Arnold M. Sookne

The Rate of Drying of Fabrics

It is frequently stated that one fabric dries faster than another, usually with reference to house hold conditions of drying on a line. However, the data of this report show that by and large all fabrics dry at the same rate under these conditions (rate being expressed as weight of water evaporating per unit area per unit time), but that the time of drying depends upon the amount of water originally held, so that some fabrics dry sooner than others. The main portion of the drying time shows this constant rate of drying, although there is a final period which is short compared to the main drying period, during which the rate of drying decreases. The water-holding capacity of a fabric depends upon how the fabric is supported (vertically or horizontally) and upon the mechanical treatment given to remove water. For simple drainage in the vertical position, the water-holding capacity of small samples is more closely correlated with fabric thickness than with fabric weight. The kind of fiber—i.e., wool or cotton-and large differ ences in moisture affinity, as shown with Vinyon, also affect the water-holding capacity. How ever, these factors have almost no effect on rate of drying, since this is controlled by the resistance of air layers to the passage of heat. The thickness of these air layers is sufficient under ordinary conditions to smooth-over the fabric surface irregularities, even when these are rather large, as in rib knits or in cellular or waffle fabrics. Increasing the hairiness of the surface in order to give more area for evaporation is sometimes proposed as a means of increasing the drying rate, but results show that this is without effect except for extremely high, open naps, for which the effect is the opposite-the thickness of the layers of still air is increased and the drying retarded.

The Improvement of Luster of Cotton: Part I: Measurement of Reflectance Characteristics Related to Luster

Practical details are given for using two different instruments for measurement of the reflectance aspects of the luster of cotton yarns. Typical reflectance curves for cotton yarns differing in luster because of mercerization are discussed and compared with the reflectance and visual properties of fabrics made from these yarns. The physical measurements on yarns are much better correlated with what the eye sees in the yarns or in the fabrics than are the meas urements on these particular fabrics. This indicates that the study of yarns by these methods is useful both for yarn and fabric. In winding the yarns for examination, a cover factor of more than 40 is found to be needed to eliminate the effect of the backing. Other points of tech nique, such as tension in winding, humidity, and the size of apertures in the optical system, produce small variations which, however, need to be cared for by standardization of technique when small differences in luster are being examined.

A Simple Quantitative Test for the Felting of Wool Top

A simple, rapid procedure for evaluating the feltability of wool in the form of top is pre sented. The method consists of subjecting a sliver to controlled wet mechanical action, and measuring its change in length. It yields results which correlate well with the shrinkage during laundering of garments made from the top; the method thus provides a useful tool for con trolling the application of some chemical shrink-resistant treatments in the mill. In addition, this method shows promise of usefulness as a tool for investigating the nature of felting.

The Felting of Shrink-Resistant Wool as Related to Some Properties of the Single Fiber

the work of extension, and a and b are constants. This equation was found to hold for untreated wool tops in a wide variety of reagents. The extent of shrinkage of wool which has been subjected to a chemical antifelting treatment would also be expected to be influenced by the nature of the felting medium, depending upon the extent to which the wool has been modified in processing. Much of the study of fiber properties in relation to the feltability of shrinkresistant wool has heretofore emphasized the importance of the surface of the fiber. Thus, it has been clearly established that chemical treatments for conferring shrink-resistance to wool which involve the use of active chlorine result in a decrease in the direc-

Electrophoretic Studies of Wool

A new investigation of the electrophoretic properties of wool shows that phthalate ion, used in buffers in earlier work, exhibits a specific ion effect, and shifts the isolectric point to lower pH values. In acetate buffers, the isoelectric point of wool scales and cortical cells was found to be at pH 4.5. Samples of ground or powdered wool show an isoelectric point at pH 4.2. Much of the confusion which exists concerning the location of the isoelectric point has arisen from the assumption that the isoionic and isoclectric points are identical. The significance of both of these points in wool processing is discussed.

Crease Recovery of Fabrics Part I: Some Tensile Properties of Wool, Vicara, and Rayon Fibers and Their Relationship to Fabric Crease Recovery

A study has been made of some single fiber properties of wool, rayon, and Vicara zein fibers at various relative humidities, and the crease recoveries of fabrics made from the same fibers have been measured under identical conditions. In general, the wool and Vicara are similar in many load-extension properties. A fair correlation was found between fabric crease recovery on the one hand, and fiber tensile and work recovery on the other hand at low and normal humidities. At high humidity, and particularly with wet fabrics, however, this relationship no longer holds. A general correlation also seems to exist between fabric crease recovery and work returned by stretched fibers during retraction from extension to 4%.

Some Felting Properties of Wools of Different Geographical Origins

It is generally believed that wools may differ considerably in the rate or extent to which they will felt in a fulling mill or stocks. This property is often a basis for the selection of wools for blends, particularly in the manufacture of felts, where the feltability is obviously an important economic consideration. Not only are such differences in feltability widely recognized but measurements supporting their exist-

An Appraisal of Shrink-Resistant Treatments for Wool

A review is presented of the mechanisms by which wool shrinks, and of the several classes of treatment available for making shrink-resistant wool. Some of the virtues and deficiencies of the better known classes of shrink-resistant processes are listed. The competitive position of shrink-resistant wool is examined in a number of end-use items. It is concluded that a number of low cost, adequate shrink-resistant processes are cur rently available, and that wool requires shrink resistance in order to compete with man- made fibers in end uses requiring ease-of-care.

The Felting in Laundering of Wool Blends

The fibers used were as follows: wool, 60’s grade; viscose, 2 ;-in. staple, 3 denier; nylon, 3 z-in. staple, 3 denier; Vicara, 4-in. staple, 3 denier. Blends were made by gilling the slivers in an intersecting gill box, using at least 4 passes per blend. The nominal proportions sought were 75%, 50%, 25%, and 10% of the non-wool component in each case. The resulting blends were sampled at several places along the final sliver, and analyses were made in the appropriate case for nylon or for viscose by solution in 70% H2S04 [1]. The wool content of Vicara blends was estimated by solution in 5% KOH

The Relation of Cation Exchange to the Acidic Properties of Cotton

It has long been known that cellulosic materials exhibit acidic properties which influence many of their physical and chemical characteristics. Thus, the acidic groups of the fibre bind small amounts of ash which have a considerable effect on the electrical conductivity of cotton fibres, and on the viscosities of solutions of some cellulose derivatives. The ash may also affect the dyeing properties of the fibre, and may be related to the application of finishing agents. Since the ash of washed cotton consists prin cipally of cations held by acidic groups, the problems of measuring the ash and the number of acidic groups on the fibre are intimately related. In addition, if some of the acidic groups of purified cot ton are a part of the cellulose molecule, such as end-groups, the number of these groups may be a measure of its chain length, which is of primary importance in determining the strength and other physical characteristics of the fibre. As part of a general program for the investigation of the acidic and basic properties of textile fibres, a study has been made of the manner in which hydrochloric acid is bound by cotton, and of the dependence of the amount of acid bound on the concentration of the aoid solution in contact with the fibre. The effect on this dependence of different amounts of an added neutral salt, potas sium chloride, has also been studied. A comparison of the acid bound with the cationic ash (the total content of the cations of inorganic bases) as determined by an electrodialysis method leads to the conclusion that the maximum acid-binding capacity is equivalent to the cationic ash, and that therefore the acid bound at any acidity depends upon the ash. A comparison of the results for dewaxed cotton with those for de pectinized cotton shows that most of the acidic groups of cotton are contributed by the pectic substance. Cotton freed of pectic substance retains a small number of acidic groups. Although other possibilities exist, it seems likely that these are an integral part of the cellulose molecule, such as an end-group. If this is actually the case, the results show that the cotton cellulose ~rnolecule has an equ.ivatent weight of about 100,000 which corresponds to a minimum chain length of about 600 glucose residues.