Saminathan Ratnapandian

Summary

The above sections broadly outline the experiments carried out in this thesis. The specifications of the fabrics, dyes and chemicals used have been listed. A logically progressive framework of pad-dyeing experimental procedures has been laid out. Standard tests that were followed for evaluating the desirable fastness properties have been introduced. Procedures and equipment less widely employed were described in detail. Further details of the experiments will be discussed and the results analysed in the following chapters.

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Chapter 3

Padding and its optimisation

1. Introduction

This chapter details the investigations into the padding of natural mordant dyes derived from Acacia catechu (Thar) and Acacia nilotica (Caspian). The optimisation and evaluation methods are described. FTIR investigations regarding the bonds originally present in the dyes, mordants and cotton and the changes they underwent on combining to form the final dyed fabric are discussed. AAS procedures used to determine the metal content in the dyed fabric are given. The results obtained are discussed.

2. Equipment

   1. Padding mangle

Padding was carried out on a laboratory-scale two-bowl padding mangle, with horizontal squeeze-roller geometry, manufactured by Werner-Mathis. The nip between the rollers created the trough for pad liquor. Pressure, used to adjust the wet pick up, was controlled using compressed air. The fabric was guided vertically through the pad liquor and between the squeeze rollers, shown in Figure 3.1.
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Guide rollers
Pad liquor
Fabric

Squeeze rolls

Figure 3.1 Padding mangle geometry

2. Steamer

A laboratory-scale steamer (Figure 3.2) manufactured by Werner Mathis was employed for the steaming of samples. The equipment featured a fully-contained steam atmosphere with temperature and humidity controls. The period of sample exposure was controlled using an integrated timer. In addition, this equipment could be used as a
curing chamber by excluding steam. Samples were mounted on pins set in a frame and then introduced into the steaming chamber.

Figure 3.2 Laboratory scale steamer

3. Dryer

An Electrolux TS 560 forced-air-flow convection drying chamber was used to dry the samples. The samples were dried at either 40^○C or 65^○C in a tension-free state. Uniform airflow minimised shade differences between the face and back of the fabric.

4. 
   Attenuated Total Reflectance Fourier Transform Infra-Red (ATR-FTIR) A Perkin Elmer Spectrum 400 with a universal single bounce diamond ATR attachment (Figure 3.3) and associated software (Spectrum version 6.3.5) was used to analyse dyes, mordants, dye-mordant complexes, undyed fabric and dyed fabrics. Other than the fabrics, all samples were examined as dry powders.
   

Figure 3.3 Perkin Elmer Spectrum 400 FTIR

5. Atomic Absorption Spectrometer (AAS)

A Varian-AA-280-FS AAS (Figure 3.4) was used to quantify the metal content in different fabric samples. An acetylene flame in air was employed to excite the metal atoms. Iron and copper were detected at wavelengths of 248.5 nm and 324.7 nm respectively.

Figure 3.4 Varian AA 280 FS (AAS)

3.