Transverse and in-plane pore structure characterisation of paper

X-ray microtomography has been shown to be a viable technique for non-destructively and non-intrusively visualising the three-dimensional structure of the entire thickness of paper and paperboard. A method has been developed to determine the traditional pore structure descriptors such as porosity, fibre-void interface area and pore size distribution for the three-dimensional structure. Results with varying sheet structures compare favourably with conventional mercury intrusion porosimetry data. X-ray microtomography combined with digital image analysis has also been shown to be capable of independently evaluating the in-plane and transverse pore structure characteristics of paper and paperboard. Interestingly, the transverse pore structure appears to be more open with larger pore size distribution compared to the in-plane pore structure. This may help explain the differences in liquid and vapour transport through the in-plane and transverse structures during the paper manufacturing process and during end-use application.