Search

The total water capacity of a series of never-dried and re-wetted cellulosic fibres has been shown to correlate with the accessible volume described by a thermodynamic model. The model was applied to interpret the adsorption behaviour of a range of reactive dyes in electrolyte solutions and was successful in accounting for differences in fibre anionic charge. Comparative solute exclusion data indicated the existence of a population of very small spaces in never-dried cellulosic fibres, which may be associated with water disrupting the cellulose \({1\overline{1}0}\) crystal planes. Such intra-crystalline spaces may provide sites for uptake of planar substantive dyes and may also be accessible to sodium ions. The study showed that never-dried lyocell undergoes a large reduction in total wet capacity following initial drying, which is believed to be due to both exudation of crystal water and to inter-fibrillar crystallisation. This crystallisation mechanism may not be so effective for viscose and modal, which have poorer structural organization. Re-wetted lyocell exhibits high dye adsorption, which may result from the development of a uniform fibrillar morphology with a high surface area. This structural aspect is not expressed by the thermodynamic model.

The majority of synthetic and regenerated cellulose fibers are crimped after spinning in order to possess natural appearance and texture, warmth and handle. Depending on the circumstances in processing, fibers may experience complex combinations of tensile, compression, flexural and torsional, deformation, abrasion, etc. that may cause a variety of fiber damages. One of the most important applications of microscopy of textile fibers is in the study of damage. In this study optical microscopy and scanning electron microscopy were used to study the surface characteristic of lyocell fibers. More importantly, kink bands with sharp ridges and transverse lines in crimped lyocell fibers were observed. The angles between the kink band and the fiber axis were measured. Fourier-transform infrared spectroscopy was applied, in combination with measurements of strength, fluidity and moisture regain to detect microstructural changes in lyocell fibers produced during crimping processing.

A short study has been conducted to examine the efficiency of different alkaline reduction-clearing conditions on Ingeo [poly(lactic acid)] fibres, dyed with disperse dyes. The results indicate that the preferred conditions are 15 min at 60 °C in the presence of 2 g/l sodium carbonate and 2 g/l 'hydros', conditions which avoid any significant change of shade by colour loss and lead to optimised wash fastness.

Fourier-transform infrared (FTIR) spectroscopy has been applied in combination with wide-angle X-ray diffraction and measurements of strength, fluidity, yellowness, birefringence, and moisture regain to detect microstructural changes in lyocell fibres, a regenerated cellulose fibre, subjected to direct heat and annealing treatments. TMA, and SEM were used to show the effect of direct heat and annealing on lyocell fibres. The FTIR spectroscopy results show that a decrease in intermolecular hydrogen bonding occurs at 70 and 80 °C for annealed and directly heated samples, respectively. The results demonstrate increase of the intensity of O–H stretching vibrations, this associated with hydrogen bonds reforming around 130 °C. Lyocell fibres shrink with direct heating in the temperature range 130–160 °C. The crystallinity decreases gradually with increasing temperature. There is no significant change in colour of the samples annealed up to 150 °C. A continuous increase in the fluidity occurs for the annealed samples in the range 150–230 °C. The tenacity and breaking extension of heated samples decrease with increasing temperature. The lower annealing temperatures cause no observable change in the smooth and void-free surface, but in the annealing temperature range 170–230 °C, substantial non-uniformity is apparent on the surface of the fibres.

Exhaust application of a given reactive dye to never-dried lyocell, viscose and modal fibres gave virtually identical levels of exhaustion on each fibre, whether in the presence of salt alone or in salt plus alkali, as well as similar levels of fixation. This suggests that the accessibility and reactivity of the three never-dried fibres for selected reactive dyes, during a typical exhaust dyeing process, are the same.

This paper examines the influence of processing parameters on the physical properties and structure of yarns constructed from poly( l -lactic acid) (PLLA) fibres. Commercially produced spun- and false-twist texturised (FTT) PLLA yarns, and knitted fabrics derived there from were characterised in terms of their tensile properties, and structurally using differential scanning calorimetry (DSC) and wide angle X-ray diffraction. The effects of pre-dye heat-setting at 130 °C for varying times was assessed in terms of the resultant tensile properties of the yarns. The as-received FTT yarns (and hence their derived fabrics) differed in properties and fibre microstructure as compared to the spun yarns (and fabrics). More significantly, for both FTT and spun materials, differences in fibre properties and structure were observed between yarns removed from the fabrics and their respective feed-yarns. We associate this with possible thermomechanical influences experienced by the fibres during the knitting process. The duration of heat-setting influenced the tensile properties and DSC spectra for both types of yarn. Scouring following heat-setting was also carried out, and this produced no measurable additional effect on the spun yarns, but FTT yarns heat-set for less than ca 45 s showed instability to scouring.

A study has been conducted into the effect of heat setting on the dimensional stability and dyeing properties of spun and false-twist texturised poly(lactic acid) yarn. It has been shown that acceptable levels of dimensional stability can be achieved after heat setting for 30-45 s at 130 °C, false-twist texturised yarn exhibiting greater shrinkage than spun yarn. The exhaustion level and visual colour yield of a number of disperse dyes have been evaluated on each type of poly(lactic acid) yarn and shown to be essentially independent of the time of heat setting.

This research investigates changes occurring in lyocell fibers resulting from exposure to simulated sunlight, FTIR microspectroscopy is used in combination with measurements of tensile properties, fluidity, moisture regain, yellowness, weight loss, and birefringence. X-ray diffraction and SEM are used to determine crystallinity and fiber surface changes, respectively. The results indicate no significant changes in physical properties up to 96 hours' exposure. At 168 hours, open pores appear on the fiber surface, probably due to the release of gaseous products, accompanied by an increase in moisture regain.

The first section of this paper examines some of the major causes of appearance loss in tufted pile carpets due to foot traffic. The effects of shading, loss of tuft definition, fiber damage, and other factors are discussed, and a brief review is given of existing research in this field. The second section concerns a visual and microscopical study of nylon and polyester cut-pile carpets following wear trials in the traffic range 0- 100,000 treads. Optical and scanning electron microscopy are used to assess changes in pile geometry and the significance of fiber damage. The relative performance of nylon and polyester carpets is discussed in light of the differing mechanical properties of the two fiber types, in particular, the higher recoverability of nylon from large deformations. An interesting observation is the relatively poor retention of tuft defi nition in the nylon carpet, for which a possible explanation is offered in terms of fi ber crimp.