Copolyester studies. VII. The dyeing behavior of undrawn fibers derived from tetramethylene terephthalate: Poly(tetramethylene oxide) random block copolymers

A series of copolymers based on poly(tetramethylene terephthalate) containing poly(tetramethylene oxide) blocks whose molecular weights ranged from 1000 to 5000 in concentrations from 10 to 30% by weight was prepared. The polymers were melt spun into fibers and the undrawn fibers dyed with a disperse dye at three temperatures. The equibrium adsorption and diffusion coefficient of the dye increased with both the molecular weight and concentration of the polyether. The equilibrium adsorption varied linearly with both the molecular weight and concentration. It has been assumed that the equilibrium dye partition coefficient K_M gives a parameter of the accessibility, V, of the fiber for dye. If the diffusion coefficient D_M is given by D_M = VD_o/τ, where D_o is the diffusion coefficient of the dye in the amorphous regions and τ is a tortuosity factor, a good correlation can be obtained between K_M and D_M, suggesting that changes in D_o/τ vary in a systematic fashion.