The Effect of Fine Structure on the Thermal Shrinkage of Polyethylene Terephthalate Film

폴리에틸렌 테레프탈레이트 필름의 미세구조가 열수숙성에 미치는 영향

The effect of drawing and annealing treatment on the thermal shrinkage behavior of polyethylene terephthalate film was studied. The results are as follows; In the shrinkage along the direction of fiber axis and the swelling along the direction perpendicular to fiber axis, the curve of dimensional change versus annealing temperature take nearly the form of symmetry. Below the draw ratio 1.5, the glass transition temperature where the sample begins to shrink decreases with the increase of draw ratio, but the situation is in reverse, above the draw ratio 1.5. A similar dependence of glass transition temperature and density on the draw ratio was observed. At the draw ratio of about 3.5, the shrinkage shows the minimum value, and then it increases slowly again with the increase of draw ratio. It was found that the shrinkage arise below 8$0^{\circ}C$ was mainly due to the relaxation of amorphous region, but above the medium draw ratio and at 14$0^{\circ}C$, the shrinkage behavior has relation with the crystallization mechanism.