Chapter 11 Silk Fibers
Yiping Qiu
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 better color
Chapter 12 Cotton Fibers
TMS211
Yiping Qiu
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 dye
Chapter 14 Rayon
TMS 211
Yiping Qiu
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
Yiping Qiu
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 better color
Chapter 12 Cotton Fibers
TMS211
Yiping Qiu
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 dye
Chapter 14 Rayon
TMS 211
Yiping Qiu
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
