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

Introduction
properties, filler characteristics and processing methods. 52 The various filler
characteristics that influence the elastometer reinforcement are as follows.
Surface area
The total surface area of the filler is the most important parameter that
influences the reinforcement. Particle size naturally is directly related to
surface area by simple geometric considerations, in the absence of porosity.
Other factors like shape of particle, size distribution and pattern of particle
packing etc, affect the total surface area of a given quantity of filler. In reality
there is always a distribution of sizes that can be averaged in various ways 53
and particles are usually far from round. 54
Porosity
Frequently particles are porous. In particular the presence of
microspores, of diameters below 0.5 nm, excludes part of the particle surface
from direct interaction with the larger elastomers molecules or segments,
thereby influencing reinforcement. Carbon black particles with pores and
cracks have surface area greater than blacks of similar size without such
features. This leads to an increased number of particles per unit weight. Thus
porous blacks gives decreased resilience and increased electrical conductivity
when compared with equal weight loadings of non-porous blacks.
Wolff studied the chemical aspects of rubber reinforcement by fillers. 55
Bound rubber is regarded to be the result of rubber-to-filler interaction and is
therefore often taken as a measure of surface activity of the filler, which is
also a function of specific surface area. 56-58
Morphology of aggregates
While elementary filler particles may be spherical, such particles have
often coalesced into larger, irregular shaped aggregates. Moreover, such
aggregates are most frequency united into larger agglomerates by attractive
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