Influence of n-ZnO Morphology on Sulfur Crosslinking and Properties of Styrene-Butadiene Rubber Vulcanizates

Abstract

This paper examines the influence of the morphology of zinc oxide nanoparticles (n-ZnO) on the activation energy, vulcanization parameters, crosslink density, crosslink structure, and mechanical properties in the extension of the sulfur vulcanizates of styrene-butadiene rubber (SBR). Scanning electron microscopy was used to determine the particle size distribution and morphology, whereas the specific surface area (SSA) and squalene wettability of the n-ZnO nanoparticles were adequately evaluated using the Brunauer–Emmet–Teller (BET) equation and tensiometry. The n-ZnO were then added to the SBR in conventional (CV) or efficient (EV) vulcanization systems. The vulcametric curves were plotted, from which the cure rate index (CRI) rate of the vulcanization and the activation energy were calculated. The influence on the mechanical properties of the SBR vulcanizates was stronger in the case of the EV curing system than when the CV curing system was used. Of the vulcanizates produced in the EV curing system, the best performance was detected for n-ZnO particles with a hybrid morphology (flat-ended rod-like particles on a “cauliflower” base) and high SSA. Vulcanizates produced using the CV curing system showed slightly better mechanical properties after the addition of nanoparticles with a “cauliflower” morphology than when the rod-like type were used, irrespective of their SSA. In general, nanoparticles with a rod-like structure reduced the activation energy and increased the speed of vulcanization, whereas the cauliflower type slowed the rate of the process and the vulcanizates required a higher activation energy, especially when using the EV system. The crosslink structures were also more clearly modified, as manifested by a reduction in the polysulfidic crosslink content, especially when n-ZnO activators with a rod-like morphology were applied.

Degradation by Electron Beam Irradiation of Some Elastomeric Composites Sulphur Vulcanized

“…The type of vulcanization system determines the type of bonds that are formed during the vulcanization process, as well as the mechanical properties and the way that the rubber-based materials behave when they are subjected to a degradation process. Thus, during the vulcanization process, poly- and disulphidic cross-links and monosulphidic cross-links are formed in different percentages, depending on the applied vulcanization system (CV, semi-EV, or EV) [ 35 , 36 , 37 ], as shown in Table 6 .…”

“…As the concentration of the accelerator increases (from 1 phr in mixtures A, B, and D to 1.5 phr in mixture C), other types of reactions, such as desulphuration or decomposition, may occur. Desulphurization results in the formation of mono- and disulfide bonds, while decomposition leads to the formation of cyclic sulfides and conjugated dienes [ 35 , 36 , 37 ]. An increase in temperature during irradiation causes the polysulfide bonds to break into mono- and disulfide bonds and leads to a decrease in tensile strength associated with the degradation of the vulcanized material.…”

A Multifaceted Approach for Cryogenic Waste Tire Recycling

“…A large number of other chemicals are also added to tire rubber, such as: vulcanizing agents (sulfur and sulfur compounds), catalysts, inhibitors, pigments, etc. Vulcanizing agents and various additives are used in tires to create a cross-linked structure and provide resistance to various physical and chemical influences [ 65 , 66 ]. Other micro-additives such as calcium, magnesium, sodium, potassium, chloride, etc.…”

Influence of active, nano, and functionalized zinc oxide particles on the mechanical, cytotoxicity, and thermal stability of carbon black filled SBR/NR blends

“…12 In order to increase the Zn (II) center accessibility in the curing process by improving its dispersion in the matrix, numerous methods based on nanoscale ZnO particles, zinc (II) complexes, active zinc species supported on a matrix have been presented in the scientific literature. [13][14][15][16][17] Our earlier work has suggested nano ZnO, active ZnO (AZnO), and functionalized ZnO (FZnO) modified with octylamine as sustainable activators for NR and SBR compounds in lieu of conventional microcrystalline ZnO. Due to highly active Zinc centers and efficient dispersion resulting from small particle size, the ZnO content in rubber composites were reduced to 60 and 70%.…”