The coloration of synthetic polymers: A review of the chemistry of dyeing of hydrophobic fibres

Abstract

AbstractThe dyeing methods of anionic dyes on nylon, cationic dyes on polyacrylonitrile fibres, and non‐ionic (disperse) dyes on nylon, cellulose acetate, polyethylene terephthalate, and polypropylene are surveyed and their chemical mechanism outlined.The mass coloration of plastics, and the state of disperse dyes in the fibre are also briefly discussed. Dyeing of the polar hydrophobic fibres with disperse dyes differs from all other types of dyeing in that the dye—fibre bonding is overwhelmingly hydrogen bonding, and van der Waals or hydrophobic bonding seems to have a negligible influence. All the polar groups and aromatic nuclei in the dye and the fibre can take part in the bonding, and the fibre can act as proton acceptor or donor. Because of these facts disperse dyeing has special features, including: linearity of adsorption isotherms; direct relation between water solubility and fibre solubility of dye and between number of hydrogen‐bonding groups in a dye and its solubility in the fibre; constancy of dye diffusion coefficient in the fibre, and additivity of solubility in the fibre of certain disperse dyes; and the possibility of dry dyeing, either from the vapour phase or from non‐aqueous solvents.The size, shape, and number and nature of polar substituent groups of the disperse dye molecule influence its diffusion coefficient in the fibre.Polypropylene fibre, if unmodified, has no polar or ionic groups and has no affinity for most disperse dyes; a very few however, have sufficient attraction by dispersion forces, to enable them to give weak shades on this fibre.