The Effect of Cyclic Loading on the Wicking Performance of Nylon 6.6 Yarns and Woven Fabrics Used for Outdoor Performance Clothingby A. B. Nyoni, D. Brook

Textile Research Journal

About

Year
2010
DOI
10.1177/0040517508094093
Subject
Polymers and Plastics / Chemical Engineering (miscellaneous)

Text

Textile Research Journal Article

Textile Research Journal Vol 80(8): 720–725 DOI: 10.1177/0040517508094093

Figures 1–5 appear in color online: http://trj.sagepub.com © The Author(s), 2010. Reprints and permissions: http://www.sagepub.co.uk/journalsPermissions.nav

The Effect of Cyclic Loading on the Wicking Performance of

Nylon 6.6 Yarns and Woven Fabrics Used for Outdoor

Performance Clothing

A. B. Nyoni1 and D. Brook

Performance Clothing Research Group, School of

Design, University of Leeds, Leeds, United Kingdom

The mechanical properties of textile fibers, i.e., the responses of the fibers to applied forces and deformations are probably their most important properties technically, contributing both to their behavior in processing and to the properties of the final product [1]. In use, textiles are subject to complex, variable, and probably unknown intensive dynamic loads in individual temporary cycles [1, 2], which keep changing the shape of a garment. However, due to the elasticity and viscoelasticity [2, 3] of the fibers, these changes are temporary unless the stresses are too great or last too long resulting in permanent or irreversible deformation. Most often, such deformations occur during pressing and leaning motions [4], and on those parts of garments that are exposed to the greatest stresses, i.e., the fabric covering the elbows, knees, backside, etc.[2, 5, 6] in both knitted and woven fabrics.

The link between human performance and clothing and textile products in a variety of situations, variable environmental conditions, and the development of a number of new fibers [7–12] and yarn manufacturing processes has enhanced the need for studies to yield more information about textiles that could be used in engineering fabrics which can provide not only comfort but enhance human performance.

Research [13] has shown that 3–5 % added moisture is ample to stimulate sensations of discomfort, therefore, free movement of water within fibers in a vapour phase or through the pores in a liquid phase to the fabric surface is essential if perspiration discomfort, causing fabric wetness with resulting freezing in winter or clamminess [14, 15] in summer, is to be prevented. Kisilak [2] simulated the flexing during knee or elbow movements by cyclic loading fabrics with a maximum force of 100 N and a minimum force of 0.6 N every 15 minutes. His objective was to establish the effects that different strains have on yarn and fabric wicking performance so as to facilitate the engineering of fabrics with specific wicking capabilities.1

Abstract The effects of short interval dynamic loading and unloading on yarn and fabric wicking performance were evaluated at different cyclic load ranges using the conventional extensionrecovery method on a modified Instron Tensile

Tester. This was based on the principle that during use, the constituent yarns in a fabric are continuously stressed and relaxed as the garment shape changes. Results showed that the straining forces generated between the filaments of the yarns resulted in spasmodic pumping of the liquid which was dependent on the yarn and fabric construction, contact between the yarns, volume of liquid in yarns, and duration of the force applied.

Key words cyclic loading, dynamic loading, wicking, spasmodic 1 Corresponding author: e-mail: babsnyoni_dr@yahoo.co.uk at East Carolina University on April 21, 2015trj.sagepub.comDownloaded from

The Effect of Cyclic Loading on the Wicking Performance A. B. Nyoni and D. Brook 721 TRJ

Experimental

Development of the apparatus for measuring the effect of cyclic loading on yarn and fabric wicking

The Instron Table Model 1026 [16] (see Figure 1a), a versatile and accurate tool for evaluating the stress-strain properties of materials utilizing electronic load weighing, recording, and logic control principles, was modified by substituting the bottom grip with an attachment consisting of a lower fixed holder with a grooved yarn clamp (1) that dipped into the liquid reservoir (3) fixed to a nut and bolt (4) to enable simple, precise, and repeatable placement of all samples. The upper clamp was fixed to the traversing head A. For these experiments, a 0–500 g (0–5 N) tension cell 2512-107 intended primarily for fiber, light yarn, and fine wire measurements was used and the testing load ranges used are shown in Figures 2–5.

The basic principle of this apparatus was to measure the effect of yarn and fabric displacement on the wicking rate as the samples were subjected to different ranges of cyclic loads. The test results were presented on a strip chartrecorder (8), which was driven synchronously at a wide variety of speed ratios with respect to the crosshead, thus enabling measurements of sample extension to be made with a large choice of magnification factors. The machine was connected to a computer (9) for direct reading and recording of test results with graphical output.

To change from straight-forward tensile testing to automatic cyclic operation, the crosshead A was programed to move between preset load points to facilitate extension, relaxation, and recovery during a test. The two toggle switches marked C maximum and D minimum (cycle stop) provided a selection whereby the crosshead was caused either to reverse at the cycling point or to stop. The movement of the crosshead between C and D was defined as one cycle, and the extension of the yarn as the crosshead moved from D to C as the maximum displacement.

Preliminary yarn tests

To simulate strains likely to be encountered during use and to determine their effect on the wicking performance of yarns, preliminary tests of 20 cycles were carried out at 0– 500 mg, 0–300 mg, 0–150 mg, 150–500 mg, and 300–500 mg load ranges to obtain different degrees of yarn displacement. All the five load ranges used were found suitable for testing textured yarns as it was relatively easy to set the reversing position to correspond to the set load value and to wick the yarns. However, the use of load ranges 0–500 mg, 0–150 mg, and 0–300 mg proved difficult with flat continuous filament yarns due to separation of the filaments at zero tensioning, and the wicking results obtained were not repeatable. Therefore, these methods were deemed unsatisfactory and the results obtained have not been quoted in this work.