2. INTRODUCTION
Definition
The fibre having tenacity greater than 20 g/denier
are known as high performance fibres.
High-performance fibers are those that are
engineered for specific uses that require
exceptional strength, stiffness, heat resistance,
or chemical resistance.
These fibers are driven by special technical
functions that require specific physical properties
unique to these fibers.
3. INTRODUCTION CONT….
Major applications for the high performance fibres
are transportation, aerospace, protective
clothing, marine (ropes and sails), hostile
thermal and chemical environments
(replacement for asbestos) and leisure activities
industries (golf clubs and tennis rackets).
4. INTRODUCTION CONT….
Commodity fibres
Volume driven
Price oriented
Large scale line- production
High performance fibres
Technically driven
Speciality oriented
Smaller batch type production
7. ARAMIDS.
Para Aramids ( cut resistant )
Kevlar (Du Pont),Technora (Teijin), Twaron (Teijin)
Meta Aramids ( Fire Retardant )
Nomex (Du Pont) , Teijin conex (Teijin)
8. HIGH PERFORMANCE FIBERS
All fibres except the cheapest commodity
fibres are high performance fibres.
The natural fibres (cotton, wool, silk . . .)
have a high aesthetic appeal in fashion
fabrics (clothing, upholstery, carpets . .
.)
100 years ago, they were also the fibres
used in engineering applications –
which are called industrial textiles.
9. HIGH PERFORMANCE FIBERS
The maximum strengths of commercial nylon and polyester fibres
approach 10 g/den (~1 N/tex), with break extensions of more than
10%.
The combination of moderately high strength and moderately high
extension gives a very high energy to break, or work of rupture.
Good recovery properties mean that they can stand repeated high-
energy shocks.
11. HIGH PERFORMANCE FIBERS
In the last quarter of the twentieth century, a second generation of
manufactured fibres became available.
these high-performance fibres showed a step change in strength and
stiffness.
They are high-modulus, high-tenacity (HM-HT) fibres.
12. TYPES OF SPINNING
There are typically four types of spinning for
polymers.
wet spinning.
dry spinning.
melt spinning.
gel spinning.
13. WET SPINNING
wet spinning is the oldest process.
It is used for polymers that need to be dissolved in a solvent to be spun.
The spinneret remains submerged in a chemical bath that leads the fiber to
precipitate, and then solidify, as it emerges out of the spinneret holes.
The name of the process i.e. wet spinning has got its name from this "wet" bath
only.
Acrylic fiber, rayon fiber, modacrylic fiber, and spandex fibers, all are
manufactured through wet spinning.
14.
15. MELT SPINNING
Melt Spinning is used for the polymeric fibers or the
polymers that can be melted.
The polymer is melted and then pumped through a
spinneret.
The cooled and solidified molten fibers get collected
on a take-up wheel.
The fibers, when stretched in both, the molten and
solid states, facilitate orientation of the polymer
chains along the fiber axis.
Melt spun fibers can be forced through the spinneret in
different cross-sectional shapes
16.
17. DRY SPINNING
Dope is fed from the feed-tank through pipes
to the spinning cabinets.
A metering pump is used for constant flow of
dope and then it is fed to the spinning jet. But
between the pump and spinning jet there is a
candle filter which is used to give a final
filtration and avoid trouble due to solid
particles.
The spinneret consists of a metal plate on
which a number of small holes are drilled.
The number of holes in the jet determines the
number of filaments in the yarn.
18. DRY SPINNING
In the cabinet, hot air is fed in near the bottom
at a temperature of 100°C. This evaporates all
the solvent in the dope emerging from the jets,
and the solvent-laden air is withdrawn near the
top of the cabinet and taken away to a recovery
plant, where the solvent may be recovered.
Then the filaments passes through the feed
roller from which it is guided onto a bobbin.
When the yarn has been collected on the
bobbin it is ready for textile use and this
method of spinning is called “dry spinning”.
19. GEL SPINNING
Gel spinning is used to make very strong fibers
having special characteristics.
The polymer here is partially liquid or in a "gel"
state, which keeps the polymer chains
somewhat bound together at various points in
liquid crystal form.
20. GEL SPINNING
This bond further results into strong inter-chain forces
in the fiber increasing its tensile strength.
The polymer chains within the fibers also have a large
degree of orientation, which increases its strength.
The high strength polyethylene fiber and aramid fibers
are manufactured through this process.
23. ARAMIDS (NOMEX)
Aromatic polyamides became breakthrough materials in
commercial applications as early as the 1960s, with the
market launch of the meta aramid fiber Nomex®
(Nomex® is a DuPont Registered Trademark), which
opened up new horizons in the field of thermal and
electrical insulation.
24. ARAMIDS (KEVLAR &
TWARON)
A much higher tenacity and modulus fiber was
developed and commercialized, also by DuPont,
under the trade name Kevlar® (Kevlar® is a DuPont
Registered Trademark) in 1971.
Another Para-aramid, Twaron® (Twaron® is a
registered product of Teijin), similar to Kevlar®, and
an aromatic copolyamide, appeared on the market
towards the end of the 1980s.
25. TECHNORA
Technora® (Technora® is a registered product of
Teijin) fibre.
It is more flexible, high tenacity fibre.
The manufacturing process of Technora, reacts
PPD and 3,4-diaminodiphenylether with
terephthaloyl chloride,in an amide solvent such
as N-methyl-2-pyrrolidone/CaCl2 to complete
the polycondensation.
The reaction mixture is neutralised and subjected
to spinning into an aqueous coagulation bath
The spun fibre is then brought to extraction of
solvent,superdrawn at high temperature, and
passed through finishing to give the final
product.
26. POLYMER PREPARATION
Basic synthesis
Aramids are the fibers in which the fiber-forming
substance is a long chain synthetic polyamide
in which at least 85% of the amide (—CO—NH—
) linkages are attached directly to two aromatic
rings’.
Aramids are prepared by the generic reaction
between an amine group and a carboxylic acid
halide group.
27. P-PHENYLENE TEREPHTHALAMIDE PPTA
Aromatic polyamides of the PPTA type are usually
synthesized via a low-temperature
Polycondensation reaction based on p-
Phenylene diamine (PPD) and terephthaloyl
chloride (TCl),
29. NOMEX
The earliest representative of this class which was commercialized by DuPont in 1967
was Nomex® aramid fiber. Its chemical formula is
30. Step 1: Dissolve PPD in mixture of HMPA (hexa
methylphosphoramide) and NMP (N-methyl
pyrrolidone)
Step 2: Cooling in an ice/acetone bath at -
15oC in nitrogen atmosphere.
Step 3: Add TCL (terephthaloyl chloride) and
stirr rapidly – paste like gel
Step 4: Discontinue stirring and allow the
reaction mixture to stand for gradual
warming to room temperature
Step 5: Agitate the reaction mixture with
water to wash away solvent and HCL
Step 7: Collect the polymer by filtration
33. POLYMER SOLUTION
Rigid chain macromolecules such as the aromatic polyaramids exhibit low
solubility in many common solvent systems utilised in polymer
technology
if the chains are relatively stiff and are linked to extend the chain in one
direction, then they are ideally described in terms of a random
distribution of rods.
association with the solvent may contribute to rigidity and also to the
volume occupied by each polymer molecule
Now, as the concentration of rod-like macromolecules is increased and the
saturation level for a random array of rods is attained, the system will
simply become a saturated solution with excess polymer; or more
interestingly, if the solvent/polymer relationships are right, additional
polymer may be dissolved by forming regions in which the solvated
polymer chains approach a parallel arrangement. These ordered regions
define a mesomorphic or liquid crystalline state
34. SPINNING PROCESS OF ARAMIDS
Production of fibres initially involves heating the
spinning solution up to a suitable processing
temperature, which is of the order of 80 °C for the
highly concentrated solutions in 100% (water-free)
sulphuric acid.
Polymer spinning solutions are extruded through
spinning holes and are subjected to elongational
stretch across a small air gap.
35. SPINNING PROCESS OF ARAMIDS
At this temperature, above a polymer concentration of about
10wt% the solution state corresponds to a nematic liquid
crystalline phase. The concentration limit for the polymer
in spinning solution is 20wt%. If concentrations above
this critical limit are used, spinnability is affected due to
undissolved material; therefore the resulting fibre has
inferior mechanical properties. Because these rod-like
polymers are rigid, they orientate themselves with
respect to each other, forming a nematic phase
36.
37. SPINNING PROCESS OF ARAMIDS
The spinning holes fulfill an important function. Under
shear, the crystal domains become elongated and
orientated in the direction of the deformation.
In the air gap, elongational stretching takes place.
38. DRAW RATIO
This is the ratio of velocity of the fibre as it leaves the
coagulating bath to velocity of the polymer as it
emerges from the spinning holes.
‘draw ratio’ can be fine-tuned to obtain higher
tenacities and moduli with lower elongations and
denier.
The resulting stretch in the air gap further perfects the
respective alignment of the liquid crystal domains.
39. CRYSTALLINITY AND ORIENTATION
Overall, a higher polymer orientation in the
coagulation medium corresponds to higher
mechanical properties of the fibre.
The crystallinity and orientation of the solution are
translated to the fibre.
These factors allow the production of high strength,
high modulus, as-spun fibres. Fibres can exhibit
three possible lateral or transverse crystalline
arrangements
40. EFFECT OF HEAT AND ORIENTATION ON
TENACITY
Present para-aramid products have need of a very high molecular
orientation (less than 12°), which has an almost directly proportional
relationship to fibre modulus.The tenacity of a particular fibre material
is also, but not only, governed by this molecular orientation angle. The
modulus of the as-spun yarn can be greatly affected by the drying
conditions, temperature and tension. Additional orientation inside the
solid phase occurs during drying.
Fibres prepared by a dry-jet wet-spun process have a noteworthy response
to very brief heat treatment (seconds) under tension. These fibres will
not undergo drawing in the conventional sense, showing an extension
of less than 5% even at temperatures above 500°C,but the crystalline
orientation and fibre modulus is increased by this short-term heating
under tension.As-spun fibre has an orientation angle of 12–15°; this
decreases to about 9°or less after heat treatment,with the fibre modulus
increasing from 64GPa to over 150GPa.The applications of these
principles led to development of rigid polymer systems
41. GENERAL CHARACTERISTICS
Good resistance to abrasion
Good resistance to organic solvents but sensitive to
Chlorine, Some Acids and Bases
Good thermal insulation
Nonconductive under regular conditions, but can
absorb water and salt water
No melting point, degradation starts from 500oC
Low flame-ability
Good fabric integrity at high temperatures
Sensitive to some acids and salts
42. The properties of aramid fibres depend on the
particular spinning and post-treating
conditions. In Table list the forms that are
commercially available, together with their TEM
(tenacity, elongation, modulus) properties .
Aramid Types
44. PROPERTIES OF ARAMIDS FIBER
Aramid fibres have unique properties that set them apart from other fibres.
Aramid fibre tensile strength and modulus are significantly higher than
those of earlier organic fibres, and fibre elongation is lower.Aramid
fibres can be woven on fabric looms more easily than brittle fibres such
as glass, carbon or ceramic. They also exhibit inherent resistance to
organic solvents, fuels, lubricants and exposure to flame.
the tensile modulus of a fibre will be largely determined by the details of
the molecular orientation about the fibre axis, and the effective cross-
sectional area occupied by single chains, which will, of course, be
related to the degree of chain linearity. For instance, in poly(pphenylene
terephthalamide), the polymer chains are very stiff, brought about by
bonding of rigid phenylene rings in the para position.In contrast, for
Nomex® fibres, the phenylene and amide units are linked in the meta
position, which results in an irregular chain conformation and a
correspondingly lower tensile modulus. Also in PPTA, the presence of
amide groups at regular intervals along the linear macromolecular
backbone facilitates extensive hydrogen bonding in a lateral direction
between adjacent chains.This, in turn, leads to efficient chain packing
and high crystallinity
45.
46. WHY KEVLAR FIBER IS STRONG
A single Kevlar polymer chain could have anywhere from five to a
million segments bonded together. Each Kevlar segment or monomer is
a chemical unit that contains 14 carbon atoms, 2 nitrogen atoms, 2
oxygen atoms and 10 hydrogen atoms.
A Kevlar fiber is an array of molecules oriented parallel to each other
like a package of uncooked spaghetti. This orderly, untangled
arrangement of molecules is described as a crystalline structure.
Crystallinity is obtained by a manufacturing process known as
spinning, which involves extruding the polymer solution through small
holes. The crystallinity of the Kevlar polymer strands contributes
significantly to its unique strength and rigidity.
The individual polymer strands of Kevlar are held together by hydrogen
bonds that form between the polar amide groups on adjacent chains.
The aromatic components of Kevlar polymers have a radial orientation,
which provides a high degree of symmetry and regularity to the internal
structure of the fibers. This crystal-like regularity is the largest
contributing factor in the strength of Kevlar.
47. You can see that there are many similarities and differences between
polymers. One of the similarities that seems related to strength is the
presence of aromatic amides.
48. MOLECULAR REQUIREMENTS FOR HIGH
TENACITY FIBERS
Improvement Polymeric composition
Thermal resistance Wholly aromatic polyamide Absence
of unstable linkage (urethane, urea, alkylene, etc.)
Solubility Copolymer with dissymmetrical units
Inclusion of
—O—, —CO—, —SO2—, etc. Amides rather than esters
Drawing potential High molecular weight Enhanced chain
flexibility by incorporating —O—, —CO—, —SO2—, etc. into polymer
chain
Dimensional stability Rigid molecular chain Crystallinity
51. MECHANICAL PROPERTIES OF ARAMIDS
The mechanical properties of aramid materials underlie
their significant commercial utilisation in many areas.
For instance, the as-spun Kevlar® aramid fibre exhibits
over twice the tenacity and nine times the modulus of
high strength nylon. On a weight basis it is stronger than
steel wire and stiffer than glass. Both creep and the
linear coefficient of thermal expansion are low and the
thermal stability is high. The latter properties resemble
those of inorganic fibres and, of course, can be
attributed to the extended chain morphology, high molar
mass and excellent orientation in a thermally stable
structure that does not melt. Para-aramid fibres have
utility due to a combination of superior properties allied
with features usually associated with organic fibres such
as low density, easy processibility and rather good
52. CREEP
Creep is measured either by the length variation
under tension or by the stress decrease at
constant gauge length. Para-aramids, which
exhibit little creep, differ significantly from other
highly oriented polymeric fibres, such as HMPE
fibres,which can break after several days under
intermediate load due to their high creep
properties associated with a stress slip of
molecules (compared to a structure-tightening
in the case of para-aramids). Creep is affected
by the temperature,the load relative to the fibre
ultimate strength, the water content and other
parameters.
56. PROPERTIES AND END USES
The p-aramid fibres have a very high strength, 5
times stronger than steel, little loss of strength
during repeated abrasion, flexing and
stretching. It has an excellent dimensional
stability. Both creep and the linear coefficient of
thermal expansion are low and the thermal
stability is high. The m-aramid fibres are used
for their excellent heat resistance.
Some of the main end-uses for meta-aramids
are protective clothing, hot gas filtration and
electrical insulation. Para-aramids are used to
replace asbestos in brake and clutch linings, as
tyre reinforcement, and in composites such as
materials for aircraft, boats, high-performance
cars and sports equipment. Members of police
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65. End Use End Use System Key Attribute
Composition Fabric for aircraft &
containers
Pressure vessels
Ship building
Sport goods
Plastics additive
Civil engineering
Light weight
High strength
High modulus
Good impact
strength
Wear resistance
Protective
apparels
Heat resistance work-wear
Fire blankets
Flame retardant textiles
Cut protective gloves
Cut protective seat cover
layers
Heat resistance
Flame retardation
Cut resistance
66. End Use End Use System Key Attribute
Tyers Truck & aircraft tyers
High speed tyers
Motorcycle tyers
Bicycle tyers
Low density
Weight saving
High tenacity
Dimensional
Low shrinkage
Puncture resistance
Mechanical
rubbers goods
Conveyor belt
Transmission belt
Hoses for automotive
Hydraulic hoses
Hoses in off -shore
Umbilical
High strength
High modulus
Dimensional
stability
Thermal resistance
Chemical
resistance
67. End Use End Use System Key Attribute
Friction
products and
gaskets
Brake linings
clutch facing
Gaskets
Thixotropic Additives
industrial paper
Fibre fibrillation
Heat resistance
Chemical resistance
Low flame ability
Mechanical
performance
Rope and
cables
Aerial optical fibre cable
Traditional optical fibre
cable
Electro cable
Mechanical cable
Mooring ropes
High strength
High modulus
Dimensional
stability
Low density
Corrosion resistance
Good dielectric
properties
Heat resistance
68. End Use End Use System Key Attribute
Life
protection
Bullet proof vests
Helmets
Property protection
panels
Vehicle protection
Strategic equipment
shielding
High tenacity
High energy
dissipation
Low density and
weight reduction
Comfort
