The diffusion of water into pet followed in-situ using FT-IR ATR

The diffusion of water into PET containing a comonomer has been followed in-situ using FT-IR ATR. Varying degrees of crystallinity were induced into the polymer by annealing at 85 degrees C (above the glass transition temperature). The diffusion coefficients sere calculated by a least squares fit of the experimental diffusion data to theoretical sorption curves and are found to decrease with increased crystallinity. Some evidence fora crystalline 'skin' is discussed.