Changes In Fiber Properties Research Articles

Plasma technology in wool

The textile industry processes a large quantity of fibres obtained from various animals of which wool is commercially the most important. However, it has some technical problems which affect the quality and performance of the finished products such as felting shrinkage, handle, lustre, pilling and dyeability. These problems may be attributed mainly to the presence of wool scales on the fibre surface. The scales are relatively hard and have sharp edges which are responsible for causing fibre directional movement and shrinkage during felting. Furthermore, the scales also serve as a barrier for diffusion processes which will adversely affect the sorption behaviour. In recent years, there has been an increase in the modification of wool surface scales by physical means such as mechanical, thermal and ultrasonic treatments, and chemical methods such as oxidation, reduction, enzyme and ozone treatments which can solve the felting and sorption problems to a certain extent. Hitherto, chemical treatments are still the most commonly used descaling methods in the industry. Owing to the effect of pollution caused by various chemical treatments, physical treatments such as plasma treatment have been introduced recently as they are capable of achieving a similar descaling effect. Since the 1960s, scientists have successfully exploited plasma techniques in materials science. The plasma technologies have been fully utilised to improve the surface properties of fibres in many applications. The fibres that can be modified by plasmas include almost all kinds of fibre such as textile fibres, metallic fibres, glass fibres, carbon fibres, fabrics and other organic fibres. Plasma-treated wool has different physical and chemical properties when compared with the untreated one. The changes in fibre properties alter the performance of the existing textile processes such as spinning, dyeing and finishing to produce a series of versatile wool products with superior quality. Therefore, the aim of this monograph is to give a critical appreciation of the latest developments of plasma treatment of wool. In this monograph, different surface treatments of wool including plasma treatment will be precisely described. Since plasma treatment can be used to alter material surfaces by removing outer layers, thus the method of generation of plasma and the reaction mechanisms between material surface and plasma species will be highlighted in this monograph. Similar to other chemical reactions, the factors such as (i) the nature of gas used, (ii) gas flow rate, (iii) system pressure and (iv) discharge power affecting the final results of plasma treatments will be described. The main content of this monograph includes the application of plasma treatment on wool under different industrial conditions such as dyeing and shrinkproofing processing which will be reported and discussed respectively. In addition, the common analytical methods such as Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy and Fourier Transform Infrared Spectroscopy with Attenuated Total Internal Reflectance mode analysis employed for characterising the surface properties of plasma-treated wool will be discussed. Based on the surface characterisation results, more details about the mechanism of plasma treatment that affects the wool processing such as dyeing and shrinkproofing can be explored. In the latter part of the monograph, the serviceability of plasma-treated wool fabrics is discussed and the possibility of applying the plasma-treated wool fabric to industrial use is evaluated based on standard performance specification, e.g. ASTM. The fabric performance in terms of tailorability and sewability are also discussed with reference to the Kawabata Evaluation System for Fabric (KES-F) results. As the plasma process is a “dry” process, i.e. the water used in the plasma system can be recycled, thus it can solve the industrial effluent problem resulting in providing an effective means for the modification of wool fabrics.

Dyeing behaviour of lyocell fabric: effect of fibrillation

To understand the effect of fibrillation in dyeing, non‐fibrillated lyocell fabrics and fibrillated lyocell fabrics were dyed with different types of reactive dyes. Their exhaustion, fixation and K/S values were measured and compared. It was observed that fibrillated lyocell shows lower visual colour yield than non‐fibrillated lyocell, independent of the exhaustion and fixation. It was also observed that some bifunctional reactive dyes, because of the location of reactive groups and flexibility of their structure, reduced fibrillation of lyocell through crosslinking. It was shown that defibrillating fibrillated lyocell with a cellulase enzyme increased the visual colour yield. Non‐fibrillated lyocell fabrics after dyeing were subjected to a hydroentanglement treatment to create a fibrillation effect. These properties suggest that the lower visual colour yield of fibrillated lyocell is not mainly attributed to any change in fibre properties of the fibrils, but as a result of the light scattering from the fibrillated fabric surface.

Influence of Fiber Properties on the Network Strength of Softwood and Hardwood Kraft Pulp Fibers from Different Stages of a Bleaching Sequence

During chemical pulping and bleaching operations, fiber properties are gradually changed due to mechanical and chemical treatment. The changes in fiber properties, in turn, influence network strength, i.e., the rigidity of fiber networks. In this study, the influence of fiber length, lignin content, specific surface area, total charge, and fiber flexibility on the network strength of commercial unbleached and totally chlorine free (TCF) bleached (ozone and hydrogen peroxide) softwood and hardwood kraft pulp suspensions have been investigated. The fiber length, total lignin content, and total charge decreased together with the network strength along the fiber line while the specific surface area and fiber flexibility increased. Correlations equal to or greater than 90% were found between network strength and fiber length, lignin content, specific surface area, and total charge. The interrelationship between the fiber properties indicated that for a given pulp, the total lignin content was the parameter that had the greatest influence on the network strength.

A study of damping in fiber-reinforced composites

Damping contributions from the viscoelastic matrix, interphase and the dissipation resulting from damage sites are considered to evaluate composite material damping coefficients in various loading modes. The paper presents the results of the FEM/Strain energy investigations carried out to predict anisotropic-damping matrix comprising of loss factors η 11, η 22, η 12 and η 23 considering the dissipation of energy due to fiber and matrix (two phase) and correlate the same with various micromechanical theories. Damping in three phase (i.e., fiber–interphase–matrix) composite is also calculated as an attempt to understand the effect of interphase. The contribution of energy dissipation due to sliding at the fiber–matrix interface is incorporated to evaluate its effect on η 11, η 22, η 12 and η 23 in fiber-reinforced composite having damage in the form of hairline debonding. Comparative studies of the various micromechanical theories/models with FEM/Strain energy method for the prediction of damping coefficients have shown consistency when both the effect of variable nature of stress and the fiber interaction is considered. Parametric damping studies for three phase composite have shown that the change in properties of fiber, matrix and interphase leads to a change in the magnitude of effectiveness of interphase, but the manner in which the interphase would affect the various loss factors depends predominately upon whether the hard or soft interphase is chosen. Analysis of the effect of damage on composite damping indicates that it is sensitive to its orientation and type of loading.

The Effect of the Licker-in Speed on Fibre Properties on Modern Carding Machines with a Triple Licker-in

In this study, the effect of the licker-in speed of a modern card with triple licker-in on the fibre properties of card sliver was investigated. The change in fibre properties of the card waste taken by a waste collector at various sections of the card under different licker-in speeds was also analysed. There is more fibre damage at a higher ticker-in speed according to the Uster HVI test results. The same trend was observed in the tests carried out on the Uster AFIS. Similarly, there was more reduction in fibre strength and an increase in short-fibre content when a higher licker-in speed was used. Interestingly, the fibre-breaking-elongation value seems not to be affected adversely but improved at a higher licker-in speed. On the other hand, there is no significant difference in nep size and nep count, hut the amount of trash, dust, and foreign material was higher when a higher licker-in speed was applied. The waste fibres had higher elongation values at a higher licker-in speed except for the waste taken from the licker-in zone. Another interesting point is that the fibres in the waste taken from the back part of the cylinder were longer and stronger at a lower licker-in speed.

Treatment of recycled kraft pulps with Trichoderma reesei hemicellulases and cellulases

Effects of recycling ECF-bleached softwood kraft pulp on pulp properties were evaluated in the laboratory. The tensile strength, fiber flexibility and WRV lost during drying of the pulp were recovered by refining between the cycles which, however, resulted in deteriorated drainage properties. The recycled pulps were treated with purified Trichoderma reesei cellulases and hemicellulases and the changes in fiber properties due to enzymatic treatments were characterized. The endoglucanases (EG I and EG II) significantly improved pulp drainage already at low dosage levels, and EG II was found to be more effective at a given level of carbohydrate solubilization. Combining hemicellulases with the endoglucanase treatments increased the positive effects of the endoglucanases on pulp drainage. However, as a result of the endoglucanase treatments a slight loss in strength was observed. Combining mannanase with endoglucanase treatments appeared to increase this negative effect, whereas the impact of xylanase was not significant. Although the drainage properties of the pulps could be improved by selected enzymes, the water retention capacity of the dried hornified fibers could not be recovered by any of the enzymes tested.

The Use of Cellulases to Improve the Sorption Properties of Cellulosic Wound Dressings

Staple viscose fibres, of a type commonly used in wound-dressing materials, were treated with a cellulase complex isolated from Geotricum candidum. Adsorption of cellulase onto the fibre and rates of cellulolytic hydrolysis were measured under the applied-treatment conditions. Changes in fibre properties were measured in terms of their specific surface area accessible to N2 and cellulases and in terms of their mean pore radius, moisture regain, degree of swelling, and tensile strength. In particular, it was found that the sorption of Staphylococcus aureus cells from a bacterial suspension increased to 90% for the cellulase-treated fibres compared with only 2% for the untreated fibres. Cellulase treatment is therefore recommended as a means of increasing the sorption properties of cellulosic wound dressings.

Studies on the swelling of cotton fibers in alkali metal hydroxides. III. Structure‐property relations in fibers swollen at 0°C

AbstractCotton fibers were subjected to swelling in various concentrations of LiOH, NaOH, and KOH at 0°C. Swollen fibers were characterized by measurements of physical, mechanical, and fine structural properties. Slack swelling in LiOH and NaOH produced tremendous changes in fiber properties. Clear‐cut swelling maxima, disorientation, and subsequent deterioration in tensile properties at and near the swelling maxima were evident in both LiOH and NaOH. On the other hand, KOH swelling did not produce any clear swelling maximum. Fibers swollen in this reagent showed better retention of tensile properties due to conducive changes in the structural parameters resulting from a lower but more uniform swelling. © 1993 John Wiley & Sons, Inc.

Some features of fibre preparation from a copolymer of acrylonitrile with 5-vinyl-2-methylpyridine

Increasing the content of ionogenic grups in a copolymer of acrylonitrile with 5-vinyl-2-methylpyridine leads to a change in intermolecular interaction is solutions of the polymer, and this exerts an effect on their rheological properties. The parameters of the process of spinning and fibre strengthening are determined by the composition of the copolymer, a change in fibre properties being observed at a content of active groups in the copolymer which is greater than 40% by wt.

Effect of technological spinning transitions on the properties of nickel-containing nitron fibre

The effect of technological spinning transitions on the properties of an electrically-conducting metallized Nitron fibre has been investigated. It has been shown that in mechanical crimping the mechanical and electrically-conducting properties of a nickel-containing fibre are considerably impaired. During the spinning process, a considerable leveling out of the nickel content of the fibre and of its electrical resistance takes place. Processing of the nickel-containing fibre should be carried out with elimination of the mechanical crimping process. Thereupon the change in fibre properties takes place mainly during the process of preparing the combed lap.

Changes in Cotton Fiber Properties Caused by Three Sodium Hydroxide Concentrations at Three Temperatures

Three cotton samples were treated with three sodium hydroxide concentrations at three treatment temperatures. The Digital Fibrograph, Stelometer, and Arealometer were used to measure the effects of treatment temperature and sodium hydroxide concentrations on length, mechanical properties, and fineness parameters. Temperatures and con centrations producing completely mercerized fibers showed the greatest change in fiber properties. Most of the fiber properties showed a greater effect of treatment at the lower temperatures for a given sodium hydroxide concentration.

Studies of Wrinkling Properties of Wool Fabrics

'I'he changes in certain fiber properties after treatments designed to improve the wrinkle recovery of wool fabrics (Part I) have been studied. It has been demonstrated that by obtaining a wrinkle height distribution curve in a sorp tion process according to TEFO'S conic wrinkling method, changes in fiber properties important from the point of view of wrinkling can be easily predicted. The changes in initial slope and shape of such a curve would reflect the changes in mechanical stiffening and structural sensitivity to moisture change, respectively, of wool fibers. The effect of treat ments such as annealing (heating wool at 45°C and 80% RH), crosslinking with Fixapret CPN, and polymer treatment with Synthappret LKF on the wrinkle height distribution curve, stress-strain behavior, and moisture absorption of wool fibers have been investigated. Very marked increase in mechanical stiffening of wool fibers due to annealing has been demonstrated.

Interaction of Combining Ability Effects with Environments in Diallel Crosses of Upland Cotton (Gossypium hirsutum L.)1

Ten strains of Upland cotton, Gossypium hirsutum L., reperesenting a broad array of germ plasm, were crossedin all possible combinations, and the parents and F1 progenies were reared in replicated experiments at two locations in North Carolina for 2 years. Heterosis for lint yield, measured as departure from the average mid‐parent value, was about 26% for the pooled experiments. Estimates of heterosis for boll size, lint percentage, and some fiber properties were small but significant. When summed over all environments, the estimate of general combining ability for lint yield was not significant. However, the interaction of general combining ability by locations for lint yield was significant. Significant estimates of general combining ability were obtained for boll size, lint percentage, and all fiber properties. None of the interactions of general combining ability by environments were significant for these characters. The estimate of specific combining ability for fiber yield, though fairly large, was not significant. Estimates of specific combining ability for lint percentage, boll size, and all fiber properties were not greater than zero. These results were interpreted to mean that no difficulties should be encountred in selecting for changes in fiber properties. Any gains realized should remain stable over the environments sampled. On the other hand, advances in fiber yield could be achieved only at individual locations and, even then, interactions with years and locations would reduce the effectiveness of selection. Some high‐yielding combinations with desirable lint properties were detected.

Response of Cottons to Chemical Treatments Part I: Fiber Mercerization and Urea Treatments 1

In order to determine whether different cottons respond differently to identical chemi cal treatments, single fibers from six carefully selected cottons were subjected to four treatments under a tensile force of 0.1 g. The treatments which were investigated were water, 10 M urea, mercerization, and a combination of 10 M urea and mercerization. The initial, nondestructive portion of the fiber stress-strain curve was evaluated for each fiber prior to the treatment and the entire stress-strain curve was evaluated after the chemical treatments. Thus it was possible to determine the changes in fiber properties on a fiber-to-fiber basis at least as far as the non-rupture fiber characteristics are con cerned. Fiber length, elastic modulus, breaking extension, and breaking tenacity were considered in this research. Many changes in fiber properties due to the chemical treat ments could be interpreted in terms of fibrillar orientation of the six cottons as estimated by the X-ray angle. Under mercerizing conditions, it was observed that cottons with high X-ray angles underwent greater increases in fiber length and elastic modulus and greater decreases in fiber breaking extension than did cottons with low X-ray angles. Changes in fiber breaking tenacity could not be related to known structural features of the cotton fiber.

19—THE DEPOSITION OF POLYACRYLONITRILE IN WOOL. PART III—THE PREPARATION AND PROPERTIES OF WOOL CONTAINING POLYACRYLONITRILE DEPOSITED WITH PERSULPHATE INITIATOR SYSTEMS

A method has been envolved, using persulphates as initiators, whereby polyacrylonitrile can be deposited in wool in a short time and in the presence of air. Persulphates alter the mechano-chemical properties of wool, e.g., set, supercontraction, to a much greater extent than the hydrogen peroxide–ferrous ion initiator system, which has virtually no effect on them. Polymer deposited with persulphates is almost as effective in reducing milling shrinkage as polymer deposited with hydrogen peroxide, polymer contents of 25% being sufficient to reduce shrinkage from 30% to about 5%, or from 13% to 2—4%. The effectiveness of polyacrylonitrile in reducing shrinkage cannot be attributed to changes in fibre properties usually considered to be of importance in determining the milling characteristics of wool fibres : the directional friction effect of the fibres is almost unaltered, their elastic properties are little affected, and, as loose wool is also made shrink-resisiant, “spot-welding” of the fibres is not impo...

Physical Properties of Chemically Modified Cottons

Yarns from six cottons selected for their widely different inherent fiber characteristics were partially carboxymethylated to a degree of substitution averaging about 0.125 while held at their original kngth. Moisture regain, linear density, breaking load, and elon gation at break, measured on the fibers and/or yarns, were increased by the modification. Fiber cellulose density and length decreased. Samples of the different cotton varieties were found to differ in their response to the treatment with interrelationships existing between the linear density, degree of substitution, and moisture regain. Changes in fiber properties in the caustic treatments of cottons, such as carboxymethylation and mer cerization, were found to be similar when the tensional conditions during treatment were essentially equal.

The Effect of Processing on Cotton Fiber Properties

In order to ascertain the effect of several processing steps on cotton uber mechanical properties, six cottons in one-bale quantities were manufactured under identical conditions into a standard construction sheeting Samples were removed at several processing stations including the original bale, the yarns, the scoured fabrics, the bleached and mercerized fabrics as well as resin-finished fabrics. The mechanical properties of fibers taken from these stages were determined and the effect of each processing step was examined. It was noted that cotton fiber properties are altered by processing and that the magnitude of the changegs in these properties is not constant for all cottons. In many cases the changes in fiber properties are functions of the original other properties. It was also shown that the changes in fiber properties are reflected in the changes of the fabric characteristics, thus indicating the validity of the premise that fiber properties influence the bahavior of cotton fabrics.

Cotton Quality and Fiber Properties

Several years ago Hall and Elting pointed out that certain raw cottons which had been subjected to the action of fungi in the field or immediately after harvesting suffered a deteriora tion in cotton quality characteristics upon storage in bale form. Such cotton was termed by them to be "cavitomic." This deterioration was most manifest in a reduction of processing efficiency and a lowering of yarn quality. Certain chemical tests (pH and reducible sugars) were established as methods to detect cavitomic cotton. Because there seemed to be consider able lack of information regarding the nature and primary causes of quality deterioration at tributable to cavitomic cotton, the study presented in this paper was undertaken to determine what changes in fiber properties resulting from the "cavitoma" might be responsible for the effects noted previously. The opportunity for this study was presented when it was found that 3 of 12 bales of a homogeneous lot of Deltapine 15 cotton obtained for another investigation gave positive evidence of being cavitomic. These 3 bales were set aside, stored for a year, and then made into fabric. A similar fabric was simultaneously made from a blend of the remaining 9 bales in a processing comparison. Samples at all stages of processing were taken from both cottons and carefully compared in an extensive laboratory testing program. It was found that the cavitomic cotton did, in fact, produce more processing waste; less even slivers, rovings, and yarns; 45 % more end breakage in spinning; and yarns as much as 10% weaker than the normal cotton. In the laboratory study it was found that the cavitomic sample exhibited lower flat-bundle strength at a 5-mm. clamp spacing, a lower fiber crimp, and a shorter fiber length than the normal sample. Although the length difference was barely detectable by conventional methods it was clearly established from number-length distributions based on single-fiber length measurements. It is concluded from this study that some of the fibers are subjected to a localized weakening as a result of the microbial action, either directly or as a result of enzymatic action during storage. These fibers break more easily in processing than fibers in the normal cotton, giving rise to a length distribution biased in the direction of short fibers. This difference in fiber- length distribution is believed to be responsible for the reduction in cotton quality characteristics observed in this and the previous work by Hall and Elting. These results emphasize the importance of fiber-length uniformity as a factor in raw-cotton quality and the need for more sensitive methods of evaluating this factor than are presently available.

Cotton Quality and Fiber Properties

The increased use of drying and cleaning equipment at cotton gins has occasioned complaints from spinners that the "quality" characteristics of cottons are being lowered due to "over drying" of the seed cotton prior to ginning. The present study was undertaken to clarify the effects of overdrying on the processing characteristics of cotton and to determine any changes in fiber properties relating thereto. Three 2-bale lots of cotton were prepared from a homogeneous batch of hand-picked seed cotton by drying in three parts before ginning. The first part was passed through the driers with unheated air. For the second part the air in the first drying tower was heated to 450°F ; the air in the second tower was unheated. For the third part the air in both drying towers was heated to temperatures between 170° and 290°F. Both heated cottons were dried to 3.8% moisture in the lint, well below the recommended minimum of 5%. The cottons were evaluated by means of a small preliminary spinning trial and a full-scale processing trial. Samples taken during the trials were studied to determine the properties of the fibers and the fiber assemblies. The greatest processing difference between the cottons was in the spinning end-breakage rates, which increased as much as 21.4% due to excessive drying for the high-temperature-dried sample. The yarns showed a decrease in strength, evenness, and yarn-appearance grade for the heated cottons, with similar results for roving samples. Raw-cotton samples exhibited only minor differences in fiber properties when examined by conventional methods. Alkali- centrifuge values indicated significant fiber surface damage with heating; and there was evidence to indicate a greater crystallinity for the heated cottons. Tests for the fiber number-length distributions showed that both before and especially after processing through roving the excessively dried cottons consisted of more short and fewer long fibers than the control cotton. It is believed that the presence of many short fibers is the main cause of processing difficulties and reduced yarn quality.

Permanent Finishes on Viscose Rayon depending on Cross–bonding

Evidence is presented which demonstrates the existence of cross–bonds in the molecular struoture of nine modified viscose rayons. In a resin treatment, e. g. the urea–formaldehyde anti–crease process, the greater part of the material is deposited between the molecules of cellulose in the amorphous regions of the fibre. The change in fibre properties, however, is due mainly to a muoh smaller amount of reaotant actively cross–bonding adjacent molecules. In technically important modifications of viscose rayon there is one cross–bond to each 40–100 glucose residues of the fibre cellulose. In the majority of instances the behaviour of the cross–bonds can be adequately represented by definite structural formulae. The cross–bonds studied differ widely in stability, and the technical importance of this point is indicated.The teohnical processes depending on cross–bonding are reviewed, and the anti–crease process is discussed.