Vulcanization system activators

Typically a recipe for the vulcanization system for one of these elastomers contains 2-10 phr of zinc oxide, l phr of fatty acid (e.g., stearic), 0.5-4 phr of sulfur, and 0.5-2 phr of accelerator. Zinc oxide and the fatty acid are vulcanization-system activators. The fatty acid with zinc oxide forms a salt, which can form complexes with accelerators and reaction products, formed between accelerators and sulfur. Accelerators are classified and illustrated in Table 7.1. 

The ZnCFO action as vulcanization active component of elastomeric compositions on the basis of rubbers of general and special assignment with various vulcanization systems is investigated. 

Despite of 150-year s history of vulcanization process, it is impossible to consider that fundamental and applied researches in direction of vulcanization systems perfection are completed. For today one of the ways of rubbers properties improvement is the synthesis and application of the new chemicals-additives, including, vulcanization active, that is connected, first of all, with reduction of global stocks of zinc ores as basic raw material for reception of traditional activator - zinc oxide. Besides, modem increase of industrial potential and the accumulation of big quantity wastes derivate the problems of ecological character, which require the emergency decision. Therefore creation of resourcesaving technologies of the new compounds reception from products of secondary raw material processing has paramount importance. 

An estimation of ZnCFO efficiency as vulcanization active component was carried out in modelling unfilled elastomeric compositions on the basis of isoprene, butadiene-nitrile, chloroprene and butyl rubbers of sulphur, thiuram, peroxide, metaloxide and resin vulcanization systems. 

Thus, from the analysis of results of experimental researches on estimation of ZnCFO vulcanization activity in comparison with zinc oxide in structure of various vulcanization systems (VS) follows, that its efficiency decreases in line (fig. 10) ... 

It is possible to explain the decrease of ZnCFO efficiency as component of various vulcanization systems for rubbers of general and special assignment in the earlier submitted line (fig. 10) also by character of formed morphology of compositions. So, at use of ZnCFO as the activator of sulfur vulcanization the structure of rubbers with the minimal value of parameter r is formed, and at transition from sulfur to peroxide vulcanization of elastomeric compositions the particles size of heterophase is increased (fig. 11 b). 

ZnCFO is the effective vulcanization active component of the sulfur, thiuram, peroxide and metaloxide vulcanization systems for isoprene, nitrile-butadiene and chloroprene rubbers at the same time it is not effective in resin vulcanization system for butyl rubber. On a degree of positive influence on the properties of elastomeric compositions vulcanization systems with ZnCFO are arranged in a line ... 

At the present time, an accelerated sulfur vulcanization system is used for RubCon curing. This system consists of sulfurs as the structuring agent of vulcanization, tetramethylthiuram disulfide and 2-mercaptobenzothiazole as accelerators, and zinc oxide as the activator of this process. 

Vulcanization system components Sulfur, accelerators, activators. 

Vulcanization, named after Vulcan, the Roman God of Fire, describes the process by which physically soft, compounded rubber materials are converted into high-quality engineering products. The vulcanization system constitutes the fourth component in an elastomeric formulation and functions by inserting crosslinks between adjacent polymer chains in the compoimd. A typical vulcanization system in a compound consists of three components (1) activators (2) vulcanizing agents, typically sulfur and (3) accelerators. 

Design of the vulcanization system is probably the most challenging aspect in developing a compound formulation for application in a tire. Knowledge of accelerator activity, reaction kinetics, and nature of the resulting crosslink network is important in constructing such systems. 

Rubbor Vulcanization Chomicals. The vulcanization systems consist of the following components the vulcanizing agent such as sulfur, the accelerator to activate the sulfur, a retarder to help control the rate of vulcanization, and an activator such as zinc oxide and stearic acid. 

The action of accelerators is improved by the presence of activators in practice, a combination of zinc oxide and a fatty acid is nearly always used. Specifically, the activator increases the efficiency of the vulcanizing system so that, typically, only about 5 sulphur atoms are combined for each cross-link formed. As a consequence, the vulcanizate shows improved physical properties, aging characteristics and appearance (less sulphur bloom). The use of accelerator-activator systems is standard practice in rubber compounding and a typical basic tread formulation might be as follows ... 

Rubber chemistry is today one of the most active areas of polymer science. In the past few years many new polymers have been introduced whilst there have also been important developments in vulcanization systems and in methods of protection against ageing. The study of network structures requires special techniques, several of which are peculiar to rubber chemistry, and these have been given... 

It should be realized that many latex vulcanizing systems are more active in wet latex than in the dry film, and will prevulcanize the latex over a period of one to two weeks, particularly in regions having high ambient temperatures. 

Although natural rubber (crepe) and nitrile rubber soles (common in the manufacturing of safety shoes due to its chemical inertness) are used, sulfur vulcanized styrene-butadiene (SBR) rubbers are the most common sole materials. The vulcanization system contains sulfur and activators (N-cyclohexyl-2-benzothiazole suffenamide, dibenzothiazyl disulfide, hexamethylene tetramine, zinc oxide) and fillers (silica and/or carbon black, calcium... 

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