Chapter 11 Silk Fibers
Introduction
? The larva of certain insects for use in
their building webs,climbing ropes
and cocoons
? Spiders
? Commercial silk industry,use larva of
silkworm
? Application,Mostly apparel,was also
used for parachutes.
Structure
? Macrostructure:
? Length,1000-1300 yds (915-1190 m)/cocoon
Max 3000yds (2750m)/cocoon,1 fiber/cocoon.
? Thickness,
? 9-11 mm or 1.2-1.5 denier.
? Varies,thickest in the middle thinnest
inside (maybe running out of raw material,
or maybe just make itself comfortable).
Structure
? Microstructure
? cross-section,2 triangular filaments co-
extruded by a worm,
? The two are called brins held together by
sericin (gum or silk glue).
? Wild silk worms produce ribbon-like silk
fibers
Structure
? Submicrostructure
? Silk from cultivated worm,no identifiable
submicrostructure.
? Wild silk or Tussah silk has internal
fibrillar structure.
Structure
? Fibroin protein polymer
? A chain of amino acids forming a protein called
fibroin composed of 15-18 different amino acids.
? Glycine,alanine and serine occupy 86% of the
polymer
? The side groups of the above 3 amino acids are
small compared with those in wool:
? glycine,R = H
? alanine,R = -CH3
? Serine,R = -CH2OH
? Crystallize readily,70-75%
Structure
? Fibroin protein polymer
? Pack well,lots of H-bonds,small number of ionic
bonds
? No cystine,no S-S bonds
? Configuration,pleated b-sheet
? Degree of polymerization of silk DPsilk > DPwool
Properties
? For silk producers,i.e,silk worm,
spider etc.,silk fibers are for
protection,transport and food
capture
? Mechanical properties
? Medium tenacity but higher than wool
? resulted from molecular structure,
? zigzag b-sheet of silk vs a-helix of wool
? higher crystallinity than wool
Properties
? Mechanical properties
? Medium elongation at break
? High elastic recovery at low elongation
? When elongated 2%,90% elastic recovery
? Medium modulus
? Medium abrasion resistance
? Medium resilience,(cotton < silk < wool)
pleated sheets can slide over one-
another.
Properties
? Comfort
? High heat of wetting,lots of polar groups
available
? High water absorption,up to 1/3 of its
weight
? Smooth and soft
? High luster,high crystallinity and
triangular cross-sectional shape.
? Scroop,rustling sound due to an acid
treatment that hardens fiber surface.
Properties
? Other properties
? Ignites and burns but sometimes
selfextinguishing
? Dry-cleaning preferred due to:
? lower tenacity and initial modulus when wet
? degraded by alkaline solutions
? may be hand-washed using mild detergents
? Lowest UV light resistance,avoid
prolonged exposure to sunshine
Production
? Moth,Bombyx fed on mulberry tree
leaves
? World production,145.5 million
lbs/yr
? Originally from China
? Types,
? Raw silk,silk with gum
? Tussah,wild silk
? Duppioni,2 silk worm spin their
cocoons together,having special
appearance similar to wild silk but
Chapter 12 Cotton Fibers
Introduction
? Cotton,seed hair obtained from the boll of
the cotton plant
? ~ 4000 fibers/seed,max 20,000 fibers/seed
? 250,000 fibers/boll
? Types,
? Commodity,Upland
? Long staple,
? Pima-Su Pima
? Sea island
? Egyptian
? Other,naturally colored
Introduction
? Application,
? ~55% of apparel fibers are cotton
? ~70% of men’s apparels made of cotton
? ~40% of women’s apparels made of cotton
? 65% of all cotton fibers were used for apparels
in 1990
? Additional 27% of cotton for sheets and towels
or other non-apparel household applications
? ~7% for industrial use
Structure
? Cotton fiber,single plant cell
? Macrostructure
? Staple length,1/8” - 2.5” (0.32 - 6.35
cm)
? Cotton fibers used in textile yarns,7/8” -
1.25”
? Diameters,16 - 20 mm but varies from
fiber to fiber,longer fibers are finer
? Length to breadth ratio,6000:1 to 350:1
? Relatively uniform along its length
? Color,never truly white but creamy
white to gray
Structure
? Microstructure
? Flat,twisted ribbon
? 125 twists/inch (convolutions)
? The twists reverse in direction along the
length
? Cross-section,kidney-bean shaped with
a lumen
Structure
? Submicrostructure
? 5 distinctive regions:
? Cuticle,out layer of wax,a few molecules
thick to protect seeds but can be removed
by wet processing and laundering.
? Primary wall,composed of fibrils,a sheath
of spiraling fibrils 20 - 30 degree to the
fiber axis
? Mature fibers - thicker primary walls;
? immature fibers thinner primary walls and
entangles,forming clumps called neps,leading
to nonuniform dye properties and irregular
surface of fabrics
Structure
? Submicrostructure
? 5 distinctive regions:
? Secondary wall,
? bulk of the fiber
? concentric layer of spiraling fibrils similar to
rings of trees
? ~20 rings and each corresponding to 1 day’s
growth.
? outmost layer of secondary wall,winding layer
? Lumen,hollow canal running through the
length of the fiber
Structure
? Polymer system
? Linear cellulose
? Average Degree of Polymerization 6,000 to
10,000
? Functional side group,-OH
? Crystallinity,65 - 70% but depends on how to
define.
? H-bonding sites,not -OH to -OH but OH to the O
group between the neighboring two rings,
confers strength and additional rigidity to the
fiber.
? -OH,reacting with a variety of chemicals,thus
finish can be applied easily,also attract and hold
water.
Structure
? Polymer system
? -C-O-C- bonds are more susceptible to oxidation
than C-C-C bonds
? 20 ~ 41% unoccupied space,1/3 by lumen
Properties
? Mechanical Properties
? Tenacity and initial modulus,medium
? Elongation at break,low,spiral fibrils,
makes it relatively brittle
? Elastic recovery,low,only 75% at 2%
extension,due to H-bond
Properties
? Comfort
? Fiber ends and convolutions,comfortable
to touch
? Hydrophilic,max water absorption,25-
27% regain due to -OH group and fibrils
? Upon water absorption,fibers become
softer and collapses on to skin,dries
slowly
? When it is dry,comfortable because of
water absorption,water vapor transfer
and no static charge
Properties
? Comfort
? Water resistant fabric possible,swelling of fibers
in water,no liquid water penetration
? Maintenance
? Soiling,easy to be soiled and desoiled due to -
OH groups
? Launderability,dimensionally stable and tenacity
increases when wet (10-20%) due to
improvement of fibril orientation and thus
molecular orientation.
Properties
? Maintenance
? No special precautions for laundering,
high temperature,any detergents,and
bleaches can be used.
? Shrinkage likely due to relaxation of yarn
tension induced by processing
Properties
? Other properties
? acids cause degradation of cotton or
cellulose,acid free paper for long lasting
items
? not affected by most of organic solvents
? damaged by fungi and bacteria
? prolonged exposure to sunlight,yellow
? heat resistant
? low luster
? high cover power
Properties
? Other properties
? no pill but lint
? highly flammable and can smolder
without fire for hours,need flame-
retardant treatment for many end uses
? biodegradable
? can be boiled and sterilized,good for
hospital use
Mercerized cotton
? Process:(applied to either fibers or
yarns)
?cold bath of 18-27% NaOH for 1 minute
or less
?rinsed and neutralized by a cold acid
bath
?tension applied to break H-bonds
?polymer rearranged and reoriented,
untwist
?rounder cross-section and the
convolutions are nearly gone
? Stronger,more lustrous and easier to
Chapter 14 Rayon
Introduction
? Rayon,ray of light on
? Invented 1884
? Definition,manufactured fibers
composed of 100% regenerated
cellulose,as well as manufactured
fibers of regenerated cellulose in
which substituents have replaced not
more than 15% of the hydrogens of
the -OH groups.
Introduction
? Made from 4 processes:
? Nitro cellulose,made in U.S,during
20’s-40’s and easy to explode.
? Viscose,95% today spun in U.S.
? Cuprammonium,use cuprammonium
hydroxide solvent as spinning solution
? Lyocell
Introduction
? < 4% of total fiber consumed in the
U.S.
? Usage,
? 52.4% apparels
? 26.8% nonwovens
? 20.8% households
Structures
? Macrostructure
? Continuous filaments or staple,1.5-15
denier
? Microstructure:
? Surface,striated
? Cross-section,serrated
? Submicrostructure
? Skin-core structure,caused by spinning
process
? Skin,small crystal,imperfect,darker
? Core,large,more perfect crystal
Structures
? Molecular
? Regular viscose rayon,DP~400 (cotton
6k-10k)
? 35 - 40% amorphous
Properties
? Mechanical
? Medium tenacity and elongation
? Low initial modulus
? Low elastic recovery
? Low bending rigidity
? Tenacity and modulus drops drastically
upon water absorption,-50%,
Elongation to failure +20%.
Properties
? Comfort
? Hydrophilic and high moisture regain,
13% at 70% RH,more absorbent than
cotton due to more amorphous region,
High heat of wetting
? High cross-sectional swelling
? Irregular surface next to skin,
comfortable
? No static charge build up
Properties
? Maintenance
? difficult to launder due to mechanical
property change in water
? degrades in medium acids,strong
alkalies,bleaches and sunlight more
than any other cellulosic fibers
? highly flammable
Production
? Viscose process,
? purified cellulose in sheet form
? viscose solution
? pumped through spinnerets into a
coagulation bath
? solid cellulose
Production
? Preparation of spinning solution
? cellulose extracted from wood (sheet
form
? steeped in NaOH
? cellulose swell and converted to alkali
cellulose
? the alkalied pulp sheets are pressed and
shredded into crumbs
? crumbs are aged (chemical reaction
occurs between cellulose and O2 to
reduce DP of cellulose)
Production
? Preparation of spinning solution
? react with carbon disulfide CS2
? bright orange crumbs,cellulose xanthate;
ready for spun
? crumbs then dissolved in dilute NaOH to
form a honey colored liquid and aged to
correct viscosity and filtered
Introduction
? The larva of certain insects for use in
their building webs,climbing ropes
and cocoons
? Spiders
? Commercial silk industry,use larva of
silkworm
? Application,Mostly apparel,was also
used for parachutes.
Structure
? Macrostructure:
? Length,1000-1300 yds (915-1190 m)/cocoon
Max 3000yds (2750m)/cocoon,1 fiber/cocoon.
? Thickness,
? 9-11 mm or 1.2-1.5 denier.
? Varies,thickest in the middle thinnest
inside (maybe running out of raw material,
or maybe just make itself comfortable).
Structure
? Microstructure
? cross-section,2 triangular filaments co-
extruded by a worm,
? The two are called brins held together by
sericin (gum or silk glue).
? Wild silk worms produce ribbon-like silk
fibers
Structure
? Submicrostructure
? Silk from cultivated worm,no identifiable
submicrostructure.
? Wild silk or Tussah silk has internal
fibrillar structure.
Structure
? Fibroin protein polymer
? A chain of amino acids forming a protein called
fibroin composed of 15-18 different amino acids.
? Glycine,alanine and serine occupy 86% of the
polymer
? The side groups of the above 3 amino acids are
small compared with those in wool:
? glycine,R = H
? alanine,R = -CH3
? Serine,R = -CH2OH
? Crystallize readily,70-75%
Structure
? Fibroin protein polymer
? Pack well,lots of H-bonds,small number of ionic
bonds
? No cystine,no S-S bonds
? Configuration,pleated b-sheet
? Degree of polymerization of silk DPsilk > DPwool
Properties
? For silk producers,i.e,silk worm,
spider etc.,silk fibers are for
protection,transport and food
capture
? Mechanical properties
? Medium tenacity but higher than wool
? resulted from molecular structure,
? zigzag b-sheet of silk vs a-helix of wool
? higher crystallinity than wool
Properties
? Mechanical properties
? Medium elongation at break
? High elastic recovery at low elongation
? When elongated 2%,90% elastic recovery
? Medium modulus
? Medium abrasion resistance
? Medium resilience,(cotton < silk < wool)
pleated sheets can slide over one-
another.
Properties
? Comfort
? High heat of wetting,lots of polar groups
available
? High water absorption,up to 1/3 of its
weight
? Smooth and soft
? High luster,high crystallinity and
triangular cross-sectional shape.
? Scroop,rustling sound due to an acid
treatment that hardens fiber surface.
Properties
? Other properties
? Ignites and burns but sometimes
selfextinguishing
? Dry-cleaning preferred due to:
? lower tenacity and initial modulus when wet
? degraded by alkaline solutions
? may be hand-washed using mild detergents
? Lowest UV light resistance,avoid
prolonged exposure to sunshine
Production
? Moth,Bombyx fed on mulberry tree
leaves
? World production,145.5 million
lbs/yr
? Originally from China
? Types,
? Raw silk,silk with gum
? Tussah,wild silk
? Duppioni,2 silk worm spin their
cocoons together,having special
appearance similar to wild silk but
Chapter 12 Cotton Fibers
Introduction
? Cotton,seed hair obtained from the boll of
the cotton plant
? ~ 4000 fibers/seed,max 20,000 fibers/seed
? 250,000 fibers/boll
? Types,
? Commodity,Upland
? Long staple,
? Pima-Su Pima
? Sea island
? Egyptian
? Other,naturally colored
Introduction
? Application,
? ~55% of apparel fibers are cotton
? ~70% of men’s apparels made of cotton
? ~40% of women’s apparels made of cotton
? 65% of all cotton fibers were used for apparels
in 1990
? Additional 27% of cotton for sheets and towels
or other non-apparel household applications
? ~7% for industrial use
Structure
? Cotton fiber,single plant cell
? Macrostructure
? Staple length,1/8” - 2.5” (0.32 - 6.35
cm)
? Cotton fibers used in textile yarns,7/8” -
1.25”
? Diameters,16 - 20 mm but varies from
fiber to fiber,longer fibers are finer
? Length to breadth ratio,6000:1 to 350:1
? Relatively uniform along its length
? Color,never truly white but creamy
white to gray
Structure
? Microstructure
? Flat,twisted ribbon
? 125 twists/inch (convolutions)
? The twists reverse in direction along the
length
? Cross-section,kidney-bean shaped with
a lumen
Structure
? Submicrostructure
? 5 distinctive regions:
? Cuticle,out layer of wax,a few molecules
thick to protect seeds but can be removed
by wet processing and laundering.
? Primary wall,composed of fibrils,a sheath
of spiraling fibrils 20 - 30 degree to the
fiber axis
? Mature fibers - thicker primary walls;
? immature fibers thinner primary walls and
entangles,forming clumps called neps,leading
to nonuniform dye properties and irregular
surface of fabrics
Structure
? Submicrostructure
? 5 distinctive regions:
? Secondary wall,
? bulk of the fiber
? concentric layer of spiraling fibrils similar to
rings of trees
? ~20 rings and each corresponding to 1 day’s
growth.
? outmost layer of secondary wall,winding layer
? Lumen,hollow canal running through the
length of the fiber
Structure
? Polymer system
? Linear cellulose
? Average Degree of Polymerization 6,000 to
10,000
? Functional side group,-OH
? Crystallinity,65 - 70% but depends on how to
define.
? H-bonding sites,not -OH to -OH but OH to the O
group between the neighboring two rings,
confers strength and additional rigidity to the
fiber.
? -OH,reacting with a variety of chemicals,thus
finish can be applied easily,also attract and hold
water.
Structure
? Polymer system
? -C-O-C- bonds are more susceptible to oxidation
than C-C-C bonds
? 20 ~ 41% unoccupied space,1/3 by lumen
Properties
? Mechanical Properties
? Tenacity and initial modulus,medium
? Elongation at break,low,spiral fibrils,
makes it relatively brittle
? Elastic recovery,low,only 75% at 2%
extension,due to H-bond
Properties
? Comfort
? Fiber ends and convolutions,comfortable
to touch
? Hydrophilic,max water absorption,25-
27% regain due to -OH group and fibrils
? Upon water absorption,fibers become
softer and collapses on to skin,dries
slowly
? When it is dry,comfortable because of
water absorption,water vapor transfer
and no static charge
Properties
? Comfort
? Water resistant fabric possible,swelling of fibers
in water,no liquid water penetration
? Maintenance
? Soiling,easy to be soiled and desoiled due to -
OH groups
? Launderability,dimensionally stable and tenacity
increases when wet (10-20%) due to
improvement of fibril orientation and thus
molecular orientation.
Properties
? Maintenance
? No special precautions for laundering,
high temperature,any detergents,and
bleaches can be used.
? Shrinkage likely due to relaxation of yarn
tension induced by processing
Properties
? Other properties
? acids cause degradation of cotton or
cellulose,acid free paper for long lasting
items
? not affected by most of organic solvents
? damaged by fungi and bacteria
? prolonged exposure to sunlight,yellow
? heat resistant
? low luster
? high cover power
Properties
? Other properties
? no pill but lint
? highly flammable and can smolder
without fire for hours,need flame-
retardant treatment for many end uses
? biodegradable
? can be boiled and sterilized,good for
hospital use
Mercerized cotton
? Process:(applied to either fibers or
yarns)
?cold bath of 18-27% NaOH for 1 minute
or less
?rinsed and neutralized by a cold acid
bath
?tension applied to break H-bonds
?polymer rearranged and reoriented,
untwist
?rounder cross-section and the
convolutions are nearly gone
? Stronger,more lustrous and easier to
Chapter 14 Rayon
Introduction
? Rayon,ray of light on
? Invented 1884
? Definition,manufactured fibers
composed of 100% regenerated
cellulose,as well as manufactured
fibers of regenerated cellulose in
which substituents have replaced not
more than 15% of the hydrogens of
the -OH groups.
Introduction
? Made from 4 processes:
? Nitro cellulose,made in U.S,during
20’s-40’s and easy to explode.
? Viscose,95% today spun in U.S.
? Cuprammonium,use cuprammonium
hydroxide solvent as spinning solution
? Lyocell
Introduction
? < 4% of total fiber consumed in the
U.S.
? Usage,
? 52.4% apparels
? 26.8% nonwovens
? 20.8% households
Structures
? Macrostructure
? Continuous filaments or staple,1.5-15
denier
? Microstructure:
? Surface,striated
? Cross-section,serrated
? Submicrostructure
? Skin-core structure,caused by spinning
process
? Skin,small crystal,imperfect,darker
? Core,large,more perfect crystal
Structures
? Molecular
? Regular viscose rayon,DP~400 (cotton
6k-10k)
? 35 - 40% amorphous
Properties
? Mechanical
? Medium tenacity and elongation
? Low initial modulus
? Low elastic recovery
? Low bending rigidity
? Tenacity and modulus drops drastically
upon water absorption,-50%,
Elongation to failure +20%.
Properties
? Comfort
? Hydrophilic and high moisture regain,
13% at 70% RH,more absorbent than
cotton due to more amorphous region,
High heat of wetting
? High cross-sectional swelling
? Irregular surface next to skin,
comfortable
? No static charge build up
Properties
? Maintenance
? difficult to launder due to mechanical
property change in water
? degrades in medium acids,strong
alkalies,bleaches and sunlight more
than any other cellulosic fibers
? highly flammable
Production
? Viscose process,
? purified cellulose in sheet form
? viscose solution
? pumped through spinnerets into a
coagulation bath
? solid cellulose
Production
? Preparation of spinning solution
? cellulose extracted from wood (sheet
form
? steeped in NaOH
? cellulose swell and converted to alkali
cellulose
? the alkalied pulp sheets are pressed and
shredded into crumbs
? crumbs are aged (chemical reaction
occurs between cellulose and O2 to
reduce DP of cellulose)
Production
? Preparation of spinning solution
? react with carbon disulfide CS2
? bright orange crumbs,cellulose xanthate;
ready for spun
? crumbs then dissolved in dilute NaOH to
form a honey colored liquid and aged to
correct viscosity and filtered
