Vulcanization retarder

Retarders. The purpose of vulcanization retarders is to delay the initial onset of cure in order to guarantee sufficient time to process the unvulcanized mbber. Three main classes of materials are used commercially, including organic acids and anhydrides, cyclohexylthiophthalimide (Santogard PVI or CTP), and a sulfenamide material (Vulkalent E). 

Thiophenium salt derivatives, 23 715 Thiophilic adsorption, 6 405 Thiophosgene, 23 625-626, 4 837 reactions of, 23 625-626 Thiophthalimide vulcanization retarders, 21 800... 

Uses Chemical intermediate for A-phenyL/ -phenylenediamine rubber processing (vulcanization retarder). 

Uses. Formerly used as a vulcanization retarder in the rubber industry... 

In a preliminary study we have recently reported (1) that the air in three rubber and tire industry plants was contaminated with several N-nitroso compounds. The compounds included N-nitrosomorpholine (NMOR), N-nitrosodimethylaminne (NDMA), and N-nitrosodiphenylamine (NDPhA). The latter compound is used as a vulcanization retarder, so its presence near processes employing it was not surprising. Bismorpholine-carbamylsulfonamide, a cross-linking accelerator used in rubber tires was found in tire factories and may be contaminated with NMOR. The source of the NDMA was not identified, but it could arise from nitrosation of amines which may be decomposition products of diamine based accelerators, as pointed out by Yeager, et al (2). 

Use Primary accelerator in natural and nitrile rubber and SBR, plasticizer and vulcanization retarder in neoprene type G, cure modifier in neoprene type W, oxidation cure activator in butyl. For extruded and molded goods, tires and tubes, wire and cable, sponge. 

Diphenylamine is used as an intermediate in the production of dyes and in the form of N-nitrosodiphenylamine as a vulcanization retarder. In some countries, e.g. in West Germany, the application of this nitroso compound is banned, because of its carcinogenicity, particularly in combination with secondary amines. 

It is difficult to alter the scorch properties of bromobutyl/general-purpose rubber blends with classical retarders such as N-(cyclohexylthio)phthalimide. For instance, salicylic acid is a vulcanization retarder for general purpose rubbers (GPRs), but an accelerator for bromobutyl rubber. Alkaline retarders used with bromobutyl rubber are often accelerators for GPR. Therefore, the scorch time of blends is best set by... 

Cyclohexyl thiophtalimide is a rubber chemical widely used as a vulcanization retarder. Sensitization sources are perhaps protective gloves. 

Vulkanisieren, Vulkanisation vulcanizing agents Vulkanisationsmittel, Vulkanisationschemikalien vulcanizing retarder/ antiscorcher Vulkanisationsverzogerer... 

WO produced from sulfur monochloride is white WO, which is more likely to be used as erasers than as a rubber compounding ingredient. This is because any residual acidity from the sulfur chloride vulcanization retards the sulfur cure of the rubber compound. Instead, the brown WO products, which are crosslinked with elemental sulfur, are commonly used as rubber compounding ingredients because they have less effect on the cure rate of the rubber compound. 

FLALffiRETARDANTS - PHOSPHORUS FLALffi RETARDANTS] (Vol 10) -vulcanization accelerator [RUBBERCITEMICALS] (Vol 21)... 

The thiophthalimide (CTP) and sulfenamide classes of retarders differ from the organic acid types by thek abiUty to retard scorch (onset of vulcanization) without significantly affecting cure rate or performance properties. Much has been pubUshed on the mechanism of CTP retardation. It functions particularly well with sulfenamide-accelerated diene polymers, typically those used in the the industry. During the initial stages of vulcanization, sulfenamides decompose to form mercaptobenzothiazole (MBT) and an amine. The MBT formed reacts with additional sulfenamide to complete the vulcanization process. If the MBT initially formed is removed as soon as it forms, vulcanization does not occur. It is the role of CTP to remove MBT as it forms. The retardation effect is linear with CTP concentration and allows for excellent control of scorch behavior. 

Another commercially available retarder for sulfur vulcanization is based on an aromatic sulfenamide. Like CTP, this product is most effective ki sulfenamide cure systems, but it also works well ki thiazole systems. Performance properties are generally not affected except for a slight modulus kicrease. In some cases this feature allows for the use of lower levels of accelerator to achieve the desked modulus with the added potential benefits of further scorch delay and lower cost cure system (23). 

To assist in control of the onset of vulcanization, a retarder or prevulcanization iuhibiter (PVI) is used. Retardation of the onset of cure does not mean that the rate of cure is slowed, in fact cure rate may actually be increased. Rather, there is an induction period prior to cure. 

Rubber Chemicals. Sodium nitrite is an important raw material in the manufacture of mbber processing chemicals. Accelerators, retarders, antioxidants (qv), and antiozonants (qv) are the types of compounds made using sodium nitrite. Accelerators, eg, thiuram [137-26-8J, greatly increase the rate of vulcaniza tion and lead to marked improvement in mbber quaUty. Retarders, on the other hand (eg, /V-nitrosodiphenylamine [156-10-5]) delay the onset of vulcanization but do not inhibit the subsequent process rate. Antioxidants and antiozonants, sometimes referred to as antidegradants, serve to slow the rate of oxidation by acting as chain stoppers, transfer agents, and peroxide decomposers. A commonly used antioxidant is A/,AT-disubstituted Nphenylenediamine which can employ sodium nitrite in its manufacture (see Rubber chemicals). 

New efficient vulcanization systems have been introduced in the market based on quaternary ammonium salts initially developed in Italy (29—33) and later adopted in Japan (34) to vulcanize epoxy/carboxyl cure sites. They have been found effective in chlorine containing ACM dual cure site with carboxyl monomer (43). This accelerator system together with a retarder (or scorch inhibitor) based on stearic acid (43) and/or guanidine (29—33) can eliminate post-curing. More recently (47,48), in the United States a proprietary vulcanization package based on zinc diethyldithiocarbamate [14324-55-1]... 

Vulkanisatjons-mittel, n. vulcanizing agent, -probe, /. vulcanizing test or sample, -ver-zdgerung, /. retardation vulcanization. 

Rubber chemicals (accelerator, antioxidant, retarder, peptizer, blowing and vulcanizing agents)... 

Solomon (3, h, 5.) reported that various clays inhibited or retarded free radical reactions such as thermal and peroxide-initiated polymerization of methyl methacrylate and styrene, peroxide-initiated styrene-unsaturated polyester copolymerization, as well as sulfur vulcanization of styrene-butadiene copolymer rubber. The proposed mechanism for inhibition involved deactivation of free radicals by a one-electron transfer to octahedral aluminum sites on the clay, resulting in a conversion of the free radical, i.e. catalyst radical or chain radical, to a cation which is inactive in these radical initiated and/or propagated reactions. 

---