The Noncrystalline State Within PET Fibers—Meaning and Characterization by Mechanical-Relaxation Measurements

Abstract

The performance of synthetic fibers cannot be completely understood without any knowledge of the structure in the noncrystalline regions. X-ray diffraction measurements led to the conclusion that the noncrystalline regions in PET fibers can be divided into isotropic noncrystalline (amorphous) and oriented noncrystalline fractions, the amount of which is dependent on the thermal and mechanical history. But x-ray diffraction data, thermal analysis, and dyeing experiments left many effects unexplained: the dependence of glass-transition and dye uptake on thermal history, the real order-disorder situation within the noncrystalline regions, certain mechanical properties, and their time-dependence such as relaxation. The glass-transition temperature Tg of PET fibers, as determined by viscoelastic measurements, runs through a maximum depending on the heat-setting conditions. This can be explained by the assumption that the average size of crystallites reaches a minimum, and therefore the number of crystallites per unit volume shows maximum values at a heat-setting temperature of about 190°C. By raising the heat-setting temperature above 190°C, the crystallites become larger. Segregation of the crystallites in the noncrystalline matrix occurs.

Superhydrophobic fabric mixed with polyester and cotton yarns modified by alkaline treatment and thermal aging

“…The commercial dry-cleaning solvent used in the experiment is a hydrocarbon-based solvent containing the anionic surfactant. The hydrophilic groups of the surfactant are adsorbed and arranged while facing the fabric surface, 48,49 then the hydrophilic groups in the fibers are migrated onto the fiber surface. Thus, as the number of dry-cleaning cycles increases, the static contact angles were decreased and shedding angles were increased.…”

Nature of the Crystalline and Amorphous Phases in Oriented Polymers and Their Influence on Physical Properties

“…Mechanical relaxation measurements have also been used [72] to characterise the state of the amorphous phase. The effect of amorphous orientation on the melting point and birefringence of PET fibres has already been discussed earlier (Table 4).…”

Determination of radial structural properties and spectral dispersion curves of poly(aryl ether ether ketone) fibre

“…The anisotropy is related to fibre structural properties. These properties can vary due to complicated factors acting during processing, starting with spinning and ending in the manufacture of ready‐made clothes 5. Some manufactured fibres, especially those spun at high speeds, reveal their transverse birefringence gradients and even significant inhomogeneities in optical anisotropy when one or both refractive indices are measured at marginal and central zones of the fibre 4.…”