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Kevlar
BY:
Richmond Te
Emilio Tan
Mark Go
Tomas Delos Reyes
History
• Kevlar is the registered trademark for a paraaramid synthetic fiber, related to
other aramids such as Nomex and Technora.
Developed at DuPoint in 1965, this high
strength material was first commercially used
in the early 1970s as a replacement for steel in
racing tires.
Structure
• When Kevlar is spun, the resulting fiber has a tensile strength of
about 3,620 MPa, and a relative density of 1.44. The polymer owes
its high strength to the many inter-chain bonds. These intermolecular hydrogen bonds form between the carbonyl groups and
NH centers. Additional strength is derived from aromatic stacking
interactions between adjacent strands. These interactions have a
greater influence on Kevlar than the van der Waals interactions and
chain length that typically influence the properties of other
synthetic polymers and fibers such as Dyneema. The presence
of salts and certain other impurities, especially calcium, could
interfere with the strand interactions and caution is used to avoid
inclusion in its production. Kevlar's structure consists of relatively
rigid molecules which tend to form mostly planar sheet-like
structures rather like silk protein.
Properties
• Kevlar maintains its strength and resilience
down to cryogenic temperatures (−196°C); in
fact, it is slightly stronger at low temperatures.
At higher temperatures the tensile strength is
immediately reduced by about 10–20%, and
after some hours the strength progressively
reduces further. For example at 160°C (320°F)
about 10% reduction in strength occurs after
500 hours. At 260°C (500°F) 50% strength
reduction occurs after 70 hours.
Grades of Kelvar
• Kevlar K-29 - in industrial applications, such as
cables, asbestos replacement, brake linings, and
body/vehicle armor.
• Kevlar K49 - high modulus used in cable and rope products.
• Kevlar K100 - colored version of Kevlar
• Kevlar K119 - higher-elongation, flexible and more fatique
resistant.
• Kevlar K129 - higher tenacity for ballistic applications.
• Kevlar AP - has 15% higher tenacity than K-29.
• Kevlar XP - lighter weight resin and KM2 plus fiber
combination.
Purposes
• Protection
– Armor- Kevlar is well-known component
of personal armor such as combat
helmets, Ballistic face masks, and Ballistic vests.
– Personal Protection- Kevlar is used to manufacture
gloves, sleeves, jackets, chaps and other articles of
clothing designed to protect users from cuts,
abrasions and heat.
– Sport Equipment- It is used as an inner lining for
some bicycle tires to prevent punctures, and due
to its excellent heat resistance, is used for fire
poi wicks. In Table tennis, plies of Kevlar are added
to custom ply blades or paddles, in order to
increase bounce and reduce weight. It is used
for motorcycle safety clothing, especially in the
areas featuring padding such as shoulders and
elbows. It was also used as speed control patches
for certain Soap Shoes models.
• Music
– Audio equipment- Kevlar has also been found to have
useful acoustic properties for loudspeaker cones,
specifically for bass and midrange drive units
– Drumheads- Kevlar is sometimes used as a material on
marching snare drums. It allows for an extremely high
amount of tension, resulting in a cleaner sound.
– Woodwind reeds-Kevlar is used in the woodwind reeds of
Fibracell. The material of these reeds is a composite of
aerospace materials designed to duplicate the way nature
constructs cane reed.
• Other uses
– Rope, cable, sheath
– Electricity generation
– Building construction
– Brakes
– Expansion joints and hoses
– Particle physics experiment
• Sources:
• http://en.wikipedia.org/wiki/Kevlar#Structure
_and_properties