Synthesis and characterization of in-situ precipitated silica filled rubber composite
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Date
2015
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Publisher
Uva Wellassa University of Sri Lanka
Abstract
In-situ precipitated silica can be used to replace carbon black partly in tires as well as in other rubber
materials to increase strength, to reduce rolling resistance and heat build-up and hence to bring down
the fuel consumption in tires. There have been numerous efforts to improve silica dispersion in
conventional rubber/silica composites such as varying the chemistry and content of the coupling
agents (Bokobza, 2006), improving the mixer rotor design (Miloskovska et al., 2012), ultrasound
pre-treatment of the silica particles (Prasertsri et al., 2011), but dispersion still remains a serious issue
for conventional rubber/silica composites.
The current research was carried out to enhance the properties of rubber such as tensile strength,
swelling properties, hardness, water absorption properties and density using in situ precipitated silica.
A relatively high cost method for reinforcing natural rubber (NR) using in-situ precipitated silica by
swelling method has been reported previously (Murakami et al., 2000). The present work aims to
prepare in-situ precipitated silica filled rubber composites with a better in-situ silica dispersion within
rubber matrix than conventional silica composites using a low cost method (using solvent
combination) of sol-gel technique.
Methodology
Sample was compounded according to the tire tread formulation (Murakami et al., 2000). The
resulting sample was half cured and was cut in to five pieces (15 cm × 5 cm). Using a swelling test,
the best solvent combination of Toluene:T-butylalcohol was found to be 70:30 volume ratio. Four
half-cured samples were soaked for different times in a solution containing the best solvent and
Tetraethylorthosilicate (TEOS). Next they were soaked in 10% aqueous .n-butylamine for two days
and the samples were dried. Finally, the remaining half of the curing process was carried out and in-
situ silica percentage in each sample was calculated. Using the same procedure, four more samples
were prepared by gradually increasing the in situ silica percentage by weight. A sample without in-
situ precipitated silica was used as the reference. Mechanical properties of the samples such as tensile
strength, modulus, tensile strain at break and hardness were determined. Finally, samples were
characterized for its density, swelling in toluene and water absorption.
Results and Discussion
Results of swelling analysis are graphically represented in Figure 01. In principle, the presence of
inorganic filler should lead to a reduction of the swelling ratio with respect to the unfilled vulcanized
rubber, since the filler does not absorb the solvents during the experiment. In the present case an
opposite trend is observed. Results show that the swelling ratio is increased with increasing silica
percentage thus decreasing the cross linking density of the rubber matrix (Kapgate et al., 2012). This
clearly indicates an interfering effect of the sol–gel reaction of TEOS to silica on the vulcanization
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process of the rubber (Morselli et al., 2013) and the extent of the cross linking of the natural rubber
phase was limited.
Description
Keywords
Science and Technology, Technology, Rubber Production, Rubber Technology, Mineral Sciences, Materials Sciences