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The electromagnetic spectrum is comprised of several non-visible rays, of which the visible region for human eye is approximately between 380 to 750 wavelengths.
Optical brighteners are synthetic chemicals that make fabrics appear to glow in the presence of ultraviolet light. These optical Brightening Agents reacts with the yellowish color in the fabric and increases the reflection of Blue light radiation.
Surfaces with contact angles against water of 90 degrees or higher are usually considered hydrophobic surfaces and are good water-repellent surfaces?
3 factors affecting brightening of fabric are?
pH of the bath, temperature of the bath and time required for the process
Distilled water is the same as deionized water?
People line dried their white laundry in their yards as sunlight and oxygen are natural bleaching agents?
Surfactant acts as a wetting agent by lowering surface tension?
Bleaching with H202 and bleaching with Hypochlorite are the ONLY two ways to bleach cotton?
A surfactant is a surface tension reducing agent?
___________________ causes water to beat up on surfaces (glass, fabric, leaf) which slows wetting of the surface and inhibits the cleaning process.
Four major difference between soaps and detergent?
-Soap is produced from natural ingredients where are detergent is from a synthetic source.
-Soap requires a lot of water to be removed from a fabric whereas detergent requires less to be cleaned out of fabric.
-Soap cannot clean fabric in hard water where as detergent can.
-Soaps are biodegradable where as not all detergents are.
Name six bleach agents. Write their chemical formula and common name?
-Hydrogen peroxide H2O2
-Sodium hypochlorite NaOCI (Bleach)
-Sodium chlorite NaCIO2 (Chlorous acid)
-Calcium hypochlorite Ca(CIO)2
-Sodium Borate Na2[B4O5(OH)4] 8H2O (Borax)
-Sodium Bicarbonate NaHCO3 (Baking Soda)
Explain how detergent cleans textile surfaces?
Surfactant molecules contain a hydrophilic end and a hydrophobic end. These molecules aggregate in water forming micelles. Micelles consist of hydrophobic interior regions, where hydrophobic tails gather around soil and dirt till it is loosed from the substrate.
Define surface tension?
A tension of the surface film of a liquid caused by the attraction of the particle in the surface layer by the bulk of the liquid, which tends to minimize surface area.
Write four significances of the scoring process?
-Removes all foreign matter from fabric such as oils, natural grease, waxes, starch, soil, tint or color additive.
-Make the fabric more hydrophilic
-Increases the absorbency and cleans the fabric
-Renders fabric suitable for the next process of bleaching, dyeing, printing and finishing
Write four difference between distilled water and DI water?
-Distilled water has been removed of its impurity's where as deionized water has been demineralized
-Distilled water is less pure than deionized. Deionized water is considered highly pure
-Distilled water is produced by distillation (water is boiled and then condensed) where as deionized is produced by using ion exchange resins that remove ions from water.
-Distilled is drinkable but has no nutritional value where as deionized is corrosive.
What are the four major objectives of pretreatment?
-Convert fabric from hydrophobic to hydrophilic state
-Remove dust, dirt, waxes, coating, lint, oil etc. from fabric
-Achieve the degrees of desired whiteness or color or finish
Is surfactant a detergent?
Yes it is, surfactant will space apart.
How does the surfactant help reduce the surface tension of water?
Surfactant is also known as a wetting agent that lowers the surface tension of a liquid allowing for easier spreading.
The reason for the reduction in the surface tension when surfactant molecule adsorb at the water surface is that the surfactant molecules replace some of the water molecules in the surface and the forces of attraction between surfactant and water molecules are less than those between two water molecules.
Why is reducing the surface tension of water in wet chemical process of textiles crucial?
Water (which is universal solvent) is primarily used in wet chemical processing in the textile industry. However, a surfactant has to be added during any wet chemical processing to reduce the surface tension of water. This helps decrease the wet processing time which may otherwise require 50 min without. When surfactant is presence takes about 15- 20 min. Saving time in wet processing means saving energy and production cost.
Write four examples of desizing agents-
-Hydrochloric acid HCL (muriatic acid)
-Sodium hydroxide NaOH (caustic soda)
-Sodium carbonate Na2CO3 (soda ash)
-Sulfuric acid H2SO4 (hydrogen sulfate)
State all the important parameters for bleaching with hydrogen peroxide bleach-
-Nature and quality of goods
-Water hardness and other impurity's
-Concentration of alkali when bleaching with H2O2
What is textile fiber morphology?
Fiber morphology is a study of the arrangement of polymer chains inside a fiber. Giving an indication of its possible performance.
Why is it important to understand the textile fiber morphology in wet chemical processing of textiles?
If we know about the morphology we can understand the chemical structure to know what chemicals are safe to use on the fabric to meet the intended results.
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