network) and rubber covalent crosslinks deformation. For the sample with 10 phr
ZDMA, the developed ionic network is not formed, since the sample with 10 phr
ZDMA and NR gum do not show such a loss peak. At high strain amplitudes (near
10
, equal to % 140 %), more energy dissipated in deforming of the rubber crosslink
network, thus G
00 show an apparent increase [58]. Compared to uncured compounds, the vulcanizates yield much higher G
0 and G
00 because of the chemical
crosslinks and nano polymerized ZDMA.
When the strain amplitude increases to a certain degree, both the covalent and
ionic crosslink networks will be stretched to be deformed. At this moment, some
debondings may occur similar to the situation of carbon black [61, 62], since the
presence of nano-particles of poly-ZDMA. Moreover, lots of ionic bonds will be
slipped and simultaneously, new ionic crosslinks can be formed rapidly [61]. This
instantaneous ionic crosslink network can adapt to the status and cease back to the
initial structure. This results in a weak recovery and a high softening behavior of G
0
at high ZDMA loading. The weak recovery of G
0 is attributed to the reconstruction
of poly-ZDMA nano-particle network and the elastic NR crosslink network. However, in the case of conventional reinforcing filler such as CB [61, 63], the
reconstruction of the CB filler-filler structures results in a remarkable recovery of
G
0 . The results of consecutive strain sweeps for NR/ZDMA vulcanizates are shown
in Fig. 12 [58]. After three consecutive scans at 60
C, the temperature was firstly
raised to 100
C and kept for 30 min. After that, the sample was kept intact within
the confinement of the cavity of RPA 2000 and the temperature was reduced to
60
C to undergo the forth scan. The sample was kept at 100
C isothermally for
30 min, in order to accelerate the recovery of stress-softening. Differing to the
uncured compounds, the vulcanizates showed an apparent stress-softening behavior. After the first scan, the LVE region of vulcanizates was shorten with increasing
ZDMA, the recovery degree of G
0 at the forth scan was also reduced with increasing
ZDMA. Thus, Chen and Xu [58] attributed it to the disrupture of the developed
ionic crosslink network during the stretching or tearing. After the first sweep, the
disappearance of the LVE region of 30 phr and 40 phr ZDMA revealed that the rigid
filler-filler network became fractured that initiated the sharp decrease of modulus at
low strain amplitude. This demonstrated that a more developed ionic crosslink
network might handicap the reformation of filler-filler networks.
Effect of Double Networking on Non-Linear Viscoelasticity of Elastomers
179
ZDMA, the developed ionic network is not formed, since the sample with 10 phr
ZDMA and NR gum do not show such a loss peak. At high strain amplitudes (near
10
, equal to % 140 %), more energy dissipated in deforming of the rubber crosslink
network, thus G
00 show an apparent increase [58]. Compared to uncured compounds, the vulcanizates yield much higher G
0 and G
00 because of the chemical
crosslinks and nano polymerized ZDMA.
When the strain amplitude increases to a certain degree, both the covalent and
ionic crosslink networks will be stretched to be deformed. At this moment, some
debondings may occur similar to the situation of carbon black [61, 62], since the
presence of nano-particles of poly-ZDMA. Moreover, lots of ionic bonds will be
slipped and simultaneously, new ionic crosslinks can be formed rapidly [61]. This
instantaneous ionic crosslink network can adapt to the status and cease back to the
initial structure. This results in a weak recovery and a high softening behavior of G
0
at high ZDMA loading. The weak recovery of G
0 is attributed to the reconstruction
of poly-ZDMA nano-particle network and the elastic NR crosslink network. However, in the case of conventional reinforcing filler such as CB [61, 63], the
reconstruction of the CB filler-filler structures results in a remarkable recovery of
G
0 . The results of consecutive strain sweeps for NR/ZDMA vulcanizates are shown
in Fig. 12 [58]. After three consecutive scans at 60
C, the temperature was firstly
raised to 100
C and kept for 30 min. After that, the sample was kept intact within
the confinement of the cavity of RPA 2000 and the temperature was reduced to
60
C to undergo the forth scan. The sample was kept at 100
C isothermally for
30 min, in order to accelerate the recovery of stress-softening. Differing to the
uncured compounds, the vulcanizates showed an apparent stress-softening behavior. After the first scan, the LVE region of vulcanizates was shorten with increasing
ZDMA, the recovery degree of G
0 at the forth scan was also reduced with increasing
ZDMA. Thus, Chen and Xu [58] attributed it to the disrupture of the developed
ionic crosslink network during the stretching or tearing. After the first sweep, the
disappearance of the LVE region of 30 phr and 40 phr ZDMA revealed that the rigid
filler-filler network became fractured that initiated the sharp decrease of modulus at
low strain amplitude. This demonstrated that a more developed ionic crosslink
network might handicap the reformation of filler-filler networks.
Effect of Double Networking on Non-Linear Viscoelasticity of Elastomers
179