Materials having rubber like properties at room temperature are called elastomers .... are blends of poly~chloroprene (CR) and epoxidised natural rubber. (ENR) ...
CHAPTER I
-
INTRODUCTION
Materials having
rubber
like
properties
at
room temperature
a r e called elastomers. Rubbers a r e macromolecular substances capable of passing, under the effect of vulcanisation,
from a predominantly
plastic state to a predominantly. elastic state. Rubbers have a glass transition
temperature
a r e used
and
randomly
agglomerated
introduced rubber
is
of
and
converted
into
the
long
temperature
a
When
technically
does not
Elasticity on
the
-
chemical
they
which a r e bonds
utilizable material, within a broad
dissolve
technological point 1 properties of rubber ;re important . 1.
From
which
which
are
molecules by vulcanisation, the raw
large r e v e r s i b l e deformations and
at
flexible molecules
entangled.
between neighbouring
temperature
solvents.
than
are composed
is capable of of
lower
of
but
only
view,
which range
swells
the
in
following
The a b i l i t y to undergo large, reversible deformation
application
of
relatively
small
stress.
The
flexibility
combined with elasticity is a characteristic property of rubber. 2.
Ability
to
accumulate a
considerable amount of
input
energy
during deformation, with low hysteresis. 3.
Considerable chemical resistance.
4.
Under suitable conditions. rubber has a long service life.
5.
Rubber
compounds
can
be
processed
operations to give different products. 6.
The products a r e relatively inexpensive.
by
relatively
simple
1.2
REASONS FOR BLENDING ELASTOMERS
In recent
years,
research and developmental activities in the
field of polymer science and technology have been concentrated more on the modification
of
existing polymeric materials rather than on
synthesizing new polymers. compositions
having
blending
of
on
basis
the
two
or of
the
required
properties
more
polymers.
All
their
relationship.
The
additivity of
properties.
mixed
with
most
another
The easiest method to develop polymer
-
property important
involves
materials
processing
concept
in
-
physical
attract interest cost-performance
polymer
blends
is
By t h i s we mean that when a polymer is
polymer,
the
resulting
blend
has a
property
which is the weighed average properties of the individual polymers. Modulus is one of additivity
such properties that is expected to obey some
relationship
2
.
For
blends
the
weighing functions of
composition will be sensitive to the morphology.
A very
possibility,
is
property.
although
less
frequently
observed,
the
intriguing
synergism
Here w e refer to a situation where some property,
in such
as tensile strength, for t h e blend is higher than that of the pure components. The success of a new material depends on several factors such a s combination of
properties and cost dilution.
For example.
when we blend a high thermal resistant polymer having poor processability thermal
