High Performance Fibers

1. Aramid Fibers
By; Syed Ahmed Khizar TEXT-176 Submitted to; Sir Imran Raza
Contents
01. Basic Terms To Understand Aramids
02. Meaning of Aramids
03. Types of Aramids
04. Short History of Aramids
05. Chemical Structure
06. Properties
i. Physical Properties
ii. Chemical Properties
07. Manufacturing
08. Uses

2. Aramid Fibers
By; Syed Ahmed Khizar TEXT-176 Submitted to; Sir Imran Raza
Basic Terms to Understand
Aramids
Poly-Amide Fibers:
“Synthetic fibers of polymers containing amide linkages.”
Exception:
Types of Poly-Amide Fibers:
There are two types of poly-amides;
1. Nylons
2. Aramids
If only one carbon is between alternate
amide linages then it is protein.
Amide
Amide Linkage
Linkage is used to connect
two things together that’s
why it has two valency.
Nylons
This definition is not applicable for
some nylons like Nylon 6,T and Qiana.
Poly-amides containing less than 85% amide
linkages directly attached two aromatic
rings.
TFPIA Definition:
Aramids
Poly-amides containing atleast 85% amide
linkages directly attached two aromatic
rings.
TFPIA Definition:
Or
Poly-amides containing (CH2)n chain
between two alternate amide linkages.
General Definition: Or
Poly-amides containing aromatic ring
between two alternate amide linkages.
General Definition:

3. Aramid Fibers
By; Syed Ahmed Khizar TEXT-176 Submitted to; Sir Imran Raza
Amide linkages attached with two aromatic rings also called
aromatic polyamides.
Meaning of Aramids
Ar – amid
Origin: Aromatic Amides
Meaning:
Types of Aramids
There are many types of aramids, some of them are following:
Nomex (Meta-Aramid)
Kevlar (Para-Aramid)
Twaron
Technora
Heracron
etc…
}These two are the most
common types of aramids.

4. Aramid Fibers
By; Syed Ahmed Khizar TEXT-176 Submitted to; Sir Imran Raza
Short History of Aramids
Polish-American chemist Stephanie Kwolek
invented the 1st
Para-Aramid fiber which was
Kevlar.
On the other hand Dr. Wilfred
Sweeny, a Scottish-born scientist
was responsible for the
discoveries leading to Nomex the
Meta-Aramid fiber.
In 1960, DuPont introduced
meta-aramid in
commercial applications
under the trade name Nomex.
They were also the 1st
one to
introduce Para-Aramid fibers under the
trade name Kevlar.

5. Aramid Fibers
By; Syed Ahmed Khizar TEXT-176 Submitted to; Sir Imran Raza
Chemical Structure
Kevlar:
1. Polymer Structure:
2. Charge Distribution
Over Polymer:
3. Monomers:
Amide Linkage
These Linkages are attached to para positions of
aromatic rings that’s why called as para-aramids.
Negative Charge
Positive Charge
Structure Shows there is greater amount of negative charge on polymer
>
Due to these monomers IUPAC name of polymer is poly(para-phenylene terephthalamide).

6. Aramid Fibers
By; Syed Ahmed Khizar TEXT-176 Submitted to; Sir Imran Raza
Nomex:
1. Polymer Structure:
2. Charge Distribution
Over Polymer:
3. Monomers:
Amide Linkage
These Linkages are attached to para positions of
aromatic rings that’s why called as para-aramids.
Negative Charge
Positive Charge
Structure Shows there is greater amount of negative charge on polymer
But its electro positive hydrogen is more exposed unlike Kevlars, due to
this more water molecules can attract over positive center.
>
Isophthaloyl Chloride m-phenylene diamine
Due to these monomers IUPAC name of polymer is poly(meta-phenylene isophthalamide).

7. Aramid Fibers
By; Syed Ahmed Khizar TEXT-176 Submitted to; Sir Imran Raza
Properties Of Aramids
Physical Properties
01.Optical Properties:
a.Color:
Nomex = white
Kevlar = golden
b.Lustar:
Depends upon cross section shape.
Circular: more luster.
Dogbone: less luster as compared to circular.
Note: Luster can be controlled by finishes.
c. Effect of Some Rays:
Beta = No effect
Gamma = No effect
UV rays = Starts to Degrade and lose strength
02.Mechanical Properties:
a.Tenacity(g/d):
Nomex Kevlar
Dry 4.0 - 5.3 18 – 26.5
Wet 3.0 – 5.3 17 – 25.0
Very high as compared to nylons.
Easy to Break one joint. Hard to Break more than one joint.
Simple logical Reason:
Kevlar Nomex

8. Aramid Fibers
By; Syed Ahmed Khizar TEXT-176 Submitted to; Sir Imran Raza
b.Stress-Strain Relaion:
The initial modulus of aramid fibers is
higher than that of nylons as shown in
graph.
The rato of stress to strain (slope of
curve) is used to measure the stiffness
of the fiber.
Kevlar = most stiff
Nomex = less stiffer than Kevlar.
c. Density(g/cm3
):
Kevlar = 1.44 – 1.47 g/cm3
Nomex = 1.38 g/cm3
03.Thermal Properties:
a.Melting Point:
Kevlar = above 500o
C (930o
F)
Nomex = 350o
C (660o
F)
Note: At these temperatures they not only melts but also starts to decompose.
b.Glass Transition Temperature:
Kevlar = starts from 170o
C
Nomex = from 120 – 220o
C
c. Specific Heat Capacity:
Kevlar = 1420 J/K.Kg
Nomex = 1200 J/K.Kg
d.Highly Flame Resistant:

9. Aramid Fibers
By; Syed Ahmed Khizar TEXT-176 Submitted to; Sir Imran Raza
04.Other Properties:
a.Moisture Regain:
Kevlar = 1.2 – 4.3%
Nomex = 6.5%
 Non-flexible chains.
 Reason: Two alternate rings try to oppose each
other by repulsion of aromatic rings which keeps
the fiber straight and non-flexible.
 Hydrogen-bonding between chains there by
forming a sheet like structure (of fibrils).
 Reason: Shown in Picture.
 Fibrils (sheets) separated by elongated voids.
 Reason: Because each sheet is a plane whose both faces are negatively
charged because of Aromatic Rings (similar to graphite sheets) due to this
elongated void is created between fibril sheets.
Aramid Fiber
Fibrils Sheets Chemical Structure.
Gaps between Fibril Sheets

10. Aramid Fibers
By; Syed Ahmed Khizar TEXT-176 Submitted to; Sir Imran Raza
Chemical Properties
a.Resistance To Alkalies:
Nomex Kevlar
Dilute(at Room Temp.) No effect No effect
Conc.(high Temp.) Degrades Weaken
b.Resistance To Alkalies:
Nomex Kevlar
Dilute(at Room Temp.) No effect No effect
Conc.(high Temp.) Weaken Weaken
Strong Acids Degrades Weaken
c. Resistance To Dye:
Because of high negative charge repulsion its hard to dye but in
extreme conditions support electrophilic substitution reaction.
d.Resistance To Bleach:
Resistant to bleaches that’s why its hard to change the natural
golden color of Kevlar.

11. Aramid Fibers
By; Syed Ahmed Khizar TEXT-176 Submitted to; Sir Imran Raza
Manufacturing
Steps For Manufacturing:
1. Polymer Formation:
We normally use suspension polymerization technique for aramids. The
di amine is dissolved in water, with an acid acceptor (Na2CO3). The acid
chloride is dissolved in a solvent (CTC or cyclohexanone).
Two solutions are then mixed intensively which cause rapid polymerization
reaction at liquid interface. This technique is known as interfacial
polymerization.
2. Spinning:
a. Dope Formation:
Nomex: Its polymer is dissolved in a mixture of dimethylformamide
and lithium chloride.
Kevlar: Its polymer is dissolved in Sulphuric Acid.
b. Extrusion:
Then dope is extruded through spinneret’s hole to give shape of
filament.
Important Point
Aromatic polyamides should be prepared from aromatic dicarboxylic
acid and aromatic diamines. But aromatic dicarboxylic acid are
unreactive that’s why we use more reactive aromatic acid chlorides.

12. Aramid Fibers
By; Syed Ahmed Khizar TEXT-176 Submitted to; Sir Imran Raza
c. Solidification:
Nomex: It is solidified in hot air and the solvents are recovered by
distillation. (Dry Spun)
Kevlar: It is solidified in water or dilute sulphuric acid bath.
(Wet spun)
Uses
Technical Textile:
1. Buildings: Aramids are used for fire proofing of
walls because of their flame resistant property.
Also used as insulation of electric wires used in
buildings to prevent breakage by heat because of high specific heat.
2. Protective Textile: Used to prepare protective
products like uncut able gloves, helmets, bullet proof
waist, suits of fire fighters, suits of astronauts etc.

13. Aramid Fibers
By; Syed Ahmed Khizar TEXT-176 Submitted to; Sir Imran Raza
3. Sports: Used in sports products like rackets, tires
of formula one cars, boats, whole bicycles are made
up of aramids because of its light weight and
strength.
Also ropes and cables because of its strength.
Worldwide usage of synthetic fibers