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Aramid Fibers
Douglas J. Gardner
Professor
Wood-Polymer Hybrid Composites
Aramid Fibers
Aramid fibres consist of
long molecular chains
produced from polyparaphenylene
terephthalamide (PPD-T).
The chains are highly
oriented with strong
interchain bonding which
result in a unique
combination of properties.
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Polymer Preparation
Aramid fibers are
made from the
condensation reaction
of paraphenylene
diamine (PPD) and
terephthaloyl chloride
(TCL) in a dialkyl
amide solvent.
NH2 NH2
PPD
ClOC COCl
TCL
Polymer Solution Behavior
PPD-T polymer is
insoluble in conventional
solvents.
Concentrated acids such
as sulfuric, nitric and
hydrochloric are used.
PPD-T/sulfuric acid
solution at 10% polymer
concentration is
anisotropic.
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Liquid Crystalline Behavior
Anisotropic polymer
solutions will exhibit
liquid crystalline
behavior.
Liquid Crystalline Behavior
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Fiber Spinning
A dry-jet wet spinning
process for spinning
anisotropic solutions
of aramid polymer to
produce fibers.
Aramid Fiber Structure Development
Anisotropic solution
extruded through a
spinneret capillary
Liquid crystalline
domains orient
Filament attenuation
in the air gap under
spinning tension
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Aramid Thermal Properties
High melt temp >530 C
High Tg > 375 C
Relatively high thermal
stability
Zero strength temperature
~ 640 C
Negative coefficient of
thermal expansion with
increasing temperature
Aramid Physical and Mechanical
Properties
Low combustibility
Nonconductive
Good dielectric
properties
High specific strength
and modulus
Low creep
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Aramid Environmental and
Chemical Exposure
Sensitive to ultraviolet
radiation
Good environmental
stability in sea water,
oils, solvents
Good oxidative
stability at 180 C
Retains some moisture
Aramid Chemical Resistance
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Aramid (Kevlar7) Forms
Continuous Filament
Yarn
High Tensile Strength
Processable on
Conventional
Looms,Twisters, Cord
Forming, Stranding
and Serving
Equipment
Aramid (Kevlar7) Forms
Staple
Very High Cut
Resistance
Spun on Conventional
Cotton or Worsted
Spinning Equipment
Precision Cut Short
Fibres, 1/4 Inch or
Longer
Processable on Felting
and Spun Lace
Equipment
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Aramid (Kevlar7) Forms
Pulp-Wet and Dry,
Floc
Precision Cut Short
Fibres, 1/4 Inch
or Shorter
High Surface Area
Miscible in Blend
Composites
Thermal Resistance
Excellent Friction and
Wear Resistance
Cord
High Tensile Strength and
Modulus at
Low Specific Weight
Retention of Physical
Properties at High and Low
Temperature Extremes
Very Low Heat Shrinkage
Very Low Creep
Good Fatigue Resistance
Aramid (Kevlar7) Forms
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Aramid (Kevlar7) Forms
Fabric and Prepreg
Excellent Ballistic
Performance at Low
Weights
Excellent Friction and
Wear Performance
Against Other
Materials
Excellent Resistance to
Cuts and Protrusion
combined with
comfortable wear
Aramid Product Applications
Armor Systems
Rubber goods
Tires
Belts
Hoses
Ropes and Cables
Pulp
Friction products
Gaskets
Industrial Paper