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Transcript of fiber science
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Fiber Science
Fiber Science is the study of the formation, structure, and properties of fibers on micro to macroscopic levels.
The study of fibrous materials and their use in a variety of conventional and non-conventional applications.
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Type of fibers
1- Manmade/Manufactured
a)- Synthetic ( Nylon, polyester, acrylic)
b)- Regenerated ( Rayon)
2- Natural Fibers
a)- Cellulosic origin
b)- Protein origin
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Fiber Length
Length of fiber ClassUnit of
measurement Appearance
Long Filament fibers Yards/meters
Short Short fibers Inches/centimeters
Classification of fibers on the basis of length
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Fiber Applications
Home Textile
Technical Applications
Apparel
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Apparel Applications
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Home Textiles
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Technical Textiles
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Fiber Science
Properties of fibers
1-Physical Properties
2-Chemical Properties
3-Mechanical Properties
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Fiber Science
Physical Properties of fibers
Length
Fineness
Crimp
Maturity
Toughness
Elongation
Lusture etc.
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Fiber Science
Mechanical Properties of fibers
Strength
Elasticity
Extensibility
Rigidity
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Fiber Science
C) Chemical Properties
Solubility in aqueous salt
Solubility in organic salt
Chemical composition
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Chemical structure of synthetic fibers
Monomers Vs Polymers
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Synthetic Fibers
Monomer Vs Polymer
(Polyethylene terephthalate (PET)
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Synthetic Fibers
Nylon 6 is synthesized by polymerization of caprolactam
caprolactam Nylon 6
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Synthetic Fibers
Polyester is formed by Poly-condensation of PET monomer
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Synthetic Fibers
In PET fibres, the molecules are mainly arranged in fiber, film and in package form
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Flax
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Cotton
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Silk
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Wool
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Cashmere and Mohair
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Synthetic Fibers
• Rayon –1st artificial fiber from wood
• Acetate – artificial from wood (satin)
• Nylon –1st synthetic fiber• Olefin – synthetic (carpet)
• Acrylic – synthetic wool• Polyester – most common syn.• Specialty fibers – Kevlar, Spandex
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Rayon
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Acetate
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Nylon
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Olefin and Acrylic
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Polyester
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Manufactured fibers
Manufactured (MF) fibers (formerly termed “man-made”) are formedfrom a suitable raw material as a thick, sticky liquid, which is “spun”or extruded through spinneret holes, forming streams that aresolidified into fibers
The raw material for MF fibers may be itself a natural substance, or itmay be synthetic (synthesized from basic chemical units), but it isconverted into textile fibers by a manufacturing process
While there are MF fibers made of natural rubber (as well as ofsynthetic rubber), there is no such thing as a natural rubber fiber.Similarly, Tencel lyocell is not a natural fiber; it is an MF fiber made ofa natural material, cellulose
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Textile fibers are made up of molecules, these fiber molecules are called polymers.
The Unit of polymer is called monomer ( mono-one: mer-part)
At molecular level, polymer is extremely long and linear whereas monomer is very small
Monomers are usually reactive whereas polymers tend to be unreactive
This causes the monomers to join end to end to form a polymer called polymerization
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Polymerization
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Length of polymer is most important. All fibers, both natural and man made have long to extremely long polymer lengths
Measuring length of polymer is complicated yet not impossible
Degree of polymerization (DP) is therefore calculated
Degree of Polymerization=
Average molecular weight of polymer
Molecular weight of the repeating unit in the polymer
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• 5000 DP for cotton means 5000 repeating units (cellobiose)
• Polymerization of natural polymers are not known
• Polymerization of synthetic polymer is categorized into
a. Addition Polymerization
a. Condensation Polymerization
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a)- Addition Polymerization
Monomers add or join end to end without liberating any by product on polymerization.
Some fibers which consist of addition polymerization are acrylic, modacrylic, polyethylene, polypropylene etc.
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b) Condensation Polymerization
In this process monomers join end to end and liberate a by product
This product is a simple compound, e-g water, ammonia, hydrogen chloride
Some fibers consisting of condensation polymerization are elastomeric, nylon and polymers.
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• Polymers of cotton, acetate, flax, silk, triacetate, viscose andother regenerated fibers and wool don’t fit into aboveclassification because not enough is yet known about theirpolymers and synthesis
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Types of polymers
1-Homopolymer ( Same or one kind of polymer)
2-Copolymer ( Two or more different polymers)
Copolymers are further divided into
i. Alternating copolymer
ii. Block Polymer
iii. Graft Polymer
iv. Random polymer
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Types of Polymer
Homopolymer Homos is “same” or one kind of polymer
Nylon, vinyl chloride, polypropylene
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The lack of branches in its structure
allows the polymer chains to pack closely
together, resulting in a dense, highly
crystalline material of high strength and
moderate stiffness.
500,000 atomic units for High Density
Polyethylene
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Copolymer
Polymerized from two or more monomers
• Silk is composed of 16 different amino acids
• Wool is composed of 20 different amino acids
Copolymers are sub categorized into four groups
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A thermoplastic resin produced by the
copolymerization of styrene and maleic
anhydride
A rigid, heat-resistant, and chemical-resistant
plastic, it is used in automobile parts, small
appliances, and food-service trays
most of the copolymers contain about 5 to 20
percent maleic anhydride, depending on the
application, and some grades also contain
small amounts of butadiene for better impact
resistance.
Alternating copolymer
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Copolymers can be used to tailor functionality or generate
new behaviors.
Block copolymer, example:
Poly(styrene)-block-poly(butadiene)
Random copolymer, example:
Poly(styrene-ran-butadiene)
Graft copolymer,
example:
Poly(styrene)-graft-
poly(butadiene)
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Combs, brushes and ladders give you ways to stiffen a polymer.
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Rod like polymers are used for very high strength, liquid crystals, efficient viscosification
S
N
S
N
* *n
Rodlike because of helix
Rodlike because of linear backbone
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Crystalline and amorphous
regions
Crystalline regions provide
strength and amorphous regions
provide stretch
Amorphous and crystalline regions
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(a) Linear structure; thermoplastics such
as acrylics, nylons, polyethylene, and
polyvinyl chloride have linear structures.
(b) Branched structure, such as
polyethylene.
(c) Crosslinked structure; many rubbers
and elastomers have this structure.
(d) Network structure, is highly cross-
linked; examples include thermosetting
plastics such as epoxies and phenolics.
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Possible arrangement of monomers in a polymer
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Chemical Bonds
The basic nature and reactivity of the fiber can be derived bythe type of chemical bond that holds the polymers together
A chemical bond is an attraction between atoms that allowsthe formation of chemical substances that contain two or moreatoms
The bond is caused by the electromagnetic force attractionbetween opposite charges, either between electrons and nuclei,or as the result of a dipole attraction
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Classification of Bonds
Chemical bond can be broadly classified as follows
• Intra-polymer bonds
• Inter-polymer bonds
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Intra-polymer Bonding
• Bonds holding the atoms together to make up the fibre polymer is
called intra-polymer bonding.
• Textile fibre polymers are mainly organic compounds, expect some
natural mineral and man-made inorganic fibres.
• They are predominantly composed of carbon and hydrogen atoms,
with some oxygen, nitrogen, chlorine and/or fluorine atoms.
• In general, single covalent bonds join the atoms forming the polymer
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Intra-polymer Bonds
The major bonds that are used for intermolecular bonding are as follow
• Covalent bonds
• Amide or peptide group
• Benzene ring
• Ether linkages
• Ester groups
• Hydroxyl group
• Nitrile group
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Covalent bonds
Covalent bonding is a common type of bonding, in which theelectro negativity difference between the bonded atoms is smallor nonexistent.
Their bond energy or bond strength is between 330 and 420kilojoules
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The amide or peptide group:
In chemistry, an amide is an organic compound that contains the functional group consisting of a carbonyl group (R-C=O) linked to a nitrogen atom (N).
When present in nylon polymers it is called the amide group.
It is also present in silk, wool, mohair and all other animal or protein fibres and then it is called peptide group
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Benzene rings
They are sometimes referred to as the aromatic radical.
It is a hexagon shaped molecule composed of mainly carbon and hydrogen
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Ether linkages
• The ether linkages may be found in polymers such as cellulose, elastomeric, ester-cellulose and polyesters.
• It exists between carbon and oxygen atoms.
• Ethers are chemically unreactive. One reason for this is the great chemical stability of the carbon-oxygen linkages found in every ether molecule.
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Ester groups
• They are formed by replacing the hydrogen of an acid with an organic radical.
• In fibre polymers they are usually the reactions between:
a. A carboxyl group (-COOH), also called carboxylic acid
b. A hydroxyl group (-OH)
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Inter polymer bonds
• In basic senses these bonds are responsible for holding the polymers together for the formation of a fibre.
• The major bonds used for interpolymer bonding are as follows,
Van der Waals forces
Hydrogen bonds
Salt linkages
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Van der Waals forces:
They are weak forces which exist in the interpolymer forces of attraction when the atoms come close to one another.
They are formed between atoms along the length of adjacent polymers when these are less than 0.3 nm apart but no closer than about 0.2 nm.
They occur between all fibre polymer system and their bond energy in 8.4 KJ.
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Hydrogen bonds
They are formed between hydrogen and oxygen atoms, and hydrogen and nitrogen atoms on adjacent polymers when these are less than 0.5 nm apart.
They occur within the natural polymers, regenerated cellulose polymers, nylon polymers, polyvinyl alcohol, polyester polymers, protein and secondary cellulose acetate fibres.
Their bond energy is 20.9 KJ
The hydrogen bonds are mainly responsible for the tenacity and the elastic-plastic nature of the natural, regenerated cellulose, nylon, PVA and protein fibres
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Salt linkages
• They are formed between the carboxyl radical on one polymer and the positively charged amino group on an adjacent polymer.
• They exist mainly in the protein and nylon fibre polymers.
• Their bond energy is 54.4 KJ.
• They are responsible for the attraction of the water molecules and they too contribute to the strength of the fibre.
• The presence of salt linkages is necessary for dye absorption