Research On The Near-Infrared Property Of Textile

Digital camera can receive not only visible light but also 700-1200nm near-infrared light. Near-infrared light can pass through some thin or transparent materials, such as plastic, ink, fabric, etc. Some lawbreakers take this advantage to make perspective pictures, which causes psychological burden on victims. Some research was done on the transmission property of the 700-1400nm near-infrared of fabrics. The results can help to provide references of related textiles design and fabric usage.Firstly, factors that influence the transmission property of near-infrared light were studied. Both single factors and multivariate factors experimental plans were designed. In single factors programs, factors including fabric pattern, weaving density, yarn twist, moisture content and disperse dyes were studied. Then, SPSS software was used in multivariate factors experimental plans. Contingency table analysis, correlation analysis, principal component analysis and regression analysis were used to study the combined influence of the materials, thickness, weight per square meters and porosity. New impact factors were found and a regression equation was built to predict the near-infrared transmittance.Secondly, two different methods were developed in this paper to improve the fiber's anti-near-infrared light transmission property. One was based on the light's reflection, scattering and absorption properties of particles. The other was by the means of thin film interference, which need coat a series of certain films on the fiber in order to reduce high near-infrared light transmittance.Main results were as follows:1) single factors:the changes of weave patterns used in this paper affected little to the near-infrared transmission but the main causes of the difference was thickness or covering factor; the transmission of the near-infrared would be larger as the fabric density added; the increase of the yarn twists would increase the porosity of the fabric leading to more transmission; the more water the fabric contained, the higher transmission it would have. And if the fabric were completely wet. the transmission would not changed greatly. The transmission of the fabrics made by polyester with 6% TiO2 did not change with the changes of azo dyes concentration changed, which meaned such kind of dyes could not absorb near-infrared.2) multivariate factors:using contingency table analysis and correlation analysis, the relationship between materials and near-infrared transmission was studied. And thickness, weight per square meters and porosity were the three main factors to determine the transmission based on principal component analysis. Two new principal components were picked up and a regression equation was built, in which the error frequency was below 5%.3) Nanometer Al2O3 had better anti-near-infrared characters than that of the same size of nanometer SiO2. Different sizes of particles would have different transmission property under the influence of mass fraction. SiC with micron scale had excellent anti-near-infrared character.4)λ0/ 4 films used as a method to design some films:when Si and SiO2 were used as high and low refractive index materials respectively and covered only five layers, it showed a good anti-near-infrared property; when TiO2 and SiO2 were used and had three central wavelength with the structure of A|0.2125(HL)20.2125H0.2875(HL)20.3125(HL)2|F,it showed better property. What was more, when two central wavelength films overlaid, and the periodicity was six, it already had good transmittance property. While the periodicity was five, it had best overall performance.