Cotton Morphology and Cellulose Chemistry - Nonwovens Technical Guide: (2022)

Cotton for Nonwovens Technical Guide

Cotton Morphology and Chemistry

Cellulose Chemistry

After scouring and bleaching, cotton is 99% cellulose. Cellulose is a macromolecule –– a polymer made up of a long chain of glucose molecules linked by C-1 to C-4 oxygen bridges with elimination of water (glycoside bonds). The anhydroglucose units are linked together as beta-cellobiose; therefore, anhydro-beta-cellobiose is the repeating unit of the polymer chain (see Figure 5 ). The number of repeat units linked together to form the cellulose polymer is referred to as the “degree of polymerization.”

Cotton Morphology and Cellulose Chemistry - Nonwovens Technical Guide: (1)

Figure 6 Chemical Structure of Cellulose

Wood pulp, rayon and cellophane (all three derived from wood cellulose) are also constructed of cellulose polymers. Cotton cellulose differs from wood cellulose primarily by having a higher degree of polymerization and crystallinity. Crystallinity indicates that the fiber molecules are closely packed and parallel to one another (as illustrated in Figure 6 ). Table 5 (see page 24) shows the average degree of polymerization and the average crystallinity of the cellulose fibers cotton, viscose rayon and wood pulp. Higher degree of polymerization and crystallinity are associated with higher fiber strengths.

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The cellulose chains within cotton fibers tend to be held in place by hydrogen bonding. These hydrogen bonds occur between the hydroxyl groups of adjacent molecules and are most prevalent between the parallel, closely packed molecules in the crystalline areas of the fiber.

The three hydroxyl groups, one primary and two secondary, in each repeating cellobiose unit of cellulose are chemically reactive. These groups can undergo substitution reactions in procedures designed to modify the cellulose fibers or in the application of dyes and finishes for crosslinking. The hydroxyl groups also serve as principal sorption sites for water molecules. Directly sorbed water is firmly chemisorbed on the cellulosic hydroxyl groups by hydrogen bonding.

Cotton Morphology and Cellulose Chemistry - Nonwovens Technical Guide: (2)

Figure 7 Amorphous and crystalline Areas of Polymers

Of particular interest in the case of cellulose fibers is the response of their strength to variations in moisture content. In the case of regenerated and derivative cellulose fibers, strength generally decreases with increasing moisture content. In contrast, the strength of cotton generally increases with increased moisture. This difference among fibers in their response to moisture is explained in terms of intermolecular hydrogen bonding between cellulose chains and their degree of crystallinity (see Tables 5 and 6 ).

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Table 5 Degree of polymerization and crystallinity of cellulose fibers
FiberAverage Degree
of Polymerization*
Average
Crystallinity (%)**
Cotton9,000–15,00073
Viscose rayon
Regular
250–45060
High tenacity500–650
High wet modulus400–550
Wood pulp600–1,50035

* Joseph, M., Introduction to Textile Science, 5th Edition, 1986.
** Shirley Institute; measured by X-ray diffraction.

Thermoplastic fibers melt at elevated temperatures and have a glass transition temperature at some point below the polymer’s melting point. At the glass transition temperature, a thermoplastic fiber becomes brittle and loses its elasticity. Cotton is not a thermoplastic fiber; therefore, it has no glass transition temperature and remains flexible even at very low temperatures. At elevated temperatures, cotton decomposes instead of melting. Long exposure to dry heat above 300°F (149°C) causes cotton fibers to decompose gradually, and temperatures above 475°F (246°C) cause rapid deterioration.

Table 6 Dry and wet strengths of fibers (g/tex)
FiberDryWet
Cotton27–4530–54
Rayon (regular)22–2710–14
Wood pulp27–5427–54

Cotton’s Unique Fiber Morphology

A mature cotton fiber has the following six parts.

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The “cuticle” is the outer waxy layer, which contains pectins and proteinaceous materials. It serves as a smooth, water-resistant coating, which protects the fiber. This layer is removed from the fiber by scouring.

The “primary wall” is the original thin cell wall. Mainly cellulose, it is made up of a network of fine fibrils (small strands of cellulose). This makes for a well-organized system of continuous, very fine capillaries. It is well known that fine capillaries rob liquids from coarse capillaries. The fine surface capillaries of each cotton fiber contribute greatly to cotton’s wipe-dry performance.

The “winding layer” (also called the S1 layer) is the first layer of secondary thickening. It differs in structure from both the primary wall and the remainder of the secondary wall. It consists of fibrils aligned at 40 to 70-degree angles to the fiber axis in an open netting type of pattern.

The “secondary wall” (also called the S2 layer) consists of concentric layers of cellulose, which constitute the main portion of the cotton fiber. After the fiber has attained its maximum diameter, new layers of cellulose are added to form the secondary wall. The fibrils are deposited at 70 to 80-degree angles to the fiber axis, reversing angle at points along the length of the fiber. The fibrils are packed close together, again, forming small capillaries.

The “lumen wall” (also called the S3 layer) separates the secondary wall from the lumen and appears to be more resistant to certain reagents than the secondary wall layers.

The “lumen” is the hollow canal that runs the length of the fiber. It is filled with living protoplast during the growth period. After the fiber matures and the boll opens, the protoplast dries up, and the lumen naturally collapses, leaving a central void, or pore space, in each fiber.

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Figure 8 shows a schematic structure of a mature cotton fiber, identifying its six parts.

Throughout the fiber structure, there are variously sized pores or capillary spaces between the variously sized fibrils in each of the six fiber parts. Thus, the cotton fiber can be viewed as a microscopic physical sponge with a complex porous structure. This internal structure makes cotton fibers accessible to liquids and vapors. The capillary action of the fibrils pulls liquid in, where it is held in pores between the fibrils. This structure accounts for cotton’s wickability and unique absorbing capacity.

The cotton fiber, when observed in its entirety, is a flat, twisted ribbon, with 50 to 100 convolutions per inch. The fiber is tapered on one end and fibrillated on the other, where it was joined to the cottonseed. This provides the fiber with a soft touch or feel, because it has no sharply cut ends, as do synthetic staple fibers.

Select the Right Fiber

Some absorbent nonwoven products, such as surgical sponges, sanitary napkins, tampons and cosmetic pads and puffs can be satisfactorily made from by-product cotton fiber (gin motes, comber noils and other mill waste). Most of these products evolve from a bleached cotton coil (an oversized sliver) that needs little integrity (fiber-to-fiber cohesion). However, roll goods from lightweight webs made by carding or air-forming require textile-grade fiber. Table 7 shows recommended fiber properties, testing methods and performance criteria for manufacturing nonwoven roll goods that can be used in cover stock for diapers and feminine pads or as fabrics for the protective clothing and home product areas.

Table 7 Properties of bleached cotton for nonwoven roll goods
PropertyCriterionTest Method
Micronaire≥ 4.9HVI
Length≥ 0.95 in.HVI
Length uniformity≥ 81.0%HVI
Strength≥ 23.0 g/texHVI
Non-lint content≤ 0.8%MDTA-3
Fiber-to-fiber cohesion≤ 1,700 gICI fiber
cohesion test
Fiber openness≥ 100 cc/gITT test method

Fiber length and strength are important in the manufacture of lightweight roll goods, for obvious reasons. However, good fabric appearance is more important than fabric strength in certain nonwoven products, and fiber micronaire is a major consideration for these items. An undesirable characteristic for such items is high nep content. High-micronaire cotton tends to have lower nep content after ginning and is less prone to form additional neps in subsequent processing.

To study the influence of micronaire on nep formation, three bales of cotton of both high and low micronaire were selected, based on HVI data. Care was taken to keep other fiber variables constant to obtain a true measure of micronaire’s influence on nep formation. The bales were bleached at a commercial operation using normal production procedures, and the nep content at various stages of processing was determined with the Zellweger Uster AFIS nep tester.

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Table 8 compares the properties and nep content of the two groups of cotton. The high-micronaire cotton showed some increase in nep content due to bleaching, most likely attributable to the fiber opening stages before and after drying. In contrast, the low-micronaire cotton showed substantial increases in nep content during bleaching and during nonwoven web formation. The benefits of using a higher micronaire cotton are dramatic.

Table 8 Influence of micronaire on nep formation during processing
PropertyHigh MicronaireLow Micronaire
Micronaire4.53.0
Length (inches)1.01.0
Length uniformity (%)79.478.8
Strength (g/tex)25.025.0
Elongation (%)7.07.4
Neps per gram:
Original bale375574
Mechanically cleaned354860
Bleached5201140
Card web5402406

FAQs

What is morphological structure of cotton? ›

It is a sub-shrub, 1 to 1.5 m tall, its stem thick and rigid and, leaves horizontally placed. Leaves and twigs are sparsely hairy and rarely glabrous. Fruit or boll is rounded, beaked 3 or 4 lobular with 11 to 10 seeds per loculus. Seeds have short fuzz and lint.

What are the 3 properties of cotton? ›

Cotton fibers are natural hollow fibers; they are soft, cool, known as breathable fibers and absorbent.

What is cotton GPT? ›

Strength. Strength is measured in terms of grams force per tex (GPT). A bundle of fibres are clamped between a pair of jaws and increased separation force is applied until the bundle breaks. A reading of 28-‐30 is considered average.

What is cotton cellulose? ›

Cotton, like most other plant fibers, is made of a carbohydrate called cellulose. Cellulose is a polymer made up of glucose, a type of sugar.

What is called morphology? ›

morphology, in biology, the study of the size, shape, and structure of animals, plants, and microorganisms and of the relationships of their constituent parts. The term refers to the general aspects of biological form and arrangement of the parts of a plant or an animal.

What are the 4 types of cotton? ›

Types of cotton
  • Upland cotton (Gossypium hirsutum)
  • Egyptian cotton (Gossypium barbadense)
  • Cambric.
  • Canvas.
  • Corduroy.
  • Denim.
  • Flannel.
  • Gauze.

What is the chemical properties of cotton? ›

5.1 Chemical Properties

Cotton fibers are composed of about 95% of cellulose after ginning and mechanical cleaning. Cellulose is a polysaccharide composed of β-d glucopyranose units covalently linked through 1,4-glycosidic bonds.

How is quality of cotton measured? ›

Official USDA cotton quality classifications measure three factors: grade, staple, and micronaire (10). 1/ Grade depends on the color, trash content, and preparation (smoothness) of the sample. Staple is the average length of the individual fibers. Micronaire is a measure of fiber fineness and maturity.

What is raw cotton called? ›

Cotton Staple, Virgin Cotton, Raw Cotton, #1 Raw Cotton – Cotton fibers that are removed from the cotton seed by the gin. This is the main product from the gin and is sold on the open market. The by-products of the gin are cotton seed and gin motes.

What is +B value in cotton? ›

In Indian cottons, the +b value usually lies in between 6.0 to 11.0. It is advisable to maintain the range below 2.5 or the maximum acceptable limit is 2.6 in one variety cotton mixing. The relationship between Reflectance (Rd) and Yellowness (+b) is given in Table 1. Table 1: Classer's designation for Rd and +b.

What are the grades of cotton? ›

The quality of cotton fibre differ from place to place and plant to plant. The difference in quality can be expressed in grading and staple length. Grade is generally determined from three factors viz.
...
Trash Content.
Strict Good Middling:DGM
Low middling:LM
Strict good Ordinary:SGO
Good ordinary:GO
4 more rows
15 Sept 2016

Which color standard is used for cotton? ›

USDA maintains fifteen physical grade standards for American Upland cotton. Seven of the White color grade standards also serve as official leaf grade standards for American Upland cotton.

What is the formula for cellulose? ›

Cellulose is an organic compound with the formula (C6H10O5)n, a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units.

How do you make cotton cellulose? ›

The waste cotton cloths collected from the landfill were sterilized and cleaned using supercritical CO2 (scCO2) technology. The cellulose was extracted from scCO2-treated waste cotton cloths using alkaline pulping and bleaching processes. Subsequently, the CNCs were isolated using the H2SO4 hydrolysis of cellulose.

What is cellulose the main compound of cotton fiber? ›

After scouring and bleaching, cotton is 99% cellulose. Cellulose is a macromolecule –– a polymer made up of a long chain of glucose molecules linked by C-1 to C-4 oxygen bridges with elimination of water (glycoside bonds).

What are the three types of morphology? ›

Root, derivational, and inflectional morphemes

Besides being bound or free, morphemes can also be classified as root, deri- vational, or inflectional. A root morpheme is the basic form to which other Page 4 Delahunty and Garvey 124 morphemes are attached. It provides the basic meaning of the word.

What are the basic morphology? ›

Morphology is the study of the internal structure of words and forms a core part of linguistic study today. The term morphology is Greek and is a makeup of morph- meaning 'shape, form', and -ology which means 'the study of something'.

How many types of morphology are there? ›

There are two main types: free and bound. Free morphemes can occur alone and bound morphemes must occur with another morpheme.

What is the highest quality of cotton? ›

Pima Cotton

Pima is considered the finest cotton on earth. As an extra-long staple (ESL) cotton, its long fibers make it extra soft and extra strong. The result? Luxuriously smooth fabric that is resistant to fraying, tearing, pilling, wrinkling, and fading.

Why cotton is called King of fibre? ›

Cotton is the most important natural textile fiber, as well as cellulosic textile fiber, in the world, used to produce apparel, home furnishings, and industrial products. Worldwide about 40% of the fiber consumed in 2004 was cotton.

Which chemical can damage the cotton fiber? ›

- Effect of Acids – Cotton fibres are weakened and destroyed by acids. Acids hydrolyze the cotton polymer at the glycosidic oxygen atom which connects the two glucose units to form the cellobiose unit. Mineral acids being stronger than organic acids will hydrolyse the cotton polymer more quickly.

Is cotton physical or chemical property? ›

Like all textile fibers, cotton has its own physical and chemical properties which require to know for better processing in spinning, weaving, knitting, dyeing, printing as well as finishing. It is important to know the physical and chemical properties of cotton fiber.

What is the tensile strength of cotton? ›

Table 3
FibreDensity (g/cm3)Tensile strength (MPa)
Cotton1.5–1.6287–597
Jute1.3–1.46393–800
Flax1.4–1.5345–1500
Hemp1.48550–900
11 more rows

What are advantages of cotton? ›

The main features and benefits of cotton are:
  • Cotton is comfortable.
  • Cotton is naturally sustainable.
  • Cotton supports farmers and communities.
  • You sleep better with cotton.
  • Cotton is hypoallergenic.
  • Cotton is odour-free.
  • Cotton is low maintenance.
  • Cotton isn't clingy.

What is the application of cotton? ›

Cotton can be easily processed into a number of products that we use on a daily basis, like coffee filters, book binding, paper, and bandages. Cottonseed oil, which is made from crushed seeds of cotton plants, is used in a multitude of products including soap, cosmetics, and margarine.

Why is cotton important? ›

Cotton is the most widespread profitable non-food crop in the world. Its production provides income for more than 250 million people worldwide and employs almost 7% of all labor in developing countries. Approximately half of all textiles are made of cotton.

Is 100% cotton a good quality? ›

Which T-shirt material should you choose? Go with 100% cotton if you want shirts that are soft, comfortable, breathable, gentle on the skin, non-clingy, and can be customized with any method. Cotton tees are popular with everyone, so it's a safe bet.

What is SFI in cotton? ›

a sample of cotton based upon an algorithm that. calculates a short fiber index (SFI) from the other. conventional HVI measures of length, strength, and micronaire (Gipson, 1999).

What is cotton count? ›

Cotton Count is specifically a way of describing the size of spun fibers and yarns. Now let's take a closer look at what that means. Cotton Count looks at one pound of the material and describes how many 840-yard lengths of spun fiber it contains.

What is cotton chemical name? ›

The chemical name of cotton is Cellulose.

Is cotton polar or nonpolar? ›

Cotton, linen, and rayon, which are cellulose fibers, are somewhat less polar than wool and silk and are more difficult to dye directly.

What are the 2 types of fibres? ›

There are 2 different types of fiber -- soluble and insoluble. Both are important for health, digestion, and preventing diseases. Soluble fiber attracts water and turns to gel during digestion.

Who discovered cotton? ›

3000 B.C. - Cotton first cultivated as a fabric in the Indus River Valley (present-day Pakistan). 2500 B.C. - Chinese, Egyptian and South American civilisations begin weaving cotton fabrics.

Which country is the largest producer of cotton? ›

Currently, India is the world's leading producer of cotton, surpassing China recently. Although yields in India are well below the global average, cotton area in India dwarfs that of any other country, accounting for approximately 40 percent of the world total.

What is the yarn structure of cotton? ›

A cotton yarn is a heterogeneous material. It consists of a large number of individual cotton fibers which are held together by twist. The fibers are not uniform in length, cross section, and strength. They are unequally distributed throughout the length of the yarn.

What is the microscopic structure of cotton fibre? ›

The cell wall of a cotton fiber consists of a primary and a sec ondary wall. The latter, which comprises the bulk of the fiber, con sists of innumerable spirally oriented cellulose fibrils enclosed by a winding which also makes a spiral, but in the opposite direction from the former.

What is the chemical formula of cotton? ›

After scouring and bleaching, cotton is 99% cellulose. Cellulose is a macromolecule –– a polymer made up of a long chain of glucose molecules linked by C-1 to C-4 oxygen bridges with elimination of water (glycoside bonds).

What is the structure of wool? ›

Wool's interior is intricate being made up of membrane, cortex, cortical cell, microfibril, matrix, microfibril, and the twisted molecular chain and helical coil. Membrane – dyes and moisture can penetrate the membrane and it's this which enables fibre to absorb humidity.

What is cotton chemical name? ›

The chemical name of cotton is Cellulose.

What is the basic unit of cotton? ›

Threads are the basic units of a fabric.

What is raw cotton called? ›

Cotton Staple, Virgin Cotton, Raw Cotton, #1 Raw Cotton – Cotton fibers that are removed from the cotton seed by the gin. This is the main product from the gin and is sold on the open market. The by-products of the gin are cotton seed and gin motes.

Which part of cotton plant contains fibre? ›

Solution: (a) Cotton is obtained from the fruit of the cotton plants. The cottonseed which is a fruit which on ripening splits open to release white fibers of cotton.

What are chemical properties of cotton? ›

5.1 Chemical Properties

Cotton fibers are composed of about 95% of cellulose after ginning and mechanical cleaning. Cellulose is a polysaccharide composed of β-d glucopyranose units covalently linked through 1,4-glycosidic bonds.

What chemicals are present in cotton? ›

Cotton fibres are comprised of 88%–97% of cellulose, and waxes, proteins and pectin are the remaining constituents.

What is the polymer unit of cotton? ›

It is also known as cellobiose. Hence, cellobiose is the polymer unit of cotton.. Note: Cotton is known as a linear and cellulose polymer.

What are the 3 properties of wool? ›

They give wool its flexibility, elasticity and resilience, which delivers easy-to-live with, durable and wrinkle-resistant products. The epicuticle is one of the outer cuticle cell layers, on the surface of the wool fibre.

Which protein is present in wool? ›

Wool fibre is primarily composed of proteins called hard α-keratins [2]. These have a high sulphur content, consistent with having a high relative abundance of the amino acid cysteine.

Videos

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3. The production of viscose fibres at Kelheim Fibres GmbH
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4. Wrinkle Resistant Finishing
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