Four samples of poly(ethy1ene terephthalate) film of various crystallinities and orientation were dyed with p-nitroaniline and disperse dyes. When these films were heated under a 2-3 X lo-* mm Hg vacuum at a specified temperature T, the dye sublimed out of the dyed specimen. The amount (Mr/Mm) of sublimed dye is in linear proportion to the square root of the sublimation time, t1I2, where M t and Mm are the amounts of dye sublimed for times t and t = 0 3 . The diffusion coefficient D, calculated from the slope of the above plot, is independent of the dye concentration of the film.
When log D is plotted against l/T"K over the temperature range 320-520°K, the relation is composed of two to four intersecting lines with the slope decreasing with elevation of temperature and with the breaks a t about 89"-98", 122"-135", 155' and 175"-176°C.
the first is the glass transition temperature T , the second and the fourth are the amorphous transitions corresponding to the crystalline transition points, i.e., the cold crystallization temperature and the smectic-triclinic transition temperature. With some exceptions, these amorphous transitions are found also by dilatometry and electrical conductivity measurements. The apparent activation energy for diffusion decreases from about 100 kcal/mole for the glass state to 22-24 kcal/mole for the region above 180°C. The activation energy for each region changes slightly with the size of dye molecule and the crystallinity and orient,at,ion of the film.