Vulcanization accelerators

Rubber vulcanization accelerators  [c.862]

Lead sesquioxide is used as an oxidation catalyst for carbon monoxide ia exhaust gases (44,45) (see Exhaust control), as a catalyst for the preparation of lactams (46) (see Antibiotics, P-lactams), ia the manufacture of high purity diamonds (47) (see Carbon, diamond-natural), ia fireproofing compositions for poly(ethylene terephthalate) plastics (48), ia radiation detectors for x-rays and nuclear particles (49), and ia vulcanization accelerators for neoprene mbber (50).  [c.69]

Piperidines. A significant use of piperidine (18) has been ia the manufacture of vulcanization accelerators, eg, thiuram disulfide [120-54-7] (115) (see Rubber chemicals). Mepiquat dichloride [24307-26-4] the dimethyl quaternary salt of (18), is used as a plant growth regulator for cotton (qv). Piperidine is used to make vasodilators such as dipyridamole [58-32-2] (116) and minoxidil [38304-91-5] (117), and diuretics such as etozoline [73-09-6] (118).  [c.341]

Salts of Ai-substituted dithiocarbamic acid [594-07-0] are used as fungicides (qv) and mbber vulcanization accelerators (see Rubber chemicals).  [c.434]

Pyrazino[2,3-fc]pyrazine, decahydro-as vulcanization accelerator, 3, 368 Pyrazino[2,3-fc]pyrazine, 2,3-dimethyl-cations  [c.769]

There is also a large number of synthetic heterocyclic compounds with other important practical applications, as dyestuffs, copolymers, solvents, photographic sensitizers and developers, as antioxidants and vulcanization accelerators in the rubber industry, and many are valuable intermediates in synthesis.  [c.47]

The largest user of phenol in the form of thermosetting resins is the plastics industry. Phenol is also used as a solvent and in the manufacture of intermediates for pesticides, pharmaceuticals, and dyestuffs. Styrene is used in the manufacture of synthetic rubber and polystyrene resins. Phthalic anhydride is used in the manufacture of DMT, alkyd resins, and plasticizers such as phthalates. Maleic anhydride is used in the manufacture of polyesters and, to some extent, for alkyd resins. Minor uses include the manufacture of malathion and soil conditioners. Nitrobenzene is used in the manufacture of aniline, benzidine, and dyestuffs and as a solvent in polishes. Aniline is used in the manufacture of dyes, including azo dyes, and rubber chemicals such as vulcanization accelerators and antioxidants.  [c.55]

These compounds are commercially important as accelerators in the vulcanization of rubber (Scheme 83).  [c.260]

In both mbber thread and spandex fibers, mechanical properties may be varied over a relatively broad range. In mbber, variations ate made ia the degree of cross-linking or vulcanization by changing the amount of vulcanizing agent, usually sulfur, and the accelerants used. In spandex fibers, many more possibihties for variation ate available. By definition spandex fibers contain urethane linkages with the foUowiag repeat stmcture (1)  [c.304]

Vulcanization was first reported in 1839 with the discovery that heating natural mbber with sulfur and basic lead carbonate produced an improvement in physical properties (2). In 1906, aniline was the first organic compound found to have the abiUty to accelerate the reaction of sulfur with natural mbber (3). Various derivatives of aniline were soon developed which were less toxic and possessed increased acceleration activity.  [c.219]

Thiuram Sulfides. These compounds, (8) and (9), are an important class of accelerator. Thiurams are produced by the oxidation of sodium dithiocarbamates. The di- and polysulfides can donate one or more atoms of sulfur from their molecular stmcture for vulcanization. The use of these compounds at relatively high levels with litde or no elemental sulfur provides articles with improved heat resistance. The short-chain (methyl and ethyl) thiurams and dithiocarbamates ate priced 2/kg. Producers have introduced ultra-accelerators based on longer-chain and branched-chain amines that are less volatile and less toxic. This development is also motivated by a desire to rninirnize airborne nitrosamines.  [c.222]

Dithiophosphates. These compounds (13) are made by reaction of an alcohol with phosphoms pentasulfide, then neutralization of the dithiophosphoric acid with a metal oxide. Like xanthates, dithiophosphates contain no nitrogen and do not generate nitrosamines during vulcanization. Dithiophosphates find use as high temperature accelerators for the sulfur vulcanization of ethylene—propylene—diene (EPDM) terpolymers.  [c.223]

Other Accelerators. Amine isophthalate and thiazolidine thione, which are used as alternatives to thioureas for cross-linking polychloroprene (Neoprene) and other chlorine-containing polymers, are also used as accelerators. A few free amines are used as accelerators of sulfur vulcanization these have high molecular weight to minimize volatility and workplace exposure. Several amines and amine salts are used to speed up the dimercapto thiadiazole cure of chlorinated polyethylene and polyacrylates. Phosphonium salts are used as accelerators for the bisphenol cure of fluorocarbon mbbers.  [c.223]

The main producers of organic accelerators for mbber vulcanization are shown in Table 3. This table is not meant to be completely comprehensive, but rather to indicate the principal historical suppHers to the mbber industry. Most producers offer chemical equivalents in the largest-volume products. Within the range of smaHer-volume specialty accelerators, chemical equivalents become less common. Each producer may offer different products to achieve the same purpose of rapid cross-linking, resistance to thermal degradation, or other performance characteristics. Many offer proprietary blends of accelerators.  [c.223]

Zinc oxide is a common activator in mbber formulations. It reacts during vulcanization with most accelerators to form the highly active zinc salt. A preceding reaction with stearic acid forms the hydrocarbon-soluble zinc stearate and Hberates water before the onset of cross-linking (6). In cures at atmospheric pressure, such as continuous extmsions, the prereacted zinc stearate can be used to avoid the evolution of water that would otherwise lead to undesirable porosity. In these appHcations, calcium oxide is also added as a desiccant to remove water from all sources.  [c.225]

Sulfur vulcanization leads to a variety of cross-link stmctures as shown in Figure 1. AH the sulfur does not result in cross-links some of it remains as pendent accelerator polysulftde groups and internal cycHc polysulftdes. These alternative stmctures do not contribute to load bearing or strength properties and are more prevalent in unaccelerated or weakly accelerated vulcanization systems. Additional heating can also reduce the polysulftde rank of the cross-links. In some elastomers, this leads to a larger number of cross-links. However, in natural mbber or its synthetic polyisoprene equivalent, the overaH result is a loss of cross-links, especiaHy at temperatures over 160°C.  [c.226]

Thiazole disulfides absorb at 235 and 258 nm (320-322) and characteristic infrared bands are reported in Ref. 320. The activities of 2-cyclo-hexyldithiomethylthiazoles as vulcanization accelerators have been correlated with their mass-spectral fragmentation patterns (322).  [c.412]

The N,]S3-dialkyl-/)-PDAs (where the alkyl group may be 1-methylheptyl, l-ethyl-3-methylpentyl, 1,4-dimethylpentyl or cyclohexyl) are the most effective in terms of their reactivity towards ozone (24—26). These derivatives increase the critical stress required for the initiation of crack growth, and they also reduce the rate of crack growth significantly (15). The alkyl group is most active, for reasons that ate as yet not completely clear. The drawbacks of these derivatives are their rapid destmction by oxygen, ie, shorter useful lifetimes their activity as vulcanization accelerators, and hence increased scorchiness their tendencies to cause dark red or purple discoloration and the difficulty in handling because they are Hquids. The dialkyl- -PDAs are seldom used alone in mbber compounds, although they can be used effectively when blended with alkyl-A/-aryl-/)-PDAs.  [c.237]

Barium hydroxide is used in the manufacture of barium greases and plastic stabihzets such as barium 2-ethylhexanoate, in papermaking, in sealing compositions (see Sealants), vulcanization accelerators, water purification, pigment dispersion, in a formula for self-extinguishing polyurethane foams (see Fire-extinguishing agents), and in the protection of objects made of limestone from deterioration (see Fine ART EXAMINATION AND CONSERVATION Lime AND limestone). Uses of the octahydrate include use as a low temperature latent heat storage material in combination with Na or KNO or NaOAc (22) use as a nucleating agent to reduce supercooling of CaBr2 solution (7) and removal of CO and C02 by passing through a bed of sohd mono- or octahydrate.  [c.481]

Carbon disulfide was first prepared nearly two hundred years ago by heating sulfur with charcoal. That general approach was the only commercial route to carbon disulfide until processes for reaction of sulfur and methane or other hydrocarbons appeared in the 1950s. Significant commercial production of carbon disulfide began around 1880, primarily for agricultural and solvent appHcations. Both the physical and chemical properties of carbon disulfide are utilized in industry. Commercial uses grew rapidly from about 1929 to 1970, when the principal appHcations included manufacturing viscose rayon fibers, cellophane, carbon tetrachloride, flotation aids, mbber vulcanization accelerators, fungicides, and pesticides. Production of carbon disulfide in the United States has declined in recent years. Other chemical fibers and films, as well as environmental and toxicity considerations related to carbon tetrachloride, have had significant impact on the demand for carbon disulfide. Worldwide annual production capacity in 1991 was approximately 1.3 million tons, with actual production estimated at about one million metric tons.  [c.26]

Phthalides — see Benzo[c]furan-l (3H)-one Phthalimide, 2-amino-pyridazine synthesis from, 3, 53 Phthalimide, N-cyclohexylthio-as vulcanization accelerator, 1, 404 Phthalimide. methylidine-polymerization, 1, 273 Phthalimide, N-(trichloromethylthio)-biocide, 1, 399 Phthalimide, 1-vinyl-polymerization, 1, 273 Phthalimide, N-vinyl-copolymer  [c.745]

Synthetic rubber or elastomers, in its raw state is too plastic for most commercial applications. Through a curing process termed vulcanizing, raw rubber can be made to lose plasticity and gain elasticity. By compounding the raw or "neat" rubber with various types and amounts of additives before the vulcanizing, tensile strength, abrasion resistance, resiliency, heat aging, and other desirable properties can be imparted to the rubber. The proportions and types of additives (including vulcanizing agents) compounded into the raw rubber, and the vulcanizing temperature, pressure, and time are varied in accordance with the properties desired in the final product. After the rubber is compounded, it is formed into the desired shape and then cured at the required temperature. In the forming steps, large amounts of organic solvents are often used in the form of rubber adhesives. Types of additives that are compounded into the rubber may be classified as vulcanizing agents, vulcanizing accelerators, accelerator activators, retarders, antioxidants, pigments, plasticizers and softeners, and fillers. Vulcanizing agents include peroxides and sulfur. Vulcanizing accelerators include aldehyde-amines, guanidines, and thiuram sulfides which are used to decrease the time and temperature required for vulcanization. Accelerator activators include zinc oxide, stearic acid, litharge, magnesium oxide, and amines which supplement the accelerators and, in addition, modify the finished product characteristics for example, they increase the modules of elasticity. Examples of retarders include salicylic acid, benzoic acid, and phathalic anhydride to retard the rate of vulcanization. Antioxidants include many organic compounds, mostly alkylated amines, which are used to retard deterioration of the rubber caused by oxidation and improve aging and flexing ability. Pigments include such ingredients as carbon black, zinc oxide, magnesium carbonate, and certain clays which are used to increase tensile strength, abrasion resistance, and tear resistance. Iron oxide, titanium oxide, and organic dyestuffs are used to color the rubber. Plasticizers and softeners include resins, vegetable and mineral oils, and waxes which are used to improve resiliency, flexibility, and mixing and processing characteristics. Fillers include whiting, slate flour, barytes, and some of the pigments previously mentioned are used to improve processing properties and lower the cost of the finished product. In the compounding of blends, the accelerators are added first to the mass of raw rubber being milled or mixed. Then a portion of the plasticizers (if present in the blend recipe) are added, followed by the reinforcing pigments, the remainder of the plasticizers, the antioxidants, and any inert fillers or coloring agents. The vulcanizing agent is usually introduced as the last ingredient.  [c.444]

Complexes of these ligands have been extensively studied during the past few decades not only because of the intriasically interesting structural and bonding problems that they pose but also because of their varied industrial applications.These include their use as highly specific analytical reagents, ehromatographic supports, polarizers in sunglasses, mode-locking additives in neodymium lasers, semiconductors, fungicides, pesticides, vulcanization accelerators, high-temperature  [c.674]

Johnson et al. (17) have coupled an SEC system, operating in the normal phase mode, using Micropak TSK gels with THE as the eluent, to a gradient LC system in the reversed phase mode, using MicroPak-MCH (monolayer octadecylsilane phase) with acetonitrile-water as the eluent, for the analysis of various additives in rubber stocks. These additives include carbon black, processing oils, antioxidants, vulcanizing accelerators and sulfur. The rubber stocks that were analyzed were butadiene-acrylonitrile (Chemigum N-615) and styrene-butadiene (Plioflex 1502) copolymers. The compositions of the compound rubber stocks is presented in Table 12.1.  [c.315]

Copolymerization can be carried out with styrene, acetonitrile, vinyl chloride, methyl acrylate, vinylpyridines, 2-vinylfurans, and so forth. The addition of 2-substituted thiazoles to different dienes or mixtures of dienes with other vinyl compounds often increases the rate of polymeriza tion and improves the tensile strength and the rate of cure of the final polymers. This allows vulcanization at lower temperature, or with reduced amounts of accelerators and vulcanizing agents.  [c.398]

The long-chain urethane polymer molecules ia spandex fibers ate substantially linear block copolymers comprising relatively long blocks ia which molecular iateractions ate weak, iaterconnected by shorter blocks ia which iateractions ate strong. The weakly interacting blocks, commonly referred to as soft segments, ate from the polyether or polyester glycol component whereas the blocks having strong iateractions result from diisocyanate and chain extender reactions and ate referred to as hard segments. The hard segments ate usually aromatic-aUpathic ureas that connect with the soft segment through urethane linkages. With fiber formation, hard segments from several chains associate iato stroagly boaded cluster domaias. These form islands of a discontinuous phase and convert the polymer to a three-dimensional network (10). The principal interchain forces ate hydrogen bonds between NH groups and carbonyls, but crystallizability is also favored by the rigid and planar configuration of the aromatic rings. Interchain bonding must be not only strong enough to prevent molecular sHppage, but also concentrated so that the connecting soft segments can comprise a large fraction of the polymer chain. This result ia high stretch aloag with low modulus. Urea hard segments that comprise less than 25% of polymer mass provide this needed concentrated bonding force. In contrast, the network stmcture ia mbber depeads oa covaleat boads betweea chaia molecules that result from vulcanization with sulfur. Ia both polyurethanes and mbber, modulus is directiy related to tie-poiat density. Similarly, the relationship for maximum elongation is an iaverse function of tie-poiat deasity. la mbber fibers, tie-poiat deasity is coatroUed by the amouat of vulcanizing ageat, accelerant, and reaction conditions. In polyurethanes, tie-poiat (hard segment) deasity is coatroUed by the soft segment molecular weight and the molar ratio used to prepare the glycol—diisocyanate prepolymer.  [c.304]

Although it has been studied since the 1950s, the exact mechanism of accelerated sulfur vulcanization remains unresolved, including whether it proceeds by a radical or ionic process. One review (11) suggests that the nature of the reaction may change, depending on the polarity of the particular polymer (solvent) and whether or not zinc oxide is present. Sulfur vulcanization employs a combination of zinc oxide, fatty acid, sulfur, and at least one accelerator. These materials react as shown in Figure 2 to form a complex (I) in which the eight-member sulfur ring has been opened (12). The complex then abstracts a hydrogen on an alpha-carbon position to the double bond in the polymer to form a mbber-bound pendent accelerator polysulftde (II), a cross-link precursor. In Step 3, a zinc complex and an adjacent polymer chain react with the pendent polysulftde to form the polysulftde cross-link while regenerating the zinc—accelerator complex. The cycle is continued until aH the sulfur is consumed.  [c.226]

See pages that mention the term Vulcanization accelerators : [c.35]    [c.52]    [c.396]    [c.397]    [c.438]    [c.338]    [c.338]    [c.456]    [c.604]    [c.943]    [c.989]    [c.989]    [c.1075]    [c.557]    [c.611]    [c.847]    [c.498]    [c.10]    [c.136]    [c.204]   
Thiazole and its derivatives Ч.2 (1979) -- [ c.438 , c.440 , c.441 ]