Metal complexes as new pro-ecological crosslinking agents for chloroprene rubber based on heck coupling reaction

Abstract

The influence of new pro-ecological curing agents on the crosslinking process of chloroprene rubber (CR) was examined. The proposed curing system used a simpler recipe (no need to apply harmful products such as zinc oxide and ethylene thiourea) and cost less than standard metal oxides. It was expected that the mechanism of crosslinking would be similar to that of Heck-type reactions. Heck-type reactions are powerful tools for the creation of new C¼C bonds. They provide the simplest and most efficient way to synthesize a variety of important compounds used in many areas, such as pharmaceuticals, antioxidants, ultraviolet absorbers, and industrial applications. However, despite their wide application, Heck-type reactions have not been used in the rubber industry so far. Rubber blends containing acetylacetonates with different transition metals as new crosslinking agents were filled with fumed silica Aerosil 380 or carbon black Corax N-550. It was found that metal complexes are active crosslinking agents of the CR composites. The obtained vulcanizates were characterized by a high degree of crosslinking and good mechanical properties. Considering the high tensile strength and degree of crosslinking, iron acetylacetonate was the most effective curing agent of the used metal complexes. Compared with the reference sample cured with metal oxides, the CR samples crosslinked using metal acetylacetonates had a higher activity.