Bleaching with sodium hypochlorite: Interactions of temperature, time, pH and concentration with stain removal and fabric strength

Abstract

In response to recent concern for energy conservation while laundering at lowered temperatures, this study investigated stain removal and fabric degradation effects of sodium hypochlorite bleach on stained cotton fabrics. Blue and green reflectance readings were used to calculate both whiteness values and percentage of stain removal values, while tensile strength measurements were used to determine fabric degradation. An “acceptable bleach treatment” category was established, having a minimum of 75% whiteness and 90% of origi‐nal breaking strength. Temperature, bleach concentration, time and pH were investigated, with each factor except pH being significant. Low bleach concentration was more satisfactory than high concen‐tration, while cold and warm temperatures were more acceptable than very cold and hot temperatures. An overnight bleach soak treatment of up to 16 hr was not damaging if a cold temperature of 25 C was chosen. Selecting cold (room) temperatures for chlorine bleaching could provide energy savings for the consumer, textile mill or commercial laundry, while providing acceptable whiteness and fabric strength retention.

Cost optimization of sodium hypochlorite bleaching washing for denim by combining ensemble of surrogates with particle swarm optimization

“…From Figure 5, we can find that the influences derived from TEMP on all profiles are the most obvious, and this phenomenon is in accordance with the results achieved in the work of Simpson and Riggs. 6 The main reason of this phenomenon may be that relatively high temperature will promote the hydrolysis reaction of NaClO and produce more ClO- which has strong ability of oxidizing. On the contrary, the treatment time has the least contributions in most situation, which is owing to that the bleaching effects of sodium hypochlorite can last for a long time (up to 16 h or even more), and the most significant effect usually appears after 1 h or later.…”

“…On the contrary, the treatment time has the least contributions in most situation, which is owing to that the bleaching effects of sodium hypochlorite can last for a long time (up to 16 h or even more), and the most significant effect usually appears after 1 h or later. 6 However, in actual production, long treatment time is not permitted because of the low efficiency, thus TT has less contributions compared with the other two variables in the selected ranges. The production cost optimization was completed by PSO, which was coded in MATLAB2019a software.…”

“…[1][2][3] Over the past few decades, different washing techniques have been developed to create varied designs of denim garments, some normally used applications were summarized by Kan. 4 Among various washing techniques, the sodium hypochlorite bleaching washing, also named as chlorine bleaching, has been applied for a long time, and it still plays a dominant part in industrial production because of fine performances. Some related researches [4][5][6] had indicated the chlorine bleaching effect mainly depends on sodium hypochlorite quantity, temperature and treatment time. However, few previous works constructed a quantitative mapping model between input variables and washing effects, which results in that the trial-and-error method is still extensively conducted in the chlorine bleaching process for denim garment production, and may bring about a great waste of resources in some extent.…”