Properties of ultraviolet and water-repellent silk fabrics using extract pigment from coffee grounds by grinding

Abstract

Coffee grounds are by-products of coffee drinks, and are mostly discarded or used with low value. In this study, we compared the traditional water bath extraction method and the new room temperature grinding extraction method to extract coffee pigment from coffee grounds and investigated the influence of acid and alkali environments on the extraction of pigment, the particle size, and the absorbance of coffee pigment. We also studied the influence on the functional coloring of silk fabrics. The color intensity of colored fabrics, ultraviolet protection factor, water resistance, and air permeability were tested. The results show that, for an ethanol/water ratio of 4/6 (vol%) and a NaOH concentration of 5 g/L, the particle size of the coffee pigment solution obtained using the grinding extraction method was 255 nm, and the particle size distribution was narrow. The extraction efficiency for this method was better than that for the water bath extraction method and other acid–base (Na₂CO₃, C₆H₈O₇, and CH₃COOH) medium grinding extraction methods, and coffee pigment exhibited high absorbance. The color intensity of silk fabrics dyed using the grinding method was 8.96, which is 13.27% higher than that obtained using the traditional water bath extraction method. The ultraviolet protection factor was 400+ and the contact angle was 139.1°. Compared with conventional synthetic dyeing methods, coffee ground extraction not only minimizes environmental impact but also significantly improves textile functionality. This study provides a theoretical basis for the one-bath method for producing ultraviolet resistant, water-repellent, and multi-functional integrated coloring.