WhatisRubber???
Rubberisasticky,elasticsolidproducedfroma
milkyliquidcalled"latex“,andmodifiedinto
productssuchaselectricinsulation,elasticbands
andbelts,tiresetc.
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Rubber Processing Technology-Mechanical Engineering-Project Presentation, Study Guides, Projects, Research of Mechanical Engineering
This presentation is for project of Mechanical Engineering course. Project was supervised by Gopi Chopra at Ambedkar University, Delhi. Its main points are: Rubber, Processing, latex, Production, Finished, Goods, Compunding, Mixing, Shaping, Vulcaniza=ing
Typology: Study Guides, Projects, Research
2011/2012
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What
is
Rubber
^ Rubber
is^ a^
sticky,
elastic
solid
produced
from
a
milky
liquid
called
"latex“,
and
modified
into
products
such
as^ electric
insulation,
elastic
bands
and^
belts,
tires
etc.
Production
of
Rubber
^ Production
of^ rubber
goods
can
be^ divided
into
two
basic
steps: ^ Production
of^ the
rubber
itself.
^ Processing
of^ the
rubber
into
finished
goods.
PRODUCTION
OF
RUBBER
^ Rubber
is^ produced
from
two
sources
^ Natural
Source ^ Called
as^ Natural
Rubber
^ Petroleum
Source ^ Called
as^ Synthetic
Rubber
Natural
Rubber
^ Tapped
from
Rubber
Trees
Hevea brasiliensis
as^ LATEX.
^ The
trees
are^
grown
on^ plantations
in
Southeast
Asia
and
other
parts
of^ the
world.
Recovering
Rubber
From
Latex
^ The
preferred
method
of^ recovering
rubber
from
the latex
involves
coagulation
^ The latex
is^ diluted
with
water
to^ about
half its^ natural
concentration.
^ An
acid
such
as^ formic
acid
(HCOOH)
or^ acetic
acid
(CH^3
COOH
)^ is
added
to^ cause
the^ latex
to^ coagulate
after
about
12 hours.
^ The
coagulum,
now
in^ the
form
of^ soft
solid
slabs,
is^ then
squeezed
through
a^ series
of^ rolls
that
drive
out^ most
of^ the
water
and reduce
the^ thickness
to^ about
3 mm.
Drying
Of
Rubber
^ The
sheets
are^
then
draped
over
wooden
frames
and
dried
in
smokehouses. Ribbed
Smoked
Sheet
=>^
dried
in^ Smoke Houses
^ Air
Dried
Sheet
=>^ Dried
in^ Hot
Air
^ Pale
Crepe
Rubber
=^ >^ Dried
in^ Warm
Air^ ,^ Involve
more
mechanical
working
COMPOUNDING
OF
RUBBER
^ Different
Additives
are^
added
in^ Rubber
to^ satisfy
the given
application
in^ terms
of^ properties,
cost,
and
process
ability.
^ Additives
include
^ Carbon
Black ^ colloidal
Form
of^ Carbon
^ black
in^ color ^ obtained
from
the^ thermal
decomposition
of^ hydrocarbons
(soot)
^ Increases
tensile
strength
^ resistance
to^ abrasion
and tearing
of^ the
final
rubber
product
^ protection
from
Ultra
‐Violet
Radiation
^ parts
Black
in^ color
because
of^ Carbon
Black
Content
^ Hydrous
aluminum
silicates
(Al2Si2O5(OH)4)
^ provide
less^
reinforcing
than
carbon
black
^ used
when
the^ black
color
is^ not
acceptable
^ Calcium
carbonate
(CaCO3)
^ non
‐reinforcing
filler
^ reduces
cost
^ Silica
(SiO2) ^ Styrene ^ PVC ^ Phenolics ^ Recycled
Rubber
MIXING
OF
ADDITIVES
^ The
additives
must
be^ thoroughly
mixed
with
the^
base
rubber
to
achieve
uniform
dispersion
of^ the
ingredients.
^ A
two
‐stage
mixing
process
is^ usually
employed:
^ Master
Batch
=>^ In
the^ first^
stage,
carbon
black
and^
other
non
‐
vulcanizing
additives
are^ combined
with
the^ raw^ rubber. The
term
master
batch
is^ used
for^ this
first
‐stage
mixture.
^ After
thorough
mixing
has^
been
accomplished,
and time
for^ cooling
has^ been
allowed,
the^ second
stage
is^ carried
out^ in^ which
the
vulcanizing
agents
are^ added.
Equipment
For
Mixing
^ Equipment
for^ Mixing
Include
^ Two
Roll Mill ^ Internal
Mixer
Extrusion
^ Screw
extruders
are^
generally
used
for^ extrusion
of^ rubber.
^ The
L/D
ratio
of^ the
extruder
barrels
is^ less,
in^ the
range
10 to
to^ reduce
the risk
of^ premature
cross–linking
^ Die
swell
occurs
in^ rubber
extrudates because
it^ exhibits
the
memory
property.
Calendaring
^ This
process
involves
passing
rubber
stock
through
a^ series
of
gaps
of^ decreasing
size
made
by^ a
stand
of^ rotating
rolls.
^ The
rubber
process
must
be^ operated
at^ lower
temperatures
,^ to
avoid
premature
vulcanization
^ The
output
of^ the
process
is^ a^
rubber
sheet
of^ thickness
determined
by^ the
final
roll^
gap.
Molding
And
Casting
^ Many
foamed
rubber
parts
are^
produced
by^ molding.
^ Injection
Molding
^ Compression
Molding
^ Transfer
Molding