First, the sun protection principle of the umbrella?
To understand the sun protection principle of a parasol, first understand what the sunshade covers.
The sunshade covers the ultraviolet rays that cause us to sunburn and tanning. The ultraviolet rays are different in wavelength and have different damage values to human skin. The main damage to our skin is UVB and UVA, of which UVA has the strongest penetrating power and becomes the key target of parasols. The national standard requires that the UVA transmittance of the umbrella, that is, T (UVA) AV < 5%.
In addition to UVA, the national standard for umbrellas also has a UPF value. UPF (Ultraviolet Protection Factor), the UV protection factor, refers to the ratio of the average effect of ultraviolet radiation calculated when the skin is unprotected to the average effect of ultraviolet radiation calculated when the skin is protected by fabric. The greater the UPF value, the better the isolation of UV light. When a UPU is 50, it means that 1/50 of the UV light can pass through the umbrella surface. When the UPF is greater than 50, the effect of ultraviolet light transmitted through the umbrella surface on the human body is almost negligible. The national standard stipulates that the umbrella's UPF>40, when 40<UPF≤50, it is marked as UPF40+; when UPF>50, it is marked as UPF50+.
Second, what kind of umbrella sunscreen effect is better?
Choosing a parasol can start from four aspects.
1. Look at the product identification, tag or package without the following two signs should be cautious.
1. National standard number, ie GB/T 23147-2008.
2. UPF value. When 40<UPF≤50, it is marked as UPF40+. When UPF>50, it is marked as UPF50+.
2. Look at the material, the umbrella surface material is polyester umbrella, anti-UV performance is strong. For sun protection umbrellas, it is the fabric that protects. From the perspective of fabric raw materials, in chemical fibers, the order of intensity of reflected ultraviolet light is: polyester fiber (polyester) > nylon > rayon, silk. Among the untreated fibers, the ultraviolet ray resistance of the polyester fiber is the best because the benzene ring in the molecular structure of the polyester has a strong absorption of ultraviolet rays of less than 300 nm. Therefore, the umbrellas on the market are mostly polyester fabrics.
Third, look at the color, the sunscreen color of the umbrella surface is better.
Dyes are selective for light absorption, the darker the fabric, the lower the UV transmission, and the better the UV protection. Therefore, under the same conditions, dark shades of dark shades such as black and navy are lower.
4. Look at the coating, double-sided silver glue or black plastic coated umbrella, better than ordinary silver glue, and the coating is best inside the umbrella surface. At present, the umbrellas on the market are generally coated. The principle of coating UV protection is to uniformly disperse the ultraviolet shielding agent into the coating liquid, perform precise coating on the surface of the fabric, and then heat-treat to form a film on the surface of the fabric. Common parasol coatings are mainly black rubber, silver glue, and no glue. Among them, double-sided silver glue or black plastic coated umbrellas have better sun protection effect than no glue and ordinary silver glue. In addition, the coating is outside the umbrella and is easily peeled off after a period of use, so it is best to choose a coated parasol.
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