Summer weather is either scorching sun or thunderstorms. In cloudy weather, many people like to carry a parasol with them. When it rains, when the umbrella hits, when the sun is exposed, it is used as a parasol. However, the reader Ms. Zhang called the hotline of this column and asked her own question: "Is it all said that rain will reduce the sunscreen effect of parasols? Is this really the case?" To verify this statement, the reporter walked into Shimadzu Under the guidance of the molecular spectroscopy application engineer Duan Weiya, the Beijing Analysis Center of the company conducted a set of experiments with reference to the national standards GB / 23103-2008 and GB / T18830-2009. The results show that if the umbrella is used as an umbrella, its sun protection effect will be greatly reduced.
survey
9 adults use umbrellas as umbrellas
The reporter randomly interviewed 28 passers-by on the street, and 26 of them said that they have always used umbrellas as umbrellas. When asked if they knew that umbrella rain would reduce the sun protection effect, most people answered "heard a little" and "understand, but don't know the true and false." Only one young girl said that she knew that umbrellas were not raining well, so umbrellas and umbrellas were never mixed. Even if there are too many things in her backpack, she has to install two umbrellas, one is a sunshade and the other is an umbrella.
The reporter found through the investigation that the reason why more than 90% of the investigators would mix umbrellas and umbrellas is that the weather is often abrupt, which makes the umbrellas have to be "umbrellas". Another reason is that many readers feel that they need to take one Umbrellas are too cumbersome, just use one umbrella as two kinds of umbrellas.
experiment
Measure the UV transmittance of two new and old umbrellas
In order to verify whether the rainwater will affect the performance of the parasols to block ultraviolet rays, the reporter came to the Beijing Analysis Center of Shimadzu Corporation to conduct on-site measurements of the two parasols with different degrees of old and new. Among them, one parasol is brand new, coated with silver-gray paint, and the other parasol has been used for more than half a year. Its material is pearlescent fabric, and it has been used as an umbrella many times.
The instrument for testing the anti-ultraviolet properties of textile materials is the commonly used ultraviolet-visible spectrophotometer in chemical laboratories, which can measure the ultraviolet transmittance and reflectance of samples. "To test the anti-ultraviolet performance of the umbrella surface material, first measure the ultraviolet transmittance of the sample, and then perform data processing through the national standard method." Duan Weiya said that before testing the actual sample, a blank baseline measurement, that is, determination The 100% transmittance of ultraviolet light without sample absorption is used as a reference to facilitate comparison of subsequent measurement results.
When the umbrella is used for half a year, the sun protection function is reduced by half
The reporter selected a two-centimeter-square umbrella surface material on the sunshade for measurement, and placed it on the solid membrane support in the instrument, covering the light-transmitting hole on the support for measurement. Duan Weiya said that the initial data obtained after the measurement, and then through a series of formula calculations, can finally get the long-wave ultraviolet transmittance T (UVA) value and UPF value of the umbrella surface material. According to the national standard "Assessment of UV Protection of Textiles", only materials with UPF> 40 and T (UVA) <5% can be called UV protection products.
After measurement, the reporter saw that the umbrella used for an umbrella for half a year had a UPF value of 22.313 and a T (UVA) of 18.04%. Far lower than the nominal UPF of 30 to 50 at the time of purchase, T (UVA) <5%. In other words, the ultraviolet transmittance of this parasol is as high as 18.04%. According to relevant national standards, this parasol is no longer a UV protection product. In contrast, the value of the new parasol in the experiment is quite reassuring, t (uva) is only 1.91%, and the UPF has reached more than 50.
The sunscreen effect will also decrease after the new umbrella gets wet
Why does the anti-ultraviolet function of the sunshade be greatly reduced after being used as an umbrella? In order to verify that the anti-ultraviolet function of the parasol will be reduced after being wet, the reporter took the new parasol for 10 minutes after rain treatment, and then measured it again. The new parasol T (UVA) after the rain treatment was 2.60%. Sure enough, this time the UV transmittance is significantly higher than before the rain treatment.
So, how high is the umbrella's blocking rate of ultraviolet rays? What if the umbrella is used as a sunshade? Duan Weiya measured ordinary umbrellas and found that the UPF value of the umbrella is 13.002, and T (UVA) is 27.98%. It can be seen that the umbrella has little effect on ultraviolet protection.
in conclusion
Umbrellas are best not used as umbrellas
The experimental results show that the sun protection function of the sunshade will indeed decrease after it gets wet. Therefore, if you want to keep the sunshade effect of the sunshade from decreasing, it is best not to use it as an umbrella. Experts from the Textile Fiber Inspection Institute of the Beijing Municipal Quality Supervision Bureau also pointed out that if a good-quality parasol is used for long-term rain protection, it will be affected by the acidic and alkaline substances in the rainwater, which can make the coating aging and reduce the umbrella's sunscreen quality.
concept
What is UVA?
Many sunshade trademarks will indicate the index of UV protection, and generally will mark the UVA occlusion rate. So what is UVA? Ultraviolet refers to electromagnetic waves with a wavelength from 10 nanometers (one nanometer equals one billionth of a meter) to 400 nanometers in the electromagnetic spectrum. Ultraviolet rays are divided into long-wave ultraviolet rays UVA, medium-wave ultraviolet rays UVB, and short-wave ultraviolet rays UVC according to wavelengths. Among them, UVA refers to ultraviolet rays with a wavelength between 320 nanometers and 400 nanometers. UVA penetrates clothing and human skin far more than medium-wave ultraviolet rays, and can penetrate the surface layer of the skin, penetrate deep into the tissues below the dermis, destroy collagen, The fine structure inside the skin, such as elastic fiber tissue, produces wrinkles and fine lines, which makes the skin relax and aging, which is called photo-aging in medicine. In the energy distribution of ultraviolet rays, UVA is 15 times that of UVB, which is the main reason for skin tanning. It can reduce the content of hyaluronic acid in the skin, make the skin dry, accelerate the formation of melanin, and darken the complexion. It is also an important cause of skin cancer.
What is UPF?
According to the definition in the national standard, UPF refers to "the ratio of the average effect of ultraviolet radiation calculated when the skin is not protected to the average effect of ultraviolet radiation calculated when the skin is protected by the fabric". The higher the UPF value, the better the UV protection. But the highest UPF value of textiles in the national standard is 50+, which means UPF> 50. Because the UPF is greater than 50, the impact on the human body is completely negligible.
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