Effect Of Dye-VD On The Color Change Of Fabric During Home Laundry

Dye-VD is a kind of blue-violet direct dye added to the liquid detergent,the whitening effect is significant after the dye dyed clothing moderately.However in the common washing conditions,in order to clean the serious dirt completely,the consumers would directly apply the liquid detergent containing the dye-VD to the collar,cuffs and other dirty points of the clothing and stay for some time,then wash the clothes with washing machine.The results showed that after washing in this manner,shadow will appear on the area especially the white or light-colored clothing parts which liquid detergent directly applied to,it can affect the color of the fabric whiteness and the appearance.Currently,the reason of this phenomenon during washing is still not conclusive.Therefore,assess the effect in the home laundry,analysis the coloring mechanism will provide guidance while the dye-VD used as the washing additives in the liquid detergent reasonably.Based on consumer feedback information and market conditions,we choose 66 kind of fabrics,covered all important consumer relevant fiber types,such as cotton,polyester,cotton/polyester,nylon,rayon,silk,and fabric types,such as plain weave,twill,stain,single jersey,double jersey,pique etc.Each fabric is set two types,unprewashed fabric and prewashed fabric.Four kinds of detergents are used.The fabrics are pretreated by the detergents for 5 minutes or 48 hours before the washing,and then measure the color change of the pretreated area with a colorimeter.The final data should compare the pre-wash and post-wash to each other to create a Delta E result.To further understand the cause of the color change of fabrics before and after pretreatment and washing,we analyze from dye-VD and fluorescent whitening agent.The results show that prewash process could cause certain effect on fabric color change.After pretreatment,the percentage of the fabrics that the color change of unwashed type is greater than prewashed type reaches 80%.80%of polyester and nylon fabrics have a small color change less than 2,80%of cotton,rayon and silk fabrics have a more obvious color change greater than 2;Increased pretreatment time also increase the color change,fabrics pretreated for 48 hours have obvious color changes than 5 minutes.Dye-VD contained in detergents is an important factor that affects the color change of the fabrics.The molecular formula structure of dye-VD determined that the dye has a strong bonding force with the cellulose fibers.The reflectance spectrum curves of pre-wash and post-wash as well as before and after pretreatment show that fluorescent whitening is also a factor affects the fabric color change.Fluorescent whitening agent adsorb on fibers during washing,to improve the whiteness of fabric and affect the color of the fabric.