Unsaturated Hydrocarbon Rubbers

The strueture of cis-1,4-polybutadiene is very similar to that of the natural rubber molecule. Both materials are unsaturated hydrocarbons but, whereas with the natural rubber molecule, the double bond is activated by the presence of a methyl... 

Like NR, SBR is an unsaturated hydrocarbon polymer. Hence unvulcanised compounds will dissolve in most hydrocarbon solvents and other liquids of similar solubility parameter, whilst vulcanised stocks will swell extensively. Both materials will also undergo many olefinic-type reactions such as oxidation, ozone attack, halogenation, hydrohalogenation and so on, although the activity and detailed reactions differ because of the presence of the adjacent methyl group to the double bond in the natural rubber molecule. Both rubbers may be reinforced by carbon black and neither can be classed as heat-resisting rubbers. 

Carbon, hydrogen and possibly oxygen Resin and derivatives Natural drying oils Cellulose derivatives Alkyd resins Epoxy resins (uncured) Phenol-formaldehyde resins Polystyrene Acrylic resins Natural and synthetic rubbers Carbon monoxide Aldehydes (particularly formaldehyde, acrolein and unsaturated aldehydes) Carboxylic acids Phenols Unsaturated hydrocarbons Monomers, e.g. from polystyrene and acrylic resins... 

Uses Production of isooctane, butyl rubber, polyisobutene resins, high octane aviation fuels, tert-butyl chloride, ferf-butyl methacrylates copolymer resins with acrylonitrile, butadiene, and other unsaturated hydrocarbons organic synthesis. 

The coefficient of vulcanization is usually defined as the number of units of weight of sulphur combined with 100 units by weight of unsaturated hydrocarbon. Ebonites prepared from natural rubber are... 

Furan-2-carbaldehyde (furfural) is widely used in the vegetable oil, plastics, rubber and petroleum industries as well as being a versatile starting material for furan syntheses. It is the major source of commercial furans. It is used to extract unsaturated hydrocarbons from hydrocarbon mixtures, a process important in the purification of petroleum and vegetable oils. The chemistry of furfural has been extensively studied because of its industrial importance and availability. 

Sulfur and selenium react with many organic molecules. For example, saturated hydrocarbons are dehydrogenated. The reaction of sulfur with alkenes and other unsaturated hydrocarbons is of enormous technical importance hot sulfurization results in the vulcanization (formation of S bridges between carbon chains) of natural and synthetic rubbers. 

The alkyne series of hydrocarbons is characterized by having molecules with one triple bond each. They have the general formula C H2 2 and the name ending -yne. Like other unsaturated hydrocarbons, the alkynes are quite reactive. Ethyne is commonly known as acetylene. It is the most important member of the series commercially, being widely used as a fuel in acetylene torches and also as a raw material in the manufacture of synthetic rubber and other industrial chemicals. 

The polymers of rubber plastics have unsaturated hydrocarbon chain structure, since they are polymerized from alkadienes. The general formula of poly(l,3-butadiene) or butadiene rubber (BR) and polyisoprene or natural rubber (NR) is drawn in Scheme 12.5, where X is hydrogen in BR and methyl group in synthetic polyisoprene or NR. The free radical mechanism of thermal decomposition starts by homolytic scission of the alkyl C-C bonds. Two primary macroradicals (4 and 5) are formed for which the rearrangement... 

In order to overcome thfe drawbadr, new types of multi-unsaturated hydrocarbon monomers have been synthedzed in recent years and their behavior in ethylene-propylene copolymerization has been extensively studied. Such mcmomers are characterized by the presence of one unconjugated double bond suitable for copolymerization and of a system of two or three cmijugated double bonds, the high reactivity of which makes them competitive with conventional diene rubbers in sulfur vulcanization despite their low concentration. 

Place in an eight-inch tube 5 ml of the unsaturated hydrocarbon and 5 ml of cold 70 per cent sulfuric acid. Cool the mixture in tap water, place a solid rubber stopper in the mouth of the tube, and shake with cooling until the hydrocarbon dissolves and a clear liquid results. Add 6 g of ammonium sulfate dissolved in 8 ml of water. Insert the separatory stopper, and remove the aqueous acid layer. The liquid which is left in the reaction tube can be tested with bromine water or alkaline permanganate to show that it is not an olefin. If it is desired to purify the alcohol, add 1 g of anhydrous calcium sulfate and shake from time to time over a period of fifteen minutes. Pour the crude alcohol into a distilling tube. Heat with a small flame and collect the proper fraction. If amylene is used, and the water is not completely removed by the drying agent, a constant boiling mixture will be formed which boils at 87°. 

Buna 85 is polybutadiene (the number represents Mooney viscosity), molecular weight -80,000. Hard rubber has high softening point and excellent chemical resistance. The coefficient of vulcanisation to the ebonite stage is 39.3. The coefficient of vulcanisation is the number of unit weight of sulfur combined with 100 units by weight of unsaturated hydrocarbons. Buna S is a butadiene styrene copolymer with 70/30 to 68/32 ratio. Buna SS contains a high proportion of styrene. Perbunan are nitrile rubbers... 

Hard rubber or ebonite whether from natural rubber or from synthetic rubber, can be defined as highly vulcanised rubber, containing a large proportion of combined sulfur. Hard rubbers made from natural rubber have vulcanisation coefficients between 25 and 47. The theoretical vulcanisation coefficient value for natural rubber is 47 and for synthetic rubbers it is in the range of 35 to 47. The coefficient of vulcanisation is usually defined as the number of units by weight of sulfur combined with 100 units by weight of unsaturated hydrocarbon. The theoretical coefficients are corrected for impurities/non rubber constituents in the raw rubber. 

Secondary aromatic amines are effective antioxidants in the protection of saturated hydrocarbon polymers (polyolefins) against autooxidation. Their role in the stabilization of unsaturated hydrocarbon polymers (rubbers) is more complex depending on their structure, they impart protection against autooxidation, metal catalyzed oxidation, flex-cracking, and ozonation. The understanding of antioxidant, antiflex-cracking and antiozonant processes together with involved mechanistic relations are of both scientific and economic interest. 

Due to the high reactivity of ozone with unsaturated hydrocarbons moieties, surface cracking of stressed or flexed NR, BR, NBR, and SBR vulcanizates arises. Rubber goods designed for outdoor applications must therefore be stabilized against both C>2 and 0 attacks. Antioxidant protection mechanisms have been discussed in detail ( 1). Discussions dealing with antiozonant mechanism involve some contradictory experimental observations. 

Surface oxidation of carbon blacks generally leads to increased rates of wear with highly unsaturated hydrocarbon rubbers (38. 39), but the opposite behavior is observed with butyl rubber. This behavior has been ascribed to differences in interfacial adhesion (see Section III). 

Solubilization plays an important role in emulsion polymerization of unsaturated hydrocarbons, leading to the production of latexes, which are aqueous dispersions of synthetic rubber. The polymerization process primarily occurs in micelles containing solubilized hydrocarbon, rather than in the hydrocarbon emulsion droplets. Emulsion polymerization usually yields spherical particles of uniform size [22],... 

INHAM-3 [131] contains up to 97 wt% PE and copper in the metal-polymer with the formula [—CH2—CH2—]nCum, dispersed rubber. Cl, unsaturated hydrocarbons of oil and PE copolymer with polyformaldehyde. This material shows high impact viscosity (see Table 4.13), resistance to thermooxidative aging (the strength does not impair upon thermal aging) and frost resistance (down to —70°C). 

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