Research On The Key Skills Of Preparation And Testing Of Opaque Fabrics

Visual shielding property is one of the most important properties of textiles. In the clothing field, it influences the basic function of the clothes-masking human bodies; in the decorating and military field, it involves some special functions, such as one-direction perspective, camouflage and so on. With the development of textiles becoming lighter and thinner, the confliction of which with visual shielding property is increasing. In order to cater to people's aesthetic and to meet market demands, the development of a new kind of fabrics which are both light-thin and opaque becomes a problem need to be solved. Along with the research of new fabrics, the relevant evaluation system also need to be set up.Firstly, the key technology point of development of opaque fiber was studied in this paper which was how to select and optimize particles. According to Mie scattering theory, the scattering and extinction properties of particles (including spherical solid particles and hollow particles) were analyzed in details. The influences of relative refractive index, scale parameter and the wavelength of light on extinction performance are discussed. Secondly, according to dispersion theory, through the derivation of the mean reflectance of fabric surface in the visible wavelength range, the model including dispersion theory was made and it could be used to evaluate visual shielding of fabrics. Lastly, the feasibility and applicability were discussed whether common evaluation indices could be used to express the visual shielding properties of fabrics. Those indices included whiteness, average transmittance under visible light area, brightness, transparency, opaqueness and etc. Then the total flux transmission was used to show the visual shielding property on the basis of the transmission of different light wavelength and the visible function curve. A new index according to the variation of gray was tried to evaluate the visual shielding property of fabrics, this index was received via image process extracting gray changes from fabrics covered by standard black and white board.Main results were as follow:(1) For spherical solid particles, the particle size parameters, relative refractive index, particle size distribution and incident light wavelengths have significant influences on extinction performance. The optimal range of particle size for TiO2 is studied based on the Mie scattering theory in this paper, and then the optimal particle-size distribution function is also calculated according to visible function curve.(2) Spherical hollow particles have the same factors of influencing extinction performance as spherical solid particles. The only difference is that the spherical hollow particles are also influenced by wall thickness, and a specific extinction effect could be achieved using different combinations of particle diameter and wall thickness. Generally, the extinction performance of spherical hollow particles is better than that of spherical solid particles when they are the same particle sizes.(3) The surface reflective property of fabrics is one of the most important influence factors. According to Fresnel equation, the surface reflectivity has relationship with the refractive index, which can be influenced by the incident light wavelength. Therefore, the average reflectivity of fabrics surface based on dispersion theory is made in the visible light range, and the model including dispersion is established to evaluate the visual shielding property of fabrics.(4) The comparison is made between the evaluation indices commonly used to express the visual shielding properties of fabrics and total flux transmission ratio in order to evaluation their applicability and feasibility. The result shows:the whiteness and the total flux transmission of fabrics are not relevant, however they have a good agreement only when the fabrics are white, so whiteness can be used to indicate the visual shielding properties when fabrics are white; brightness can be used to show the visual shielding properties when fabrics have different colors; both transparency and opaqueness can be used to indicate the visual shielding of all fabrics; the transmittance index is good to evaluate the visual shielding property when under light's wavelength is 550nm, the same result comes out while the average transmittance is under visible light area, but their reflectivity indices can only represent the visual shielding properties of white fabrics. When there is no criterion to reflect the visual shielding properties of fabrics, the transmittance when under light's wavelength is 550nm is recommended to use.