Effect of organoclay reinforcement on the curing characteristics and technological properties of SBR sulphur vulcanizates

Abstract

Styrene-butadiene rubber (SBR) nanocomposites with different organoclay contents (up to 15 phr) were prepared by a melt compounding procedure, followed by a compression-molding step in which the SBR matrix was sulfur crosslinked. The vulcanizates were characterized in respect to their curing, mechanical and viscoelastic properties, and thermal stability. The optimum cure time decreased with increasing organoclay content. This effect was attributed to the ammonium modifier present in the organoclay, which takes part in the curing reaction acting like an accelerator. The results of mechanical test on the vulcanizates showed that the nanocomposites presented better mechanical properties than unfilled SBR vulcanizate, indicating the nanoreinforcement effect of clay on the mechanical properties of SBR/organoclay nanocomposites. The addition of organoclay did not significantly change the glass transition temperature. However, the heights of tan d value at the glass transition temperature for the nanocomposites are lower than that of the unfilled SBR. This suggests a strong interaction between the organoclay and the SBR matrix as the molecular relaxation of the latter is hampered. The temperature at which 50% degradation occurs (T 50 ) and the temperature when the degradation rate is maximum (DTG max ) showed an improvement in thermal stability, probably related to the uniform dispersion of organoclay.

Microstructure, morphology, and mechanical properties of styrene‐butadiene rubber/organoclay nanocomposites

“…This type of surface enrichment has been observed previously in polymer clay nanocomposites, and it has been suggested that it could influence water absorption [20]. After careful normalization of the spectra on the styrene peak at 697 cm −1 and by employing spectral subtraction methods to remove the stearate contribution, no clear evidence for the formation of new components in the rubber was found, in agreement with previous work [21, 22] where it was suggested that the nanoclay accelerates the rubber vulcanization reaction but does not form any new components.…”

Exfoliated/intercalated silicate/hot styrene butadiene rubber nanocomposites: Structure–properties relationship

“…The nanosilicate incorporation led to a decrease in crosslink density values (Table III). This behavior was unusual but we observed a similar trend in the crosslink density of cold SBR reinforced with organoclay 24. During vulcanization, sulfur free radicals are formed and they attack polymer chains to form macroradicals.…”

Preparation and properties of natural rubber/organo-montmorillonite: from lab samples to bulk material

“…Several researchers [29][30][31] have evaluated the influence of organoclay on the rubber vulcanization characteristics. In general, it has been widely reported in the literature that, regardless of the nature and polarity of the elastomer, the organoclays behave as catalysts, accelerating the vulcanization reaction, simultaneously and sensibly decreasing the scorch time and optimum cure time.…”