Studies on sublimation of disperse dye out of dyed polymers. II. Rate of sublimation and amorphous transition of polypropylene

Abstract The diffusion coefficient D of disperse dyes through unmodified polypropylene (dyed at 120° and 137°C) was measured at 50°–160°C in the dry system. The diffusion transition points indicated by the breaks in the log D versus 1/ T °K were obtained at about 70°, 90°, and 115°C. The 70° and 115°C transitions are in good accordance with the transition temperature of smectic into monoclinic phase and with the temperature of abrupt change in lattice expansion of monoclinic crystal, respectively. These phenomena were explained on the basis of the intimate correspondence between amorphous and crystalline transitions, as expressed by one of us for poly(ethylene terephthalate). The 115°C transition was confirmed by the same sort of diffusion transition occurring, expectedly, at 83°C in the case of polyethylene, an abrupt increase in lattice expansion of which had been found at about 80°C. The diffusion transitions were also confirmed by dilatometry and shrinkage measurement. The 90°C transition has never been reported and it cannot be explained at present.