DEVELOPMENT OF HALOCHROMIC FABRICS BASED ON NATURAL FIBERS FOR ACID-BASE DETECTION

This research work aimed to develop halochromic fabrics based on natural fibers for acid-base detection. Phenolphthalein (PP) and p-nitrophenol (p-NP) were mixed and used as the mixed halochromic dye to provide a wide range of pH detection. The pH transition range of p-NP is 5.4-7.5, at which its solution appears colorless below pH 5.4 and yellow above pH 7.5. On the other hand, PP has a pH transition range of 8.3-10.0, at which its solution appears colorless below pH 8.3 and pink above pH 10.0. The mixed halochromic dye was covalently immobilized on cotton fabrics via a phenol-formaldehyde-based reaction. Several reaction variables affecting the color change of the halochromic fabrics including the molar ratio of PP and p-NP, the concentration of the mixed PP and p-NP solution, the reaction temperature, and the reaction time were studied so as to find an optimum reaction condition for covalently immobilizing the mixed halochromic dye on the cotton fabric. The reaction conditions that provided the clear color change of the halochromic fabrics were that the concentration of the mixed halochromic dye was equal to 1 % w/v (acetone), the molar ratio of PP to p-NP was 1 to 3, the reaction temperature was 100 °C, and the reaction time was 4 h. Additionally, the halochromic properties of the developed halochromic fabrics such as pH transition range, color reversibility, and halochromic dye leaching were also investigated. The results of the halochromic dye leaching and color reversibility of the developed halochromic fabrics could reflect the reusability property of the developed halochromic fabrics.