Study On The Influence Of Washing On Fabric Whiteness And Assessment Method For Detergency

Laundry detergents have gained great attention as its efficiency, economy, and security overthe past twenty years. However, there is no laundry detergents able to keep white clothes washafter wash. Therefore, the technology of wash and care of white clothes need to be furtherresearched. And one of the primary work is completed the assessment method of detergency.According to the requirement of the project to the P&G Company, this paper studies on theinfluence of various factors on the whiteness changes of washed fabrics, and then make somesuggestions to improve the assessment method for detergency.Firstly, the relation of fiber-type, fabric structure, finished fabric, detergent, water quality,dimension and whiteness of washed fabric are examined under no dirt wash condition with orwithout soap flakes. The dimension and whiteness of cotton fabric change heavily after washingbecause of the shrinkage of cotton fabric. And the whiteness changes are linked to the fabricstructure. Interlock cotton fabric own a good surface coverage and change smaller in whitenessafter washing. Fluorescent whitening fabrics present unstable CIE whiteness value after washing.Fabrics treated by water repellent agent or softness agent also show unstable whiteness in waterwashing condition. While it is opposite in the soap washing condition, which get smallerwhiteness change. No UV testing condition can not completely exclude the influence offluorescent whitening agent on the fabric whiteness. Tap water cause unstable fabric whitenessand lower whiteness change. In a word, fabrics used to assess the detergency of one detergentshould be polyester fabrics or cotton fabrics of good surface coverage, and these standardsamples have to be only half bleached and well cleaned before experiment. Besise, the waterused to experiment should be clearly specified and exclude tap water. Further advice,above-mentioned regulations can be included in the planning assessment method of the P&GCompany. Secondly, the effect of typical dirt on the detergency of fabrics is determined by whitenesschange, brightness change and hydrophily change. The dirt is as follows: dye, mixture ofrapeseed-oil and sauce, waste engine-oil, clay and black tea. Fabric structure, fiber-type, fabricsurface energy and properties of dirt are closely linked to the contamination situation of fabric. Afluffy structure, such as weft-knitted fabric, is good for dirt to adsorb and diffuse into the fabric,and lead to heavily contamination of knitted fabric. The stronger affinity between fiber and dirt,the more obviously contamination of the fabric, for example, direct dye (or black tea) to cottonfabric, or clay to polyester fabric. But small diffusion depth of the dirt can weaken suchconnection, disperse dye for example. Lower surface energy can prevent the fabric from thecontamination of clay, while can also result to serious contamination of waste engine-oil. Claywith deep color and small size make heavy contamination. In addition, brightness value andwhiteness value can be used to evaluate the contamination of fabric, and brightness valueprovide more objective evaluation for light color or blue hue dirt.Lastly, based on the front work, the application of assistant detergents is determined bystandard fabrics and typical dirt. The assessment method shows good reproducibility. In oilywashing bath, P.D that is block polymer achieves good detergency on polyester fabric. Inwashing bath containing black tea or clay including Hangzhou yellow clay, India red clay orArizona dust, all detergent auxiliaries can improve the detergency both of cotton fabric and ofpolyester fabric. P.A that is anionic polymer does the best on cotton fabric, while the P.D and P.Edo the best on polyester fabric. However, all detergent auxiliaries cannot improve the detergencyof cotton fabric in dyes or waste engine-oil washing bath, as well as the polyester fabric in dyeswashing bath.