26—THE KINETICS OF WATER-VAPOUR SORPTION IN WOOL: PART I: AN IMPROVED SORPTION VIBROSCOPE

An improved design of the sorption vibroscope previously developed for wool–water-sorption studies is described. In particular, the improved equipment incorporates a novel vibration-detection transducer and a linear differential transformer, which allows simultaneous measurement of longitudinal swelling with moisture uptake.

The accuracy of the sorption vibroscope for studies of the sorption kinetics of the wool-water system is assessed.     

Increase in Regain during Vacuum-steaming

The importance of lateral pressure in the tension and bending behaviour of yarns and fabrics is discussed. To determine the lateral pressure between fibres, a specific model is considered, that of a filament helically wound around a cylinder. The equations governing the equilibrium of the filament are derived and both account for the helical geometry of the filament and allow for the variation of the helix angle. The filament is assumed to possess both bending and torsional rigidities. The special case of constant helix angle yields expressions for the lateral-force intensity as a function of the tension in the filament, bending and torsional rigidities, bending curvature, and torsion. Specific examples are considered to show the relative contributions of the bending and torsional rigidities to the lateral force     

26—THE RÔLE OF WATER IN THE SETTING OF WOOL: A STUDY OF SETTING AT TEMPERATURES ABOVE 100°C: PART I: DEGREE OF SET

Permanent setting of wool fabrics can be achieved by setting in steam autoclaves at temperatures above 100°C. An account is given in this paper of experiments performed on a laboratory scale and on full-scale equipment in which fabrics were set in rolls. One of the main problems in this kind of process is to ensure an even setting throughout the roll. Temperature and moisture regain are rate-determining factors in steam-setting, so a study was made of the temperature and moisture-regain changes in the different parts of the roll during heating up and subsequent steaming. The degree of set also depends on the steaming time and acidity of the cloth, but these factors are more easily controlled.

The investigation shows that the steam-setting of wool-containing fabrics imparts a very high degree of permanent set and that reproducible and even setting may be achieved, provided that all treatment variables are kept under close control. Of all the parameters studied, the moisture regain seems to be the most important.     

30—HEAT AND MOISTURE EXCHANGE IN WOOL BEDS: EQUILIBRIUM THEORY IN THE HYGROSCOPIC RANGE

Cassie's theory of propagation of heat and moisture changes in beds of wool fibres is re-examined by means of the method of characteristics. Substantial differences result in the predictions of the theory by treating the coefficients of the pertinent differential equations as functions of the dependent variables rather than as constants.     

The Effect of Environment on the Flexural Rigidity of Woven Fabrics

The concept of fabric engineering—the design of fabrics with predetermined physical properties—is used in relation to the structure of woven fabrics, and it is shown from theoretical considerations, with the aid of computer analysis, that a large discrepancy exists between the number of weaves of comparatively small size that can be woven and the number that are actually produced. Experimental results obtained on fabrics woven in accordance with a particular plan indicate that the weave has a very marked effect on both tearing strength and stiffness. The results further suggest that weave modification can provide a means of obtaining very accurate control of the two properties investigated and of their possible combinations, and the same may well be true of other physical properties of fabrics.     

28—THE SPECIFIC HEAT OF WOOL CONTAINING AN ADDITIVE AND THE HEAT OF FUSION OF THE ABSORBED WATER

Specific-heat values are presented, in the temperature range from ?70 to 100°C, for a modified wool at various water contents. The modification was analogous to a dyeing process and involved the uptake of 14% of an additive by the wool. As for untreated wool, an endothermic peak resulting from the fusion of absorbed water was found in the range from ?30 to 0°C. The absorbed water exhibits a sub-division into freezable and non-freezable fractions. Heats of fusion of freezable absorbed water are given and compared with corresponding results for untreated wool. The integral heat of fusion at saturation water content is much less for treated than for untreated wool, as is the amount of freezable water. It appears that the treatment causes the exclusion of a considerable quantity of loosely held water. This is in accord with the concept, derived from Flory–Huggins solution theory, that one effect of the additive is to swell the wool fibres and thereby cause a greater resistance to further swelling at a given water content.     

27—THE RôLE OF WATER IN THE SETTING OF WOOL: A STUDY OF SETTING AT TEMPERATURES ABOVE 100°C: PART II: FABRIC PROPERTIES

An account is given of a study of the changes in fabric properties caused by setting with steam in autoclaves. Dimensional stability, shear angles, thickness, and breaking strength were measured, and the influence of variations in setting conditions, such as humidity, temperature, time, pH, and mechanical pressure, was investigated. The controls necessary for eliminating end-to-end effects in whole pieces are discussed.