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Effects of Gaseous Diffusion in the Substrate on Light Fastness of Dyes
Author(s) -
Giles C. H.,
Shah C. D.,
Johari D. P.,
Sinclair R. S.
Publication year - 1972
Publication title -
journal of the society of dyers and colourists
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.297
H-Index - 49
eISSN - 1478-4408
pISSN - 0037-9859
DOI - 10.1111/j.1478-4408.1972.tb03059.x
Subject(s) - cellulose triacetate , polyethylene terephthalate , cellophane , polyacrylonitrile , materials science , diffusion , molecule , oxygen , substrate (aquarium) , polymer chemistry , photochemistry , composite material , chemistry , organic chemistry , polymer , physics , oceanography , thermodynamics , geology
Various disperse dyes in cellulose triacetate (cta) film and some dyes in Cellophane regenerated‐cellulose film, sealed in envelopes of undyed hydrophobic films, viz. polytetrafluoroethylene (ptfe), polyacrylonitrile (pan), polyethylene terephthalate) (pet) and cta, have been exposed to light from a 400‐W mercury lamp. Fading is retarded by the undyed films. The order of effectiveness is ptfe> pan > pet > cta. The permeability of water vapour (except for pan) or oxygen through these films decreases in the above order. The retardation is similar in magnitude to the corresponding differences in light fastness of the disperse dyes on textile fibres. It is suggested that the action, except possibly in pan, is caused by retardation of the diffusion of an oxygen molecule towards contact with a dye molecule during the short life‐time of the excited state of the dye; calculation shows that there is only a very small chance of such contact. An expression is derived which shows that the rate of fading depends on both the life‐time of the excited dye molecule and the rate of diffusion of oxygen in the substrate. The retardation effect, termed ‘diffusion‐restriction’ (dr) effect, probably operates to some extent in all fading of colorants in fibres or films.