Studies on the use of nano zinc oxide and modified silica in NR, CR ...

Chapter 7
silica particles are reduced by the antioxidant which acts as lubricants. So it
reduces the heat developed by the frictional strain.
7.3.5 Rubber-filler interaction studies
With antioxidant IPPD
130
The complex modulus G* of composites containing antioxidant
modified silica and neat silica were measured before and after curing. The
variation of G* with strain for uncured and cured samples are shown in figure
7.4(a,b) respectively. The complex modulus at low strains is a measure of the
filler-polymer interaction. 21-23 At low strains the complex modulus of
antioxidant modified silica filled composite are remarkably high compared to
higher strain. This may be due to the hydrogen bonding between silanol
groups and –NH groups in the antioxidant at lower strain.
G*(MPa)
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
Strain Sweep Uncured
NR + Neat Silica
NR + Modified
Silica
0.56 0.12 10.04 100.02
Strain (%)
G*(MPa)
4
3.5
3
2.5
2
1.5
1
0.5
0
Strain sweep cured
NR + Neat Silica
NR + Modified
Silica
0.56 0.12 10.04 100.02
Strain (%)
(a) (b)
Figure 7.4 (a) Variation of complex modulus with strain for uncured compounds
(b) Variation of complex modulus with strain for cured compounds
7.3.6 Ageing studies
a) Thermal ageing studies
Figure 7.5(a) shows variation in the tensile strength of the filled
vulcanizates of NR with time of ageing. The vulcanizate containing IPPD
modified silica shows good resistance when the ageing time is increased to
96 hrs. This shows that antioxidant is getting coated over the silica surface
and gets uniformly distributed in the rubber matrix.