8 Viscoelasticity
Elastomers are typically viscoelastic and exhibit both viscous as well as elastic
characteristics when undergoing deformations. The viscous component (σ ¼ η
dε
dt ,
where, σ is the stress, η is the coefficient of viscosity and
dε
dt is the change of strain as
a function of time) takes care of the energy dissipated as heat after a strain/stress is
applied and followed by its removal while the elastic component (σ ¼ Eε) brings
back the material towards original dimension, or, in other words, strain depends on
stress applied to the materials and time. The overall strain is then governed by the
equation where the two terms are separable, as in Eq. (2) is called as linear
viscoelasticity and usually it is applicable only for small deformations, where, t is
15
a
b
5
15
Torque/Nm
Torque/Nm
0
5
10
20
0
Time/s
Time/s
160ºC
130ºC
140ºC
150ºC
160ºC
150ºC
140ºC
130ºC
0
500
1000
1500
2000
2000
1500
1000
500
0
10
Fig. 9 Vulcanizing curves
of neat NR and CNT/NR
nanocomposites: (a) neat
NR, (b) CNT/NR
nanocomposites [104]
Nonlinear Viscoelasticity of One Dimensional Filler Reinforced Elastomer. . .
29