The end-use performance of a paperboard depends on its quality. The major properties of a good quality paperboard include consistency in the expected ratio between the thickness of the core and the coating layers, and the uniformity in the coating layer. Measurement systems using X-rays to monitor these properties could assist the paperboard industries to assure the quality of their products in a non-destructive and automatic manner. Phase Contrast X-ray Imaging (PCXI) has been used successfully to look inside a wide range of objects using synchrotron radiation sources. Recent advancements in the grating interferometer based PCXI technique enables high quality phase-contrast and dark-field images to be obtained using conventional X-ray tubes. The darkfield images map the scattering inhomogeneities inside objects and is very sensitive to micro-structures, and thus, can reveal useful information about the object’s inner structures, such as, the fibre structures inside paperboards. In this thesis, methods, using spectroscopic X-ray imaging and PCXI technique have been demonstrated to measure paperboard quality. The thicknesses of the core and the coating layers on a paperboard with the coating layer on only one side can be measured using spectroscopic X-ray imaging technique. However, the limited spectral and spatial resolution offered by the measurement system being used led to the measured thicknesses of the layers being lower than their actual thicknesses in the paperboard sample. Suggestions have been made in relation to overcoming these limitations and to enhance the performance of the method. The dark-field signals from paperboard samples with different quality indices are analysed. The isotropic and the anisotropic scattering coefficients for all of the samples have been calculated. Based on the correlation between the isotropic coefficients and the quality indices of the paperboards, suggestions have been made for paperboard quality measurements.
Quality control is an important issue in the paperboard industry. A typical sheet of paperboard contains a core of cellulose fibers [C6H10O5], coated on one or both sides with layers of calcium carbonate [CaCO3] or Kaolin [Al2Si2O5(OH)4]. One of the major properties of a good quality paperboard is the consistency of the expected ratio between the thickness of the core and the coating layers. A measurement system to obtain this ratio could assist the paperboard industry to monitor the quality of their products in an automatic manner. In this work, the thicknesses of the core and the coating layers on a paperboard with coating layer on only one side were measured using an X-ray imaging technique. However, the limited spectral and spatial resolution offered by the measurement system being used led to the measured thicknesses of the layers being lower than their actual thicknesses in the paperboard sample. Suggestions have been made in relation to overcoming these limitations and to enhance the performance of the method. A Monte Carlo N-particle code simulation has been used in order to verify the suggested method.
Recent advancements in the grating interferometer based Phase Contrast X-ray Imag- ing (PCXI) technique enables high quality dark-field images to be obtained using conventional X-ray tubes. The dark-field images map the scattering inhomogeneities inside objects. Since, the dark-field image is constructed by considering only those photons which are scattered while pass- ing through the objects, it can reveal useful information about the object inner structures, such as, the fibre structures inside paperboards. The end-use performance of paperboards, such as the printing quality and the stiffness de-pends on the uniformity in the thickness and the structures of the coating layer of the paperboards. The uniformity in the coating layer is determined by the coating techniques, the coating materials and the topography of the base sheet. In this article, the dark-field signals from four paperboard samples with different quality indices are analysed. The isotropic and the anisotropic scattering coefficients for all of the samples have been calculated. Based on the correlation between the isotropic coefficients and the quality indices of the paperboards, a new method for paperboard quality measurement has been suggested.