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elastomers-160226225508.pdf
1.
2. ELASTOMERS
CONTENTS
• What are elastomers
• Explanation
• Types of elastomers
• Advantages & disadvantages
• Uses & applications
3. ELASTOMERS….?
• Macromolecular material which returns
rapidly to approximately its initial
dimensions and shape after deformation
by a weak stress.
• Or
• An elastomer is a polymer with the
property of elasticity.
4. • An elastomer is a polymer with the
property of viscoelasticity (colloquially
"elasticity"), generally having notably low
Young's modulus and high yield strain
compared with other materials.
5. • Elastomer is a big fancy word, and all it
means is "rubber". Some polymers which
are elastomers include polyisoprene or
natural rubber, polybutadiene,
polyisobutylene, and polyurethanes.
7. WHY ELASTOMER ?
• HIGH ENERGY DENSITY
– capable of storing large amounts of energy
with small area and volume
• LOW STRAINS
– stress/strain profile suitable for low-power
electrostatic actuators with large
displacements.
8. STRUCTURE
• The long polymer chains cross-link during
curing. The molecular structure of
elastomers can be imagined as a
'spaghetti and meatball' structure, with the
meatballs signifying cross-links.
9. PROPERTIES
• Highly amorphous materials
• High randomly orientated structure
• Large reversible extensions (several
hundred percent)
• Low intermolecular forces allow for
flexibility
• Rubberoid material
• A 'spaghetti and meatball' structure, with
the meatballs signifying cross-links
10. GLASS TRANSITION
TEMPERATURE
• glass transition temperature, or Tg. This is
the temperature above which a polymer
becomes soft and pliable, and below
which it becomes hard and glassy.
• If Tg above room temp
• ......................THERMOPLASTIC
• If Tg below room
temp......................ELASTOMER
11. STRETCHING:
• Elastomers can be stretched to many
times their original length,
BOUNCING:
• Elastomers can bounce back into their
original shape without permanent
deformation.
12. CROSS LINKING
• Cross linking means that different chains
of polymer molecules have all been linked
• Advantage
• Disadvantage
17. EFFECTS OF STRESS
• These materials show very little strain
under weak deformation stresses.
18. VULCANIZATION
Rubber ball obtained from
a vulcanization process
Vulcanization is a chemical process for
converting rubber or related polymers into more
durable materials via the addition of sulfur or
other equivalent "curatives".
23. NATURAL RUBBER (NR)
• Natural rubber is a
product extracted
from the latex of
the rubber tree.
Natural rubber
occurs in almost
2000 plant
species, but only a
few of them are
industrially
Trans-polyisoprene
27. PROPERTIES OF NATURAL
RUBBER
• High tensile and tear strengths
• Resistance to wear, ,abrasion and fatigue
• High molecular weight
• Rubber is water repellent
• It shows resistant to alkalies and weak
acids
29. PROPERTIES OF BR
• Good abrasion resistance
• Elasticity and cold properties
• Lower cost (all synthetic from cheap
monomer)
• Widely used in tyres
• because of the good
abrasion resistance .
31. Silicone Rubber
• Silicone rubber is
based onpolymeric
chains featuring the
very stable,
alternating
combination of silicon
(si) and oxygen (o)
atoms in the
backbone and a
variety of organic side
groups attached to
c
o
H
S
32. PROPERTIES OF SR.
• The silicon rubbers have very low glass
transition temperatures
• Very high temperature resistance
• Low temperature flexibility
• Good electrical resistance
34. BUTYL RUBBER (IIR)
• Butyl rubber is a
copolymer of
isobutylene with a
small percentage
of isoprene (0,5-
3%) to provide
sites for curing. It is
polymerized AT
LOW
TEMPERATURES.
35. PROPERTIES OF IIR.
• Very low gas permeability
• Very high damping properties (energy
absorption)
• Excellent ageing stability
• Poor resistance to oils and fuels
• Low adhesion properties
• Good weathering resistance
36. THERMOPLASTIC
ELASTOMER (TPE)
• They are a class of copolymers or a
physical mix of polymers (usually a plastic
and a rubber) which consist of materials
with both thermoplastic and elastomeric
properties
• Sometimes referred to as thermoplastic
rubbers
37. Properties of TPE
• High elastic properties
• Thermoplastic elastomer polymers is a
weaker dipole or hydrogen bonded
• High molecular weight
• High strenght due to vulcanization
38. USES OF ELASTOMERS
• Their common uses are as
• In buildings as sealing agent
• In preparing nylon
• In tires
• In industries
• In gaskets
39. • Styrene block copolymers are used in
shoe soles for their ease of processing,
and widely as adhesives
40. • These materials find large application in
the automotive sector and in household
appliances sector
41. • Elastomers can be "compounded" or
joined with other materials to strengthen
certain characteristics. can easily be
installed next to various other materials,
such as metal, hard plastic, or different
kinds of rubber, with excellent adherence.
42. • Elastomers being very strong when struck,
hard if scratched, resistant to corrosion
from various chemicals, and resilient in the
face of humidity or water submersion,good
electronic insulators. Between different
branches of wires, they are dense and
protective.
43. • They are easy to sculpt when they are in
their softened, resinous state. Yet once
they harden, they remain impervious to
changes in most changes in temperature
as well as stress like stretching or
compressing.
44. • Elastomers form various rubbery shapes.
Many industries rely on parts made from
elastomers, especially automobiles,
sports, electronics, and assembly line
factories
45. • TPE is commonly used to make
suspension bushings for automotive
performance applications because of its
greater resistance to deformation when
compared to regular rubber
bushings.
46. • Used in adhesives, paints (e,g car
coating).
• Used in cable insulation
47. • Elastomers are good at insulating,
withstanding deformation, and molding
into different shapes. Used for wheels on
a skateboard and the soles of tennis
shoes, to the insulation covering speaker
cables and telephone lines.
48. ADVANTAGES &
DISADVANTAGES
ADVANTAGES
• These are recyclable like plastics
• They can be easily colored by most types
of dyes
• They offer better durability
• They are resistant to emulsification in
damp conditions
49. • Little or no bending
• Simpler processing
• They have less shrinkage
• Better quality control cost
• With no need to add stabilizers or cure
systems
• It consumes less energy and more
economical control of product quality is
possible.
50. DISADVANTAGES
Elastomer has some disadvantages as
• Much expensive
• General inability to bear load
• Sometimes poor chemical and heat
resistance
• Can be easily distorted
• Sometimes low thermal stability.
51. • Preventing from being used in high speed
automobile tires
• Relatively high cost of raw materials
• Poor chemical and heat resistance
• High compression set and low thermal
stability.
52. • Relatively high prices per weight
• Relatively high cost of raw materials
• Melting at elevated temperatures
• New technology unfamiliar to many rubber
processors
