Principle of mercerization process
一、The purpose of mercerization
Luster and brightness are improved after mercerization;
adsorption capacity, chemical reaction ability, improve the dye color;
shrinkage, dimensional stability, fabric flatness improved;
strength, elongation and other mechanical properties have been changed.
1. After bleaching:
Mercerizing effect is good, waste alkali is relatively clean, but the whiteness is poor, easy to stain, suitable for color cloth, especially heavy fabric.
2. Before bleaching:
Good whiteness, poor luster, easy to be damaged during bleaching, suitable for bleached cloth and printed cloth.
3. After dyeing:
Suitable for easy to bruise or not easy to evenly dyed varieties (after mercerization, the fabric feels harder, dyeing faster) In order to improve the surface effect and dyeing fastness of the fabric when dyeing dark, as well as some varieties that require high gloss, after dyeing mercerization can also be used.
4. Dyed before half mercerization, dyed after conventional mercerization:
In order to improve the adsorption and chemical reactivity of dyes.
三、Evaluation of mercerization effect
One of the main indexes to measure the appearance effect of mercerized fabric.It can be measured by variable Angle photometric method and polarized light method, but there is no unified ideal measurement method, and visual evaluation is used at present.
2. The morphology of fiber was observed by microscopic section
3. Adsorption performance:
1). Barium value method:
it is a common method to test mercerization effect. Large barium value means good mercerization effect. Barium value of cotton cloth =100, barium value > 150 means full mercerization, generally 135 ~ 150.
2). Iodine absorption.
3). Iodine stain and staining test methods:
The samples with different barium values (100-160) were treated with a certain concentration of iodine solution H or direct blue 2B dye solution to make color cards, and then the iodine stain and dyeing depth of unknown samples were compared with the color cards to quantitatively evaluate the mercerized barium value.
4. Dimensional stability:
Adopt mechanical shrinkage method or impregnation shrinkage method to measure the change of fabric length before and after treatment, and calculate shrinkage rate by formula. Generally, the shrinkage rate in warp direction is usually greater than that in weft direction, but some varieties with higher warp density produce negative shrinkage rate (door width increases).
Source: Dye&finishing Encyclopedia
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