| The color of photochromic fabrics reversibly change under ultraviolet irradiation.The response process and degree of color-changing are influenced by factors such as the type and concentration of photosensitive particles inside the textiles,ultraviolet irradiation intensity and time.Proper UV radiation can promote the body's synthesis of vitamin D,which is good for human health,but longterm exposure to UV can hurt skin and cause a series of problems.The main purpose of this thesis is to explore the color response of photochromic fabrics under different irradiation,thereby using the color of the fabric to indicate the UV intensity as well as reasonable skin UV exposure time.Under simulated different intensity of ultraviolet irradiation,the color response processes of the photochromic fabrics were observed and recorded,and then characterized by RGB and HSV.Thus a custom palette for each fabric under different ultraviolet intensity was explored,based on which,the UV intensity can be indicated by specific color of the photochromic fabrics.Combined with UV skin physiological effects theoretical analysis,the reasonable time of skin erythema under different UV intensity can be calculated,which provide valuable information for the duration of outdoor activities.The research mainly includes two parts:In the first part,the change of color of photochromic fabrics during UV irradiation response process were quantified and analyzed.Firstly,five kinds of photochromic yarns of different colors were selected,and knitted separately under the same technical parameters.The intensity of ultraviolet light was strictly controlled during the irradiation test.Standard light box was applied and D65 was used as the illumination source.The ultraviolet light source of grade 1-5 intensity were installed into the standard light box,and the color change of the fabric was recorded at a speed of 1 s/sheet by digital camera.Since the fabric color distortion was caused by digital camera and ultraviolet light,the standard color card should be photographed together with the photochromic fabrics in the same environment,which was necessary for correcting the color of the fabrics' picture.Secondly,extracted and characterized the HSV information of the color-corrected fabric,then analyzed variation trend of HSV under different ultraviolet irradiation,and record the HSV information after the color of the fabric was stabilized under various ultraviolet irradiations.Finding the standard color that is most similar to the fabric color in the color library,and formulate the standard color of the fabric under the different ultraviolet irradiation.The standard color of the fabric can be used to indicate the current UV intensity.In the second part,the physiological effects of skin and reasonable time of skin erythema under specific UV intensity were calculated and predicted as follows:Firstly,mastered the different test principle and test conditions of ultraviolet radiation,then analyzed the physiological effects of UV to skin.It was found that reasonable sun exposure time was related to UV intensity,UV protection factor and human's MED.The above three factors were expressed by the three indications of erythema UV,UPF and minimum erythema respectively.Deduce formulas by analyzing these three factors in order to calculate the appropriate protective measures at different UV intensities and the safe exposure time,finally achieve the purpose of predicting and preventing ultraviolet irradiation.The major achievements are as follows:(1)The paper establishes a scientific method to characterize the color of the UV response of the photochromic fabrics.The problem of color distortion is caused by digital camera and the UV light.According to the color characteristics of the fabric,the polynomial regression model was established,then the standard color card was used to correct the obtained fabric pictures' color.After the correction,The HSV histogram of each fabric picture was read and output.Use 80% area of the histogram's mean value of HSV to represent the fabric's color information,which was proved to be effective after being verified.(2)Research shows that the color of the photochromic fabrics can reach stability in 1 minute under different UV intensities taken by the experiment,and the HSV value won't change if the UV intensity remains constant.It was found that the hue and saturation of fabrics used in the experiment changed exponentially with the irradiation time.In the early stage,the change speed was fast,then gradually approaching steady.The stable value of hue and saturation changes with the increase of the irradiation intensive,but when the irradiation reached a certain intensity,the hue would reach critical value and wouldn't change with the increase of the irradiation,but the saturation will increase with the ultraviolet intensity under the irradiation intensive selected by the experiment.Through variance analysis,there was a significant difference in the response of the five fabrics' saturations under different ultraviolet radiation,so the ultraviolet intensity can be distinguished by fabrics' color.(3)By analyzing the various indicators of ultraviolet irradiation,the reasonable sun exposure time could be calculated by UV intensity,minimum erythema doses and sun protection factor.The erythema ultraviolet light was calculated according to the ultraviolet index,the minimum erythema doses corresponding to different skin types are found in the literature.The amount of time required to induce erythema in the skin by different UV intensities was calculated by the formula derived before,at the same time,the prolongation of exposure time of textiles with different sun protection factors were quantified. |
PDF Full Text Request