فصلنامه علوم و فناوری نساجی
سال دوم شماره 3 (پاییز 1391)

Camouflage، in visual and near infrared region (NIR)، is one of the important topics developed for military purposes. In order to impart camouflage in NIR region، the reflectance profile of the object and its surrounding should be matched. So، the reflectance profile of a selected dye in NIR region is of great importance. If the fabrics are dyed with various pigments and then examined for their power of imparting camouflage in NIR region there would be much waste of human effort and cost to use a reflectance spectrophotometer. To challenge these problems، a new method is developed and reported in this study. For this purpose، a UV-Vis absorbance spectrophotometer is employed and the transmittance profiles of the selected dyes are compared with a known NIR camouflage imparting dye. The novel dye has been studied and evaluated for its potentials as camouflage substance. Since C. I. Vat Blue 13 is one of the camouflage dyes and because structural properties of the dye such as the transmittance curve or the reflectance curve are influenced by its structure، it was concluded that C. I. Vat Blue 6 dye can be used as a camouflage dye in NIR region by similarity of its transmittance curve with that of C. I. Vat Blue 13.

The mechanical properties of polypropylene/multi-walled carbon nanotube composite fibers were investigated. Polypropylene and multi-walled carbon nanotube were melt blended using a twin screw extruder and fibers were produced by a melt spinning apparatus with different draw ratios. Optical microscopy images from cross-section of the fibers showed agglomeration on carbon nanotubes in some parts of the matrix. The Young’s modulus and breaking stress of the drawn composite fibers with draw ratios of 4 were in the given order 2% and 3. 6% higher than that of pure polypropylene fibers which were produced in similar conditions، respectively. With increasing the rotational speed of the screw in melt blending stage، the Young’s modulus and breaking stress and molecular orientation of the drawn composite fibers were increased. The obtained experimental results for Young’s modulus and yield stress of the composite fibers were compared with the amounts calculated from Halphin-Tsai، Krenchel and Pukanszky-Szazdi equations. The differences between the experimental and calculated results were probably due to the agglomeration of carbon nanotubes in the matrix and interaction of the polymer and carbon nanotubes.

In recent years، applications of conductive fabric in textile products are widely developed especially in electronic and smart clothing. Considering the importance of conductive fabric design based on the desired electrical properties، in this study the electromechanical model using finite element method to predict the electrical resistance of the conductive fabric is introduced. The electromechanical model is able to determine the effect of parameters such as fabric contact angle with electrodes، the fabric density، the fabric dimension، metal filament properties and the normal force on the fabric in relation to its electrical resistance. To verify the model performance and to predict the fabric electrical resistance، model predictions were compared with the experimental data. The results from this study are indications of good performance of the proposed electromechanical model parameters listed in the above effective parameters on electrical resistance of the conductive fabric.

The dyeing of wool fibres with Madder dyes and aluminum sulfate mordents has been investigated. To optimize the dyeing process for achieving a favorable method، first the Taguchi''s experiments design and then single factor experiments were used. The selected parameters in the dyeing of wool fibres were: temperature، time، L: G، dyeing bath type، pH and auxiliary agents. In these experiments the selection criterion of optimized dyeing method was to achieve high color strength، appropriate leveling and fastness properties which were studied by spectrophotometry and visual examinations. The results showed that the optimum conditions for dyeing are as follows: temperature: boiling، time: 2 h، pH: 4-5، clay bath and L: G=30:1.

UV/H2O2 process is used for removing colorants in wastewater treatment units in textile factories. In this research، decolorization of disperse dyes (an azo dye، Disperse Red 1 (DR1) and an anthraquinone dye، Disperse Blue 56 (DB56) by UV/H2O2 method was investigated. Efficiency and performance of this method were evaluated in different pH، hydrogen peroxide and colorant concentration and distance from UV lamp. According to the results، using 34 mmol/L H2O2 in 100 mg/L of each of the dye solutions of DR1 and DB56، the decolorizations yields were 58 and 26%، respectively. By lowering the pH of dye solutions it was found that dye removal was especially higher for DR1. Moreover، decolorization rate was significantly improved by the distance between the dye solutions and UV lamp especially for DR1 with azo structure. The experimental results revealed that the photo-oxidation technique is almost an effective method for removal of disperses dyes.

The binder materials and the yarn effects were studied in relation to fancy boucle yarns'' physical properties namely، yarn effect height، number of yarn effects، and yarn shrinkage and the mechanical properties of weft knitted fabrics، namely the coefficient of static and dynamic frictions and abrasion resistance. Three kinds of ring spun yarns، i. e. 100% viscose، 100% acrylic، and 100% cotton were used as yarn effects and binder yarn and five different kinds of yarns were produced. The core part of all samples was 100% viscose yarn. To knit 1×1 rib fabrics، a flat weft knitting machine with gauge 6 was used. The obtained results showed that the lowest static and dynamic coefficients of friction belonged to samples knitted with cotton effect yarn and viscose binder yarn. The highest value of abrasion resistance in 500، 1500، and 3000 abrasion cycles was observed in a sample with acrylic yarn as yarn effect and binder parts. The sample with 100% viscose yarns showed the lowest value of yarn effect height. Analysis of variance in 95% confidence level was used to evaluate the statistical difference between the results.