Formaldehyde-free sugarcane-derived aldehydes to co-crosslink silk fabrics with diols for improving wet resilience and minimizing pollutions from wet processing of silk

Abstract

We developed formaldehyde-free sugarcane-derived aldehydes for silk to minimize pollutions from wet processing of silk fibers via substantial improvement in wet resilience of silk fabrics. Developing effective and non-toxic crosslinkers from plant products promotes sustainability of silk textiles. The poor wet resiliency only allows silk materials for dry cleaning, which has considerable environmental and health concerns. Most silk treatments, based on non-biobased chemicals, resulted in lowered mechanical properties and unacceptable color changes to the materials. Here we applied a softener-free and plant-based co-crosslinking system using sugarcane-derived-aldehydes and diols, which ensured high degrees of crosslinkages durable to repeated home launderings for pollution alleviation. Diols increased degrees of crosslinkings and converted hemiacetal to acetal crosslinkages, indicated by 1H NMR, via reaction with aldehydes groups, thus substantially improving shape retention of silk, e.g., improvement of wet wrinkle recovery degree from 180˚ to 248˚, and smoothness after repeated launderings from Steps 1.9–3.3. The lowered crosslinking temperature provided by sugarcane-derived-aldehydes minimized the damage to silk protein fibers and enhanced the retention of dry tear strength, wet tear strength, dry breaking strength, wet breaking strength, and whiteness to 80 %, 95 %, 86 %, 120 %, and 91 %, respectively. The co-crosslinking in this work, 30–60 °C lower than common non-biobased crosslinking methods with dimethyloldihydroxyethyleneurea and butanetetracarboxylic acid, provides similar wet resilience but higher retention of mechanical properties, whiteness, and higher wet strength. The co-crosslinking system in this work provided silk fibers with high quality and free of concerns from health and the environment.