Browsing by Author "Amarathunga, H.P."

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    Synthesis and characterization of in-situ precipitated silica filled rubber composite
    (Uva Wellassa University of Sri Lanka, 2015) Amarathunga, H.P.; Jayasuriya, C.K.
    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 * process of the rubber (Morselli et al., 2013) and the extent of the cross linking of the natural rubber phase was limited.