Date post: | 22-Jan-2015 |
Category: |
Education |
Upload: | pune-institute-of-computer-technology |
View: | 828 times |
Download: | 9 times |
LIQUID CRYSTAL
POLYMERS
LIQUID CRYSTAL POLYMER
• These polymers which have a tendency to allign their chains parallel over a long distance , prior to the crystallization from their melt or solution.
• Occurrence: Liquid crystallinity in polymers may occur either by dissolving a polymer in a solvent or by heating a polymer above its
glass or melting transition point.
TYPES OF LCPs
Lyotropic LCP
Thermotropic LCP
Formed from their solution.
Formed from their melt.
CONDITIONS
• Highly polarised chain structure.
• Molecules should have aromatic rings.
• Molecules should be like disc.
Disc like structure
MISCELLAENOUS
• Liquid-crystal polymers (LCPs) are a class of aromatic polyester polymers.
• Polyester Polymers: Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most
commonly refers to polyethylene terephthalate (PET).
Preparation
PROPERTIES
• Higher crystallinity in solid state.
• High tensile strength.• Very tough.• Higher Tm and Tg.• Have property of
multiple internal reflection.
• Used at higher working
temperature.
APPLICATIONS
• For optical fibres.• Electrical and electronics
app.• Transport,automotive,mil
itary app.• Aircraft and aerospace
app.• Chemical and consumer
app.
• Used as fillers for composites.
KEVLAR
• Kevlar is the registered trademark for a para-aramid synthetic fiber.
• This high strength material was first commercially used as a replacement for steel in racing tires.
• Typically it is spun into ropes or fabric sheets that can be used as such or as an ingredient in composite
material components.
PREPRATION
Tere phthalic acid dichloride
1,4 diaminobenzene
Monomeric Unit
PROPERTIES
• Has a tensile strength of about 3,620 MPa.
• A relative density of 1.44.• 5 times stronger than steel.• Although it has high melting
point, it can be easily moulded.
• It has high heat stability.
OTHER PROPERTIES
• It is slightly stronger at low temperatures.• At higher temperatures the tensile strength is
immediately reduced by about 10–20%.• After some hours the strength progressively
reduces further.
USES
• Used for aerospace applications and aircraft industry.
• Used for puncture resistant tyres.
• Making ropes and cables.• Bulletproof vests and
helmets.
OTHER USES
• Used in sports equipments.
• Particle physics.• Some fire dancing
props.