Structure-Property Relationships in Polytetramethylene Terephthalate/ Polytetramethylene Isophthalate Copolyesters Part II : Relationships Between Dyeability and the Glass-Transition Temperature

The dyeing properties of a series of poly tramethylene terephthalate/polytetramethylene isophthalate copolyester films with C.I. Disperse Orange 3 have b investigated. Incorporating isophthalate units into polytetramethylene terephthalate leads to an increase in both the rate of dye diffusion and the amount of dye sorbed at equilibrium. The rate of dye diffusion in the series of copolyesters is found to depend on (T — T g ) for T g measured by several methods. Linear relationships between log D and (T — T g ) allow empirical equations relating the rate of dye diffusion in the series of copolyesters to (T — T g ) to be derived. An application of these equations in studies of dye diffusion in polymers is envisaged. The relationships obtained between log D and (T — T g ) for the diffusion of C.I. Disperse Orange 3 in the series of copolyesters are compared with those found by workers in other dye-fiber systems. In addition, the effects of varying annealing temperature and dyeing temperature on the dyeing properties of the series of copolyesters have been studied.