Effect of water molecules on crystallization during unixial drawing of poly(ethylene terephthalate) films

The role played by sorbed water molecules present within poly(ethylene terephthalate) film at the moment of uniaxial drawing on the appearance and the percentage of the strain-induced crystalline (SIC) phase is investigated by birefringence, X-ray diffraction, and differential scanning calorimetry measurements. We show that, for law draw ratio, water play its traditional plasticizer effects. The SIC phase appears for a draw ratio, which depends weakly on the relative humidity. The water does not modify the degree of crystallinity of drawn films but impedes the growth of a part of the crystallites and modify their crystalline size. For high draw ratio, water impedes the orientation of the amorphous phase.