Effect of uniaxial drawing on surface chain structure and surface tension of poly(trimethylene terephthalate) film

Changes in the surface chain structure and the critical surface tension of poly(trimethylene terephthalate) (PTT) film under uniaxial drawing were examined by polarized attenuated total reflection infrared (ATR-IR) spectroscopy and contact angle measurement. It was observed from the stress-draw ratio curve and density measurement that the strain-induced crystallization occurs at the draw ratio of 2.5. From the ATR-IR spectra, it was also realized that the surface chain structure changes with the draw ratio, showing a remarkable increase in the surface crystallinity at the draw ratio between two and three. The critical surface tension of uniaxially drawn films increases with the draw ratio due to an increase in the surface crystallinity developed by the strain-induced crystallization. It is concluded that the surface properties of PTT film such as the chain structure at the surface and the critical surface tension are very closely related to the condition of uniaxial drawing.