Effect of cross-sectional shape on the behaviour of cationic dyeable poly(ethylene terephthalate) fibresby S. K. Koc, S. Duzyer, R. Berger, A. S. Hockenberger

Textile Research Journal


Polymers and Plastics / Chemical Engineering (miscellaneous)


Original article

Effect of cross-sectional shape on the behaviour of cationic dyeable poly(ethylene terephthalate) fibres

Serpil Koral Koc1, Sebnem Duzyer1, Ru¨diger Berger2 and Asli Sengonul Hockenberger1


The effects of cross-sectional shape on the properties of cationic dyeable poly(ethylene terephthalate) fibres were investigated. Three different cross sections, namely tetra channel, snowflake and hollow, were used. Tensile test results showed that the hollow cross section has the highest breaking strength, while the snowflake has the lowest. In terms of thermal properties, no significant difference was observed. However, some differences in their morphology and surface topography were seen. According to birefringence studies, the hollow cross section has the highest overall orientation, while tetra has the lowest. In addition to this, hollow cross section gives the highest roughness value.

Keywords cationic dyeable poly(ethylene terephthalate), cross-sectional shape, mechanical properties, surface properties, scanning force microscopy

Polyester fibre is difficult to dye because of its high crystallinity, marked hydrophobicity, and lack of chemically active groups. Cationic dyeable poly(ethylene terephthalate) (CDPET) fibres have been developed to overcome this problem. They are produced by using varying amounts of sodium salt of dimethyl ester of 5-sulfoisophthalic acid as a comonomer in their structure. The anionic nature of this comonomer makes the

CDPET fibres dyeable with basic and cationic dyes at boiling temperatures, which makes it possible to combine them with wool, silk or other natural fibres. The addition of such comonomers also alters mechanical and thermal properties of the CDPET fibres. The level of this alteration is proportional to the amount of the comonomers in the structure. CDPET fibres have a wide range of application in industry, especially where physical properties are not primarily concerned such as apparel, home textiles, toys, accessories, etc.1–4

Regular melt-spun fibres have circular sections due to the round orifices of the spinneret. However, by using different spinneret profiles it is possible to produce fibres with different cross-sectional shapes. Crosssectional shapes of the fibres have a great influence on the surface and mechanical properties such as lustre, friction, moisture regain, bulk, crease recovery, flexural rigidity, abrasion resistance, pilling, dyeing, resiliency, tenacity, covering power, hand or feel. Thus, changing cross section affects both the production parameters and the appearance of the final product. Different cross sections give different properties to the fibres.

Owing to the internal air voids running parallel to the fibre axis, hollow fibres offer good resiliency, loftiness, heat retention, lightweight, cleaning and separation of various liquids and gases, property of capillary rising, and higher moisture absorption and adsorption. They find use in insulation, high-loft non-woven materials 1Uludag University, Faculty of Engineering and Architecture, Textile

Engineering Department, Gorukle-Bursa, Turkey 2Max Planck Institute for Polymer Research, Mainz, Germany

Corresponding author:

Dr Serpil Koral Koc, Uludag University, Faculty of Engineering and

Architecture, Textile Engineering Department, 16059 Gorukle-Bursa,


Email: skoral@uludag.edu.tr

Textile Research Journal 82(13) 1355–1362 ! The Author(s) 2012

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DOI: 10.1177/0040517512439916 trj.sagepub.com at UNIV OF CONNECTICUT on May 24, 2015trj.sagepub.comDownloaded from and composites, carpets, sleeping bags, and as membranes in artificial kidneys, reverse osmosis, and ultrafiltration. Also, from a commercial standpoint, cost savings can be achieved by using hollow fibres since, compared with solid fibres of the same outer diameter, hollow fibres require less polymer.

Multilobal cross sections such as the snowflake and tetra channel offer unique optical properties, such as the ability to hide dirt, and find use in carpet fibre technology. Since light rays are broken up by the lobes, multilobal fibres do not have a high lustre.

The multilobal structure increases the total surface area and gives better covering properties and drape.

This increased surface area also affects dye take up of the fibre. Moreover, the grooved surface provides single liquid transport along its length, therefore they have applications as sports garments.5–18

Much research has been carried out on the effect of fibre cross section on the yarn and fabric properties.9,19–21 However, less research has been carried out on the effect of cross section on the fibre behaviour.

Changing the fibre cross section changes the surface area of the fibre resulting different solidification behaviour. This causes different morphology in the fibre.

In this paper CDPET fibres with hollow, snowflake and tetra channel cross sections were characterized by their mechanical properties, thermal properties, surface characteristics and their fine structures. Investigations were performed by means of tensile tests, scanning electron microscopy (SEM), scanning force microscopy (SFM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and birefringence studies. The data obtained from this study may be helpful in understanding the characteristics of CDPET fibres with different cross sections and to predict the parameters on the production line.

Experimental details

In this study commercially available, fully drawn,

CDPET fibres with three different cross sections (tetra channel, snowflake and hollow) were used. All of the fibres were produced with the same production parameters. Some of the production parameters are given in

Table 1, and the fibre counts are given in Table 2.

Tensile properties of the fibres were measured by an

Instron Universal Testing Machine (Model No. 4301) with a gauge length of 50mm and a crosshead speed of 50mm/min in the Laboratories of Uludag University,