Mechanische eigenschaften von polyesterfasern bei kurzzeitiger zugbeanspruchung, 4. Strukturveränderungen durch kurzzeitverformung an polyester-monofilamentgarn

Interferometric measurements of a PETP-monofilament yarn show that the orientation of the high pre-orientated material decreases after stretching and relaxing. The effect of desorientation is more distinctive by a slower deformation then by a high-speed deformation. The lower decrease is caused by a slower deformation. Material strained with a rate of 10⁴%/s shows “crazes” visible by interferometry. These “crazes” are not cracks but sites with lowered orientation. For slower deformation it is visible interferometrically that the orientation of the macromolecules in the fiber is asymmetric. DTA-curves from PETP-fibres show an exothermic peak between 30 and 80°C which can be related to specific structures of the non cristalline regions. By low-speed straining this peak shifts to lower temperatures. Stress-free storing of the material causes the peak to move back to the original temperature. For material deformated at high-speeds this peak does not change its position.