Vulcanization of rubber


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

Accelerators. During sulfur vulcanization of rubber, accelerators serve to control time to onset of vulcanization, rate of vulcanization, and number and type of sulfur cross-links that form. These factors in turn play a significant role in determining the performance properties of the vulcanizate.  [c.237]

It is also useful in the rapid vulcanization of rubber, eg, in the preparation of thin rubber goods by coating molds or fabrics with mbber latex. Rubber  [c.139]

American inventor Charles Goodyear patents vulcanizing of rubber.  [c.1242]

Crosslinking may occur during the polymerization reaction when multifunctional groups are present (as in phenol-formaldehyde resins) or through outside linking agents (as in the vulcanization of rubber with sulfur).  [c.303]

Sulfur is a component of black gunpowder, and is used in the vulcanization of natural rubber and a fungicide. It is also used extensively in making phosphatic fertilizers. A tremendous tonnage is used to produce sulfuric acid, the most important manufactured chemical.  [c.39]

Ethylene-propylene-diene rubber is polymerized from 60 parts ethylene, 40 parts propylene, and a small amount of nonconjugated diene. The nonconjugated diene permits sulfur vulcanization of the polymer instead of using peroxide.  [c.1064]

Very recently Jeon and Seo used AES depth profiling to determine the effect of curing temperature on adhesion of natural rubber to brass [46]. In their investigation, natural rubber was vulcanized against a thin brass film that was sputtered onto a glass plate. After vulcanization, the rubber was removed from the glass and AES was used to construct depth profiles starting from the brass and proceeding toward the brass/rubber interphase. Fig. 42 shows the copper and sulfur profiles (top) and the zinc and oxygen profiles (bottom) that were obtained for various vulcanization temperatures between 130°C and 190°C. For the samples vulcanized at 130°C, a shoulder appeared near the end of the copper peak. This shoulder coincided with a peak in the sulfur profile, suggesting that a copper sulfide was formed. There was also a peak at the end of the zinc profile that coincided with a peak in the oxygen profile, suggesting formation of zinc oxide. Considering the atomic concentrations detected for the various elements, it was suggested that there was too much sulfur and too much zinc for only copper sulfide and zinc oxide to form. Therefore, it was also suggested that some zinc sulfide also formed at lower temperatures.  [c.293]

Changes observed in the composition of the rubber/brass interphase correlated well with results of adhesion tests carried out on brass-plated steel wires embedded in blocks of rubber [46]. The force required to pull the wires out of the blocks decreased steadily as vulcanization temperature increased. This effect was especially pronounced when the specimens were aged at elevated temperature and humidity for several days before the wires were pulled out of the rubber blocks.  [c.295]

Geon and Seo [47] also determined the effect of vulcanization time on the adhesion of natural rubber to brass-plated steel. For relatively short times, there was a peak at the end of the copper profile that corresponded well with a peak in the sulfur profile. Similarly, peaks in the zinc and oxygen profiles corresponded well. These results showed that copper sulfide and zinc oxide mostly formed at short times but some evidence for formation of zinc sulfide was also obtained. For long times, the peak in the sulfur profile no longer corresponded with that in the copper profile. Instead, the peak in the sulfur profile corresponded to the peak in the zinc profile. It was concluded that the formation of zinc sulfide increased substantially at long times. An increase in vulcanization time correlated well with a decrease in the force required to pull brass-plated steel wires out of rubber blocks.  [c.295]

Structural applications of rubber base adhesives were also obtained using rubber-thermosetting resin blends, which provided high strength and low creep. The most common formulations contain phenolic resins and polychloroprene or nitrile rubber, and always need vulcanization.  [c.574]

Resistance to weathering. Zinc oxide and magnesium oxide stabilize poly-chloroprene against dehydrochlorination. Further, zinc oxide helps vulcanize the rubber, and magnesium oxide reacts with /-butyl phenolic resin to produce a resinate which improves heat resistance of solvent-borne polychloroprene adhesives.  [c.629]

Vulcanization of the rubber. Sulphur bridges between rubber chains are actually produced.  [c.638]

Rubber base adhesives can be used without cross-linking. When necessary, essentially all the cross-linking agents normally used in the vulcanization of natural rubber can be used to cross-link elastomers with internal double carbon-carbon bonds. A common system, which requires heat to work, is the combination of sulphur with accelerators (zinc stearate, mercaptobenzothiazole). The use of a sulphur-based cross-linking system with zinc dibutyldithiocarbamate and/or zinc mercaptobenzothiazole allows curing at room temperature. If the formulation is very active, a two-part adhesive is used (sulphur and accelerator are placed in two separate components of the adhesive and mixed just before application).  [c.640]

Rubber, natural and synthetic, has been used extensively for many years in chemical process plants. Rubber is a product obtained by thermal processing (vulcanization) of a mixture of raw natural synthetic caoutchouc with sulfur.  [c.122]

Vulcanization of natural rubber latex by heating it with S diseovered by Charles Goodyear (USA).  [c.646]

Thermoplastic polyurethane (TPU) is a type of synthetic polymer that has properties between the characteristics of plastics and rubber. It belongs to the thermoplastic elastomer group. The typical procedure of vulcanization in rubber processing generally is not needed for TPU instead, the processing procedure for normal plastics is used. With a similar hardness to other elastomers, TPU has better elasticity, resistance to oil, and resistance to impact at low temperatures. TPU is a rapidly developing polymeric material.  [c.137]

Compatibilization along with dynamic vulcanization techniques have been used in thermoplastic elastomer blends of poly(butylene terephthalate) and ethylene propylene diene rubber by Moffett and Dekkers [28]. In situ formation of graft copolymer can be obtained by the use of suitably functionalized rubbers. By the usage of conventional vulcanizing agents for EPDM, the dynamic vulcanization of the blend can be achieved. The optimum effect of compatibilization along with dynamic vulcanization can be obtained only when the compatibilization is done before the rubber phase is dispersed.  [c.640]

Blend of (1) and (2) type categories mostly include the modification of engineering thermoplastics with another thermoplastic or rubber. PS-EPDM blends using a low-molecular weight compound (catalyst) Lewis acid have been developed [126]. Plastic-plastic blends, alloys of industrial importance, thermoplastic elastomers made by dynamic vulcanization, and rubber-rubber blends are produced by this method.  [c.655]

TPE s are more economical to produce than traditional thermoset materials because fewer steps are required to manufacture them than to manufacture and vulcanize thermoset rubber. An important property of these polymers is that they are recyclable.  [c.358]

Complexes with SCN throw light on the relative affinities of the two metals for N-and S-donors. In [Zn(NCS)4] the ligand is A-bonded whereas in [Cd(SCN)4] it is S-bonded. SCN can also act as a bridging group, as in [Cd S=C(NHCH2)2 2(SCN)2] when linear chains of octahedrally coordinated Cd are formed (Fig. 29.3c). A number of zinc-sulfur compounds are used as accelerators in the vulcanization of rubber. Among these are the dithio-carbamates, of which [Zn(S2CNEt2)2]2, and the isostructural Cd" and Hg" compounds achieve 5-coordination by dimerizing (Fig. 29.3d).  [c.1217]

Natural rubber is an elastomer constituted of isoprene units. These units are linked in a cis-1,4-configuration that gives natural rubber the outstanding properties of high resilience and strength. Natural rubber occurs as a latex (water emulsion) and is obtained from Hevea brasilien-sis, a tree that grows in Malaysia, Indonesia, and Brazil. Charles Goodyear (1839) was the first to discover that the latex could be vulcanized (crosslinked) by heating with sulfur or other agents. Vulcanization of rubber is a chemical reaction by which elastomer chains are linked together. The long chain molecules impart elasticity, and the crosslinks give load supporting strength. Vulcanization of rubber has been reviewed by Hertz, Jr. Synthetic rubbers include elastomers that could be crosslinked such as polybutadiene, polyisoprene, and ethylene-propylene-diene tere-polymer. It also includes thermoplastic elastomers that are not crosslinked and are adapted for special purposes such as automobile bumpers and wire and cable coatings. These materials could be scraped and reused. However, they cannot replace all traditional rubber since they do not have the wide temperature performance range of thermoset rubber.  [c.351]

The reaction is of practical importance in the vulcanization of siUcone mbbers (see Rubber compounding). Linear hydroxy-terrninated polydimethyl siloxanes are conveniently cross-linked by reaction with methyldiethoxysilane or triethoxysilane [998-30-1]. Catalysts are amines, carboxyflc acid salts of divalent metals such as Zn, Sn, Pb, Fe, Ba, and Ca, and organotin compounds. Hydroxy-terrninated polysiloxanes react with Si—H-containing polysiloxanes to  [c.26]

The salts of the 0-esters of carbonodithioic acids and the corresponding 0,i -diesters are xanthates. The free acids decompose on standing. Potassium ethyl xanthate was first prepared ia 1822 by W. C. Zeise from potassium hydroxide, carbon disulfide, and ethanol. Most alcohols, including cellulose, undergo this reaction to form xanthates, but normally phenols do not (see Fibers, regenerated cellulosics). Potassium phenyl xanthate was prepared ia 1960 from potassium phenoxide and carbon disulfide ia dimethylformamide (1). The preparation of phenoHc xanthates has been expanded by the use of dialkyl ethers of mono- or polyethylene glycols or sulfolane (2). Xanthates remained a laboratory curiosity until the turn of the twentieth century when the mbber iadustry developed a use for them ia the curing and vulcanization of mbber (see Rubber chemicals Rubber compounding). Comehus Keller s iavention of xanthates as flotation collectors for the nonferrous metal sulfides ia 1927 (3) ranks as the chemical iavention that had the greatest impact ia flotation (4) (see Flotation). This is the principal use for the nonceUulose xanthates several of the alkah metal xanthates are commercially available.  [c.359]

A. H. Jorgensen, inj. McKetta and W. Cunningham, eds.. The Enyc/opedia Chemica/Processes and Design, Vol. 1, Marcel Dekker, New York, 1976, p. 439. C. H. Lufter, "Vulcanization of Nitrile Rubber," in Hu/cani tion of E/astomers, Reinhold Publishing Corp., New York, 1964.  [c.524]

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]

The major industrial use of ZnO is in the production of rubber where it shortens the time of vulcanization. As a pigment in the production of paints it has the advantage over the traditional white lead (basic lead carbonate) that it is nontoxic and is not discoloured by sulfur compounds, but it has the disadvantage compared to Ti02 of a lower refractive index and so a reduced hiding power (p. 959). It improves the chemical durability of glass and so is used in the production of special glasses, enamels and glazes. Another important use is in antacid cosmetic pastes and pharmaceuticals. In the chemical industry it is the usual starting material for other zinc chemicals of which the soaps (i.e. salts of fatty acids, such as Zn stearate, palmitate, etc.) are the most important, being used as paint driers, stabilizers in plastics, and as fungicides. An important small scale use is in the production of zinc ferrites . These are spinels of the type Zn My Fe 04 involving a second divalent cation (usually Mn or Ni"). When jc = 0 the structure is that of an inverse spinel (i.e. half the Fe " ions occupy octahedral sites — see p. 1081). Where x = 1, the structure is that of a normal spinel (i.e. all the Fe " ions occupy octahedral sites), since Zn" displaces Fe " from the tetrahedral sites. Reducing the proportion of Fe " ions in tetrahedral sites lowers the Curie temperature. The magnetic properties of the ferrite can therefore be controlled by adjustment of the zinc content.  [c.1209]

Early humans used a variety of naturally occurring polymers to meet their material needs. They used them not with the perception of the chemistry and physics of modern high polymers, but for their survival, food, shelter, and clothing. A variety of materials made from wood, bark, animal skins, cotton, wool, silk, natural rubber, etc. were essentially playing key roles in early civilizations [1]. They could mechanically modify materials into useful tools (stone axes wood carvings animal skins the twisting of cotton, wool, and flax to form threads weaving preparation of thin-skinned papyrus and vegetable tissues for writing, etc). Embalming of corpses was one of the earliest practices that involved chemical modification (crosslinking of proteins by formaldehyde). With the growth of human civilizations, the use and applications of materials extended to metals and ceramics, and, by the nineteenth century, there were eight classical materials—metals, stones, woods, ceramics, glass, skins, horns, and fibers—of which woods, skins, horns, and fibers are organic polymers. During the past one and one half centuries, two more materials were added to the list, rubber and plastics, both of which are polymeric in nature. However, by 1900, there were only a few plastics in use, e.g., shellac, gutta percha, ebonite, and celluloid [2]. Although a variety of chemical modifications came into vogue, four great discoveries formed the foundation of the industrial use of natural polymers, which even today form the basis of continued support and maintenance of these industries against stiff competition from synthetics. They are the vulcanization of natural  [c.411]


See pages that mention the term Vulcanization of rubber : [c.10]    [c.120]    [c.293]    [c.455]    [c.582]    [c.647]    [c.35]    [c.61]    [c.73]    [c.136]    [c.144]    [c.148]    [c.204]    [c.254]    [c.347]    [c.423]    [c.428]    [c.438]   
Chemistry of the elements (1998) -- [ c.646 ]

Chemistry of Petrochemical Processes (2000) -- [ c.120 , c.351 ]