Chemistry Reference
In-Depth Information
Table 2.1
Molecular cohesion of some linear polymers
a
Polymer
Cohesion/5
˚
chain length
Polymer structure
Polyethylene
1.0
n
Polybutadiene
1.1
n
Polyisobutylene
1.2
n
Polyisoprene (
cis
)
1.3
n
Poly(vinyl chloride)
2.6
Cl
n
Poly(vinyl acetate)
3.2
n
O
O
Polystyrene
4.0
n
Poly(vinyl alcohol)
4.2
n
OH
Polyamides
5.8
O
R
NR'
n
H
Cellulose
6.2
OH
OH
O
O
OH
a
From refs [
2
,
3
], and other literature sources
the motion, and the frequency at which that occurs. This in turn determines the rate at which the
polymer molecules respond to molecular stresses. In flexible polymers, if the thermal energy is
sufficiently high, large segments can disengage and slip past each other quite readily in response to
applied stress. All elastomers possess such properties. Properties of polymers depend also upon
morpholog
or upon the arrangement of their polymeric chains. This arrangement can be amorphous
or crystalline. The term
amorphous
designates a lack of orderly arrangement. Crystalline
y
