Vulcanization chemistry

Because of the different vulcanization chemistry involved in each commercial ACM, a vulcanization system specific to the cure site present has to be adopted. Many cure systems for labile chlorine containing ACM have been proposed (45). Among these the alkali metal carboxylate—sulfur cure system, or soap—sulfur as it is called in the United States, became the mainstay of acryflc elastomer technology in the early 1960s (46), and continues to be widely used. 

Polyisobutylene and isobutylene—isoprene copolymers are considered to have no chronic hazard associated with exposure under normal industrial use. Some grades can be used in chewing-gum base, and are regulated by the PDA in 21 CPR 172.615. Vulcanized products prepared from butyl mbber or halogenated butyl mbber contain small amounts of toxic materials as a result of the particular vulcanization chemistry. Although many vulcanizates are inert, eg, zinc oxide cured chlorobutyl is used extensively in pharmaceutical stoppers, specific recommendations should be sought from suppHers. 

Sulfur chemistry [29] has also been used to crosslink rubber/resin PSAs, although the use of elemental sulfur itself yields tapes that can stain substrates. Other patents exemplify the use of typical rubber vulcanizing chemistry such as Tetrone A , dipentamethylenethiuramtetrasulfide, and Tuads , tetramethylthiu-ram disulfide [30], or zinc butyl xanthate [31] for this purpose. Early art [32] also claimed electron beam curing of both natural rubber and other adhesives that were solvent coated on tape backings. Later references to electron beam curing... 

A. B. Sullivan, C. J. Hann, and G. H. Kuhls, "Vulcanization Chemistry—Fate of Elemental Sulfur and Accelerator during Scorch Delay as Studied by Modem HPLC", Paper No. 9, presented at th eMCS Rubber Division Meeting, Toronto, Canada, May 21 —24, 1991, American Chemical Society, Washington, D.C., 1991. 

Although the vulcanization mechanisms are well established for other elastomers, vulcanization of CR is a complicated process and has not been, until now, well understood. To our knowledge, there are only a few studies that discuss the vulcanization chemistry of CR [87]. The vulcanization mechanism for CR proposed in these pioneering studies was considered to be a planar three-component reaction mechanism in which the structural and special peculiarities were fully taken into consideration. Here, we propose an explanation of the chemical coupling mechanism between the CR matrix and electron-modified PTFE powder based on the similar vulcanization mechanism of CR. Such a mechanism can also be applied to vulcanization of CR in the presence of a ethylenethiourea compound. 

Different grades (prepared from different monomer mixtures) require different types of vulcanization chemistry, with different curing systems. Examples of curing agents are (1)... 

With bromobutyl/butyl rubber blends, elastomer structures are essentially the same, but the different reactive functionalities provide different vulcanization chemistry. Since bromobutyl rubber has greater cure reactivity, accelerators that will over-cure the bromobutyl rubber phase should be avoided. Briefly... 

If a study of vulcanization chemistry is to become part of a routine technological investigation it is necessary for a technique to be developed that will give very rapidly information on the distribution of rubber-sulphur reaction products for a specified set of vulcanization conditions (e.g. sulphur level, accelerator level, cure time, cure temperature). A most useful contribution in this direction has been made by Lautenschlaeger (1977). The model compound 2-methyl-2-pentene was heated with typical curing systems in Pyrex tubes from 10 to 100 minutes over a range of temperatures from 100 C to 150 C. The reaction products were then subjected to gas... 

The diurethane vulcanization chemistry is even more interesting in the context of bonding mechanisms since certain of its rubber formulations exhibit self-adhering properties. For this reason, it would be instructive to review the diurethane chemistry briefly. 

Effect of carbon black filler on vulcanization chemistry... 

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