Dyeing cotton

Dyeing an old, faded cotton T-shirt can breathe new life into the garment. According to an article on Paula E. Burch's website, a fiber reactive dye is the best option for dying cellulose-based fabrics such as cotton. Fiber reactive dyes provide a much more vibrant color cast than all-purpose dyes, and tend to resist fading for a much longer period of time. These dyes are also simpler to use, especially for those new to dyeing. With an appropriately sized dyeing tub and some household materials, your drab cotton fabric will be colorful in no tim

·1

Determine how much fabric you will be dyeing, as this dictates the size of your dyeing tank and the amount of supplies required. To standardize the process, the steps below will describe how to dye 1 lb. of dry cotton fabric. Most containers of dye will offer proportions for both smaller and larger loads.

·  2

Pre-wash your cotton fabric to remove residue, dirt and other material which may hamper the dyeing process. Use mild laundry detergent and wash according to the care instructions on the fabric's tag.

·  3

Add 1 tbsp. of fiber reactive dye to a cup. Trickle a small amount of warm water into the cup and mix with a plastic spoon until a paste-like consistency is achieved.

·  4

Fill your dyeing tub with 3 gallons of warm water. If you do not have access to a tub of this size, a washing machine's basin will suffice. Empty the dye into the tub and stir until completely dissolved.

·  5

Measure out 3 cups of non-iodized salt and add it to the tub. Stir until the salt is completely dissolved.

·  6

Place your fabric into the dyeing tub and fully submerge it. Stir the fabric gently at five-minute intervals for 20 minutes. If you are using a washing machine basin as your tub, set the machine's cycle to "Agitate." Keep a watchful eye on the basin to prevent the dye from draining out of the machine.

·  7

Dissolve 1/3 cup of soda ash with warm water and pour it slowly into the dyeing tub as you stir the fabric. For even results, add the soda ash over a 15-minute period and avoid pouring directly onto the fabric.

·  8

Continue stirring, or agitating, the cotton fabric at five-minute intervals for another 30 minutes. For a deeper hue, allow the fabric to dye for a full hour.

·  9

Empty the tub of dye once the desired hue is achieved. Rinse the fabric with cool running water until it runs clear, or put the fabric through several "Rinse" cycles if you are using a washing machine basin.

·  10

Set the dye by washing the cotton fabric as you normally would.

polymer to fabric

Yarn Count

 Count:
Count is very important factor for the Textile Yarn Manufacturing. Maintaining the yarn count is mandatory to retain the quality of a yarn and fabrics According to the Textile Institute “Count is a number of indicating the mass per unit length or length per unit mass of yarn”.
There is several count system of yarn. These count systems have been divided in two ways. One is Direct System where length is fixed and another is Indirect system where weight is fixed.

Direct System (Length Fixed):

 A). Tex: Weight of yarn in gm present in 1000 meter length. It is a universal system of counting the yarn.

B). Denier: Weight of yarn in gm present in 9000 meter length. It is basically used for manmade fiber.
C) Pounds Per Spindle: Weight of yarn in lbs present in 1440 yards length.

Indirect System (Weight Fixed):

A). English Cotton Count: No. of hanks of 840 yds present in 1 lb of yarn.
B) Metric Count: No. of hanks of 1000 meters present in 1 kg of yarn.
C) Worsted count: No. of hanks of 560 yds present in 1 lb of Yarn. It is basically used for Wool.
D) Woolen Count: No. of hanks of 20 yds present in grain of Yarn.

Methods of Yarn Count:

ü  Wrap reel and balance method.

ü  Quadrant balance method.

ü  Knowles balance.

ü  Beesleys balance.

ü  Sliver, roving count by measuring drum.

ü  Count data system.

ü  Auto sorter by user.

Measurement of Yarn Count:

In a yarn structure, fibers represent the main component. The other component is air pockets created by the technology forming the structure. The knowledge of the real fibres volume within the yarn allows to better estimate various textile fabrics properties. Yarn diameter is used to predict fabric structural parameters such as width, cover factor, porosity, and fabric comfort and so on. Since thousands of ends or picks are presented side-by-side in the woven or the knit fabrics, a slight change in yarn diameter can result in a substantial change in the overall fabric cover factor. Measuring yarn diameter and compressibility and their effect on fabric quality is important to both the fabric designer and the textile technologist. In fact, the dimensional and mechanical characteristics of fabrics are dependent on yarn diameter, thread spacing of warp and weft in woven fabrics, courses and Wales per unit length and stitch length in knitted goods.

Many researchers studied the yarn diameter and they estimated it using empirical formula. One of the most commonly used expressions for estimating yarn diameter is that developed by Peirce in 1937 ^[7]. In this expression, yarn density was assumed to be 1.1 g/cm³. In a recent study, Elmo hazy et al in 1993 ^[5] developed empirical expressions for estimating the diameters of ring-spun, rotor-spun and MJS air-jet spun yarns. These expressions (Table 1) were developed by an extensive microscopic testing of actual yarn thickness for a wide range of yarn count and twist levels.

Measurement the rotor spun cotton yarn diameter using the image analysis method. The used yarns count range from 6 Ne to 20 Ne and they found that the actual yarn diameter can be predicted by using the formula shown in Table 1. The formulae shown in Table 1 indicate that yarns made by different spinning systems and of equal nominal count will exhibit different values of yarn diameter. This is a result of the difference in fibre arrangement and fibre compactness of different yarn types.

We should point out that the formula for ring spun yarn developed by El Moghazy in 1993 ^[5] tends to produce a value of yarn diameter that is slightly higher than that estimated by Peirce equation. The main reason for the difference was due to discrepancy in the value of yarn density, particularly in the course to medium range of yarn count. Using a combination of capacitive and optical measures of different yarns, the density of cotton ring-spun yarns can range from 0.85 to 1.2 g/cm³ depending on the spinning process, fibre characteristics, and structural parameters (count and twist).

The majority of the studies were interested in the determination of the apparent yarn diameter However, the knowledge of the real fibres volume within the yarn allows to determine the real yarn diameter. Thus, the real diameter is defined as the measurement of the yarn dimension without air. Indeed, the determination of the real diameter influences so much the fabric geometrical and mechanical properties. In this paper, the authors discuss the development of an experimental device allowing the determination of the real yarn diameter and study the effect of yarn and fibre properties on the yarn packing fraction. 

The yarn sample undergoes a uniform tension while mounting on the grips. The tension of 1 cN/ tex was applied to the yarn sample according to the French Standard NF G07-079 [3] for removal of crimp. The first yarn sample edge was fixed on one grip and they applied the pre-tension and they fixed the second edge on the other grip. 500 mm test length yarn is maintained right between the grips of the twist tester and subjected to twist increase (a step of 50 turns). For each twist step, a yarn photo is captured and examined by a Motic microscope with 40x magnification. For analysis of the yarn images, "Image-Pro-Plus 2.0" software was used. The image analysis was performed using the sequence: process, image, acquise, segmentation, processing and measurement.

With regard to the external structure, the yarn can be divided into two basic elements: the yarn core and hairiness. The core is defined as a part of the yarn that forms a compact agglomeration of fibres. It has a cylindrical form and a variable diameter. On its surface the fibres are laid along the curves characterising the twist. The rest of the yarn, consisting outlying fibres or their agglomerations, constitutes hairiness. So the yarn diameter can evaluated by determined the edges of the yarn core. For determination of them, the images were processed (Figure 2) and the yarn diameter was measured.

Average of 10 measurements were taken in 10 different positions throughout the yarn length. The initial study of variation it was decided to take 100 readings. So the average of yarn diameter was calculated by the following equation ^[1].

                                                        (1) 

where: `d : average diameter in mm Li : diameter of yarn at position i in mm

A statistical study was carried out in order to determine the more influent parameters on yarn packing fraction. This study allowed us, using Principal Components Analysis (PCA) ^[2] and contribution analysis (Path method) ^[4], to limit the number of factors. The principal component analysis (PCA) is an extraction method of the principal factors based on a quantitative analysis of the correlations ^[2]. Its goal is to study and to reduce the survey space of variables in order to simplify the raw data, to find out (graphically) some links and to identify some macro features (principal components). This method consists on subjective grouping of the correlated variables, which were represented graphically by the coordinates corresponding to two centred and reduced principal variables.

Fiber Maturity

Fiber Maturity

Fibre maturity is a fibre characteristic which expresses the relative degree of thickening of the fibre wall. In other words, it is the measure of primary and secondary wall thickness.
The fibre maturity is usually estimated by several indirect tests which are often used to find out the proportion of fibres containing a maturity greater than some selected level.

A fiber will be matured if a high degree of wall thickening took place into the fiber content during cotton growth.

There are several factors upon which the fibre maturity is basically depends. By changing theses factors you can also measure that which factors is working behind to be a fibre matured or which not.
The factors are –

1. Weather: If the weather doesn’t favor, the fiber gets less chance to be matured.
2. Types of Soil: It is proved that, in some country the fibers grows well and becomes well matured and on some other country; due to the soil, fibers don’t be so much matured and grows low quality fibres.
3. Plant Diseases: If proper care is not taken to the fibres, these become less matured due to several diseases.
4. Pests: Some pests is good for Plants and some are bad. So be careful to apply any pesticides on any plants.
5. Dead Fibers: It is natural that the dead fibers will be immature.

Measurement of fiber maturity

Fiber maturity can be measured directly using two types of dye. One is red and another is green. Both of them are used on a same bath in a liquate form. A fiber is dissolved in this bath. If the fiber became red then consider that fiber is mature and if became green then consider that fiber is immature. Because mature fibers are stained red & immature fibers are strained green. The red color being developed the cellulose of the secondary wall. Hence the little or no secondary wall thickening no red.

Yarn Twist

Yarn Twist
Yarn twist is the spiral given to the yarn standard to hold the fiber permanently according to construction. It is measured by twist per inch (TPI). If TPI increase to a certain level then the strength of the yarn will be increased and if decreased then strength will decreased. The twist of yarns and threads influences their morphology. This feature creates the thread’s properties, and at the same time is decisive regarding the processing throughput. A great amount of the literature published hitherto deals with the problem of yarn twisting, but there is a lack of sufficient information related to the twist of multi-folded threads. Technologists in the textile industry set the thread’s twist value in their ‘spinning planes’. Its actual realization on the spinning machine and ring-twisting frame is performed by selecting the spindle rotary speed and fibre stream delivery velocity. Yarn plying, i.e. twisting together some component fibre streams, causes a decrease in the linear mass irregularity (thanks to a better fibre packing in the stream), an increase in tenacity, a lowering of the bending stiffness, an increase in the abrasion resistance, and a lowering of the thread’s tendency to pilling formation. Owing to these favorable circumstances, twisting positively influences the thread’s manufacturing throughput and the barrier ability (e.g. against UV radiation) of the fabrics produced from such a yarn.

Types of yarn twist

ü  S Twist

ü  Z Twist

S twist:

A single yarn has S twist when it is held in the vertical position, the fibers inclined to the axis of the yarn conform the direction of slope to center position of the letter S.

Z twist:

A single yarn has Z twist when it is held in the vertical position, the fibers inclined to the axis of the yarn conform the direction of slope to center position of the letter Z.

Construction:

ü  This instrument has two jaws& distance of them is 1 inch.

ü  Yarn can set two jaws.

ü  That means 1 inch yarn can set two jaws.

ü  A lens is used to watch the number of revaluation properly.

Procedure

ü  At first the yarn can set two jaws.

ü  Then a weight is hung at one end of the yarn with fixed tension.

ü  The yarn led through the fixed jaw over a grid pulley & at last to the weight to maintain fixed tension.

ü  After closing the fixed jaw the turns are removed by the rotating the handle.

ü  When the twist is removed the needle is pushed through the fibers closed to the fixed jaw and gently moves towards the rotating jaw.