Characterization And Evaluation Of The Optical Properties Of Fabrics

The optical property is one of the most important performances of the fabrics. With the development of science and technology, textile materials have developed largely. Due to the development of different kinds of high performance fiber and the expending in the use of the textile materials, the characterization of the optical properties of the textile materials is becoming more difficult to finish by usual methods with the wavelength of visible light. However, it's only in single properties or in a limited spectral frequency, the optical properties of fabrics are characterized at present, such as transmittance, or reflectance, or absorption properties, or ultraviolet radiation, or visible light, or infrared properties measurement. In fact, we need to have total knowledge of the optical properties of material, so some research about them was done in this paper. -Based on the investigations of the optical transmittance, reflectance and absorption of textile materials and the corresponding characteristic parameters, testing methods and evaluation system of the optical properties, the optical transmittance, reflectance and absorption of the fabrics made of Nomex and Kevlar, and treated with the ultraviolet protection have been measured by the UV/VIS/NIR spectrometers in the range of 240~2500nm. Meanwhile, a series of different parameters are obtained by using mathematical and statistic methods, such as integral area, percentage of energy, mean, resistance, differential coefficient, finishing effect, UPF, attenuation and transmittance depending on the porosity of wearing structures. The relationship between the optical transmittance and cover factor, and the product of cover factor and thickness has also been established.Through the experiments, and evaluation of the fabrics, the conclusions achieved as follows.1. The rates of transmittance and reflectance of fabrics of Nomex and Kevlar are high to visible light, then to near infrared radiation, and low to ultraviolet radiation. However, the relationship of absorption is contrary to that.2. The Nomex fabrics with different weaves are characterized by low transmittance and absorption, high reflectance. It is fit for using as the spacesuit materials in terms of the optical properties.3. The optical properties of the Nomex fabric with PTFE coated are improvedto using as the spacesuit materials. However, the fabric with silicon rubber coated isn't improved, and even descended.4. The Nomex fabric has higher transmittance and reflectance, lower absorption than the Kevlar one on ultraviolet and visible light, and lower transmittance and absorption, higher reflectance in near infrared.5. The transmittance of Nomex fabrics on ultraviolet radiation mostly depends on the part of voids, but on the part through the covers caused in the visible light.6. The relationships between the transmittance of the Nomex fabric and cover factor, and the product of cover factor and thickness to ultraviolet radiation, visible light and near infrared radiation are studied respectively.7. For the common fabrics, the darker the color, the lower is the transmittance and reflectance, but the higher is the absorption. The UPF index of the fabric is lower than that of the standard stated, so it is necessary to do ultraviolet protection finishing for summer clothing.8. After the modifications of resistance to ultraviolet radiation, the fabrics have good resistance to UV, and high UPF. Moreover, the greater concentration of UV absorbers, the greater is the improvement. It is obvious that the resistance to ultraviolet radiation is mostly by the means of increasing absorption. The finishing effect ranks as follows: water-solubility benzophenone>nanometer zinc oxide >benzophenone>organic metal, benzotriazol>(organic metal+ nanometer zinc oxide). Meanwhile, UV absorbers of benzophenone structure and nanometer zinc oxide are stable to light.9. The optical transmittance of the undyed fabrics mostly depends on the percentage of voids. Bu...