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.

Reactive dyes exhibit a higher level of initial exhaustion, in the presence of small concentrations of electrolyte, on never-dried lyocell than on never-dried viscose and modal. This difference is particularly noticeable in the case of high substantivity bis-monochloro-s-triazinyl reactive dyes, which exhibit the same differentiated performance on the corresponding dried fibres. Low salt quantities (comparable to those used for applying direct dyes to cellulosic substrates) can therefore be used for applying high substantivity dyes and effect chemicals by an exhaustion process to both never-dried and dried lyocell substrates.

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.

A study has been carried out to correlate the wet fastness properties of dyed knitted fabrics, derived from both poly(ethylene terephthalate) and poly(lactic acid) (Ingeo) fibres, with the thermal migration properties of the disperse dyes during heat treatment. The results indicate a greater amount of disperse dye at the surface of the Ingeo fibre fabric than the poly(ethylene terephthalate) fabric, after post heat-setting using the conditions needed for fabric stabilisation, correlating well with its slightly lower wash fastness properties.

A study has been conducted to examine the effect of different preparation and dyeing processes on the physical strength of the Ingeo fibre component of an Ingeo fibre/cotton blend. An alkaline scouring process (for the cotton), followed by a two-bath, two-stage dyeing process in which the Ingeo fibre underwent a simulated dyeing with disperse dyes, followed by the cotton being dyed with reactive dyes, caused minimal deterioration to the strength of the Ingeo fibre. However, it is considered that problems might arise if the Ingeo fibre was subjected to prolonged dyeing times, particularly at neutral or alkaline pH, e.g. if an excessive number of shading additions needed to be carried out.

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.

A set of knitted fabrics comprising soybean fibers was ozonated at room temperature for periods ranging from 2.5 to 300 minutes to identify any accompanying effects on either physical properties (specifically whiteness and burst-strength), fiber surface integrity or microstructure. A hydrogen peroxide treatment was applied to some of the fabric in order to provide a comparison. Ozonation was found to produce a promising increase in whiteness which, after the maximum exposure time, was significantly higher than was achieved using hydrogen peroxide. © 2012 International Ozone Association.

A set of knitted poly(lactic acid) (PLA) fabrics was ozonated at room temperature for periods ranging from one to 60 minutes in order to identify any accompanying effects on physical properties (specifically whiteness, water-absorbency, flexural rigidity and burst strength), fiber surface integrity or internal microstructure. A significant (ca. 6% after 10 minutes of treatment) initial increase in whiteness was observed, with longer treatment times producing little further change. The fabric’s absorbency and flexibility both increased, the time of wetting having fallen by ca. 20% and the flexural rigidity by ca. 16%, respectively, after 10 minutes of treatment. Fabric strength remained virtually unaffected for short times (up to 10 minutes) of ozonation, although longer treatments caused a measurable drop (ca. 10% after 60 minutes). SEM imaging showed virtually no evidence for surface damage, even after 60 minutes of treatment, whereas peroxide treatment caused massive pitting of the fiber surface. Raman spectroscopy of the ozonated PLA fabrics indicated that the treatment had not affected the internal microstructure of the fibers. Our conclusion is that brief (no more than 10 minutes) room-temperature ozonation is potentially an effective, safe and low-energy alternative to conventional higher temperature peroxide treatment. © 2011, SAGE Publications. All rights reserved.

Water droplets falling onto finished fabrics can create spots which can spoil the appearance of the fabric. This study compares the propensity of softened filament polylactic acid and polyester fabrics to exhibit the adverse affects of 'water-spotting', and to identify suitable softeners and methods for their application to minimise and eliminate the problem. The degree of water spotting was greater on softened polylactic acid fabrics than on softened polyester fabrics. Polylactic acid and polyester fabrics with hydrophobic properties did not exhibit any water spotting. Softeners applied by an exhaustion process resulted in a finished fabric which exhibited no water spotting for either dyed polylactic acid or dyed polyester fabrics. The softening active agent was not responsible for the water spotting. The other components in the softener formulation (such as emulsifier, wetting agent), which carries the unfixed dyes with water, were found to be responsible. The water spot halo disappeared after a single machine laundering process. © 2011 The Korean Fiber Society and Springer Netherlands.

This paper addresses the relative effects of softeners having different properties and their method of application (exhaust vs pad) on the colour fastness of poly(lactic acid) fabrics dyed with a range of disperse dyes with different levels of hydrophobicity. A comparison was made with a correspondingly finished polyethylene terephthalate fabric. Possible relationships between the levels of hydrophilicity/hydrophobicity of the dye, and softener, and the colour fastness were explored. Finally, the amount of dye thermally migrated into the finish on the softened poly(lactic acid) and polyethylene terephthalate fabrics was examined in comparison with their colour fastness. Softened poly(lactic acid) fabrics dyed with CI Disperse Red 167.1 exhibited more thermal migration, and hence lower colour fastness, than the corresponding polyethylene terephthalate fabrics. Conversely, softened poly(lactic acid) fabrics dyed with Dianix Deep Red SF exhibited less thermal migration, and hence better colour fastness, than the corresponding polyethylene terephthalate fabrics. Overall, no clear relationship was found between the hydrophobic nature of the disperse dye and the hydrophobic character of the softener on the colour fastness. © 2010 The Authors. Coloration Technology © 2010 Society of Dyers and Colourists.

We have studied the effects of softeners and repeated laundering on the handle of knitted fabrics constructed from poly(lactic acid) (PLA) filament yarns derived from corn-starch. The fabrics were assessed: a) subjectively, via a panel of volunteers, in terms of their perceived softness and 'scroopiness'; and b) objectively, using a Kawabata Evaluation System for Fabrics (KES-F), in terms of their low-stress mechanical properties. The study employed two fabric variants and a range of commercial softeners in an attempt to determine the combination that would provide optimal handle and durability to laundering. We found the standard KES-F parameters B, 2HB, G, 2HG, and SMD to be generally well-correlated with the subjective assessment of softness and scroopiness. Although repeated laundering reduced somewhat the beneficial effects of the softeners, this deterioration was not severe, and we were able to identify specific formulations that can provide good handle coupled with acceptable durability. The fabric handle was seen to be influenced by the chemical nature of the softening agent, the type of emulsion employed and the degree of hydrophobicity (assessed in terms of wettability); on the other hand, the ionicity of the softener appeared not to play a significant role. © 2010 The Korean Fiber Society and Springer Netherlands.

This study investigates the influence of different finishing conditions on the amount of thermal migration and the wet fastness properties of selected red disperse dyes on polylactic acid fabrics. A comparison was made with a correspondingly finished polyethyleneterephthalate fabric, with a specific objective being to identify the conditions that would give optimum wet fastness to the polylactic acid fabric. A greater thermal migration of dye was observed on the polylactic acid compared with polyethyleneterephthalate fabric under the same heat treatment conditions, resulting in a lower level of wet fastness. The lowering in wet fastness of dyed polylactic acid fabric on processing occurs mainly as a result of thermal migration of disperse dyes during the drying stage at 110 °C. © 2009 The Authors. Journal compilation © 2009 Society of Dyers and Colourists.

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.

Recovery from strain, tensile, and shrinkage are measured for poly(ethylene 2,6-naphtha-late) (PEN), dimensionally stable polyester (DSP PET), and high tenacity polyester (HT PET). The results are considered in the context of an earlier study examining the mechanical properties of poly(ethylene terephthalate) (2GT), poly(trimethylene terephthalate) (3GT), and poly(tetramethylene terephthalate) (4GT). DSP PET and PEN show good recovery from 10% applied strain, at 30% strain DSP PET has the highest recovery overall, and at 60% strain recovery is poor for all types. In the case of HT PET, specimen breakage sometimes occurs before the recovery measurement can be completed. PEN shows the minimum shrinkage in boiling water, and DSP PET is more dimensionally stable than HT PET. However, an interesting observation is that PEN develops a crimped appearance after this treatment, which is not seen in the other two fibers. We associate this with the good recovery behavior of PEN.