56—THE WRINKLING BEHAVIOUR OF WOOL FABRICS: THE EFFECT OF THE STRUCTURE OF FORMALDEHYDE CONDENSATION POLYMERS ON THE STABILIZATION OF ANNEALED WOOL

An investigation is reported of the use of formaldehyde condensation polymers of aromatic amines, heterocyclic amines, and phenols to stabilize the improved wrinkle-recovery of annealed wool. These polymers were formed in situ during the annealing process.

The most effective polymer networks were those obtained from the reaction of formaldehyde with multifunctional compounds such as (i) 2,4,6-triaminopyrimidine, (ii) 2,6-diaminopyridine, (iii) 3,5-diamino-1,2,4-triazole, (iv) 1,3,5-trihydroxybenzene, (v) 1,3-dihydroxybenzene, and (vi) 2,4,6-triamino-s-triazine.     

31—THE WRINKLING BEHAVIOUR OF WOOL FABRICS: THE EFFECT OF ANNEALING PARAMETERS

An investigation is described in which conditions suitable for the rapid ‘ageing’ or ‘annealing’ of wool fabrics were assessed by measurement of the resultant wrinkle-recovery properties. Maximum annealing is shown to be obtained when the fabric is heated at 15% regain (the time taken depending on the temperature of heating) and then slowly cooled. The annealing mechanism is believed to involve molecular rearrangements via labile hydrogen bonds to give a lower energy network. Wetting out of the sample changes this arrangement and results in a lower recovery on subsequent wrinkling.     

10—THE WRINKLING BEHAVIOUR OF WOOL FABRICS: THE EFFECT OF ANNEALING AND CROSS-LINKING

An investigation is described in which various polyfunctional compounds were applied to wool in attempts to stabilize the temporary improvements in wrinkle-recovery brought about by ‘annealing’. Several reactive systems involving formaldehyde were found to produce the desired permanently improved wrinkle-recovery.     

43—THE WRINKLING BEHAVIOUR OF WOOL FABRICS: THE EFFECT OF METAL SALTS ON DRY AND WET WRINKLE-RECOVERY

The dry and wet wrinkle-recovery of wool fabrics can be improved by reaction with metal salts in the anionic or cationic form. Small amounts of substantive metals are shown to have produced significant improvements in wet wrinkle-recovery, but, with the exception of chromium, only relatively large amounts of metals such as mercury, uranium, tungsten, and molybdenum improved dry wrinkle-recovery.

The mechanism by which mercuric acetate improves dry wrinkling does not appear to involve sulphur, despite extensive reaction between mercury salts and sulphur-containing residues, such as cysteine, cystine, and cysteic acid.     

42—THE STRETCH AND RECOVERY BEHAVIOUR OF ELASTOMERIC YARNS

The elastic properties of several polyurethane yarns and a natural-rubber filament have been measured. Part 1 of the paper deals with the behaviour of the materials in the condition in which they were supplied. In Part 2, the properties of the materials after thermal treatments at various temperatures within the range 20–220°C are presented and discussed.

Thermal treatment is shown to have a pronounced effect on the stress-strain behaviour of the synthetic yarns, measured relative to their set dimensions, and on the retractive stress at a given extension. The elastic recoveries of the yarns are improved, their breaking extensions increased, and their strengths slightly decreased after thermal treatment.

Relative to the synthetic yarns, thermal treatment has only a small effect on the elastic properties of rubber.     

20—WOOL–POLYMER SYSTEMS: THE EFFECT OF ELASTOMERS ON THE WRINKLE-RECOVERY OF WOOL

The wrinkle-recovery of a wool fabric may be improved by coating the fibres with elastomeric polymers. It is shown that, of those polymers investigated, the most effective were found to be polyether–hexamethylene di-isocyanate polyurethanes and cross-linked silicones. Comparison of the wrinkling behaviour of fabrics and individual fibres indicates that the observed improvement in wrinkle-recovery was due to a coupling of the elastic-recovery forces of the polymer with those of the individual fibres, Inter-fibre bonding is thought to have an adverse effect on the wrinkle-recovery.     

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.     

19—THE MEASUREMENT OF TORQUE IN CONTINUOUS-FILAMENT YARNS. PART II: THE EFFECT OF YARN TENSION

The yarn torque developed by the applied tension in the torsion-balance apparatus described in Part 1 of this series is calculated by using an expression derived in an earlier paper. Differences in shape of net-torque–twist curves are studied for nylon monofilaments and model plied yarns; these differences in shape are related to friction effects and to the mechanical properties of the constituent filaments. The torsional rigidity of the yarns is evaluated from the initial slope of the torque–twist curves for a series of nylon monofilaments; the torsional rigidity and torsional modulus are also calculated from the load–extension curve of a closely wound helical spring by employing the classical theory of elasticity.     

28—THE EFFECT OF STEAMING ON THE LONGITUDINAL STABILITY OF WOOL YARN

An account is given of an investigation of the effectiveness of steaming on the longitudinal stabilization of wool yarn. Specially prepared worsted yarns were used to study the effects of initial regain and of time and temperature of steaming.

Of the several different mechanisms proposed for the longitudinal stabilization of yarn by steaming, only permanent setting is demonstrated directly, and the effects of temperature, initial regain, and time of treatment are established. Two threshold values were observed below which no permanent setting took place—an Initial-regain threshold of 7–8% and a temperature threshold of about 88°C. It is considered possible that the threshold temperature is a function of the particular release treatment used and that it would increase with increasing severity of the conditions of release.

The contribution of permanent setting to the over-all longitudinal stabilization was apparently small, but this may have been a result of using a rather severe release treatment.     

73—WOOL–POLYMER SYSTEMS : THE EFFECT OF THE INTERNAL DEPOSITION OF POLYMERS ON THE WRINKLE-RECOVERY OF WOOL

Experiments are described in which various polymers were polymerized inside wool fibres and their effects on the wrinkle-recovery of treated fabrics evaluated. Linear polymers were found to markedly decrease the wrinkle-recovery, and cross-linked vinyl and acrylic polymers produced only small improvements.

Formaldehyde condensation polymers formed in and on the wool in aqueous solution produced significant improvements, but much larger improvements were obtained when these polymers were formed under annealing conditions.     

38—THE EFFECT OF SPINNING CONDITIONS ON THE TENSILE PROPERTIES OF CORE-SPUN YARNS

A critical assessment of the merits of core-spinning by means of comparisons of the strength and extension of core-spun yarns with all-staple-fibre yarns forms the basis of this paper. Core-spinning was done by introducing the filament under tension into the drafted strand as the latter entered the front rollers of the ring-frame. A 20-den (2.2-tex) nylon monofilament was used as core, and three types of staple-fibre covering were investigated. The effects of twist, pre-tension, and feeding arrangements on the geometrical disposition and tensile properties of the yarns were examined. Improvements in strength are, in general, realized at low twists by the incorporation of the filament and by further constraining it to occupy the core. The contribution of the components to the yarn strength and the process of breaking were also subjected to a detailed study. The studies reported provide an interesting insight into the extent of cohesion developed between the fibres during the straining of the yarn and its influence on the process of breaking and ultimately on yarn extension.     

43—THE AIR-FLOW DIAMETER OF WOOL TOPS: THE EFFECT OF COEFFICIENT OF VARIATION

Differences between the results obtained for the fineness of wool tops measured by air-flow and projection-microscope methods can arise because the coefficient of variation of the measured top is different from that of the tops used to calibrate the air-flow meter. The validity of some assumptions implicit in the air-flow calibration is examined and a correction table for precise use of the air-flow meter calculated. The corrections range from ?2% at 16 μm to zero at 36μm.     

24—THE BENDING BEHAVIOUR OF PLAIN-WEAVE FABRICS WOVEN FROM SPUN YARNS

The bending behaviour of square plain-weave fabrics spun and woven from nineteen different fibres, each in a range of cover factors, has been studied. It is shown how this behaviour is determined by the mechanical properties of the fibre and the frictional and geometrical restraints within and between yams in the fabric. The effects on these restraints of cover factor and of relaxation in wet finishing and in heat-setting are examined. Factors affecting cloth stiffness are summarized, and it is shown that two quantities, an elastic component and a frictional component, are required to specify the bending behaviour with reasonable completeness.     

32—A SIMPLIFIED METHOD OF DETERMINING THE LENGTH AND FINENESS CHARACTERISTICS OF FIBRES IN JUTE SLIVERS AND YARNS

The normal method of studying the length and fineness characteristics of fibres in jute slivers and yarns involves classifying the fibres in a sample into a suitable number of length groups and determination of the frequency and linear density of fibres in all the length groups. The simplified method described in this paper requires evaluation of the cumulative frequency and linear density of fibres of one particular length only, and is hence less time-consuming than the normal method. Graphical relations and tables are provided with the simplified method to reduce the computation time, which is considerable with the normal method. The data obtained on several yarn samples of different qualities by the normal method of testing are used to show the agreement between the results arrived at by the two methods. A procedure for carrying out the tests required in the simplified method is also suggested.     

35—AN AIR-FLOW PROCEDURE FOR DETERMINING THE FINENESS OF RAW WOOL

A satisfactory procedure has been found for determining with an air-flow meter the mean fineness of greasy wool sampled from bales by pressure-coring. A wool-model Shirley Analyser is used to remove dirt and vegetable matter from the washed wool cores. The Analyser also intimately mixes the wool fibres of a sample, which substantially improves the precision of the air-flow measurement. The effect of the Analyser on the measured value of fineness is investigated, and possible methods of calibration of the air-flow meter for use on wool cores are considered. A series of measurements on greasy-wool cores by both air-flow and projection-microscope methods is used as a basis for the suggested procedure. The precision of measurement is evaluated, and a particular calibration method is recommended. The mean fineness of a sample of greasy wool in core form can be found with a precision of ± 0 5 μm.     

42—THE ESTIMATION OF CROSS-LINKS IN WOOL FROM THE EXTENT OF SWELLING IN FORMIC ACID

An account is given of the application of a gravimetric method for measuring the extent of swelling of wool in formic acid to a series of wool samples containing decreasing amounts of randomly distributed disulphide bonds. In accordance with the Flory-Rehner equation, a linear relation was observed between disulphide content and V 5/3, where V is the volume of dry wool expressed as a fraction of the volume of swollen wool. This calibration curve was then used in conjunction with swelling data to assess the number of cross-links introduced on the treatment of wool with formaldehyde and other bifunctional reagents. The method is particularly useful for ranking in order relatively high levels of cross-linking.     

72—THE EFFECT OF PROCESSING OILS ON THE SHRINKAGE OF HERCOSETT-TREATED KNITTED WOOL FABRIC

An account is given of an investigation of the shrinkage on washing of knitted wool fabrics produced from chlorine–Hercosett-treated tops to which a range of additives had been applied. It is shown that the range of effects of the various additives is very wide and that about half of those tested had no effect on the shrinkage rate. Four increased the shrinkage rate by a factor of more than ten and thus would be clearly unsuitable for industrial use. Additives of all the types studied (mineral-oil-based, synthetic lubricants, and softeners) were capable of causing a marked increase in the shrinkage rate, but other additives of each general type had no significant effect, so that it was not possible to make a clear distinction on the basis of a general classification. It is suggested that one component, or group of components, in the additives had affected the Hercosett resin, but no firm conclusions could be drawn about the exact mechanisms.     

37—THE HISTOLOGICAL STRUCTURE OF WOOL FIBRES AND THEIR PLASTICITY

The relation between the creep behaviour (plasticity) and the proportion of the orthocortical material (expressed as ortho/para ratio) in five lambs' wools has been examined by means of electron-microscope techniques, in conjunction with thin sectioning. No correlation was found between the amount of orthocortical material, on the one hand, and either plasticity or helical conformation (the latter estimated by other workers) on the other. These results are supported by the observation of the structural differences, greater than hitherto thought, within both cortical segments (as indicated by the considerable variation in metal absorption—‘staining’), and it is believed that these have the primary effect on the plasticity. The cells of intermediate morphological appearance and reactivity (between those of the two bilateral segments and referred to as as meso-type) have a secondary influence in this respect.