Investigation Of Influence Of Fibre Spatial Orientation On The Basis Weight Of Nonwoven Fabric Using Laser Scattering Method

ABSTRACTThe laser scattering method has many advantages, for instance, non-destructive testing, dynamic response, accurate testing results and convenient for computer control. This method mainly infers the basis weight of nonwovens from the relative intensity of laser scattering. In ordinary circumstances, the heavier basis weight is the stronger the relative intensity of laser scattering obtains, but because of the existence of the spatial orientation fibers both interior and outside of the nonwovens, the intensities of laser scattering are not solely decided by the quantity of the fibers. A series of fiber assembly models with ideal orientation distribution are made, and the simulation and experiment are also made on the basis of the elementary theory of the light scattering as well as the related knowledge of nonwovens' structure. Effects of spatial orientation on the intensity of laser scattering are studied. Following conclusions have been obtained based on experiments and analyses:1．Along with the enlargement of the spatial direction oriental angle((?)), the relative intensity of laser scattering(I) is reduced, and / and cos(?) are following the exponential rule; the lighter the basis weight is the more influence the fiber assembly gets from the spatial orientation fiber. With the enlargement of the spatial direction oriental angle in nonwovens, the relative intensity of laser scattering is also reduced and tends gradually to its surface layer's relative intensity of laser scattering.2．The static testing of a series impregnated, spunbond, melt blown, spunlaced, and thermal-bonded nonwovens using laboratory instrument obtained: Not only the quantity of the fibers determine the relative strength of the diffused light, but spatial orientation fibers, smoothness of the surface of nonwovens, shape of the fiber accumulation and so on are also influential. Therefore, under the same basis weight, nonwovens with different processing have different relative intensity of laser scattering. Their relative intensity of laser scattering are decreased in turn: I>I>I>I.3．In order to remove the influences of spatial orientation fibers and so on, and to make the relative intensity of laser scattering actually reflect the quantity of fibers in nonwovens, this article computed a series of parameter revision coefficients according to the exponential curve of the ideal model. These coefficients will enhance the accuracy of the future online examination system.4．Through the test and analysis of nonwovens using simulated on-line measurement equipment, the basis weight and the intensity of laser scattering from MD direction, CD direction, as well as from both of these directions are following the exponential rule, and these exponential rule are not influenced by the motion of nonwovens. In order to obtain the intensity of laser scattering under ideal condition, parameter revision coefficients can be used to revise the intensity of laser scattering which obtained from the test.Supervised by:周胜,于伟东...