Classification of disperse dye for polyester

The SDC classification of disperse dyes is based on migration ability during exhaust dyeing, colour build-up, sensitivity to changes in temperature and the rate of dyeing.

This type of dye is often classified on the basis of dyeing rate and sublimation fastness, particularly for polyester dyeing. These two properties are a function of molecular weight and the number of polar groups in the dye molecule. Table shows the most common classification. It applies to the dyeing of acetate, of polyester with or without carrier, and of polyester/cotton, but is somewhat arbitrary.

Classification	Molecular  weight	Polarity	Dyeing Rate	Sublimation
Low energy	Low	Low	High	Low
Medium energy	Moderate	Moderate	Moderate	Moderate
High energy	High	High	Low	High

Disperse dyes can be further classified as-

1. No-suffix dye: Not suitable for polyester but for acetate & nylon.
2. Group A dye: poor sublimation fastness suitable for acetate & nylon.
3. Group B dye: Moderate sublimation fastness.
4. Group C dye: Good sublimation fastness; suitable for all method of polyester.
5. Group D dye: Maximum sublimation fastness; exclusive use for PET(Polyethylene terephthalate) dyeing.

Most dyeing and fastness properties change gradually with increase in molecular size. Small dye molecules with low polarity are leveling, rapid dyeing dyes with poor heat resistance. These are called low energy disperse dyes.

More polar, higher molecular weight dyes have low dyeing rates, poor migration during dyeing but good heat and sublimation fastness. These constitute the high energy disperse dyes. The development of disperse dyes of improved sublimation fastness required dye molecules with relatively polar and hydrophilic substituents to reduce their vapour pressure at high temperatures. This promotes somewhat higher solubility in water but the increase in molecular size reduces the dyeing rate at a given temperature. The high energy disperse dyes are those requiring a higher Thermosol temperature. The light fastness does not depend on the molecular size of disperse dye.

Dyes in a mixture are usually selected from the same energy class. Build-up of the colour on shade requires that the dyes all have about the same dyeing rate. Testing of dye recipes is essential because many disperse dyes, even dyes of the same dyeing group, are incompatible in mixtures. This is true even though they may have the same dyeing rates and build-up properties when tested separately. The dye manufacturers provide considerable information assisting the dyer to select appropriate dyes for a given application.

Drafting Plan of Design of the Textile Fabric

Drafting Plan:

A drafting plan of Design of Textile Fabric indicates the number of heald, used to produce a given textile fabric design and the order in which the warp threads or ends are threaded through the mail eyes of the healds. In the drafting plan,Space between two vertical lines indicates as warp yarn and space between two horizontal Iines indicates as heald shaft.

Straight Draft:

The warp ends are threaded through the healds according to their numerical order. A distinction is made between S- and Z- entering. 

Straight draft is the most common and can be used with any number of shafts. Each successive thread is drawn on successive shaft, the first shaft, and so on.The last thread of the warp repeat is drawn on the last shaft.Thus the number of shafts equals the warp repeat. 

Straight Draft

Pointed Draft:

Point entering is obtained by straight entering of a number of yarns followed by reverse entering of the same or a different number of yarns. Point drafts are used for weaves, which are symmetrical about the center, and they are frequently employed to produce waved or diamond effects.

The main advantage of this system is that it allows the production of quite large effects economically, which if attempted on the straight drafts would require almost twice the number of healds. The method used to construct these drafts and it will be seen that to achieve a well defined point in the design the ends are drawn in straight order starting with heald 1 and finishing with the last heald in the number employed, where upon the order of drawing-in of the

consecutive ends is reversed. The first and the Iast healds carry only one end each,

whilst all the healds in the middle carry two ends each per repeat of the draft.

Pointed Draft

Skip drafts:

The warp ends are threaded in an irregular way. Warp ends with the same action are threaded through the same shaft. This system is particularly useful in weaving very densely set fabrics where normally a small number of healds is required. In order that the mails will not be too crowded on the shaft and to reduce friction and rubbing between the ends it is customary to use more healds than the minimum necessary for the weave. For example ,in case of the plain weave, may be drawn on two healds, if the cloth is coarse;or on four healds, if the cloth is of medium fineness; or on six healds; if the cloth is very fine.

Skip Draft

Broken draft:

It can be considered as a modified pointed draft. Again it is a combination of straight drafts with different direction s of constructing. But the direction is reversed not on the last or the first shaft. When the direction is reversed the first threads of the next group is started higher or lower than the last thread of the preceding group. This small modification changes considerably the design by breaking the axis of symmetry. The order of interlacing of the last thread of the first group is opposite to that of the first thread of the preceding group. This draft is applied for producing herringbone twills, diaper design and etc.

Broken Draft

Divided draft:

This draft is employed for derived weaves, double warp weaves, two pIy weaves, pile weaves, and some others. The shafts are divided into two or more groups. A suitable type of draft is chosen for each group. The divided draft is employed for double-warp fabric. There are two systems of warp threads: the face and back ones.

Divided Draft

 Grouped drafts:

These drafts are employed for production of check and stripe designs, in which the stripes have different weaves or their combinations. A typical draft is used for producing the fabric with two different stripes containing 15 and 12 threads, respectively. The warp repeat of the first stripe equals 3 and the second 4. The weave of the first stripe requires 3 shafts, and that of the second stripe 4 shafts.All the threads of the first stripe are drawn on 3 first shafts with straight draft, and the threads of the second stripe are drawn on shafts 4,5,6,7 of the second group.The repeat of the draft is 27.

Grouped Draft

Curved draft:

These drafts are applied for fancy weaves having a large warp repeat with the purpose of reducing the number of shafts. Note, that the minimal number of shafts equals the number of threads in warp repeat with different order of interlacing. The drawing-in is done applying the rule: all warp threads which works alike are drawn on the same shaft. Curved drafts are irregular and cannot be classified.

Combined draft:

Various methods of drawing-in can be combined in one draft for producing a certain type of fabric. Two or more drafts described above can be applied simultaneously, for example, straight and skip or sateen, grouped and curved, and soon. Combined draft is the most complicated and can be chosen only if there are some technological or economical reasons.

Disperse Dye | Properties of Disperse Dye

What is Disperse Dye?

Disperse dyes are non-ionic colorants with low water solubility that, in their disperse colloidal form, are suitable for dyeing and printing hydrophobic fibers and fabrics like cellulose acetate (CA), Polyester (PE), Nylon etc.

Because these dyes are present in the dye bath as a fine aqueous suspension in the presence of a dispersing agent so these are known as Disperse Dye.

Some example of Disperse Dye-

Properties of Disperse Dye:

• Disperse Dyes are non-ionic organic compound of relatively low molecular weight.
• These are insoluble in water at low or room temperature and have only limited solubility at higher temperatures.
• They have substantivity for hydrophobic fibres such as nylon and polyester, in which they are quite soluble.
• These dyes are present in the dye bath as a fine aqueous suspension in the presence of a dispersing agent.
• Many of these dyes 130°c sublime on heating and dyeing.
• Disperse dyes have slight water solubility because of the presence of polar substituents in their molecular structure.Typical example of these
• Typical example of these substituents is hydroxy-ethyle-amino groups (–NHCH2SO3Na).