(PZDMA) radicals also reacted with NR radicals, forming NR-graft-PZDMA
[47]. Moreover, when two PZDMA radicals met or one PZDMA radical abstracted
hydrogen from a rubber chain, an un-grafted PZDMA molecule appeared [47]. The
apparent activation energy (Ea) of polymerization of ZDMA was lower than that of
curing the pure NR, thus the ability that ZDMA to capture peroxide radicals was
stronger than that of the pure NR in the same condition.
At a high concentration of ZDMA, majority of the limited peroxide radicals are
captured by ZDMA to form PZDMA while a small quantity of peroxide radicals is
consumed by crosslinking of NR; at a low concentration of ZDMA, the majority of
the limited peroxide radicals can be consumed by crosslinking of NR. Thus the
more ZDMA in the NR, the less peroxide radicals consumed in NR crosslinking at
this time. The NR/ZDMA compound cured for 1minute contains un-crosslink NR
macromolecules, primary covalent crosslink points, residual ZDMA, PZDMA and
NR-graft-PZDMA. Majority of NR-graft-PZDMA exist in the interface of NR and
0.1
1
10
0
20
40
60
80
100
120
140
test temperature 60
o C
NR
NR-10phrZDMA
NR-20phrZDMA
NR-30phrZDMA
NR-40phrZDMA
G' (KPa)
Strain (deg)
0.1
1
10
0
20
40
60
80
100
test temperature 100
o C
NR
NR-10phrZDMA
NR-20phrZDMA
NR-30phrZDMA
NR-40phrZDMA
G' (KPa)
Strain (deg)
a
b
Fig. 17 Strain sweeps for
G
0 of the NR/ZDMA
compounds cured for
1 minute, (a) test
temperature 60
C and (b)
100
C, frequency 1 Hz [57]
184
Y. Chen and C. Xu