prevented bask in, the bask in effect that has UVA~UVB concurrently namely. The choice of broadband sunscreen not only refers to the combination of different bands of UV absorbers, but also the combination of UV scatterers, which can achieve a very ideal sunscreen effect, especially for allergic people and children, is more important.
Effect of UVB sunscreen and UVA sunscreen combined WITH SPF value.
A single sunscreen agent has a smaller SPF, while a combination of UVB and UVA absorbent can not only increase the SPF but also protect against UVA. It has been mentioned in the preface that UvA accounts for about 95% of the damage caused by ULTRAVIOLET rays to human skin. Because the main sunscreen effect of sunscreen cosmetics is still L: ~SPF value, which is a kind of skin erythma reaction induced by UVB in sunlight. However, the evaluation of UvA protection effect has not yet formed a unified standard method in the world. Therefore, Mr King, chairman of Shenzhen LightS Technology Co., LTD., believes that the theoretical use of compound sunscreen is of great importance to the formulation design of sunscreen cosmetics. In particular, new materials are emerging from nanotechnology, such as nano-tioz, which can scatter ULTRAVIOLET light and prevent it from reaching the skin, can be formulated with high SPF values, and use relatively less UV absorbents. According to statistics, 50% of the sunscreen products on the market now have inorganic sunscreen added in the formula, the general dosage is 2%-8%, and almost all the products with market share * have inorganic sunscreen, especially in the formula of children's products.