RECOVERY OF AMORPHOUS POLY(ETHYLENE TEREPHTHALATE)FILM UNIAXIALLY DRAWN JUST BELOW THE GLASS TRANSITION TEMPERATURE*

 Isothermal recovery in the macroscopic length of homogeneously deformed specimens of amorphous poly(ethyleneterephthalate) (PET) film sample uniaxially drawn at 69℃ to the draw ratios λ₀=1.26～2.20 were studied at temperaturesaround the glass transition temperature (T_g = 73℃). Experimental results indicate that the length recovery took place in twodistinct steps: a fast first step (fast relaxation) followed by a slow second step (slow relaxation). The relaxation processeswere accompanied by the reversion of trans-conformers (1340cm^-1 to gauche,and the dichroic function of the 1340 cm^-1band characterizing the segmental orientation along the chain direction decreased to a very low value at the end of the fast relaxation.This fact led us to assign the fast relaxation as the segmental orientation while the slow relaxation as relaxation of the global chain orientation.It was found that the slow relaxation follows a single exponential function,with relaxation times strongly dependent on the temperature resembling the glass transition process.The fast relaxation does not follow a single exponenitial decay,presumably a distribution of relaxation times is involved.