Dear all,
I am working on the UV-Shielding properties of some materials like Graphene Oxide and Metal Oxide. As far as I know, to evaluate the effectiveness of UV-Shielding performance, people use Ultraviolet Protection Factor (UPF). However, I do not understand how to calculate UPF.
I really hope for a good answer.
Hi,
first of all I want say you that the UPF Ultraviolet protection factor is mainly used to evaluate the UV protection offered by a fabric (clothes) from the sun.
The UPF is a number which indicate how many time the solar UV radiation reaching the epidermis is reduced by the presence of the fabric. In particular the solar radiation is converted in UV radiation biologically effective for erythema. I don't know if your intention is to quantify this.
However below some information to calòculate it:
First of all you have to measure the spectral transmittance of your samples by means a spectrophotometer.
You need to know the spectral transmittance from 280 nm to 400 nm (a value of transmittance for each nanometer).
You have also to know the action spectrum for Erythema (McKinlay, A.F. and Diffey, B.L. 1987). The action spectrum is represented by a serie of coefficient, one for eachnanometer from 280 to 400 nm (this coefficient represents the effect of the light at each specific nanometer in determining Erythema). If you doesn't have such action spectrum I can send it to you.
You need also to have a typical solar spectrum for summer period during midday in clear sky condition.
At this point :
1) multiply each value of the action spectrum for the sun spectrum (nanometer by nanometer from 280 to 400). Then sum the obtained values from 280 t0 400 nm; it represents the biologically effective UV radiation for erythema in the sun.
2) multiply each value of the action spectrum for the sun spectrum (nanometer by nanometer from 280 to 400). The results has to be multiplied for the transmittance spectrum (nm by nm. Pay attention: if you have for example a transmittance at a specific wavelenght of 32% you have to use 0,32 as value in the product). Then sum the obtained values from 280 t0 400 nm; it represent the biologically effective UV radiation for erythema transmitted by your sample.
The UPF is the ratio between the values obtained in 1 and the one obtained in 2.
It is thje ratio between the Ultraviolote biologically radiation in the sun and the Ultraviolote biologically radiation transmitted by your sample.
Let me know if you have some problem
I attach you also a document with some further information to calculate Sun Protection Factor or UPF.
Md Luthfar Rahman Liman please have a look at the process of UPF calculation which is stated by Dr. Daniele Grifoni
Thank you Dr. Daniele Grifoni for your information. Can you please share the sheet of action spectrum for Erythema with me that you usually used for UPF calculation.
Is it logical to use the reflectance data of fabrics and converting them into transmittance using Fresnel Equation, T = 1-R for UPF calculation?
Your suggestion will be helpful for me.
Hi I send YOU the file with the coefficient of the Erythemal Action spectrum. Concerning the formula T+R=1 it is true for transparent material witout absorbance. In general the formula is A+T+R =1.
Excuse me, have you the possibility to use a spectrophotometer able to directly measure the transmittance of your samples?
Thank you again Dr. Daniele Grifoni for sending me the file. Yes, the formula will be A+T+R =1, sorry for that.
Previously, i collected transmittance data via spectrophotometer for calculating UPF. Unfortunately, my lab's UV spectrophotometer is not working properly at this moment due to some technical issues.
That's why i just thinking to use reflectance data through a data-color Spectroflash and converting the collected reflectance value into transmittance following the equation A=Log(1/R) and then T=1-(A+R).
My question is how much reliable my data will be by following these steps?
10.1007/s12221-021-9950-z
This paper may help you to resolve this issue.
The UPF can measured according to AATCC Test method 183, “Transmittance or Blocking of Erythemally Weighted Ultraviolet Radiation Through Fabrics (AATCC, 2002)”. UV/Visible spectrophotometer (Varian; Palo Alto, CA) with an integrated sphere attachment and a Schott glass UG-11 filter can be used for this purpose. The UPF can be calculated according to equation stated on this paper.
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