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Q1)What are the general purposes of textile coloration?

Color is one of the most significant factors in the appeal and marketability of textile products. Textile coloration is used to enhance the aesthetics and beautification.


Q2)Briefly describe how to complete an exhaust dyeing process?


Exhaust dyeing is a kind of batchwise dyeing. It dyes in rope form by using Overflow/Jet Dyeing Machine or dyes in open width form by using beam dyeing machine.


First, choose a dyeing machine based on the fabric dyeing form. We should remember the fabric wight before dyeing which is going to be dyed and then calculate dyestuff weight on weight of fabric weight in percentage. Also, we have to calculate the water amount based both the fabric and machine to get the liquor ratio.

In dyeing process, salt, soda ash and dyestuff are needed. Putting leveling agent or not is optional. Those chemicals help us to dye to color into the fabric and fix the color. We have to calculate the chemicals we used. After finished all the calculation, we can put fabric and all chemicals into the dye bath to start the dyeing.


During the dyeing process, we should control the pH of dyeing solution. And keep temperature about 60 degree and the dyeing time around 60 to 120 minutes to make sure the fabric can dye evenly.


Q3)Explain the meanings of the following terms: affinity, dye substantivity, compatibility of dye, dyeing exhaustion, liquor ratio, pick-up ratio, continuous pad dyeing, yarn package dyeing, surfactant, vat dyes.


Affinity :

It is a natural attraction. The tendency of chemical attraction or force between dye and textile that cause them to combine. Or we think it is the dye absorbing capacity of textile fibres, yarn, fabrics.


Dye substantivity :

The affinity of a dye for a given textile.


Compatibility of dye :

Dye have the similar properties and similar dyeing behavior, including tone-on-tone build-up properties, equal robustness to different dyeing conditions, and no blocking effect between them.

The compatible dyes with each other are ideal for use in color mixtures, since color is matched with3 dyes in usual.


Dyeing exhaustion :

It also can called batchwise dyeing. It is the dyeing process that textile absorbing dye in solution until reaches equilibrium and fixation is completed


.....[read full text]

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Chemicals required to regulate the dyeing process. A fixation agent or mordant might be required to improve the fastness of the dye on the fibre.


A pigment is a water insoluble colorant and has no affinity to the substrate to which is being colored. Pigment is held on the surface of a fabric by a binding agent. It widely applied in printing, more for blends. The fewer sustainability issues compared to dyes. The color strength is lower when more pigments are used and it is poor handle.


Q5)Describe the main features of reactive dye.


Reactive dye contains high wet fastness due to covalent bonding between fibers and dyes, easily dyed on fibers. The application is easy. The price of reactive dye is moderate and cost-effective. It has a wide range of shades and ecologically compatible dyeing behavior.

Reactive dye also has wide applications. Most for all cellulose goods and selective dyes can be applied on wool, silk and rayon.


However, reactive dye has low affinity to cellulose, therefore large amounts of salt are required to force the dye adsorption and diffusion. Addition of alkali is required to cause the dyes to react with the fibre.


Q6)Write down the names of the two most important chemicals used in the dyeing process of reactive dyes and specify their effects.


There are two important chemicals used in the dyeing process of reactive dyes which are electrol.....

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Reactive dyes react with cellos fibers requiring alkali condition to the carry out the fixation process. Therefore, alkali is added to excite the dye to link with the fibre with covalent bonding to it enhances wet fastness. For batchwise exhaustion, the dye bath pH range from 10.5 to 11. It contains Na2CO3, NaHCO or their combination.

The alkali selection relates to dyes and dyeing method. The fixation rate of dyes and the dyeing events can be controlled by the dosing rate of alkali.



Q8)Write down the pH range required for dyeing cotton with reactive dyeing.


The pH primarily influences the concentration of the cellusate anion (cellulose-O–) on the fibre, as well as the hydroxyl ion (-OH) concentration in the dyebath and on the fibre.


Generally increasing dyeing pH in the fixation stage can accelerate the reaction rate between dye and fibre. For batchwise dyeing method, the dyebath pH is recommended to be controlled ranging from 10.5 to 11. Even with the low reactivity dyes, a pH exceeding 11 is still not appropriate since an unduly high pH will enhance dye hydrolysis and reduce dyeing efficiency in terms of depth and fixation.


Q10)List all the available being machines and specify their application.


1)Padder :

The fabric is passed through a trough with dye solution to absorb dye. Then it is passed 2 heavy rollers which force the dye into the cloth and squeeze out the excess dye.


2.....

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Q11)Write down the names of available dyeing machines for dyeing each of the following textile materials:


a)elastic yarn

Hank Dyeing Machine


b)pure cotton knitted fabric

Padder

Package Dyeing Machine


c)pure polyester woven fabric

Hank Dyeing Machine

Jet Dyeing Machine


d)cotton/polyester blended woven fabric

.....


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