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.