Quantitative studies in photochemistry of dyes

Hojiwala, Balvantrai J (1967) Quantitative studies in photochemistry of dyes. PhD thesis, University of Glasgow.

Abstract

The first part of this thesis deals with the effect of temperature and humidity on the fading of dyes on polyamide (nylon) and polyester film substrates and also on gelatine and regenerated cellulose film (Cellophone). The results of fading obtained with disperse dyes on polyamide and polyester substrates were found in all cases to give first-order plots. This shows that dye in the substrate is probably either monodisperse or present in very small aggregates. The influence of temperature on fading of dyes on nylon and on polyester was quite considerable. In fact it was opposite to the general trend on hydrophilic substrates which is that the rate fading decreases with increase in temperature, because of loss of moisture by the fibre. The present effect with substrates which normally contain very little adsorbed moisture, might be due to change in the internal structure of the polymers when heated to a high temperature or simply to the normal effect of temperature becoming operative when the adsorbed moisture is almost entirely removed. The rate of fading test results obtained with cellulose and golatin show that the dye in these two substrates is probably present partly monodisperse and partly as aggregates. Increase in humidity greatly increases the rate of fading. Experiments to determine the quantum efficiency of dye fading on the substrate are described in the second part of this thesis. Disperse and direct dyes were applied to nylon and Cellphane films respectively. The dyed films were faded under different filters and the quantum efficiency values calculated. The values thus obtained were much lower than those which are recorded for fading of dyes in solution. This probably shows that most of the radiant energy absorbed is dissipated as heat, though in some cases it might partly have been used up in causing tendering of the substrate. The third part of the thesis describes some calculations made to reveal if any relation exists between the molecular geometry of dyes and their light-fastness. Selected dyes from various groups for which Colour index data are available were examined. The results were plotted as molecular axial ratio (MAR) i.e. ratio of molecular length to width, against the light-fastness grade. Only in the case of anthraquinone vat dyes on cotton was any significant relation found. This was an inverse one, i.e., light-fastness decreases with increase in MAR. Direct, disperse and acid dyes did not show any significant relation.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: C H Giles
• Keywords: Polymer chemistry, Textile research
• Date of Award: 1967
• Depositing User: Enlighten Team
• Unique ID: glathesis:1967-72379
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 24 May 2019 15:12
• Last Modified: 24 May 2019 15:12
• URI: https://theses.gla.ac.uk/id/eprint/72379