Vulcanization principles

By contrast the simple blending of two polymers can only yield a technically adequate product if some interaction occurs between the plastic and elastomeric domains. Polymers based on the dynamic vulcanization principles first outlined by Gessler" and extended by Coran and Patel have successfully overcome this phase morphology problem. 

Vulcanization. Vulcanization of articles made from latex compounds generally foUows the same principles and methods as in vulcanizing... 

Seeligmann, Torrilhon, and Falconnet, in a treatise on rubber published in France in 1896, recorded interesting early observations on the sol and gel components now known to be present in most specimens of undegraded raw rubber. They referred to them as the two isomeric hydrocarbides of rubber, one being the adhesive principle and the other the nervous principle. It was observed that the latter refused to dissolve on repeated treatment with fresh portions of solvent and that the approximate percentage of this constituent was roughly the same when different solvents were used to extract the soluble portion. The authors called attention also to the enormous swelling capacity of the nervous hydrocarbide. Vulcanization was attributed to a reaction of sulfur with the adhesive principle whereby the adhesive characteristics are suppressed or eliminated. 

Industrially the curing (vulcanization) of diene homopolymers and copolymers with elementary sulfur is carried out in a heated press at 100-140 °C (hot curing) this cannot be done in a normal laboratory on account of the expensive apparatus required. However, the principle of curing can be illustrated by crosslinking a butadiene-styrene copolymer (SBR 1500) with disulfur dichloride (SjCy at room temperature (cold curing) ... 

In a sense, of course, although we have emphasised that our agent is natural, the Magistery may be regarded as an artificial process, without the aid of which the action of Nature either could not proceed at all, or else would not be accomplished so rapidly. But the moving principle and our Vulcan, which stirs up the motion, are undoubtedly natural, and it is only the excitation of the one by the other that could be described as anything else. 

In applying the same treatment to various sulfur vulcanization systems Wolff found that the assumption of equal cross-link densities in filled and unfilled vulcanizates was not violated. This is in complete agreement with the authors conclusion based on an analysis of swelling data (130) by use of Eq. (10). Wolffs aF values are not only independent of the vulcanization system, but depend only very weakly on the polymer. Wolffs treatment also is consistent with the structure-loading equivalence principle stated in Section V-3 The structure dependent parameter ap enters Eq. (13) in the product with the black concentration. 

Piperidine, C5H10NH, is prepared by the electrolytic reduction of pyridine. It is one of the products of the hydrolysis of piperine the essential principle of pepper. Piperidine boils at 106° and possesses a pepper-like odor it has well characterized basic properties. It has recently been used as an accelerator in the vulcanization of rubber. 

E iles with vinylidene fluoride (VFz) copolymers in solution and have determined some reactivity principles which can be used to interpret the vulcanization behavior of related fluoco-elastomers. 

HEAT CONDUCTION AND VULCANIZATION IN MOLDS 1.3.1 Principle of the Method... 

The mechanism and chemistry of vulcanization have been reviewed earlier. It is therefore more appropriate to define the general principles governing the activity of an accelerator such as a sulfenamide. Three parameters merit elucidation ... 

The principles of compounding were reviewed earlier in this text and cover the fundamental characteristics of polymers, filler systems, and the basics of vulcanization in the context of compound development for tire applications. A compound formulation consists of four basic components the polymer network, the filler or particulate reinforcing system, the stabilizer system, and the vulcanization system (Figure 14.21). In addition a series of secondary materials such as resins, processing oils, and short fiber reinforcements may be included in a formula (Duddey, 2004 Rodgers and Waddell, 2004 Long, 1985). Elastomers used in radial tires are basically of four types ... 

Reclaiming is a procedure in which the scrap tire rubber or vulcanized rubber waste is converted, using mechanical and thermal energy and chemicals, into a state in which it can be mixed, processed, and vulcanized again. The principle of the process is devulcanization. In devulcanization, it is assumed that the cleavage of intermolecular bonds of the chemical network, such as carbon-sulfur and/or... 

Few people realize that when they stretch a rubber band - or inflate tires on their cars - they do chemistry. In this example of vulcanized rubber, the chemistry is simple - homolysis of C-C, C, or S-S bonds, but the underlying principle is anything but simple. The probability of ethyl disulflde spontaneously dissociating into radicals at room temperature is negligible. Yet this probability can increase by many orders of magnitude for the same molecular moiety when it is as part of amorphous material under mechanical load. In other words, translation of macroscopic objects (e.g., our hands) that compress, stretch, or twist polymeric material can directly control reaction rates of material building blocks. Such control of course is not seen in the vast majority of reactions studied by chemists and as a result is not accommodated in any of the existing models of chemical kinetics. 

Parallel to the process of chemical and biological degradation, components of the abraded material may also be washed out by precipitation water. The elutive behavior of tires and abraded tire material has already been investigated in a number of studies, in particular the possibility of contamination of the environment with components of rubber during utilization [19] and as the result of waste deposition [20]. These studies concluded that the environment can, in principle, be contaminated due to elutimi of antioxidants, vulcanization accelerators and the conversion products resulting from vulcanization [1]. 

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