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Reflective fabric: why differs in coefficient

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        In last article, we talked about the classification of reflective fabric. In terms of the reflective coefficient, we can classify reflective fabric into standard, high and silver one. Standard one is with low reflective coefficient of about five to ten. High reflective fabric has the coefficient of R’>100, R’>250, R’>330 and R’>420. Silver reflective fabric has the coefficient of R’>330 and R’>420. Two factors caused the differences, 

        Firstly, Glass beads we used in different reflective fabric differs in size, normally we specify its size in units of “mu”, means number of glass beads per square inch. The larger the number of MU, the smaller the glass beads; and the smaller the glass beads, the lower the coefficient.

        Secondly, as we can see, there is a quite large difference between the coefficient of standard reflective fabric and high or silver one, that’s because the standard one is without the procedure of coating aluminum. Take a simple example, why does mirror have so high reflectivity? One critical factor is the layer of mercury at back, without that layer, mirror is just a glass with low reflectivity. And the difference of coefficient between high reflective fabric and silver one is also partly due to the differences in production procedures. The high reflective fabric only coated on the back side of glass beads, so the aluminum layer is discontinuous in the gap and appears to be grey color; while the silver reflective fabric is coated both in the gap and on the back side of glass beads, which appears to be continuous silver color and is with higher reflective coefficient.

        The European standard for high visibility clothing EN 20471:2013 and the American standard for high visibility safety apparel and headwear ANSI/ ISEA 107-2007 explicitly state the requirements towards the coefficient of reflective fabric, to meet class 2 requirements, the coefficient shall be higher than 330. But for countries without national standards and seeks for cheaper products with the function of reflectivity, the standard reflective fabric is also a good option.