Definition of cotton: The seed hair of wide variety plants of gossypium family is called cotton.
Gossypium herbaceum
Gossypium arboreum.
Gossypium hirsutum.
Gossypium barbedense.
CHARATERISTICS OF COTTON
Cotton, as a natural cellulosic fiber, has a lot of characteristics, such as;
- Comfortable Soft hand
- Good absorbency
- Color retention
- Prints well
- Machine-washable
- Dry-cleanable
- Good strength
- Drapes well
- Easy to handle and sew
Chemical composition of cotton:
Cellulose | 94% |
Protein | 1.3% |
Pectin | 1.2% |
Ash | 1.2% |
Wax | 0.6% |
Total sugar | 0.3% |
Pigment | Less |
Others | 1.3% |
Total | 100% |
Chemical structure of cotton:
Structural view of cotton fibre:
The cotton fibre is a single plant cell. It cross section is oval, compared with the normal hexagonal plant cell. However, like all plant cell cotton has the following:
(i) Cuticle.
(ii) Primary cell.
(iii) Secondary cell.
(iv) Lumen.
PHYSICAL PROPERTIES OF COTTON:
- FIBER LENGTH
Fiber length is described [7] as “the average length of the longer one-half of the fibers (upper half mean length)” This measure is taken by scanning a “beard ” of parallel fibers through a sensing region. The beard is formed from the fibers taken from the sample, clasped in a holding clamp and combed to align the fibers. Typical lengths of Upland cottons might range from 0.79 to 1.36in.
Cottons come from the cotton plant; the longer strand types such as Pima or Sea Island produce the finest types of cotton fabrics [18].
- LENGTH UNIFORMITY
Length uniformity or uniformity ratio is determined as ” a ratio between the mean length and the upper half mean length of the fibers and is expressed as a percentage”[7]. Typical comparisons are illustrated below.
LENGTH UNIFORMITY | UNIFORMITY INDEX [%] |
Very High | >85 |
High | 83-85 |
Intermediate | 80-82 |
Low | 77-79 |
Very Low | <77 |
Low uniformity index shows that there might be a high content of short fibers, which lowers the quality of the future textile product.
FIBER STRENGTH
Fiber strength is measured in grams per denier. It is determined as the force necessary to break the beard of fibers, clamped in two sets of jaws, (1/8 inch apart) [7]. Typical tensile levels are illustrated. The breaking strength of cotton is about 3.0~4.9 g/denier, and the breaking elongation is about 8~10%. [20]
DEGREE OF STRENGTH | FIBER STRENGTH [g/tex] |
Very Strong | >31 |
Strong | 29-30 |
Average | 26-28 |
Intermediate | 24-25 |
Weak | <23 |
- MICRONAIRE
Micronaire measurements reflect fiber fineness and maturity. A constant mass (2.34 grams) of cotton fibers is compressed into a space of known volume and air permeability measurements of this compressed sample are taken. These, when converted to appropriate number, denote Micronaire values.
COTTON RANGE | MICRONAIRE READING |
Premium | 3.7-4.2 |
Base Range | 4.3-4.9 |
Discount Range | >5.0 |
- COLOR
The color of cotton samples is determined from two parameters: degree of reflectance (Rd) and yellowness (+b). Degree of reflectance shows the brightness of the sample and yellowness depicts the degree of cotton pigmentation. A defined area located in a Nickerson-Hunter cotton colorimeter diagram represents each color code. The color of the fibers is affected by climatic conditions, impact of insects and fungi, type of soil, storage conditions etc. There is five recognized groups of color: white, gray, spotted, tinged, and yellow stained. As the color of cotton deteriorates, the process ability of the fibers decreases.
Work at the University of Tennessee has led to color measurement using both a spectrometer CIE-based average color measurement and a color uniformity measurement using image analysis to improve the accuracy and provide additional measurement for color grading [19]. Later the investigators developed two color grading systems using expert system and neural networks.
- TRASH
A trash measurement describes the amount of non-lint materials (such as parts of cotton plant) in the fiber. Trash content is assessed from scanning the cotton sample surface with a video camera and calculating the percentage of the surface area occupied by trash particles. The values of trash content should be within the range from 0 to 1.6%. Trash content is highly correlated to leaf grade of the sample.
- LEAF GRADE
Leaf grade is provided visually as the amount of cotton plant particles within the sample. There are seven leaf grades (#1-#7) and one below grade (#8).
- PREPARATION
Preparation is the classer’s interpretation of fiber process ability in terms of degree of roughness or smoothness of ginned cotton.
- EXTRANEOUS MATTER
Extraneous matter is all the material in the sample other than fiber and leaf. The classer either as “light” or “heavy” determines the degree of extraneous matter.
- NEPS
A nep is a small tangled fiber knot often caused by processing. Neps can be measured by the AFIS nep tester and reported as the total number of neps per 0.5 grams of the fiber and average size in millimeters. Nep formation reflects the mechanical processing stage, especially from the point of view of the quality and condition of the machinery used.
Faults of cotton:
(i) Damp cotton:
These types of problems are shown due to collection the fibre in moist and cold weather. After drying in sunlight this problem can be removed.
(ii) Immature fibre:
If the tree cotton plant is affected by the insects then this problem will be shown.
(iii) Dead fibre:
About 10-15 % cotton fibre become dead when we collect it before perfect time. So, if we collect this cotton in schedule time this problem will be solved.
(iv) Cake formation:
Due to the attack of insects, this type of problem is created.
(v) Paste formation:
This type of problems also be found due to the attack of insects.
(vi) False mildew or grow mildew:
It is occurred due to attack of fungus and due to bad weather.
(vii) Cotton rust:
Due to cultivate the cotton in dry weather or after rain, cotton rust be found.
(viii) Powdery mildew:
Powdery mildew is one kind of problem which is created due to cultivating cotton in excess dry weather.
(ix) Lint rot:
To bear yellowish or brownish colour of fibre is called lint rot. This may occur when cotton be remained in damp environment after collecting.
(x) Sticky cotton:
Sticky cotton is another type of defects which is found because of attacking fungus.
RECENT DOVELOPMENTS IN COTTON:
- COLORED COTTON
Cotton fiber is dyed with chemical dyes in order to get wide range of colors. These chemical dyes and their finishing demands large amount of water in turn when these water is disposed they cause soil and water pollution. Many dyes are of chemical origin; particularly the azure ones and these are not environment friendly. Hence many countries, including India, have prohibited use of these dyes.
The negative effects of dyeing can be reduced by naturally colored cotton. This colored cotton is developed by gene transplantation. Crossing the genes from wild cotton varieties with the cultivated white ones develops this colored cotton. The research is being conducted at The University of Agricultural Sciences (UAS), Dharwad Karnataka India, to promote the cultivation of natural colored cotton. The colors that have been developed are White, Orange, Red, Yellow, Green, Purple, Brown, Blue, And Black. These negative effects of dyeing can be avoided by extensive research and growth of colored cotton. (33).
- BT COTTON
Cotton requires severe pesticide in order to combat numerous pests after some years of use of pesticide by farmers these pests develop resistance to Particular pesticide. This resistance force farmers to use more amounts of pesticides. BT Cotton is developed by transgenic technique of implanting Bacillus Thuringiens bacterial gene in to cottonseeds, which makes the cotton plant and seeds resistant to majority of pests including bollworm (A. Lepidoptera), Tobacco budworm (Heliothis virescens). Bt cotton is now one of the most widely used transgenic crops. It is currently grown throughout the United States. More than 2 million acres of Bt cotton are grown in the United States alone. Other countries include China, India, and Australia. (34) According to Dept. of Agricultural and Resource Economics, University of Arizona. Bt cotton planted from 1996 to 1998 is estimated to have yielded 5% more on average than if traditional and decreased the quantity of foliar spray [35].
- COTTON’S FUTURE TRENDS
END USES OF COTTON:
- Apparel – Wide range of wearing apparel: blouses, shirts, dresses, childrenswear, active wear, separates, swimwear, suits, jackets, skirts, pants, sweaters, hosiery, neckwear.
- Home Fashion – curtains, draperies, bedspreads, comforters, throws, sheets, towels, table cloths, table mats, napkins.
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