Volume 11, Issue 2

The pore morphology of textile filter structures is important for numerous technical applications. It determines the functional properties of surgical textiles, such as the effective barrier function and wearing comfort. Surgical and protective textiles must fulfil both of these contradictory functions. To date, basic research has not been successful, either theoretically or experimentally, in describing the complex correlation between the 3D pore structure of woven textiles and their barrier properties while simultaneously remaining permeable. In an attempt to clarify this issue, high density multi-filament woven textiles were categorised according to their geometry, pore morphology, permeability and retention properties by virtual modelling of their 3D pore morphology. Differentiation was made between mesostructures (pores between the yarns) and microstructures (pores within the yarn itself). In this process it was possible to identify the influence of weaving parameters on the pore morphology and determine their resulting functional properties. Various new testing methods were developed and successfully implemented to characterise and evaluate the barrier properties. The experiments show that by selecting specific yarns and weave constructions, the permeability and woven structure can be positively influenced and adapted to fulfil a wide range of requirements. A major finding is that the permeability and retention properties of the weave can be independently controlled by choosing suitable machine parameters. Specifically, by varying the shed closing time a clear shift in the pore size distribution to smaller pore diameters can be achieved without altering the air permeability. A correlation between the construction and processing parameters and the 3D pore morphology of the woven textile was ascertained. The relation between the properties of a weave and the machine and construction parameters is extremely complex due to their interaction.

An attempt has been made to optimise the engineering attributes of a plain weave fabric according to certain requirements. A simplified algorithm was used to solve fabric geometrical model equations, and relationships were obtained between useful fabric parameters such as thread spacing and crimp, fabric cover and crimp, warp and weft cover. Such relationships help in guiding the direction for moderating fabric parameters. The full potential of the Peirce fabric geometrical model for plain weave has been exploited by soft computing. The interrelationships between different fabric parameters for jammed structures, non-jammed structures and special cases in which the cross-threads are straight were obtained using a suitable algorithm. It is hoped that the fabric designer will benefit from the flexibility in choosing fabric parameters for achieving any end use with the desired fabric properties.

The maximum weavability limit is predicted by extending Peirce's geometrical model for non-plain weaves for circular and racetrack cross-sections by soft computing. This information is helpful to weavers in that attempts to weave impossible constructions can be avoided, thus saving time and money. It also helps in anticipating difficulties in weaving and in taking the necessary steps in warp preparation. The relationship between the cover factors in the warp and weft directions is demonstrated for circular and racetrack cross-sections for plain, twill, basket and satin weave. Non-plain weave fabric affords further flexibility for increasing fabric mass and fabric cover. As such, they enlarge the scope of the fabric designer.

Principal objective of this paper is a description of a special testing device (VibTex). This device allows testing of textile materials (threads, samples of fabrics, etc.) during cyclical stress at a high frequency. Control of the VibTex allows harmonic and non-harmonic elongation of the textile samples. Results of the tests with harmonic elongation can be used for calculations of the dynamic characteristics of textile samples. In the final part of the paper, values of the dynamic modulus and loss angles are determined at frequencies of 10 Hz and 100 Hz for various yarns.

It has long been recognised that heat transfer through clothing is a main constraint to the comfort properties of clothing. The present work relates to the development of a mathematical model for the prediction of heat transmission through multilayer clothing with air in between two successive layers of fabric in a multilayered clothing assembly. A mathematical model was developed using general equations of heat transfer through porous media and was validated using experimental results. A series of multilayered fabric assemblies were created with different combinations of fabric layers and air gaps of different thicknesses. The predicted total thermal resistance of these fabric assemblies was obtained from the model and the values were compared with experimental results. The total thermal resistance of these fabric assemblies were measured using a guarded hot plate for validating the model. Fairly good correlations between the predicted and experimental values of thermal resistance were observed.

Textile discharge printing is the most versatile and important of the methods used for introducing design to textile fabrics. In discharge styles, the pattern is produced by the chemical destruction of the original dye in the printed areas. The discharging agents used can be oxidising or reducing agents, acids, alkalis and various salts. However, the most important methods of discharging are based formaldehyde sulphoxylates and thiourea dioxide. Recently, environmental and industrial safety concerns have increased the potential for the use of enzymes in textile processing to ensure eco-friendly production. Formaldehyde sulphoxylate (NaHSO2.CH2O.2H2O) is one of the most powerful discharging agents; however, it is quite toxic and produces formaldehyde, a known human carcinogen associated with nasal sinus cancer and nasopharyngeal cancer. In this work, a hazardous chemical has been replaced with eco-friendly horseradish peroxidase enzyme in textile discharge printing. Enzymatic discharge printing was carried out with a phenol oxidising enzyme system such that the reactive dye was selectively discharged from the cotton fabric in selected areas, creating a printed surface. The effects of enzyme concentration, pH of the printing paste, treatment time and the temperature of enzymatic treatment were studied. The optimum conditions for enzymatic discharge printing were found to be pH 8.5 at 70°C with a dye concentration of 80 g/L and 60 min as the treatment time.

The technical feasibility of using Aloe vera gel as a new thickener for printing polyester with disperse dyes was examined. The results indicate that the properties of the printed fabric samples (colour strength, K/S, overall fastness properties, handling and sharpness) were dependent on gel concentration, the type and concentration of additive (i.e. urea or citric acid), as well as the fixation conditions using the super-heated steam technique. The optimum conditions for printing polyester fibre with disperse dyes using Aloe vera gel as a thickener were as follows: 30 g/kg disperse dye, 50 g/kg urea, 15 g/kg citric acid, 500 g/kg Aloe vera thickener and 50% drying at 100°C for 3 min followed by steam fixation for 6 min at 180°C.

Comparative studies on the efficiency of anchor molecules for the finishing of cotton with chitosan are presented. Four different anchors were used: cyanuric chloride (CNC), butane-1,2,3,4-tetracarboxylic acid (BTCA), glycidyloxypropyltrimethoxysilane (GPTMS) and sodium hydroxydichlorotriazine (Na-HDCT). Two types of chitosan with different molecular weights were used. The type of anchor used for fixation of chitosan on cotton fabric had a distinct effect on the antimicrobial efficiency of chitosan. By using increasing the concentration of anchor chemicals, the ability of chitosan to inhibit the growth of bacteria increased. Using GPTMS as an anchor for chitosan improved the ion binding capacity for Cu2+-ions more than other anchors. The highest colour strength was achieved when using a low amount of anchors from the chlorotriazine system (up to K/S 3.3), whereas carboxylic or trialkoxysilane anchors at the same ratio of anchoring chemical to glucose units achieved comparatively low K/S values. The polyelectrolyte values of treated cotton fabric were also measured. SEM was used to investigate the surface morphology of the treated cotton fabric samples.