Saminathan Ratnapandian

Research methodology

1. Introduction

This chapter deals with the research methodology for investigating the pad-dyeing of natural dyes. It discusses the design of experiments based on which suitable materials and methods were selected. Evaluation techniques and procedures that were employed for determining either the effect of experimental variables or the desirable properties of dyed fabrics are described.

The research focused on two aspects of sustainability, namely 1) reducing the quantity of chemicals and dyes to obtain a desired shade; and 2) replacing harmful chemicals with relatively benign chemicals. A synergistic approach that benefits from the developments in technology as well as the renewable characteristic of natural dyes was adopted for the investigations.

2. Design of experiments

The feasibility of padding natural dyes in a sustainable manner was the prime objective of this study. Mordant and vat were the two classes of dyes selected for evaluation so as to obtain a broad perspective. The experimental design for the two classes is outlined in Figure 2.1. Exhaust dyeing recipes provided by the dye supplier were used to produce benchmark samples for the selected dyes. In the case of the vat dye, the performance of the natural dye was compared with its chemically equivalent synthetic counterpart.

Padding of natural dyes was approached in the following steps:

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  determine optimum process sequence
  
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  identify ideal padding recipe
  
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  analyse the bonds formed during dyeing and develop a theory that explains the dyeing mechanism
  
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  develop an improved padding process and identify additional benefits
  
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  enhance current colouration methods by using chemicals with lower environmental impact.