Cleaning process and pretreatment processes:
Not only does cotton fabric contain natural impurities, besides cellulose, it also includes warp sizing, impurities contaminated during processing from fiber to fabric, requiring processing in order to achieve Be fully qualified, prepare for the following processing. Furthermore, it requires pretreatment to significantly increase usage values by applying one or more complete processes.
singeing-2 Burning or Singeing is the machining process to burn the ends of the fibers on the surface of the fiber from the fabric to have a smooth flat surface. The fabric is passed through the brushes to build up the ends, then burns the ends by passing the fabric over the top of the gas flames by adjusting the machine speed and appropriate exposure conditions.
Depending on the type of sizing used on the warp yarn to strengthen the yarn prior to the weaving process, the fabric may be soaked so that the paste may hydrolyze in dilute acid and then be washed, or enzymes may used to break these membranes and wash away.
scouring-and-un-scouringCouring-and-un-scouring is a stage in pretreatment that is carried out on cotton to remove wax and cellulose-free impurities. In addition to the main component of about 80 -90 %% cellulose, the rest are the components: pectin glue and hemicellulose 4% – 6%, protein 0 -1,5%, fat, wax and fat 0,5% _ 1% , ash 1% -1.8% and the remainder is 6% – 8% water, these components are insoluble in water and encapsulated as a part of cellulose which limits the natural absorbency of cotton fibers that need to be removed. The fabric is boiled in an alkaline solution, the saponification reaction takes place between the alkali and these insoluble ingredients that help eliminate them, to get pure cellulose. This process also contributes to the removal of sizing on the warp, although previously, desizing has been done as a separate step.
In addition to the above impurity components, cotton yarn has the yellow color of natural color compounds. Bleaching is also a necessary stage after this cooking stage.
Bleaching is a chemical process that oxidizes natural color compounds in the cotton fiber composition, giving the cotton the necessary whiteness and eliminating the remaining traces of impurities from the cotton; The required level of bleaching is determined by the required whiteness of the post-dyeing processes of the process. In addition, the absorbency of cotton fibers is also resolved to facilitate the subsequent processing stage. Bleaching is usually done by the role of oxidizing agents, such as sodium hypochlorite or hydrogen peroxide. If the fabric is dyed in a dark color, low-level bleaching is possible, but if a high whiteness is required, an optical brightener or Optical Brightener white dye needs to be used. white.
the-picture-shows-the-thread-structure-of-the-unmercerized-and-mercerized-fabric-equivalent-1 Polishing is a process that helps cotton fabrics achieve a high gloss due to the light reflection effect of the fiber cellulose. In concentrated cool caustic soda solution, the cellulose fiber expands to its diameter, the cross section of the fiber changes from a flat or folded corner to a round shape. The yarn results in enhanced gloss, toughness as well as later dye absorption. The fabric is treated with glossiness in the tensile state and is washed caustic soda after the reaction, the shrinkage is also recovered at this stage, so it is sometimes called the process of alkali contraction. The polishing process can be performed directly on a rustic cloth or after being bleached.
After the above processes, cotton fibers can now easily for the dyeing process. That is, the fabrication process makes the fabric as colorful as possible. The dyed fabric is capable of absorbing and reflecting certain wavelengths in the white light spectrum to produce colors. This selective absorption or reflection capacity depends on the specific molecular structure of the dyes.
The dyeing process generally varies according to the nature of the dye and the bond between the dyestuff and the fiber. The group of dyes with high durability, bright colors, common for cotton such as: reactive dyes, reconstituted … Other dyes have lower durability, limited freshness like direct dyes , luu sulfur… .. Each type will require different dyeing process and auxiliaries. Depending on the demand or the cost of processing … people choose the appropriate process accordingly.
hand-silk-screened-printed-fabricIn is another form of dyeing. Here, the color is processed onto fabric with a designated pattern, or can be called local dyeing.
There are many different printing techniques, as well as printing with different dyes. Based on the reaction of the dyes and fibers, appropriate printing technologies will be applied.