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

Use of nano zinc oxide in natural rubber
Cure behavior of gum and filled compounds are given in the Table 4.3
and figure 4.1. Comparing the cure characteristics of filled and gum
compounds, compounds with 2phr ZnO(p) and ZnO(s) exhibited higher rate
and extent of cure over that of 5phr and 2phr of conventional ZnO
compounds. This indicates ZnO(p) and ZnO(s) with larger surface area
developed the full potential of the accelerator, there by making vulcanization
faster. Scorch safety has increased, and cure time was found to be lower
for ZnO(p) and ZnO(s) compounds compared to conventional ZnO
compounds. Compounds with 2phr ZnO(p) and ZnO(s) show faster curing
compared to compounds containing 1phr ZnO(p) and ZnO(s).
4.3.2 Properties of gum composites
Tensile properties
Compound
Table 4.4 Tensile properties of gum vulcanizates
Tensile strength
(MPa)
Elongation at
break (%)
Tensile modulus
at300%
elongation (MPa)
Tear strength
(N/mm)
N-1 23.02 1735 1.17 38
N-2 22.94 1591 1.46 40
N-3 23.06 1656 1.25 40
N-4 20.80 1899 1.04 33
Tensile properties of gum vulcanizates with ZnO(c), ZnO(p) and
ZnO(s) are shown in Table 4.4. Gum vulcanizate with 2phr conventional ZnO
has relatively low tensile properties compared to vulcanizates with 5phr
conventional ZnO, 2phr ZnO(p) and ZnO(s). Modulus and tear strength
values for vulcanizates with 2phr ZnO(p) and ZnO(s) are slightly greater than
vulcanizate with 5phr ZnO(c). Elongation at break is decreased for N-2 and
N-3 vulcanizates compared to N-1 vulcanizate. Tensile strength values for
N-2 and N-3 vulcanizates are comparable with N-1 vulcanizate. These values
show that the reinforcement effect of ZnO(p) and ZnO(s) are influenced by
the larger surface area of activator. Small size of particles can give good
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