Study On Non-Circular Cross Section Fiber And The Shielding Properties Of Fabrics

Most of the textiles in general are required to have good optical opaque or shielded,so as to meet the requirements of warmth,protection of individual privacy,blocking out light sunburn and so on.However,for thin sloppy type fabric,especially in light-colored and white fabric,the optical shielding effect often fail to accomplish its requirements,leaving problems between the aesthetic properties and light shielding properties of fabric.So,how to improve the shielding properties of the fabric is a major issue placed in front of us.So far,the common way to enhance the performance of light shielding is by increasing the content of flatting agent in chemical fiber. However,it can play a limited role because of a lot of difficulties was involved in spinning technology in terms of constraints.Another way was expected to improve the shielding properties of the fabric and the effect of fiber cross-section and fabric structure on light shielding properties of the fabrics are as a started work of this thesis,the testing method on light shielding properties of the fabrics was to be confirmed,and the main content and conclusions of this research are as follows:(1) The geometry models of non-circular cross-section fiber was established,the ratio Irz of the refracted light intensity to the incident light intensity was simulated theoretically under the same characteristic parameters in a round,quadri-lobal and trilobal cross-section fibers and the diffidence of that does not differ greatly in general.The results showed that the ratio Irz were in the range of 0.95～0.96 generally regardless of different cross sections.But at different point in cross-section,refraction angleβt of light in the quadri-lobal and trilobal cross-section fibers changes more complex than the circular ones,and the refraction angleβt of light along the diameter direction in a single fiber were descending from small to big,from big to small and a number times non-monotonic changes and put negative effect on the image of the single fiber,that is the non-circular cross section fiber will help to improve the light shielding performance of fiber. The differences between non-circular cross section fiber and circular cross-section in light shielding properties are similar to that of frosted glass and flat glass;(2) Experimental studies of the feasibility and applicability of the value of whiteness R₄₅₇ and transparency T of whiteness tester in the characterization of the light shielding properties of fabrics were conducted,as well as the reflection coefficient R%and the transmittance coefficient T%of UV-Vis spectrophotometer tested in the range of visible light.It is found that the transparency value T of whiteness tester can be a reflection of the visual clarity to a certain extent in instrument testing,but its effects were subjected to the color of the fabrics more obviously, because the index of whiteness tester is a single band of light reflectance ratio.For colored fabrics, the correlation between the transparency value T of whiteness tester and the visual clarity of the fabric decreased,the transmittance coefficient T%of the monochromatic measured by using UV-Vis spectrophotometer -curve with the optical wavelength,the average of the transmittance coefficient T_j%monochromatic light within the range of visible light is suitable for characterization and evaluation of the shielding performance of the fabric and for different colored fabrics,and the correlation between the average transmittance coefficients T_j%of UV-Vis spectrophotometer and visual clarity is even closer than that of the transparency value T of the single-band whiteness tester and visual clarity.The average transmittance coefficient T_j%of the fabrics tested by UV-Vis spectrophotometer can be used to evaluate the shielding properties of the fabrics;reducing random error of subjective evaluation,and it is an effective,simple and objective instrumental testing methods.The smaller value the average transmittance coefficient T_j%of the fabric,the better the shielding performance.And the experiment proved that the visual clarity sense of the fabrics that the average transmittance coefficient T_j%are more than 40%are sharply, most ones that T_j%less than 20%are still opaque,but white fabrics with T_j%in the range of 15-25%are still transparent,and 20-40%of the inter-regional are to be studied in the follow-up experiments;(3) The PET DTY/cotton union fabrics and weft knitted fabrics with quadri-lobal cross section and circular section PET DTY filaments manufactured by using the same semi-dull polyester chips,the transmittance coefficient of these fabrics were measured by using UV-Vis spectrophotometer in the range of visible light,it can be concluded that in three comparable groups fabrics,the average transmittance coefficient T_j%of quadri-lobal cross section fiber fabrics are less than ordinary circular cross section fiber fabrics,under the same conditions of fabric weave and structure,yarn count,ending spacing and pick density,whether it is woven or knitted fabric,the shielding properties of the fabric with quadri-lobal cross section filaments is superior to that of fabrics with ordinary circular cross section,and for the same density and yarn count,more interwoven frequencies of woven fabrics are conducive to improving the shielding properties of the fabric,but the difference in the shielding performance of fabrics caused by fiber cross section morphology is not significant.As the non-circular cross section fiber fabric are widely welcomed by consumers due to its good characteristics of touch,moisture,gloss and other properties,it still have an important practical value to develop light shielding and multifunctional composite non-circular cross-section fibers.