This document provides information on different types of fibres, including their classification, characteristics, and analysis. It discusses natural fibres like silk, wool, cotton, flax, and hemp as well as man-made fibres such as polyamide, polyester, and regenerated fibres. Fibres are classified based on their origin as either natural or man-made, and further divided into categories like animal, vegetable, mineral, synthetic, and regenerated. The properties of different fibres depend on their chemical composition and molecular structure. Fibre analysis involves examining characteristics like morphology, refractive index, and molecular orientation using microscopy techniques.

1. Types of fibres

2. What is a fibre?
• a slender and greatly elongated substance capable
of being spun into yarn.
• Fibres are deemed the fourth most important
evidence when DNA, fingerprints, and footwear
are available.

3. Fibre evidence used for 3 reasons:
• Intelligence information
• Associative evidence
• To reconstruct a crime scene.

4. • When fibres are brought in from a case study,
they are analysed using microscopy to recognize
characteristics to compare to a suspect sample
• However, the first thing that will be done will
be to identify what type of fibre it is.

5. • The transfer of fibres from article to article lends
itself to identify who has come in with contact
these objects.
• The transfer of fibres depends on the shedding
ability of the fabric and the persistence of these
fibres on other types of fabric.
• The easier these fibres are shed, the more
chance there will be for secondary, tertiary or
even quaternary transfer.

6. Classification of Fibres

8. Classifying fibres
• Fibres are divided into two main categories:
– 'Natural fibres' are fibres that occur in nature: wool, cotton,
asbestos, etc.
– 'Man-made fibres' is the term applied to fibres that have
been manufactured by humans from either naturally
occurring fibre-forming polymers (for example viscose,
acetate and rayon) or synthetic fibre-forming polymers (for
example polyester).

9. Manmade fibres
Man-made fibres can be divided into three subdivisions:
– Synthetic fibres' are man-made fibres spun from
synthesized fibre-forming polymers.
– 'Regenerated fibres' are man-made fibres that have
been produced from naturally occurring polymers by a
technique that includes the regeneration of the
polymer structure (casein, viscose, acetate, etc.)

10. – other fibres (carbon, glass, metal, etc).

11. Subdivisions of Natural fibres
• animal (protein)
• vegetable (cellulose)
• and mineral (asbestos)

12. Subdivisions of animal fibres
• Divisions based on protein composition and
utilization.
• silk (fibroin)
• wool (keratin)
• hair fibres (also keratin).

13. Vegetable fibres
• Groups of vegetable or cellulosic fibres: based
on the part of the plant that is the source of
the fibre
• (i) seed fibres (cotton, kapok, and coir)
• (ii) bast (stem) fibres (flax, hemp,jute,ramie)
• (iii) leaf fibres (manila, sisal, etc.).

14. Characteristics of fiber polymers
• linear molecular chains which possess some
degree of extension to the fibre axis- making it
stronger longitudinally than transversely
• streamlined molecular chains- allowing for
close packing of the polymer chains

15. Characteristics of fiber polymers
• the molecular chains should be flexible and
hence impart extensibility to the fibres.
• a high molecular weight-imparting both a
high melting point and low solubility in most
solvents

16. Natural fibres-Silk
• Silk is obtained from a class of insects called
Lepidoptera (scaled winged insects).
• The principal species cultivated for the
commercial production of silk is Bombyx mori or
mulberry silkworm.

17. • The production of silk can be divided into two
areas – sericulture and silk reeling.
– Sericulture is the production of cocoons from eggs
– Silk reeling is where the cocoon is converted into
the thread.

18. Cocoon of Bombyx mori

19. • Silk is composed of the proteins fibroin and
sericin
• Has crystalline regions where the protein chains
are fully extended in the B-sheet structure with
maximized hydrogen bonding.
• has a markedly different amino acid composition
than other animal fibres.

20. Silk Fibres

21. SEM silk fibres

22. • No Cysteine, and therefore disulphide crosslinks
are not present in silk.
• Consequently, silk will dissolve in powerful
hydrogen bond-breaking solvents such as
cuprammonium hydroxide, in which other
animal fibres will not dissolve.

23. • Silk is extensible and elastic
– Silk has a reversible extension of up to 4%, beyond which
recovery is slow with some permanent set.
• Silk almost equals nylon in resistance to abrasion
and toughness (the ability to absorb work) – as a
result of crystalline structure.

24. • Raw silk has a regain of 11%, but that of de-
gummed silk is about 10%, the sericin having a
higher water-absorbing capacity than the fibroin.
• Silk more susceptible to acids than wool, but is
more resistant to alkalis, though low
concentrations at high temperatures will cause
some tendering.
• Still silk is not readily attacked by warm dilute acids,
but dissolves in strong acids.

25. • Silk is very resistant to all organic solvents, but is
soluble in cuprammonium hydroxide and
cupriethylene diamine, the latter solvent being
used for fluidity tests.
• Silk is more susceptible to oxidizing agents and
exposure to sunlight than cellulosic or synthetic
fibres
• More resistant to biological attack than other
natural fibres
• Easily dyed with a wide range of dyestuffs
including acid, basic, and metal complex dyes.

26. Summary Properties of silk
• Strong
• Tough
• high regain
• Resistant to creasing
• Good draping properties
• Luxurious appearance.

27. Draping silk textile

28. • Used in apparel and drapery industries
• High cost restricts use of silk
• Since silk is a continuous filament fibre, with a
smooth surface, fibre transfer during contact is
unlikely-poor shedder

30. Wool
• Wool is made of the protein called keratin.
• hair, feathers, beaks, claws, hooves, horn, and even
certain types of skin tumour are also made of keratin.
• Arguably the most common hair fibre used in textiles.
• The fineness, quality, and properties of wool depend
on the sheep breed

31. • Merino wool is soft, fine and strong
• Leicester, Cheviot and Corriedale are medium wools used in knitting
yarns, blankets etc.
• Even within the same breed, differences in diet, health,
climate make wool show considerable variation in
physical and chemical properties:
For example, one expects considerable variation in
physical properties such as fibre diameter, length, and
crimp as well as the chemical constitution of the fibres.
• Wool can be difficult to analyse and interpret due to
differences in hair over the whole body of the sheep.

32. • Wool, like other hair fibres, contains a
substantial quantity of the amino acid
cysteine.
• Cysteine residues in wool play a very
important role in the stabilization of the fibre
structure owing to the crosslinking action of
their disulphide bonds

33. • Since wool is a staple fibre, with a rough
'scaly' fibre surface, wool fibres may transfer
readily during contact, especially from loosely
constructed fabrics.
• Wool sheds more readily than man-made
fibres.

34. SEM wool Fibres

35. Specialty hair fibres
• The hair fibres, sometimes referred to as
'specialty' hair fibres, can be divided roughly
into three groups:
• fibres from the goat family (mohair, cashmere)
• fibres from the camel family (camel hair,
alpaca, vicuna)
• fibres from other fur-bearing animals, in
particular the rabbit (angora).

36. Goat Hair fibres
• Mohair is from the angora goat. Fibres are
between 20-30 cm for a full year’s growth.
Identification of mohair can be difficult as similar
to wool
• Cashmere is from the Asiatic goat and is
chemically identical to wool. The extra softness is
due to cashmere fibres being finer. There have
been many cases of Cashmere fraud over the
years.

37. Camel (family) hair fibres
• Alpaca fibres are from Lama pacos species inhabiting
South America
• Alpaca fibres are more easily identified as they have a
distinct scale structure and medullation.
• Fibres vary from alpaca to alpaca and in some alpacas
there may be a higher incidence of medullated fibers,
compared to wool and mohair.
• Medullated fibers can take less dye, standing out in
the finished garment, and are weaker

38. • Strands of alpaca fiber are smooth and therefore
feel less prickly or itchy next to the skin than wool
• Alpaca insulates from cool and warm
temperatures and is comfortable for any season-
hollowness of fibre.
• Most people who have wool-based allergies will
not be allergic to alpaca- no lanolin

39. Rabbit fibres
• Rabbit fibres are usually from the angora species of
rabbit.
• These rabbits are bred primarily for their fur. Angora
fibres are retrieved by shaving the pelts of the rabbits
and then separated by blowing.
• Often used in hats or jumpers but mixed with wool or
nylon.

41. SEM of various fibre types

42. Vegetable fibres
• Vegetable fibres are spilt into 3 categories:
• Seed fibres
• Bast fibres
• Leaf fibres
The chemical constituents can vary dramatically. The main
constituents to note are cellulose, pectins, fats, waxes and
lignins.

43. Seed Fibres
Cotton
• is retrieved from the seed of the species
Gossypium which is found in subtropical
countries.
• A boll is formed on the plant which bursts into
sections. Fibres are formed inside and mature
as cellulose is deposited on the interior surface
of the boll.
• The convoluted shape is due to the shrinking of
the fibre as it dries.

44. • This convoluted staple fibre may transfer
readily during contact.
• Since a very high proportion of cotton is
marketed in 'white' products, colourless
cotton fibres have little, if any, value as
evidence.

45. Bolls of cotton

46. Convoluted cotton fibres

47. Kapok
• Fibres obtained from the kapok tree, native to Mexico
Central America and the Caribbean
• Pods are picked from the tree and broken
open and dried in the sun.
• Kapok fibres can be identified by their low density.
• Fibres are resistant to water. Buoyant but highly
flammable.
• Used to make lifebuoys and mattresses

48. Pod

50. Coir
• A fruit fibre from coconuts
• Husks are soaked for a week, dried and passed through a
crusher.
• The best coir is from unripe husks. This is used for ropes,
matting.
• Coir from mature husks is coarser and so used for
brushes, brooms.
• Has great tensile strength

51. Coconut fruit

52. Bast Fibres
• Bast fibres are from the stems of plants which are bundled
under the bark.
Flax
• Scientific name Linum usitatissimum.
• Has been cultivated for over 6000 years
• Flax is stronger than other natural fibres but is much less
pliable and elastic.
• Also absorbs and desorbs water rapidly
• smooth fibre surface makes it very easy to launder, hence
linen found great use in the manufacture of table cloths
and bandages.

53. Linum
usitatissimum

54. • Flax grown for the fibre which is linen and the seed
which is linseed
• Flax strength due to its compact structure
Hemp
• Scientific name Cannabis sativa
• Used mainly for ropes and twine.

55. Flax

56. Leaf Fibres
• Also known as ‘hard’ fibres: thicker and harder than bast
• Obtained from certain tropical and subtropical plants
Sisal
• Scientific name Agava sisalana
• Leaves are removed and crushed and the fibres scraped
away.
• Usually easy to identify as are polygonal in cross-section.
• Used in ropes and twines.
• Other leaf fibres are Abaca and New Zealand hemp. These
are not widely used and commercial quantities have
dramatically decreased

57. Agava sisalana

58. Abaca/ manila
• Leaf fibre,
Abaca Plant and
fibre produced.

59. New Zealand
Hemp: Plant and
fibres

60. Mineral fibres
ASBESTOS-MEANS
INCOMBUSTIBLE
HEALTH CONSIDERATIONS
HAVE GREATLY REDUCED THE
INDUSTRY.
REPLACED WHEREVER
POSSIBLE BY OTHER FIBRES
SUCH AS GLASS AND NOMEX

61. Analysis of natural fibres
Differs from man-made fibres
• Primarily use of compound microscopes
• Can include the following:
– Overall morphology
– Length
– Cross-sectional shape
– Thickness of lumen
– Determination of refractive index
– Lignification – Phloroglucinol reagent
https://www.youtube.com/watch?v=HHNeoefK1ow
– Herzog test- plant fibres molecular orientation
– https://www.youtube.com/watch?v=sC9GlUKjBDE

62. • Herzog test can be used to differentiate
between flax, hemp and cotton.
• Cotton looks multi-coloured
• Hemp is look purple horizontally and blue
vertically
• Flax looks blue horizontally and purple
vertically
• Used to tell the type of twist a fibre has.

63. Herzog test results
• A Z-twist fibre is said to turn yellow when parallel to the
polarizer and blue when parallel to the analyser, while
for a S-twist fibre the situation is exactly opposite.
– Hemp and jute have Z-twist and flax and ramie have S-twist.
• The modified Herzog test can also be used to distinguish
between bast fibres and other plant fibres.
– For example, in cotton, a seed fibre, the microfibrils change
their twist directions at short intervals

64. Man-Made Fibres
• There are two types of Man-made fibres:
– Regenerated fibres: made from natural polymers
• Eg. Rubber and viscose
– Synthetic Fibres: made from synthetic polymers
• Eg. Polyamide and polyester

65. Manufacture of Man-Made fibres
• Process is called spinning or extrusion
• The concentrated, viscous polymer, either in
solution or in a molten state, is forced through
the tiny holes of a spinneret
• The emerging filaments are immediately
precipitated or cooled to form the solid-state
fibre.

66. • Types of spinning:
– Wet spinning : concentrated solution of polymer dissolved in
aqueous or organic solvents. The extruded filaments are
immediately precipitated in a coagulation bath.
– Dry spinning: concentrated solution of polymer dissolved in
volatile solvent systems which allow rapid evaporation of the
solvent, effecting fibre solidification after extrusion.
– Melt spinning: The molten polymer is extruded and the
filaments are solidified by simple cooling (applies to
thermoplastics only)
• Type used determined by physical and chemical property of
polymer

67. Effects of Spinning
• Spinning causes the polymer chains to become
more aligned (or oriented) in the direction of the
longitudinal axis of the fibre.
– maximizes the inter-polymer forces of attraction
between polymer chains, leading to an increase in
polymer crystallinity and fibre strength.
– Parts of the fibre will be crystalline and others
amorphous- influencing the property of the fibre

68. • Extrusion method (eg. Shape of spinnerets or rate
of cooling) determine the longitudinal and cross-
sectional appearance of man-made fibres

69. Types of synthetic polymers
Condensation polymers:
• Monomers bearing two reactive or functional groups
from one or more compound(s) condense by normal
chemical reaction to produce a linear polymer.
• Repeating units are joined by inter-unit functional
groups (ester, amide, urethanes)
• The linkages are susceptible to hydrolysis – acids and
alkalis
– Eg. polyamides and aramids, polyesters, and polyurethanes.

70. Condensation polymerization

71. • https://youtu.be/-d14DmSBuAQ

72. Addition polymers
• Occur when monomers containing double bonds from
one or more compounds add together at the double
bond to form a polymer confined to an aliphatic
carbon chain. Results in no loss of atom or molecule
– Has strong C-C bonds in polymer backbone
– Not susceptible to cleavage hence more stable than
condensation polymers- non-biodegradable
– Eg. Polyolefins and polyvinyl derivatives.

74. Addition polymerization

75. Eg. Addition polymers

76. • The degree of polymerization attained for
addition polymers is usually much higher than
that for condensation polymers because of
the nature of their respective polymerization
reactions.
• https://www.youtube.com/watch?v=sk6h4oa
ArE0

77. Polyamides
• Polyamides may be synthesized via the
condensation of diamine (H2N–R1–NH2) and
dicarboxylic acid (HOOC-R2-COOH) monomers, or
by the polymerization of an -amino acid
• R group may be either aliphatic (straight carbon
chain), alicyclic (ring), or aromatic (benzene ring)
• Polymer has the amide functional group:
(–CONH–)

78. Naming polyamide fibres
• Aliphatic polyamide fibres: named according to the
number of carbon atoms in the repeating unit.
– eg if the repeating unit is derived from a diamine and a
di-acid, the polymer is designated by two numerals:
• the first indicating the number of carbon atoms in the diamine
• and the second the number of carbon atoms in the
dicarboxylic acid
• Eg. Nylon 6.6

79. • Nylons synthesized from an -amino acid are
designated by a single numeral denoting the
number of carbon atoms in the amino acid.
– Eg. Nylon 6

80. Nylon
• Most common polyamides
• Smooth, regular longitudinal appearance results in a
highly lustrous and translucent fibre
– Requires the addition of a delustring agent (for example
titanium dioxide)
– Nylon fibres are melt spun- can be texturized by heat
treatment( improves appearance and resilience)
• Many hydrogen bonds between polymer chains -Polar
amide linkages along backbone plus absence of bulky
side groups

81. • Hydrogen bonds :
– Crystalline
– makes it strong with good elastic recovery
• Wetting causes nylon to increase in fibre extensibility and
decrease in elasticity and tensile strength.
• Crystalline structure:
– cause it to exhibit outstanding resistance to abrasion
– Has low moisture regain- the crystalline structure
prevents water entering
– Not very conductive – develops static electricity

82. • Amide linkages:
– Nylon is relatively stable in alkalis. Hydrolyzed by acids.
• Nylon fibres are soluble in phenols and concentrated acid
– oxidation by sunlight- weakening the fibre
• ideal for the carpet and hosiery industries,
– Eg.Nylon 6.6: Antron, Rhodiastar, Tactel, Ultron
Nylon 6: Anso, Enkalon, Patina, Perlon, Zeftron

83. Aramids
• Aramids are aromatic polyamides defined as
having at least 85% of their amide linkages
attached directly to two aromatic rings.
• Eg.Kermel, Kevlar, Nomex, Teijin Conex, Twaron
• Nomex and Kevlar are the most commonly
encountered aramids,

84. • Kevlar
• Nomex

85. • The molecular chain linearity (due to aromatic ring)
and hydrogen bonding- results in almost perfect
molecular orientation of polymer chains
• better alignment of polymer chains than seen in
aliphatic polyamides:
– Higher specific gravity
– higher tensile strength,
– higher modulus (resistance to stretching),
– and extremely high chemical and heat resistance (up to
300°C).
– insoluble in most common solvents and therefore
require the use of special solvent systems for extrusion
into filaments.

86. • The fibres char and decompose rather than melt at
temperatures above 300°C.
• Expense to manufacture aramid fibre - limits
applications to high-performance products.

87. Applications
• Nomex is principally used for fire/heat retardant
purposes such as in heat protective clothing
• Applications of Kevlar include high-performance
tyres and conveyor belts, and reinforcement
fibres in sporting goods and in the aerospace
industry, bullet proof vests.
• (Kevlar is 5 times and 10 times stronger than
steel and aluminum respectively)

88. Polyester
• Eg. Dacron, Diolen, Fortrel, Grilene, Tergal, Terital,
Terlenka, Terylene, Teteron, Trevira
• Polyesters are synthesized by the condensation of a diol
(for example ethylene glycol) and a dicarboxylic acid
(for example adipic acid) with formation of an ester
linkage (–COO–) along the polymer chain backbone.
– The most common polyester manufactured is based on the
polymer polyethylene terephthalate (PET)
• Polyesters are melt-spun: The fibres are fine, regular,
and translucent, and are usually textured, as is nylon,
by a heat treatment.

90. • Carbonyl groups present are weakly polar:
hydrophobic interactions such as weak van der
Waals' forces holds adjacent polymer chains
together
• The para-substituted benzene rings reinforce the
linearity of the polymer, thus maximizing the van
der Waals' attractive forces.
– Making fibre very crystalline
– Resistant to abrasion
– strong

91. – No loss of strength on wetting because of the
hydrophobic nature of the polymer chains.
– Para-substituted benzene ring makes polyester
textiles stiff (not elastic)
• requiring twice the force required by nylon to produce
similar extension.

92. – Wrinkle resistant
– Low moisture regain- due to high crystallinity and
hydrophobic properties (produces static)
– Polyester is insoluble in most organic solvents, including
90% o-phosphoric acid, which will digest most other
textile fibres derived from organic polymers.
– Dissolves in chlorophenol and hot 90% phenol.

93. – Unlike nylon, the ester linkage in polyester is hydrolyzed
by alkalis (surface damage mostly) but stable even in
concentrated acids (dissolving only in hot sulphuric acid)
– More resistant to sunlight degradation than nylon.
– Difficult to dye
– Static electricity

94. • Both nylon and polyester fibres have:
– strength
– abrasion resistance
– thermal stability
– ability to hold a heat-setting treatment
• Polyester has more applications than nylon-
due to higher modulus and lower production
cost

95. Overcoming the limitations of
polyester
• Increase moisture absorbency by blending with
absorbent fibres to increase wear comfort.
• Treatment with antistatic agents serves to dissipate
static charge
• Dyeing with carriers swells the fibre, facilitating the
penetration of disperse dyes e.g.
Orthophenylphenol, Benzyl benzoate

96. Applications
• Apparel: Staple fibre blending with wool or cotton
for making apparel. Easy care and toughness of
polyester render it very suitable for apparel
• Continuous filament polyester suitable for
industrial applications such as:
– ropes,
– conveyor belts,
– seat belts, and
– tarpaulins.

97. Polyurethane (elastane)
• Eg. Acelan, Dorlastan, Cleerspan, Glospan, Lycra, Opelon
• Contain at least 85% of organic units joined by urethane
linkages (–NH–COO–).
•
• Reacting a diisocyanate ( two isocyanate functional groups)
with a long chain polygycol monomer ( two hydroxyl or
alcohol groups). Properties vary depending on monomers.
• Polyurethane fibres commonly used in textile industry are
very complex polymers combining a flexible segment
(provides lots of stretch and rapid recovery of an elastomer),
with a rigid segment (confers strength of a fibre).

98. • The flexible segments can be one of two types, a
long polyether or polyester chain
• rigid segments are composed of a diphenyl methyl
group attached to a urethane group.
• Polyurethane elastomers are usually solution spun
Thermoset plastic-excessive amounts of heat can
disrupt the elastic properties of the fibre.

99. Polyurethane

100. • The polymer network of polyurethanes is largely
amorphous as a result of the long, flexible
polyether or polyester chains which are folded on
themselves.
• The interconnecting hard segments tend to be more
aligned, with hydrogen bonding between the
urethane groups of adjacent chains contributing to
polymer strength and crystallinity.
• distinctive highly extensible, 'snap-back' property of
elastomeric fibres- due to the inter-chain region
between the crystalline region.

101. • hydrophobic nature of the flexible region and the
crystalline nature of the rigid region.
– Low moisture regain
– Prone to static electricity
– Difficult to dye
– not susceptible to attack by corrosive although alkalis
will readily attack the ester linkages of the polyester
type of polyurethanes
• Usually combined with fibres like nylon that dye
more readily.

102. Applications
• Used in apparel where stretch and recovery
are important
– swim wear and
– active wear

103. Polyolefins
• Polyethylene: Dyneema, Polysteen, Spectra,
Vestolan
• Polypropylene: Asota, Danaklon, Downspun,
Gymlene, Herculon, Meraklon,
Novatron, Vegon

104. • Polyethylene and polypropylene polymers are
polymerized from the petroleum-based products
ethylene and propylene, respectively (addition
polymerization).
• Both polypropylene (PP) and polyethylene (PE) are
melt-extruded (thermoplastics)

105. • High degree of polymerization/The dense packing of linear
polymer chains/ - maximize the van der Waals' inter-chain
forces:
– Very crystalline
– Lower modulus than polyester
• highly crystalline and hydrophobic nature
– extremely difficult to dye
– fibre with high tenacity (similar to nylon and polyester).
High performance PE as strong and stiff as aramids.
– Zero moisture regain
– very resistant to attack by corrosive chemicals.
– abrasive resistant but less so than nylon

106. – highly resistant to chemical degradation by acids and
alkalis but soluble in hot hydrocarbon solvents and
cannot be dry-cleaned.
– 'wicking', which allows moisture to be transferred rapidly
between fibres without actually being absorbed by the
fibres.
• Pigmentation is achieved by dying before melt spinning or
addition of modifying chemicals to the spinning dope (act
as light stabilizer and mordant)
• Use limited by low melting points ( PE(135°C) and PP
(165°C).
• The fibre is flammable, although self-extinguishing.

107. • Degraded by sunlight- need to be treated with
ultra violet stabilizers for some indoor and out
door applications
• inert material that is also resistant to bacterial
growth

108. Applications
• next-to-skin active wear
• furnishings
• PP Backing for carpets
• Carpet face yarns
• PP Fishing nets and cordage (replacing sisal
and jute)

109. Polyvinyl Derivatives
• Acrylics (85% by weight of acrylonitrile units)
: Acrilan, Beslon, Cashmilon, Courtelle,
Dolan, Dralon, Leacril, Vonnel, Orlon, Dynel
• Modacrylics (at least 35% but not more than 85% of
acrylonitrile units) : Kanecaron, Kanekalon, Nonbur,
SEF, Velicren FR polyacrylonitrile
• Velicren FR Polyacrylonitrile is the commonest
addition polymer

110. • Acrylic and modacrylic fibres are solution spun
(either wet or dry spun)
• acrylonitrile units are largely non-polar, and
the polymer system is therefore held together
predominantly by van der Waals' forces.

112. • High polymerization results in long chains-maximize
van der Waals' forces and results in high
crystallinity.
– Polyacrylonitrile (100%) is extremely difficult to dye,
being non-polar and highly crystalline.
–
– low moisture regain, as a result of the predominantly
hydrophobic character and highly crystalline nature
– Acrylic fibres have only moderate tensile strength
compared to nylon and polyester

113. – Static charge
– Little penetration of acids and alkalis, with only
hot concentrated alkalis causing surface
hydrolysis.
– Acrylic fibres are insoluble in most organic
solvents, but will dissolve in boiling
dimethylformamide and dimethylsulphoxide

114. • Acrylic polymers are generally copolymerized with up
to 15% of different monomers
– Comonomers open up the polymer structure and/or to
incorporate anionic or cationic groups within the polymer
system- attracting and allowing dyes to penetrate
– Basic dyes are commonly used on acrylic fibres, producing
bright shades with good light fastness.
• often delustred
• processed into staple fibre

115. • loss in strength when wet
• Wrinkles: indicating slippage of polymer chains due
to weak inter-chain forces
• Resistant to degradation by sunlight ( most, of all
textile fibres)

116. • Acrylics very heat-sensitive
– Acrylics are readily flammable on close approach to a flame;
they burn with a characteristic smoky flame.
– Flammability retarded by copolymerization with vinylidene
chloride monomers - produce flame-resistant polymers-
degradation of C-Cl bond is endothermic.
– shrink when subjected to steam (more than other textiles)
– chlorine-containing modacrylics have lower heat stability
than acrylics in that they soften more readily from heat
application (150°C) and shrink markedly in boiling water.

117. Applications
Acrylic fibres are most commonly blended with other fibres in:
• Knitted outerwear,
• furnishings,
• carpet, and
• fabrics for outdoor use (awnings etc.).
These applications make use of their high bulk characteristics,
bright colours,
Modacrylics:
• Hair in wigs
• Apparel lining
• Furlike outerwear

118. • Modacrylics are also usually blended with
other fibres to impart flame retardancy in
apparel and furnishings.