Influence of zinc oxide during different stages of sulfur vulcanization. Elucidated by model compound studies

Abstract

The addition of zinc oxide (ZnO) as an activator for the sulfur vulcanization of rubbers enhances the vulcanization efficiency and vulcanizate properties and reduces the vulcanization time. The first part of this article deals with the reduction and optimization of the amount of ZnO. Two different rubbers, solution-styrene-butadiene rubber and ethylene-propylene-diene rubber, have been selected for this study. The results demonstrate that the curing and physical properties can be retained when the level of ZnO (Red Seal) is reduced to 1 or 2 phr, respectively. Of particular interest is nano-ZnO, characterized by a nanoscale particle distribution. The cure characteristics indicate that with nano-ZnO, a reduction of zinc by a factor of 10 can be obtained. In the second part, model compound vulcanization is introduced to investigate the effects of ZnO during the different stages of vulcanization. Experiments are described with two models, squalene and 2,3-dimethyl-2-butene, both with benzothiazolesulfenamide-accelerated vulcanization systems. The results demonstrate the influence of ZnO during the different stages of the vulcanization. With ZnO present, a marked decrease can be observed in the sulfur concentration during an early stage of vulcanization, along with a slight delay in the disappearance of the crosslink precursor. The crosslinked product distribution is influenced as well.

Optical Properties of ZnO Nanoparticles Synthesised from a Polysaccharide and ZnCl2

“…It has also attracted attention as a promising phosphor for field emission displays (FEDs) [2] compared with the conventional sulfide phosphors. The biggest users of ZnO are manufacturers of rubber; the content of ZnO in vulcanized rubber can be reduced to 10 times if nanosized ZnO is used instead of the conventional micro ZnO [3]. Previous research reports [4][5][6] revealed that the vulcanized rubber products can last longer and have improved properties if nanosized ZnO is used as the activator and accelerator instead of micro ZnO, and this approach in turn can greatly reduce the quantity of micro ZnO in the vulcanization of rubber [5,6] and the release of toxic zinc metal into the environment [6].…”

Evaluating Performance of Magnesium Oxide at Different Sizes as Activator for Natural Rubber Vulcanization

“…Its mechanism during vulcanization process [4,8,9,12] and its effects on the properties of the vulcanizates [3][4][5][6][7]9,11] has long been known and investigated. However, ZnO release into the environment that occurs during production, disposal and recycling of rubber products, which is in soluble zinc compounds is classified as ecotoxic to aquatic organisms [5,7,[9][10]. Moreover, usage of ZnO is also associated with a problem related to mold fouling that occurs during rubber manufacturing [9,[13][14].…”

“…However, ZnO release into the environment that occurs during production, disposal and recycling of rubber products, which is in soluble zinc compounds is classified as ecotoxic to aquatic organisms [5,7,[9][10]. Moreover, usage of ZnO is also associated with a problem related to mold fouling that occurs during rubber manufacturing [9,[13][14]. There is evidence that during vulcanization, a considerable amount of ZnO is consumed and transformed into zinc sulfide (ZnS), which is a by-product of the vulcanization reactions.…”

Synthesis of Zn/Mg oxide nanoparticles and its influence on sulfur vulcanization

“…These authors also compared the effect of different metal oxides with EPDM 9 and SBR. 9,13 In EPDM with tetramethylthiuram disulphide (TMTD) as accelerator, none of the metal oxides studied was as active as ZnO.…”

“…9,13 In EPDM with tetramethylthiuram disulphide (TMTD) as accelerator, none of the metal oxides studied was as active as ZnO. In SBR with TBBS as accelerator, the substitution of ZnO by MgO did not cause large effects on the cure and physical properties.…”