Design of pH Responsive Textile as a Sensor Material for Acid Rain.

Viktor Stojkoski,Mateja Kert

doi:10.3390/polym12102251

Abstract

The chemical composition of rainwater can serve as an indicator of the excess of acidifying air pollutants. The pH value of rainwater in the presence of sulphur dioxide and nitrogen oxides, the precursors of acid rain, falls below pH 5.6, which is the limit value for acid rain. In this research, the tailoring of halochromic textile was examined for the design of a functional textile that can serve as a sensor and inform the wearer about the presence of pollutants in the air by means of an immediate colour change. For this purpose, a polyamide 6 fabric was dyed with the pH-sensitive Bromocresol green dye, which causes a colour change below pH 3.6 (yellow) and above pH 5.4 (blue). In addition, the dyed polyamide 6 fabric was treated with a water and oil repellent finish. Colour and colour change before and after immersion of unfinished and finished dyed samples in buffer solutions with different pH values were evaluated spectrophotometrically using the CIELAB colour space. The colour fastness to rubbing, washing, and light, and the water and oil repellency of the dyed fabrics were determined according to valid SIST EN ISO standards. The results showed that the unfinished dyed polyamide 6 fabric undergoes a reversible colour change faster and more clearly than the finished dyed polyamide 6 fabric. The dyed polyamide 6 fabric had good colour fastness to rubbing and domestic and commercial laundering, while the colour fastness to light was poor. In addition, the dyed polyamide 6 fabric was pH-sensitive, despite dye degradation under xenon light, regardless of whether it was finished.

Highlights

During the second half of the previous century, gradual but major changes in rainwater and groundwater quality occurred as a result of an excess of environmentally harmful atmospheric emissions associated with rainwater acidification
polyamide 6 (PA6) fabric was successfully dyed with pH-sensitive Bromocresol green (BCG) dye using a conventional exhaust dyeing process
The dyed PA6 fabric changed colour in the pH range between 3 and 5, indicating that the selected dye applied to the PA6 fabric could serve as an indicator of a change in the pH of rainwater

Summary

Introduction

During the second half of the previous century, gradual but major changes in rainwater and groundwater quality occurred as a result of an excess of environmentally harmful atmospheric emissions associated with rainwater acidification. After extensive and comprehensive studies to gain a substantial understanding of how acid deposition alters ecosystems, it was found that air pollution is closely related to rainwater quality. The pH of rainwater drops and becomes more acidic due to atmospheric emissions of air pollutants, almost exclusively caused by destructive human activities, in particular the burning of fossil fuels, industrial and agricultural activities, and car exhaust fumes. The acid rain phenomenon remains topical, despite extensive research and continuous monitoring of acid deposition and air pollution being carried out for at least half a century, following several cross-border agreements, protocols, and policies [1]. Emissions have decreased significantly in Western European countries, North America, and some others, Southwest China and Southeast Asia countries are among the worst affected areas [2]

Objectives

Methods

Results

Conclusion