The Influence of Curing Systems on the Cure Characteristics and Physical Properties of Styrene-Butadiene Elastomer.

Magdalena Maciejewska,Monika Siwek

doi:10.3390/ma13235329

Abstract

The goal of this work is to study the influence of different curing systems on the cure characteristics and performance of styrene–butadiene elastomer (SBR) filled with carbon black or nanosized silica. A multifunctional additive for rubber compounds, namely Activ8, was applied as an additional activator and accelerator to increase the efficiency of sulfur vulcanization and to reduce the content of zinc oxide elastomers cured in the presence of 2-mercaptobenzothizole or 1,3-diphenylguanidine as a primary accelerator. The influence of the curing system composition on the crosslink density and physical properties of SBR vulcanizates, such as mechanical properties, thermal stability, and resistance to thermo-oxidative aging, is also reported. Activ8 effectively supports the vulcanization of SBR compounds, especially filled with nanosized silica. It reduces the optimal vulcanization time of SBR compounds and increases the crosslink density of the vulcanizates. Moreover, vulcanizates with Activ8 exhibit higher tensile strength and better damping properties than elastomer with zinc oxide. Activ8 allows the amount of ZnO to be reduced by 40% without detrimental effects on the crosslink density and mechanical performance compared to the vulcanizates conventionally crosslinked with ZnO. This is an important ecological goal since ZnO is classified as being toxic to aquatic species.

Highlights

Vulcanization is one of the oldest and undoubtedly most important processes in elastomer technology, leading to the transformation of a plastic rubber compound into a highly elastic finished product—that is, a vulcanizate, characterized by specific functional properties
We studied the influence of different curing systems containing Activ8 on the cure characteristics and performance of styrene–butadiene elastomer (SBR) composites filled with carbon black or nanosized silica
To find out whether Activ8 allowed to reduce the amount of ZnO in the SBR, some of the rubber compounds contained three parts per hundred of rubber of ZnO instead of 5 phr and increased to 2 phr of Activ8

Summary

Introduction

Vulcanization is one of the oldest and undoubtedly most important processes in elastomer technology, leading to the transformation of a plastic rubber compound into a highly elastic finished product—that is, a vulcanizate, characterized by specific functional properties. Since vulcanization has been a known process for over 180 years, many different curing systems have been developed across this period to vulcanize rubber compounds, the most important of which are based on the use of sulfur, peroxides, and metal oxides [2]. The choice of a proper curing system results mainly from the chemical nature of the rubber (e.g., the degree of unsaturation) and the presence of functional groups suitable for crosslinking reactions (e.g., carboxyl and chlorosulfone). The most widely used curing agents in the rubber industry are elemental sulfur for rubbers with some degree of unsaturation [3] and peroxides for saturated copolymers, e.g., ethylene–propylene copolymer [4]

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