Hygral Expansion Research Articles

The Role of Stenter Settings in Determining the Dimensional and Mechanical Properties of Wool Fabric

A study of the relationship between stenter settings, the resulting fabric dimensional change, and some fabric properties of a finished wool fabric has revealed a significant interaction. It is shown that, with many stenter dryer settings used by the industry including overfeed, a wool fabric is stretched during drying. The study also indicates that the amount of stretch imparted during drying can have a direct influence on the important fabric properties of extensibility and hygral expansion.

Relationships between Hygral Expansion, Relaxation Shrinkage, and Extensibility in Woven Wool Fabrics

If a wool fabric is restrained during drying, as in tentering, there is a close relationship between the relaxation shrinkage that is induced and the hygral expansion. A high correlation also exists between the hygral expansion and extensibility of relaxed fabrics. For conventional woven fabrics, this relationship is independent of fabric structure and the finishing routine used. Separate relationships for warp and weft directions exist between extensibility (of relaxed fabric) and relaxation shrinkage in commercial fabrics. The difference in extensibility (at 500 gf/cm) for a relaxed fabric, and the corresponding unrelaxed fabric, is related to the relaxation shrinkage in the unrelaxed fabric.

Simple Instruments for Quality Control by Finishers and Tailors

Recently developed by CSIRO for quality control and assurance of fabrics, FAST, or fabric assurance by simple testing, consists of a series of instruments that are in expensive, robust, and simple to use, and their related test methods. FAST is specifically designed for use by tailors and worsted finishers; it measures fabric properties that are closely related to the ease of garment making-up and the durability of worsted finishing. FAST- I gives a direct reading of fabric thickness over a range of loads with micrometer resolution. FAST-2 measures the fabric bending length and its bending rigidity. FAST- 3 measures fabric extensibility at low loads. Fabric shear rigidity is calculated from the 45° bias extensibility. FAST-4 is a quick test for measuring fabric dimensional stability, including both relaxation shrinkage and hygral expansion.

Measuring Hygral Expansion in Woven Wool Fabrics

Hygral expansion measurements of woven wool fabrics are influenced by the way in which wet fabric, after relaxation in water, is dried. If the wet fabric is dried directly in an oven, the hygral expansion values are relatively low, but if the fabric is allowed to dry under ambient conditions before oven drying, the values are relatively high (and closer to the "true" values). An interlaboratory trial conducted using thirteen commercial worsted fabrics includes a statistical analysis of different methods for determining the magnitude of hygral expansion. The fabric drying conditions have an important bearing on the magnitude of the dry dimension, and this in turn influences the hygral expansion value obtained.

Effects of Structure and Finishing on the Mechanical and Dimensional Properties of Wool Fabrics

We have investigated the effects of the interaction between fabric cover factor and finishing on fabric properties with a systematically designed array of fabric structures and finishing treatments. Permanent setting induced in finishing had the greater effect on fabric mechanical and dimensional properties. For lightly finished fabrics with a low degree of set, the influence of cover factor was significant. For the entire range of plain weave and twill fabrics, the hygral expansion could be related to the weave crimp and the shear properties of the fabric. There was also a contribution from yarn cur vilinear expansion.

Minimising the impairment of the physical properties of wool during dyeing by restricting the level of permanent set

If permanent setting of the wool fibre, which occurs during dyeing, can be restricted, the impairment of physical properties is reduced. This can be achieved by adding an oxidising agent, such as potassium bromate or hydrogen peroxide, to the dyebath. Oxidising agents also restrict the extent to which hygral expansion increases as a result of piece dyeing. When used in the presence of dyes, oxidants may cause differences in the colour of the dyed wool.

Effect of Photodegradation on the Mechanical Properties of Wool and Wool/Polyester Fabrics

The effect of sunlight exposure on the mechanical properties of wool and wool/ polyester fabrics has been investigated. Instrumental analysis shows that the fabrics become stiffer, rougher, and less elastic with irradiation. This research reveals some differences compared to previously published results for wool fabric irradiated with an artificial light source. Subjective analysis suggests that changes in the mechanical properties can be detected at shorter irradiation times for the 100% wool fabric than for the wool/polyester fabrics. The hygral expansion of wool is unaffected by sunlight irradiation.

FABRIC MECHANICAL AND PHYSICAL PROPERTIES RELEVANT TO CLOTHING MANUFACTURE —

In Part 1 of this series of papers, we investigated the importance of fabric overfeed in the sewing operations during tailoring. It was also shown how fabric bending rigidity, formability, shear and hygral expansion are important in clothing manufacture. The present paper is concerned with the measurement and experimental study of seam balance, breaking elongation and bending properties of seams. The aim is to evaluate quantitatively the consumption of sewing thread and the relationship between the degree of fabric overfeed during sewing and the curvature of the seam in the garment. Balanced seams have much higher breaking elongation and more symmetrical bending properties than unbalanced seam structures. A natural curvature and curling couple result from fabric overfeed during sewing. The value of the curvature is time‐dependent because of fabric viscoelastic effect and also depends on the level of fabric overfeed, the tensile and longitudinal compressive module of the component fabrics and the structure of the seamed composite. The natural curvature of the seam may be derived quantitatively from the relative lengths of overfeed fabrics using a modified theory for a bimetallic themostatic strip.

The Hygral Expansion of Surfactant- treated Wool at Various Temperatures

It is shown that there is a trend towards a lower maximum hygral expansion in surfactant-treated lightweight worsted fabrics as the testing temperature increases. It is also shown that the moisture regain at which the maximum hygral expansion occurs in these fabrics decreases with increase in surfactant uptake and increase in temperature.

FABRIC MECHANICAL AND PHYSICAL PROPERTIES RELEVANT TO CLOTHING MANUFACTURE —

The mechanical properties of fabric longitudinal extension and compression, shear and bending have an important influence on the performance of fabrics during tailoring and also on the performance of garments during use. Fabrics are overfed or underfed in tailoring during the sewing operations in such a way that longitudinal compression and extension are allowed in the fabric plane in order to produce the three‐dimensional shape or fullness of the garment. Fabric buckling or puckering at the seams should not occur, or if it does, should be removed during subsequent steam pressing operations. An experiment is described to measure the maximum limit of overfeeding that is possible during seaming without the subsequent formation of seam puckers. The relationships are studied between the maximum degree of overfeed, the bias angle between the feed direction and the fabric warp or weft, fibre type and fabric mechanical properties, especially fabric formability defined as the product of fabric bending rigidity and fabric longitudinal compressibility. When fabrics are extended or compressed longitudinally at a bias angle to the warp or weft direction during seaming in order to produce garment fullness, the warp and weft threads are rotated relative to each other in such a way that a local shear deformation is applied to the fabric adjacent to the seam‐line. Measurements are reported of the variations in the local shear angle along the shoulder seam‐line of a men's jacket and the measured values are related to the high degree of overfeed required in the bias direction in this area of the garment. Finally, hygral expansion measurements for wool fabrics and yarns unravelled from the fabrics are measured and compared for six different wool fabrics.

Relationship between set and bulk of package–dyed wool yarns

The loss of bulk in hand–knitting yarns as a result of package dyeing has been investigated. Simulated dyeing of packages, prepared with and without axial compression, has revealed a correlation between the bulk of the relaxed dyed yarns and the permanent longitudinal set imparted to the yarns. The strain in the yarn in the wet package, and hence the longitudinal set, is related to the hygral expansion of the yarn and the strain imposed on the yarn during winding of the package. The role of axial compression of the package in determining loss of bulk is also considered. Finally it is shown that by adding reagents to the dyebath that inhibit the setting reaction, the loss of bulk can be markedly decreased, provided also that the yarns are fully relaxed after being dyed.

A Quick Test for Measuring Fabric Dimensional Stability

A test that takes less than one hour as opposed to the conventional one day test is proposed for measuring the relaxation shrinkage and hygral expansion of fabrics. There is no need for a controlled environment, the only equipment required being a household microwave oven and a scaled ruler. The test's simplicity makes it suitable for use in a commercial environment, especially for quality control during fabric finishing and garment making.

Using Milling to Control the Hygral Expansion of Piece-dyed Worsted Fabrics

(1988). Using Milling to Control the Hygral Expansion of Piece-dyed Worsted Fabrics. The Journal of The Textile Institute: Vol. 79, No. 3, pp. 511-516.

Hygral Expansion of Wool Yarns

(1986). Hygral Expansion of Wool Yarns. The Journal of The Textile Institute: Vol. 77, No. 2, pp. 146-150.

Hygral Expansion of Woven Wool Fabrics

An experimental study is reported of the hygral expansion behavior of a wide range of laboratory produced and some commercially produced wool woven outerwear fabrics. A fabric hygral expansion apparatus simultaneously measures changes in fabric length and fabric moisture regain which occur when the relative humidity of the ambient environment is altered. Fabric and yam hygral expansion curves are analyzed and discussed in terms of the following parameters: hygral expansion coefficient (slope of the initial linear part of the hygral expansion versus moisture regain curve), hygral expansion at 25% regain, and hygral expansion at 30% moisture regain. F bric hygral expansion behavior depends largely on the magnitude of the weave crimp. The effect of weave construction on the fabric hygral expansion is very small at high moisture regains; at low regains, plain-weave fabrics tend to show slightly higher expansion than the corresponding twill structures of similar crimp magnitude. The effect of fiber properties on hygral expansion behavior has been examined for a series of wool plain-weave fabrics produced from yams of the same linear density.

24—THE EFFECT OF FIBRE PROPERTIES AND WEAVE CRIMP ON THE HYGRAL EXPANSION OF WOVEN WOOL FABRICS

A study is reported in which 53 plain-weave and 55 twill-weave fabrics were produced under nominally identical conditions from different wool lots ranging greatly in fibre properties. The hygral expansion of these fabrics was measured and related to the various fibre properties and weave crimp. It was found that fabric geometry, as reflected in weave crimp, was the most important factor contributing to hygral expansion, higher weave crimp leading to higher hygral expansion. Weave crimp also increased with an increase in staple crimp, as did hygial expansion, the effect of staple crimp being largely due to its effect on weave crimp. Results obtained on the 108 all-wool fabrics and on six mohair fabrics produced under identical conditions to the all-wool fabrics indicated that weave crimp rather than fibre properties per se plays the main rôle in determining hygral expansion.

4—THE PREVENTION OF BUBBLING IN WOOL CHECK FABRICS

The underlying causes of ‘bubbling’ in check fabrics are examined for three groups of fabrics. One group consisted of tartans drawn from normal commercial production, the other two groups being checks specially woven from yarns having known characteristics. It is shown that bubbling can occur even in the absence of differential yarn shrinkage and hygral expansion. However, it can be prevented by increasing the shrinkage of the dark-coloured yarns to about 1.5% above that of the undyed yarns.

44—THE CONTRIBUTION OF THE BILATERAL STRUCTURE OF WOOL TO HYGRAL EXPANSION

Measurements are reported of the hygral expansion of yarns extracted from permanently set fabrics made from merino and Lincoln wools. For yarns having similar crimp, the hygral expansion of merino-wool yarn is much greater than that of Lincoln-wool yarn. The values in both cases agree with predictions based on single-fibre behaviour. It seems certain that this difference is caused by the presence of a consistent bilateral structure in merino wool, which is absent from Lincoln wool.

Variation of Woven Fabric Length and Thickness with Regain

A theory of the hygral expansion of simple woven fabrics is proposed, based on Olofsson's theory of woven fabric struc ture. Hygral expansion is seen as the result of the competing effects of yarn swelling, yarn compression, and yarn curvi linear length extension with regain. Early attempts by the author to reconcile theoretical predictions with experimental data showed that it was necessary to suppose a yarn curvilinear-length expansion with regain in excess of that expected from the straightforward contribution from the fiber longitudinal expansion with regain. Taking into account measured yarn curvilinear expansion, which was found to be of the order of 3-4% dry-to-wet, a fair qualitative agreement of theory and experiment is obtained for unset fabrics. There is disagreement in the case of set fabrics below normal regain, which could be attributed to separation of the cross yarns. The fabrics are set wet and, as the yarns dry out and are affected by hygral "contraction," they could separate.

The Modification of Wool by Certain Organic Sorbates

The pleat retention, load—extension behavior, bursting strength, hygral expansion, felting rate, abrasion resistance, wrinkle recovery, and bending length of fabrics treated with additives of the type described in Part I have been investigated. Those additives of the anionic detergent type which contain more than 50% alkyl chain per molecule bring about the least improvement in pleat retention and the greatest modification in the wrinkle recovery and extensional properties of the fabric, whereas those which are naphthalene sulfonic acid derivatives accelerate photochemical decomposition of the fabric. The treatments are fast to dry-cleaning and to water but not to alkali. All the additives examined decrease the hygral expansion and felting rate of the fabric and in crease its resistance to abrasion.