The influence of different treatment media on the structure of PET fibres

Abstract.

The changes of supramolecular structure of PET fibres upon supercritical fluid (SCF) dyeing, conventional water dyeing, hot air thermofixation at 130 °C, respectively were studied. The following observations were made; the increase in crystallinity is nearly alike with the SCF and water treated sample, while hot air results in lower crystallinity change. There is only a very slight change in the periodical structure along the fibre axis, determined by the long period. The diminution of the long period by the treatment at 130 °C is nearly alike with SCF and hot-air treatment, while water medium decreases the long period less. The strongest influence on dimensions of crystallites is observed with water, while hot air and supercritical CO₂ cause a smaller diminution of the crystallite sizes. After the treatments a slight disorientation is observed irrespective of the medium used. Perhaps water represents the medium where the relaxation process occurs easier and a slightly greater fall of orientation function is detected. Compared to SCF treatment of PET fibres both other treatment media cause a more pronounced change of the micro-void system and the inhomogeneity form factor additionally increases with the latter two treatment media. From only very slight differences between the samples treated at 130 °C in different media a conclusion follows: obviously the medium used is not the main influence, but temperature used has the greatest influence.