properties and application of technical textile fibers

Technical fiber or High functional fibers
High functional fibers are those, which have high technical properties based on the end uses. The properties are high tensile strength, high modulus, good chemical resistance, high dimensional stability, low thermal resistance.

1. Technical fiber or High functional fibers
High functional fibers are those, which have high technical properties based on the end uses. The
properties are high tensile strength, high modulus, good chemical resistance, high dimensional stability,
low thermal resistance.
They are designed and developed to satisfy the physical and chemical requirements of the final product.
Example of High functional fibers

Fiber Trade name producer

Para- Aramid Kevlar Du pont/ USA
Twaron

Meta-Aramid Nomex Du Pont/ USA

Carbon (basis PAN) Tenax Germany

Ultra high molecular weight Polyethylene Spectra USA
(UHMPE)
Polyetheretherketon (PEEK) Zyerex

Glass R-glass, E-glass
Metal fiber (steel, aluminium) Bekinox
polypropylene

Required properties of technical fibers

 High strength, high stiffness (strength, compression, torsion, bending)
 Fatigue and aging resistance
 Resistance to microbes and other chemicals (corrosion resistance)
 Low density
 Abrasion resistance
 Soil resistance and easy
 high flammability
 Resistance to sunlight and UV degradation
 Low thermal expansion
 Thermal conductivity
 Electrical conductivity
 Softer handle and touch

2. Carbon fiber
Carbon fiber is a material composed of carbon atoms in its structure with diameter of 50 to 10
micrometer. These carbon atoms are linked between each other with a crystal structure, more or less
oriented along the direction of the fibers.

The properties of the carbon fiber, such as a high flexibility, high resistance, low weight, high-
temperatures resistance and a low thermal expansion coefficient make it a popular choice of aerospace
industries, engineering, military applications, motor sports along with several other sports.

It is produced by extruding precursor of acrylics, pitch or specially purified viscose rayon into filament
and then carbonized to get carbon.
Carbon Fiber Properties
 High Strength to weight ratio
 Good Rigidity
 Corrosion resistant
 Low UV ray protection capability
 Electrically Conductive
 Fatigue Resistant
 Good tensile strength but Brittle
 Fire Resistance/Not flammable
 High Thermal Conductivity in some forms
 Low coefficient of thermal expansion
 Non poisonous
 Biologically inert
 X-Ray Permeable
 Self Lubricating
 Excellent EMI (Electromagnetic Interference) Shielding Property
 Relatively Expensive

Production of carbon fiber
PAN fiber based carbon fiber production
Important stages of carbon fiber production
1. Spinning (wet spinning to manufacture PAN fiber)
2. Stretching or drawing 3. Stabilization 4. Carbonization
5. Graphitization

3. Figure: Production process of carbon fiber from PAN fiber

Figure: Temperature used in different stages for the production of carbon fiber

4. Manufacturing process of carbon fiber
Poly-acrylonitrile (PAN) and pitch i.e. rayon are the two most common raw materials used to
produce carbon fibers.
 In the stabilization stage, the PAN fibers are first stretched to align the febrile networks
within each fiber axis and they are oxidized in air at about 200
0
C to 250
0
C. The fibers
incorporate about 8% oxygen into their structure during this process.

 In carbonization the stabilized PAN based fibers are heated until they become transferred
into carbon fibers by the elimination of O, H and N from the precursor fiber. In this step
the fibers are stretched between 50 to 100% elongation and the carbonization heat
treatment is usually carried out in inert atmosphere at temperature ranging from 1000
0
C
to 1500
0
C.

 Graphitization treatment is done if an increase in the modulus of the elasticity as well as
high tensile strength is desired. It is usually carried out at the temperature of 1800
0
c to
3000
0
C.

 Finally surface modification of carbon fiber is done if required.

Figure: Chemical structure changes during production of carbon fiber from PAN

5. Application of Carbon Fiber
 Aerospace, road and marine transport, sporting goods.
 Missiles, aircraft brakes, aerospace antenna and support structure, large telescopes,
optical benches, waveguides for stable high-frequency (GHz) precision measurement
frames.
 Audio equipment, loudspeakers for Hi-fi equipment, pickup arms, robot arms.
 Automobile hoods, novel tooling, casings and bases for electronic equipments, EMI and
RF shielding, brushes.
 Medical applications in surgery and x-ray equipment, implants, tendon/ ligament repair.
 Chemical industry; nuclear field; valves, seals, and pump components in process plants.
 Carbon fiber can be found in a wide range of performance vehicles including sports cars,
superbikes, pedal bikes (where they are used to make frames), powerboats etc.

6. Aramid fiber
Aramid is a manufactured fiber, where the fiber forming substance is a long-chain synthetic
polyamide in which at least 85% of the amide (-CO-NH-) linkages are attached directly between
two aromatic rings.

In 1960, DuPont introduced meta-aramid in commercial applications under the trade name
Nomex. They were also the 1
st
one to introduce Para-aramid fibers under the trade name Kevlar.
Nowadays different types of aramid fibers are found worldwide. Among them the following are
well known in the area of technical textiles.
 Kevlar (made by Dupont)
 Nomex ( made by Dupont)
 Conex (made by Teijin, Japan)
 Technora (made by Teijin, Japan)

Production of P-Aramid fiber (Kevlar)
Spinning technique: Wet or dry spinning
After treatment: wash/dry, modification of surface

Figure: Chemical structure of p-aramid fiber (Kevlar)

7. Properties of Kevlar fiber:
The p-aramid fibers can be produced with tenacity around 23 g/den and elongation at break up to
3.5%.
 High tensile strength as well as elasticity
 High modulus (Structural rigidity)
 Excellent dimensional stability
 Fatigue resistance is high
 Low elongation at break
 Low thermal shrinkage
 High chemical resistance
 High cut resistance
 Flame resistant and self-extinguishing
 Yellow in color
 Useful temperature range ( -200
0
C to 350
0
C)
 Excellent bulletproof/ Ballistic properties

Production of m-Aramid fiber (Nomex)
Spinning technique: Wet or dry spinning
After treatment: wash/dry, modification of surface

Figure: Chemical structure of m-aramid fiber (Nomex)
Properties of Nomex fiber:
Meta aramid fibers generally have a tenacity of about 5.6 g/den, which can compare to mid-
tenacity nylon and polyester fibers.
 Low elongation at break
 Possible to dye the fiber
 Low thermal shrinkage

8.  High chemical resistance
 Flame resistant and self-extinguishing (up to 400
0
C)
 White in color
Spinning of Aramid fiber


Figure: Wet Spinning technique for producing Aramid fiber

9. Figure: Comparison among Melt, Dry and Wet Spinning Process
Differences between Nomex and Kevlar Fiber

Kevlar fibers can be produced with tenacity around 23 g/den and elongation at break up to 3.5%.
Nomex fibers generally have a tenacity of about 5.6 g/den, which can compare to mid-tenacity of
nylon and polyester fibers. So, tensile strength and structural rigidity of Kevlar products are
higher than Nomex fabrics or products.
Application of Kevlar fiber
This fiber is used for bullet proof & anti-ballistic apparel, racing cars, protective gloves, helmet,
industrial protective clothing, in hot gas filtration, structural composite for aircraft’s, optical fiber
cable sheath, sail cloths and special tyre cords.
Application of Nomex fiber
Application of m-aramid fiber i.e. Nomex fibers include electrical insulation, protective clothing
for firefighters, auto racers, military personnel, automotive heat shields and aerospace
applications.

10. Glass Fiber
Glass is an amorphous material that consists of a silica (SiO2) backbone with various oxide
components to give specific compositions and properties. It is an inorganic and isotropic fiber. It
has high strength, chemical resistant, electrical resistant, flame resistance and low elongation at
break are the salient features of glass. It has high specific gravity (2.5 – 2.7).
Applications
It is used in industrial applications including fire proof, filtration, insulation, and in
reinforcement.
Types of Glass fiber
E-glass, S-glass, C-glass, quartz
E-glass:
This is the most popular and inexpensive glass fibers. The designation letter ‘E’ means
‘Electrical’ (E-glass fiber is excellent insulator). The composition of E-glass ranges from 52-
56% SiO2, 12-16% Al2O3, 16-25% Cao and 8-13% B2O3.
S-glass:
This type of fiber is stronger than E-glass fibers (the letter ‘S’ means ‘strength’). High strength
glass fiber is generally known as S-type glass in the United States, R-glass in Europe and T-glass
in Japan. S-glass is used in military applications and in aerospace. S-glass fiber consists of Silica
(SiO2), magnesia (MgO), alumina (Al2O3). It is also high temperature stable.
C-glass:
This is corrosive and chemical resistant glass fibers. To protect against water erosion, a moisture
resistant coating such as a silane compound is coated on to the fibers during manufacturing.
Adding resin during composite formation provides additional protection. C-glass fibers are used
for manufacturing storage tanks, pipes and other chemical resistant equipment.

Production of glass
Component: aluminium, calcium and magnasium oxide

11. Figure: Melt spinning process of Glass fiber production

Properties of Glass fiber
• Glass is generally a good impact resistant fiber but weighs more than carbon or aramid
fiber
• Glass fibers have excellent characteristics, equal to or better than steel in certain forms
• Composites made from this fiber exhibit very good electrical and thermal insulation
properties
• Glass fibers are also transparent to radio frequency radiation and are used in radar
antenna applications
• Glass fibers resist water, rot, mildew and chemicals. But hydro chloric acid and hot
phosphoric acid causes harm to the glass fiber.
• Glass fiber fabrics will not stretch or shrink. Nominal elongation break is 3-4%. Low
thermal expansion
• Fibers are brittle

Applications of Glass Fiber
It is used in industrial applications including –
• Noise abatement

12. • Fire protection
• Temperature control
• Air purification
• Insulation and roofing materials
• Filters
• Safety glass and windows
• Glass fiber reinforced circuit boards
• Glass reinforced plastic
• Glass as a rubber reinforcement
• Mattress covers for hotels
• Optical fibers
It is also used in
• Airspace and aircraft manufacturing
• Corrosion resistant products
• Industrial tool, gears, frame of automobiles
• constructions

13. P-phenylene-2.6 benzobisoxazole (PBO)
It has very high strength and tensile modulus, which is greater than any other fiber. Good flame
resistance and heat resistance (68% LOI) and high decomposition temperature (600
o
C).
Application
It is used in the anti-ballistic vest, protective apparel for fire fighters, lightweight armor for
vehicle and for personal.
Ultra high molecular weight polyethylene (UHMPE)
It has high molecular weight, produced by gel spinning technique. It has low specific gravity
(0.97), high chemical and abrasion resistance, and high strength compare to kevlar.
Application
It is used in anti-ballistic apparel, floatable ropes, and nets.
Other manmade fibers in technical textile

14. Thermal properties of Technical fiber