Adducts of Carbon Black with a Biosourced Janus Molecule for Elastomeric Composites with Lower Dissipation of Energy

Abstract

Elastomer composites with low hysteresis are of great importance for sustainable development, as they find application in billions of tires. For these composites, a filler such as silica, able to establish a chemical bond with the elastomer chains, is used, in spite of its technical drawbacks. In this work, a furnace carbon black (CB) functionalized with polar groups was used in replacement of silica, obtaining lower hysteresis. CBN326 was functionalized with 2-(2,5-dimethyl-1H-pyrrol-1-yl)-1,3-propanediol (serinol pyrrole, SP), and samples of CB/SP adducts were prepared with different SP content, ranging from four to seven parts per hundred carbon (phc). The entire process, from the synthesis of SP to the preparation of the CB/SP adduct, was characterized by a yield close to 80%. The functionalization did not alter the bulk structure of CB. Composites were prepared, based on diene rubbers—poly(1,4-cis-isoprene) from Hevea Brasiliensis and poly(1,4-cis-butadiene) in a first study and synthetic poly(1,4-cis-isoprene) in a second study—and were crosslinked with a sulfur-based system. A CB/silica hybrid filler system (30/35 parts) was used and the partial replacement (66% by volume) of silica with CB/SP was performed. The composites with CB/SP exhibited more efficient crosslinking, a lower Payne effect and higher dynamic rigidity, for all the SP content, with the effect of the functionalized CB consistently increasing the amount of SP. Lower hysteresis was obtained for the composites with CB/SP. A CB/SP adduct with approximately 6 phc of SP, used in place of silica, resulted in a reduction in ΔG′/G′ of more than 10% and an increase in E’ at 70 °C and in σ300 in tensile measurements of about 35% and 30%, respectively. The results of this work increase the degrees of freedom for preparing elastomer composites with low hysteresis, allowing for the use of either silica or CB as filler, with a potentially great impact on an industrial scale.

Influence of Processing Oil Content on Rubber-Filler Interactions in Silica/Carbon Black-Filled Natural Rubber Compounding

“…Rubber is usually combined with reinforcing fillers to increase its mechanical qualities [1]. However, large silica/carbon black loading causes processing difficulties due to higher compound viscosity [2]. In order to minimize compound viscosity and increase filler dispersion, rubber processing oil must be added [3].…”

Pyrrole Compounds from the Two-Step One-Pot Conversion of 2,5-Dimethylfuran for Elastomer Composites with Low Dissipation of Energy

“…The -SH and -SS- functional groups were reported to react with the unsaturated elastomers [ 46 ]. The functionalization of silica and of sp 2 carbon allotropes, mainly carbon black, with the two mentioned families of PyCs improved the properties of elastomeric composites for a large-scale application such as that in tire compounds [ 46 , 47 ]. The development on an industrial scale was announced by a major player in the tire field [ 48 ].…”

Bio-Based Pyrrole Compounds Containing Sulfur Atoms as Coupling Agents of Carbon Black with Unsaturated Elastomers

“…The functionalization of sp 2 carbon allotropes with pyrrole compounds (PyC) was presented by some of the authors [43,44]. Functional groups were covalently bound to the surface of carbon black [43][44][45], nanosized graphite [46], and carbon nanotubes [47] by first mixing them with a pyrrole compound, donating either mechanical or thermal energy. To explain these findings, the domino mechanism, shown in Figure 1, was elaborated [48].…”

“…The reasoning behind the research activity was the choice of SHP and SSP for functionalizing CB: the pyrrole ring was expected to form a covalent bond with CB, in line with the prior art [43][44][45][46][47][48], and the sulfur-containing functional groups were expected to react with the unsaturated elastomers. The reaction of SH with a terminal C=C double bond is known as thiol-ene click chemistry, which is expected to be simple, highly efficient, and without by-products [49].…”

“…The characterization of the PyC was performed using 1 H-NMR and GC-MS analysis. The functionalization of CB with SHP and SSP was carried out by mixing CB with the sulfurated pyrrole compounds, providing thermal energy [43][44][45]. The CB/SHP and CB/SSP adducts were characterized by means of solvent extraction and thermogravimetric analysis (TGA).…”