Use this URL to cite or link to this record in EThOS:
Title: An investigation into the in-plane structural and optical uniformity of paper
Author: Dooley, Nicola J.
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2002
Availability of Full Text:
Access from EThOS:
This thesis presents an experimental investigation into the relationship between the in-plane structure of paper and its optical uniformity. Analysis has been carried out on a range of different papers, including laboratory formed handsheets, pilot machine made papers and commercial grades. Techniques have been developed to allow light transmission and radiographic images of the same sample area to be compared zone by zone over a range of scales. For a given sample the coefficient of variation of local transmittance determined over a range of scales, has a linear relationship with the coefficient of variation of local grammage and this passes through the origin. The gradient of this relationship is almost always less than one. This linear relationship presents the possibility for mass distribution statistics at all scales of interest to be determined from measurements of local grammage and transmittance at one scale. It is shown that a distribution of local grammage values may be associated with a given transmittance value and that this is well approximated by the Gaussian distribution and as such may be characterised by its mean and coefficient of variation. A technique that allows local grammage data to be stochastically recovered from light transmission data using knowledge of the characterising statistics of these distributions is presented. The theory of Kubelka and Munk is applied to samples in an attempt to provide the basis for a calibration based upon the optical properties of the sheet. The global average specific light scattering and absorption coefficients of many samples are considered with respect to physical sheet properties, to investigate what governs the nature of the linear relationship between the coefficient of variation of local transmittance with that of local grammage over a range of scales of inspection. The potential for this information to be utilised in simulation studies to determine information about local transmittance distributions is demonstrated. The effects of global apparent density on the optical properties of samples are considered. It is shown that the distributions of local transmittance for samples with a given apparent density fall within transmission curves determined from the Kubelka-Munk theory for sheets which are considerably more or less dense. Theoretical curves fitted heuristically to such transmittance and grammage data allow the range of local densities for the sample to be inferred.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available