Thesis

Optical spectroscopic techniques for in-situ characterisation of the milling of concenttrated pigment dispersions

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Awarding institution
  • University of Strathclyde
Date of award
  • 2013
Thesis identifier
  • T13449
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Abstract
  • The use of UV-visible, mid infrared, near infrared (NIR) and Raman spectrometries for monitoring the milling of polymer-pigment dispersions was investigated. Experiments showed that both NIR and Raman showed possibility for in-situ monitoring of particle size reduction and were both investigated further. A fundamental investigation of the information content of NIR spectra was completed, showing the influence of particle size on the scattering properties of the pigment dispersions. This was used to rationalise observations made from spectra collected in-situ during particle size reduction experiments on different scales. Cyan, magenta and yellow pigment dispersion NIR spectra, collected in-situ, during milling, showed an increase in baseline offset as pigment size was reduced. Experimentation was performed on < 1 kg scale to develop and assess the technique before applying to larger scale 10 kg and 200 kg milling experiments. Qualitative and quantitative, univariate and multivariate, modelling approaches were explored for monitoring experiments performed on different scales. < 1 kg scale milling experiments showed errors in prediction of between 0.90 -7.96 % for samples at the end point of milling (with particle sizes ranging from 100 to 114 nm). A calibration model derived from < 1 kg experiments was applied to 10 kg milling experiments with an error of prediction of 4.14 % for particles of 110 nm. Qualitative univariate modelling of 200 kg pigment dispersion milling experiments was able to show where faults occurred and where particle size reduction was no longer progressing. The work has demonstrated that in situ NIR measurements could potentially replace the current off-line particle size method. Raman spectroscopy also showed potential for following particle size reduction processes (< 1 kg scale) for cyan and yellow pigment dispersions using a wide area illumination Raman probe. Issues with fluorescence were encountered for magenta pigments and alternatives were explored to remove this.
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  • Strathclyde theses - ask staff. Thesis no. : T13449
DOI
Date Created
  • 2012
Former identifier
  • 991373

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