Yaa Cationization Of Cotton Fiber Past Times Using Chitosan For Reactive Dyeing To Avoid Electrolyte (Part-3)
Monday 17 December 2018
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Cationization of Cotton past times Using Chitosan for Reactive Dyeing to Avoid Electrolyte (Part-3)
Md. Obydullah
Md. Shibli Sadique
Dhaka University of Engineering & Technology,
DUET, Gazipur-1700, People's Republic of Bangladesh
Md. Shibli Sadique
Dhaka University of Engineering & Technology,
DUET, Gazipur-1700, People's Republic of Bangladesh
Previous Part
2.6 Chemical Reactions betwixt Reactive Dyes as well as Fibers:
a) Nucleophilic Substitution:
Nucleophilic exchange characterizes dye-fiber fixation that occurs when a leaving grouping inward the reactive organization is displaced every bit a outcome of an interaction amongst a nucleophilic grouping on the polymer chain. Nucleophilic exchange is facilitated past times the electron withdrawing properties of the aromatic nitrogens, as well as the chlorine, as well as the anionic intermediate is resonance stabilised every bit well. This resonance agency that the negative accuse is delocalised onto the electronegative nitrogens.
For example:
The major fibre-reactive grouping which reacts this way contains six-membered, heterocyclic, aromatic rings, amongst element of group VII substituents.
For example, the Procion dye-
The reaction of a monochlorotriazine reactive dye amongst a hydroxy grouping of cellulose is typical of this process.
a)
 |
| Figure: 2.5 Reaction of a Monochlorotriazine Dye amongst Cellulose |
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| Figure: 2.6 Hydrolysis of a Monochlorotriazine Dye |
Nucleophilic add-on characterizes the dye-fiber reaction inward which a nucleophilic grouping inward the fiber adds across an activated carbon-carbon double bond inward the reactive group. Most of reactive systems used comprise a vinylsulphone moiety. The vinylsulphone reactive grouping itself is commonly non introduce inward commercial cast of the dyes employed. Instead, to a greater extent than stable precursor such every bit the β-sulphatoethylsulphone grouping is used. The two-stagenprocess associated amongst fiber fixation is structurally related dyes containing a β-sulphatoethylsulphamoyl grouping in all probability cast a cyclic chemical compound capable of reacting amongst cellulose to hit cellulose ether.
Systems based on activated double bonds every bit good undergo a competitive hydrolysis reaction.
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| Figure: 2.7 Nucleophilic Addition Involving to a Vinylsulphone Dye as well as Cellulose. |
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| Figure: 2.8 Reaction of Water amongst a Vinylsulphone Dye |
CHAPTER 3
COTTON FIBER
COTTON FIBER
3.1 Cotton Fibre
Cotton is unique inward nature which has the highest percent of cellulose. It varies from 90% to 95%. This concentration depends upon many factors, such that maturity flat as well as diversity of cotton, house on cottonseed from where it is drawn. In cotton wool fiber at that topographic point is for sure non-cellulosic matter, which plays of import role inward increment as well as on forth coming processes. These are located either on the surface of the fiber or inward pump of fiber agency within the lumen. Being a natural fiber, at that topographic point are many factors which impact the construction of cotton wool cellulose. There are primary as well as secondary walls inward the cotton wool cellulose. Primary wall or outer wall is less crystalline as well as has less percent of cellulose. Whereas, secondary wall is about the lumen as well as consist of pure cellulose cotton wool fiber is composed of the crystalline as well as amorphous structure.
3.2 Chemical Structure of Cotton Fiber
The molecular construction of cellulose has e'er been of peachy involvement to scientists as well as over fourth dimension several structures direct hold been proposed. The linear polymer, β-D-glucopyronose amongst 1,4-glycosidic bonds, is the widely accepted construction for cellulose. Consequently it may live considered every bit a polyhydric alcohol. Each glucopyranose band inward the cellulose chain contains iii hydroxyl groups, a primary hydroxyl grouping inward the 6- seat as well as secondary hydroxyl groups inward the 2- as well as 3- positions.
 |
| Figure: 3.1 Cellubiose Unit. |
The basic ingredients, that are responsible for complicated interconnections inward the primary wall, are cellulose, hemicelluloses, pectins, proteins as well as ions. These components are introduce throughout the primary wall. The alone divergence is the concentration as well as nature of each component, every bit when approaching the secondary wall. In the secondary wall, alone crystalline cellulose is present, which is highly ordered as well as has compact construction the cellulose fibrils inward the secondary wall are laying parallel to i another.
Table: 3.1 Typical Composition of Dry Mature Cotton Fiber
| Constituents | Composition (%) | |
| Whole fiber | Outer layer | |
| Cellulose | 94 | 54 |
| Waxes | 0.6-1.3 | 14 |
| Pectin substances | 0.9-1.2 | 9 |
| Protein (nitrogen substances) | 0.6-1.3 | 8 |
| Ash | 1.2 | 3 |
| Organic Acid | 0.8 | - |
| Others | 1.4 | 12 |
a. Cellulose: 94%. It is primary component subdivision of the cotton wool fiber as well as secondary wall posse’s highest percent of the total cellulose
b. Waxes: 0.6-1.3%. It is higher monovalent alcohol-tractional, palmitic, oleic acid, glycerin. Its melting betoken is 77.0. It is establish on surface as well as inward primary wall.
c. Pectin’s: 0.9 -1.2%. These are ploygalacturonic acid, as well as its magnesium salts, methyl ester, xylose. These are mainly introduce inward primary wall.
d. Proteins: 0.6-1.3%. These are protoplasm ease inward lumen as well as aspartic, glutamic acid as well as proline, 0.2-0.3% of nitrogen are establish inward primary wall
e. Ash: 1.2%
f. Organic acids: 0.5-1.00%. Salts of citric as well as L-maleic acid
g. Others: (i) Mineral salts: 0.7-1.6%. Hypochlorites of sulphates, phosphates, oxides of silicon, calcium, potassium, magnesium. (ii) Sugar: 0.3%. Glucose, galactose, fructose, pentose. (iii) Toxine: 0.9%. Endotoxine, evolved from bacterial cells.
3.4 Fiber Macro Structure
Under a microscope, a cotton wool fiber appears every bit a really fine, regular fiber. It ranges inward length from nearly 10mm to 65 mm, depending upon the character of the fiber. Each cotton wool fiber is composed of concentric layers. The cuticle layer on the fiber itself is separable from the fiber as well as consists of wax as well as pectin materials. The primary wall, the most peripheral layer of the fiber, is composed of cellulosic crystalline fibrils. The secondary wall of the fiber consists of iii distinct layers. All iii layers of the secondary wall include closely packed parallel fibrils amongst spiral winding of 25-35o as well as correspond the bulk of cellulose within the fiber. The innermost component subdivision of cotton wool fiber- the lumen- is composed of the remains of the jail cellular telephone contents. Before boll opening, the lumen is filled amongst liquid containing the jail cellular telephone nucleus as well as protoplasm. The twists as well as convolutions of the dried fiber are due to the removal of this liquid. The cross department of the fiber is bean-shaped, swelling almost circular when wet absorption takes place.
The overall contents are broken downwards into the next components.
3.5 Polymer System of Cotton
The density method used to create upwards one's heed cellulose Crystallinity is based on the density slope column, where 2 solvents of dissimilar densities are partially mixed. Degree of Crystallinity is, then, determined from the density of the sample, piece densities of crystalline as well as amorphous cellulose forms are known (1.505 as well as 1.556 respectively). Orientation of untreated cotton wool fiber is wretched because the crystallites are contained inward the micro fibrils of the secondary wall, oriented inward the steep spiral (25-30o) to the fiber axis.
3.6 Chemistry of Cotton Cellulose
Cellulose is an insoluble kernel as well as mainly composed of polysaccharide, which holds chains of glucose monomers. It is alone soluble inward some specific solvents. It is the primary constituent of works life jail cellular telephone walls as well as every bit good every bit of vegetable fibers. Cotton is i of the vegetable fibers which direct hold the highest percent of cellulose. There is a various structures as well as compositions of cellulose of cotton. Its construction makes it divergent from other naturally occurring matters. Cotton cellulose is unique inward many ways as well as possesses distinct characteristics which larn inward highly useful for many purposes. It has been assumed that cotton wool cellulose construction is based on glucose unit of measurement only. However, it is every bit good believed that at that topographic point is small-scale amount of pentose is present, which is removed during scouring process. They farther study that it has been notices from the chromatographic analysis that glucose, xylose, arabinose as well as a line of rhamnose are every bit good introduce inward raw cotton. There is no evidence of the presence of pentose. Cotton cellulose is highly crystalline inward nature as well as good oriented as well as has along as well as stiff molecular structure. The 1,4-D glucopyranose are the regulation edifice blocks of cotton wool cellulose chain as well as are linked past times l,4-glucodic bonds. Free rotation of the anhydrogluco-pyranose C-O-C link is stopped past times steric effects. There are iii hydroxyl groups attached to each anhydroglucose. One grouping is attached at C-6 as well as 2 at C-2 as well as C-3. Due to the presence of hydroxyl groups as well as the chain conformation, at that topographic point are many to a greater extent than bonds possible (inter molecule as well as intramolecular). Such bonds brand the fiber to a greater extent than stiff past times increasing the rigidity of the construction of cotton wool cellulose.
3.7 Cross Section of Cotton Fiber
The jail cellular telephone wall is a dynamic construction which composition as well as cast tin alter markedly, non alone during jail cellular telephone increment but every bit good afterwards the cells direct hold locomote matured. The cotton wool fiber is structurally built upwards into concentric zones as well as a hollow cardinal core known every bit the lumen.
The mature fiber essentially consists of (from exterior to inside) - the cuticle i.e. the outermost layer, the primary jail cellular telephone wall, the secondary wall as well as the lumen. Figure 1.1 systematically shows the dissimilar layers introduce inward the cotton wool fiber amongst the compositions of each layer. Cotton contains nearly 90% of cellulose as well as about 10% of non-cellulosic substances, which are mainly located inward the cuticle as well as primary wall of the fiber. Typical components inward dry out mature cotton wool fibers most of the non-cellulosic materials are introduce inward the outer layers of cotton wool fiber.
Figure illustrates schematically the distribution of cellulose as well as other non-cellulosic materials inward the various layers of cotton wool fiber.. The outermost layer is the cuticle. It is a sparse cinema of by as well as large fats as well as waxes. Owing to non-structured orientation of cellulose as well as non-cellulosic materials, the primary wall surfaces is unorganized as well as open. This gives the flexibility to the primary wall, which is required during the jail cellular telephone growth.
3.9 Different Layer of Cotton Cellulose Structure
a. Cuticle – the outermost layer
The aerial surfaces of vascular plants are covered amongst an extra cellular layer called the cuticle or cuticular membrane that overlays the jail cellular telephone wall of epidermal cells. The term “cotton waxes” has been used for all lipid compounds establish inward the cuticle of fiber. The primary role ascribed to the cuticle is to minimize H2O losses from cotton wool fiber. Other functions are, to restrict the loss of substances from fibers internal tissues, as well as to protect the fiber against physical, chemic as well as biological aggressions. The cuticle contains primary alcohols, higher obese acids, hydrocarbons, aldehydes, glycerides, sterols, acyl components, resins, cutin as well as sobering, which are called waxes. The cuticle gives a soft touching to the fiber as well as reduces the friction forces during spinning. At the same time, presence of these waxy materials is Initiation of fiber increment detrimental inward chemic processing of cotton wool yarn because it gives the fiber surface a high hydrophobicity. The cotton wool waxes are solid substances amongst rather high as well as broad hit of melting points (64°C to 214°C) as well as constitute about 0.4 to 0.8% dry out weight of raw cotton wool After handling amongst boiling NaOH, waxes are hydrolyzed into a sodium tabular array salt of the obese acid as well as alcohol. Apart from the higher upwards mentioned components inward the cuticle, at that topographic point are every bit good some complex biopolymers present.
b. The primary wall
Cotton is longest unmarried jail cellular telephone every bit compared to other agro-based fibers. Its increment initiates amongst the unmarried jail cellular telephone from the private epidermal cells on the outer integument of the ovules inward the cotton wool fruit. There is a number of cotton wool fibers grow simultaneously from the same cotton wool bowl (cotton seed). Each fiber presents a unmarried jail cellular telephone of plant. In commencement measuring this works life goes to its total length as well as during this menstruation primary wall is formed. This primary wall holds the whole jail cellular telephone works life as well as hold it aligns as well as good oriented. During this period, when the fiber is totally consisting of primary walls, fiber width is 2.98 mm as well as crystalline percent is upwards to 30%.
The primary wall inward a cotton wool fiber is a sparse cinema amongst a thickness of nearly 0.5 μm. It serves every bit the exterior surface of the fiber. In the primary wall, apart from amorphous cellulose, most of the constituents are non-cellulosic materials. This layer is flexible as well as swells uniformly inward all directions. the typical composition of the primary wall amongst details of each component. The primary wall contains amorphous cellulose, pectin’s, proteins, hemicelluloses as well as coloring components. It is of import to study the private factor as well as interconnections inward the primary wall, for attacking specific components amongst enzymes to destabilize the primary wall efficiently.
A brief description of the primary wall components, followed past times a description of their interconnections is given below.
Details of each constituent inward the primary wall
i) Cellulose:
Cellulose inward the primary wall is heterogeneous as well as has a depression flat of polymerization (DP upwards to 2000 glucose units) compared amongst cellulose inward the secondary wall. The amorphous share of cellulose inward a cotton wool fiber is characterized past times its mightiness to swell inward water. The orientation of cellulose macromolecules inward the primary wall is low, that agency that private macromolecules are non arranged inward whatsoever definite order. The cellulose micro fibrils inward the primary wall are surrounded past times a matrix of other non-celluloses. Micro fibrils of cellulose are crystalline aggregates of β(1-4)-linked glucose polymers. They are omnipresent elements of the works life jail cellular telephone wall as well as are responsible for much of its tensile strength.
ii) Hemicelluloses:
Hemi cellulose is the call of a heterogeneous grouping of branched matrix forming polysaccharides. Hemicelluloses bind non-covalently to the surface of cellulose micro fibrils inward the primary wall. They cast a coating over the cellulose micro fibrils as well as are able to cross-link them into a complex network of the primary wall. There are several classes of hemicelluloses amongst an average l glucose units that are linearly β (1-4)-linked to i another. The divergence betwixt various classes of hemicelluloses is expressed inward damage of oligosaccharide side chains
iii) Glycoprotein:
Glycoprotein every bit good known every bit extensions concern human relationship upwards to 15% of the primary jail cellular telephone wall mass. Glycoprotein contains a poly peptide backbone amongst extended rod similar carbohydrates that protrude outwards. The carbohydrates inward the glycoprotein concern human relationship for 65% of the total structure. For a cotton wool fiber, these rod shape extensions are made upwards of roughly 300 amino acids, as well as abundantly comprise hydroxyl-proline (Hyp). Most of the hydroxyl-prolines are glycosylated amongst chains of iii or 4 refined saccharify residues e.g. arabinose as well as galactose. The carboxyl-terminal peptides inward the glycoprotein molecule are covalently linked past times disulfide bonds as well as frequently comprise an oligosaccharide chain. These oligosaccharides chains are every bit good interconnected amongst other polysaccharides inward the primary wall.
iv) Pectin’s:
Pectin’s are acidic polysaccharides, which are establish inward fruits, fibers as well as vegetables. Pectin existence a non-cellulosic textile inward cotton wool fibers plays several of import roles. It contributes to the firmness as well as construction of cotton wool fiber, both every bit a component subdivision of the primary jail cellular telephone wall. Pectin acts every bit cementing textile for the cellulosic network inward the primary wall. Pectin, every bit a hydrating agent, controls the movement of H2O as well as other works life fluids through the apace growing fiber.
v) Coloring matters:
Coloring affair (pigments) inward cotton wool fibers is rarely studied. In the natural state, cotton wool is off-white, cream, brownish or greyish green, depending on the source as well as growing conditions. However these coloring components do non convey component subdivision inward the scouring process.
vi) Metal contents:
The primary wall of a cotton wool fiber contains dissimilar quantities of metallic depending on their growing weather condition as well as source. Potassium is the most abundant metallic ion inward cotton wool fibers followed past times magnesium as well as calcium. Other metallic ions which are introduce inward traces are sodium, iron, manganese, copper as well as zinc. Removal of calcium is essential during the scouring procedure for ameliorate primary wall destabilization. However, removal of ease of the metals from cotton wool fibers is every bit good important, because they tin contribute to problems during farther wet-pretreatment processes similar oxidative bleaching.
c. The secondary wall
Secondary wall formation originates only afterwards the completion of primary wall. Primary wall takes about 20-25 days as well as afterwards that secondary wall synthesis commences which takes 15-22 days as well as it continues for 30-40days. During this menstruation fiber gains weigh of 130 ng/mm, every bit compared to 2ng/mm piece primary wall was nether development. After completion of primary wall, secondary wall is formed. Secondary wall is inward the shape of a band within the subway scheme or cylinder. Notwithstanding, during this menstruation a lumen inward the pump is every bit good produced at the fourth dimension of fiber maturity. Secondary wall is an instance of pure cellulose. Study farther reveals that secondary wall is 94% of the total volume of the fiber material. Thereby secondary wall is contemplated every bit the primary responsible for all sorts of mechanical properties. There is a slight variation inward the density of the jail cellular telephone wall earlier as well as afterwards desiccation. It is 1.55 gm earlier drying as well as afterwards dehydration it reduces to 1.52 gm nether the 65% RH conditions.
Cellulose inward the secondary wall is characterized past times a higher flat of polymerization (nearly 5000 units) compared amongst cellulose inward the primary wall. Table 2.4 shows the various units as well as sub-units of cotton wool cellulose amongst their diameter. In the secondary wall of a cotton wool fiber, 2 cellulose molecules tin cast a long planar chain of β (1-4)-linked glucose units, resulting inward a ribbon similar structure. These 2 cellulose chains forms a sheet, which is called an unproblematic fibril. Micro fibrils of cellulose are crystalline aggregates of around 21 unproblematic cells (Table 2.4). Intermolecular hydrogen bonds play an of import role to stabilize chains of unproblematic fibril to locomote a micro fibril. Finally, a large numbers of such micro fibrils are laying inward parallel management forms the various layers of the secondary jail cellular telephone wall.
b. Waxes: 0.6-1.3%. It is higher monovalent alcohol-tractional, palmitic, oleic acid, glycerin. Its melting betoken is 77.0. It is establish on surface as well as inward primary wall.
c. Pectin’s: 0.9 -1.2%. These are ploygalacturonic acid, as well as its magnesium salts, methyl ester, xylose. These are mainly introduce inward primary wall.
d. Proteins: 0.6-1.3%. These are protoplasm ease inward lumen as well as aspartic, glutamic acid as well as proline, 0.2-0.3% of nitrogen are establish inward primary wall
e. Ash: 1.2%
f. Organic acids: 0.5-1.00%. Salts of citric as well as L-maleic acid
g. Others: (i) Mineral salts: 0.7-1.6%. Hypochlorites of sulphates, phosphates, oxides of silicon, calcium, potassium, magnesium. (ii) Sugar: 0.3%. Glucose, galactose, fructose, pentose. (iii) Toxine: 0.9%. Endotoxine, evolved from bacterial cells.
3.4 Fiber Macro Structure
Under a microscope, a cotton wool fiber appears every bit a really fine, regular fiber. It ranges inward length from nearly 10mm to 65 mm, depending upon the character of the fiber. Each cotton wool fiber is composed of concentric layers. The cuticle layer on the fiber itself is separable from the fiber as well as consists of wax as well as pectin materials. The primary wall, the most peripheral layer of the fiber, is composed of cellulosic crystalline fibrils. The secondary wall of the fiber consists of iii distinct layers. All iii layers of the secondary wall include closely packed parallel fibrils amongst spiral winding of 25-35o as well as correspond the bulk of cellulose within the fiber. The innermost component subdivision of cotton wool fiber- the lumen- is composed of the remains of the jail cellular telephone contents. Before boll opening, the lumen is filled amongst liquid containing the jail cellular telephone nucleus as well as protoplasm. The twists as well as convolutions of the dried fiber are due to the removal of this liquid. The cross department of the fiber is bean-shaped, swelling almost circular when wet absorption takes place.
The overall contents are broken downwards into the next components.
 |
| Figure: 3.2 Fiber Macro Structure |
The density method used to create upwards one's heed cellulose Crystallinity is based on the density slope column, where 2 solvents of dissimilar densities are partially mixed. Degree of Crystallinity is, then, determined from the density of the sample, piece densities of crystalline as well as amorphous cellulose forms are known (1.505 as well as 1.556 respectively). Orientation of untreated cotton wool fiber is wretched because the crystallites are contained inward the micro fibrils of the secondary wall, oriented inward the steep spiral (25-30o) to the fiber axis.
3.6 Chemistry of Cotton Cellulose
Cellulose is an insoluble kernel as well as mainly composed of polysaccharide, which holds chains of glucose monomers. It is alone soluble inward some specific solvents. It is the primary constituent of works life jail cellular telephone walls as well as every bit good every bit of vegetable fibers. Cotton is i of the vegetable fibers which direct hold the highest percent of cellulose. There is a various structures as well as compositions of cellulose of cotton. Its construction makes it divergent from other naturally occurring matters. Cotton cellulose is unique inward many ways as well as possesses distinct characteristics which larn inward highly useful for many purposes. It has been assumed that cotton wool cellulose construction is based on glucose unit of measurement only. However, it is every bit good believed that at that topographic point is small-scale amount of pentose is present, which is removed during scouring process. They farther study that it has been notices from the chromatographic analysis that glucose, xylose, arabinose as well as a line of rhamnose are every bit good introduce inward raw cotton. There is no evidence of the presence of pentose. Cotton cellulose is highly crystalline inward nature as well as good oriented as well as has along as well as stiff molecular structure. The 1,4-D glucopyranose are the regulation edifice blocks of cotton wool cellulose chain as well as are linked past times l,4-glucodic bonds. Free rotation of the anhydrogluco-pyranose C-O-C link is stopped past times steric effects. There are iii hydroxyl groups attached to each anhydroglucose. One grouping is attached at C-6 as well as 2 at C-2 as well as C-3. Due to the presence of hydroxyl groups as well as the chain conformation, at that topographic point are many to a greater extent than bonds possible (inter molecule as well as intramolecular). Such bonds brand the fiber to a greater extent than stiff past times increasing the rigidity of the construction of cotton wool cellulose.
3.7 Cross Section of Cotton Fiber
The jail cellular telephone wall is a dynamic construction which composition as well as cast tin alter markedly, non alone during jail cellular telephone increment but every bit good afterwards the cells direct hold locomote matured. The cotton wool fiber is structurally built upwards into concentric zones as well as a hollow cardinal core known every bit the lumen.
 |
| Figure: 3.3 Influenza A virus subtype H5N1 schematic Representation of Mature Cotton Fiber Showing its Various Layers. |
Figure illustrates schematically the distribution of cellulose as well as other non-cellulosic materials inward the various layers of cotton wool fiber.. The outermost layer is the cuticle. It is a sparse cinema of by as well as large fats as well as waxes. Owing to non-structured orientation of cellulose as well as non-cellulosic materials, the primary wall surfaces is unorganized as well as open. This gives the flexibility to the primary wall, which is required during the jail cellular telephone growth.
3.9 Different Layer of Cotton Cellulose Structure
 |
| Figure: 3.4 Influenza A virus subtype H5N1 Schematic Representation of the Cellulosic Materials inward the Cotton Fiber. |
The aerial surfaces of vascular plants are covered amongst an extra cellular layer called the cuticle or cuticular membrane that overlays the jail cellular telephone wall of epidermal cells. The term “cotton waxes” has been used for all lipid compounds establish inward the cuticle of fiber. The primary role ascribed to the cuticle is to minimize H2O losses from cotton wool fiber. Other functions are, to restrict the loss of substances from fibers internal tissues, as well as to protect the fiber against physical, chemic as well as biological aggressions. The cuticle contains primary alcohols, higher obese acids, hydrocarbons, aldehydes, glycerides, sterols, acyl components, resins, cutin as well as sobering, which are called waxes. The cuticle gives a soft touching to the fiber as well as reduces the friction forces during spinning. At the same time, presence of these waxy materials is Initiation of fiber increment detrimental inward chemic processing of cotton wool yarn because it gives the fiber surface a high hydrophobicity. The cotton wool waxes are solid substances amongst rather high as well as broad hit of melting points (64°C to 214°C) as well as constitute about 0.4 to 0.8% dry out weight of raw cotton wool After handling amongst boiling NaOH, waxes are hydrolyzed into a sodium tabular array salt of the obese acid as well as alcohol. Apart from the higher upwards mentioned components inward the cuticle, at that topographic point are every bit good some complex biopolymers present.
b. The primary wall
Cotton is longest unmarried jail cellular telephone every bit compared to other agro-based fibers. Its increment initiates amongst the unmarried jail cellular telephone from the private epidermal cells on the outer integument of the ovules inward the cotton wool fruit. There is a number of cotton wool fibers grow simultaneously from the same cotton wool bowl (cotton seed). Each fiber presents a unmarried jail cellular telephone of plant. In commencement measuring this works life goes to its total length as well as during this menstruation primary wall is formed. This primary wall holds the whole jail cellular telephone works life as well as hold it aligns as well as good oriented. During this period, when the fiber is totally consisting of primary walls, fiber width is 2.98 mm as well as crystalline percent is upwards to 30%.
The primary wall inward a cotton wool fiber is a sparse cinema amongst a thickness of nearly 0.5 μm. It serves every bit the exterior surface of the fiber. In the primary wall, apart from amorphous cellulose, most of the constituents are non-cellulosic materials. This layer is flexible as well as swells uniformly inward all directions. the typical composition of the primary wall amongst details of each component. The primary wall contains amorphous cellulose, pectin’s, proteins, hemicelluloses as well as coloring components. It is of import to study the private factor as well as interconnections inward the primary wall, for attacking specific components amongst enzymes to destabilize the primary wall efficiently.
A brief description of the primary wall components, followed past times a description of their interconnections is given below.
Details of each constituent inward the primary wall
i) Cellulose:
Cellulose inward the primary wall is heterogeneous as well as has a depression flat of polymerization (DP upwards to 2000 glucose units) compared amongst cellulose inward the secondary wall. The amorphous share of cellulose inward a cotton wool fiber is characterized past times its mightiness to swell inward water. The orientation of cellulose macromolecules inward the primary wall is low, that agency that private macromolecules are non arranged inward whatsoever definite order. The cellulose micro fibrils inward the primary wall are surrounded past times a matrix of other non-celluloses. Micro fibrils of cellulose are crystalline aggregates of β(1-4)-linked glucose polymers. They are omnipresent elements of the works life jail cellular telephone wall as well as are responsible for much of its tensile strength.
ii) Hemicelluloses:
Hemi cellulose is the call of a heterogeneous grouping of branched matrix forming polysaccharides. Hemicelluloses bind non-covalently to the surface of cellulose micro fibrils inward the primary wall. They cast a coating over the cellulose micro fibrils as well as are able to cross-link them into a complex network of the primary wall. There are several classes of hemicelluloses amongst an average l glucose units that are linearly β (1-4)-linked to i another. The divergence betwixt various classes of hemicelluloses is expressed inward damage of oligosaccharide side chains
iii) Glycoprotein:
Glycoprotein every bit good known every bit extensions concern human relationship upwards to 15% of the primary jail cellular telephone wall mass. Glycoprotein contains a poly peptide backbone amongst extended rod similar carbohydrates that protrude outwards. The carbohydrates inward the glycoprotein concern human relationship for 65% of the total structure. For a cotton wool fiber, these rod shape extensions are made upwards of roughly 300 amino acids, as well as abundantly comprise hydroxyl-proline (Hyp). Most of the hydroxyl-prolines are glycosylated amongst chains of iii or 4 refined saccharify residues e.g. arabinose as well as galactose. The carboxyl-terminal peptides inward the glycoprotein molecule are covalently linked past times disulfide bonds as well as frequently comprise an oligosaccharide chain. These oligosaccharides chains are every bit good interconnected amongst other polysaccharides inward the primary wall.
iv) Pectin’s:
Pectin’s are acidic polysaccharides, which are establish inward fruits, fibers as well as vegetables. Pectin existence a non-cellulosic textile inward cotton wool fibers plays several of import roles. It contributes to the firmness as well as construction of cotton wool fiber, both every bit a component subdivision of the primary jail cellular telephone wall. Pectin acts every bit cementing textile for the cellulosic network inward the primary wall. Pectin, every bit a hydrating agent, controls the movement of H2O as well as other works life fluids through the apace growing fiber.
v) Coloring matters:
Coloring affair (pigments) inward cotton wool fibers is rarely studied. In the natural state, cotton wool is off-white, cream, brownish or greyish green, depending on the source as well as growing conditions. However these coloring components do non convey component subdivision inward the scouring process.
vi) Metal contents:
The primary wall of a cotton wool fiber contains dissimilar quantities of metallic depending on their growing weather condition as well as source. Potassium is the most abundant metallic ion inward cotton wool fibers followed past times magnesium as well as calcium. Other metallic ions which are introduce inward traces are sodium, iron, manganese, copper as well as zinc. Removal of calcium is essential during the scouring procedure for ameliorate primary wall destabilization. However, removal of ease of the metals from cotton wool fibers is every bit good important, because they tin contribute to problems during farther wet-pretreatment processes similar oxidative bleaching.
c. The secondary wall
Secondary wall formation originates only afterwards the completion of primary wall. Primary wall takes about 20-25 days as well as afterwards that secondary wall synthesis commences which takes 15-22 days as well as it continues for 30-40days. During this menstruation fiber gains weigh of 130 ng/mm, every bit compared to 2ng/mm piece primary wall was nether development. After completion of primary wall, secondary wall is formed. Secondary wall is inward the shape of a band within the subway scheme or cylinder. Notwithstanding, during this menstruation a lumen inward the pump is every bit good produced at the fourth dimension of fiber maturity. Secondary wall is an instance of pure cellulose. Study farther reveals that secondary wall is 94% of the total volume of the fiber material. Thereby secondary wall is contemplated every bit the primary responsible for all sorts of mechanical properties. There is a slight variation inward the density of the jail cellular telephone wall earlier as well as afterwards desiccation. It is 1.55 gm earlier drying as well as afterwards dehydration it reduces to 1.52 gm nether the 65% RH conditions.
Cellulose inward the secondary wall is characterized past times a higher flat of polymerization (nearly 5000 units) compared amongst cellulose inward the primary wall. Table 2.4 shows the various units as well as sub-units of cotton wool cellulose amongst their diameter. In the secondary wall of a cotton wool fiber, 2 cellulose molecules tin cast a long planar chain of β (1-4)-linked glucose units, resulting inward a ribbon similar structure. These 2 cellulose chains forms a sheet, which is called an unproblematic fibril. Micro fibrils of cellulose are crystalline aggregates of around 21 unproblematic cells (Table 2.4). Intermolecular hydrogen bonds play an of import role to stabilize chains of unproblematic fibril to locomote a micro fibril. Finally, a large numbers of such micro fibrils are laying inward parallel management forms the various layers of the secondary jail cellular telephone wall.
 |
| Figure: 3.5 An illustration of various stages of cotton wool fiber growth. |
Next component subdivision volition seat out soon.....