Rubber isomerization

Able to form Ag salt of lower solubility than AgQ in H2O. Therefore applications in photographic processes Inhibition of histidine decarboxylase activity Antifoggant for color films Anthelmintic activity Quenching for oil composition caialj si for the industrial isomerization of cis a, (3 unsaturaied carboxylic acids rubber vul-cankzate improver... 

Elastomers. Ethylene—propylene terpolymer (diene monomer) elastomers (EPDM) use a variety of third monomers during polymerization (see Elastomers, ethyiene-propylene-diene rubber). Ethyhdenenorbomene (ENB) is the most important of these monomers and requires dicyclopentadiene as a precursor. ENB is synthesized in a two step preparation, ie, a Diels-Alder reaction of CPD (via cracking of DCPD) with butadiene to yield 5-vinylbicyclo[2.2.1]-hept-2-ene [3048-64-4] (7) where the external double bond is then isomerized catalyticaHy toward the ring yielding 5-ethyhdenebicyclo[2.2.1]-hept-2-ene [16219-75-3] (ENB) (8) (60). 

Related to stereoregularity is the possibility of cis, trans isomerism. The molecule of natural rubber is a c/s-1,4-polyisoprene whilst that of gutta percha is the trans isomer. 

When the temperamre is lowered, rubbers become stiff and brittle. All rubbers eventually stiffen to a rigid, amorphous glass at the glass transition temperature (Tg). This temperature also indicates the low-temperature service limit of the rubber. Tg values are dependent on the structure, degree of cross-linking (vulcanization) and isomeric composition of the rubber. 

Selten-gummi, n. side wall (of a rubber tire), -isomerie, /. chain isomerism, -kante, /. lateral edge, -kette, /. side chain, -ketten-isomerie, /. side-chain isomerism, -kraft, /. component force, component, -lage,/. lateral position, -l ge, /. length of a side, lateral length, -riss, m. side elevation. -lohr, n., -rohre,/. side tube, branch tube, branch pipe, seitens, adv. on behalf (of), on the part (of), seltenstandlg, a. lateral. 

FIGURE 26.56 Log Abrasion loss by a blade (solid lines) and log cut growth rate (dashed hnes) of noncrystallizing rubber compounds as function of log frictional and log tearing energy, respectively isomerized natural rubber (NR), 2 styrene-butadiene rubber (SBR), and 3 acrylate-butadiene rubber (ABR). (From Champ, D.H., Southern, E., and Thomas, A.G., Advances in Polymer Friction and Wear, Lieng Huang Lee (ed.), Plenum, New York/London, 1974, p. 134.)... 

Seeligmann, Torrilhon, and Falconnet, in a treatise on rubber published in France in 1896, recorded interesting early observations on the sol and gel components now known to be present in most specimens of undegraded raw rubber. They referred to them as the two isomeric hydrocarbides of rubber, one being the adhesive principle and the other the nervous principle. It was observed that the latter refused to dissolve on repeated treatment with fresh portions of solvent and that the approximate percentage of this constituent was roughly the same when different solvents were used to extract the soluble portion. The authors called attention also to the enormous swelling capacity of the nervous hydrocarbide. Vulcanization was attributed to a reaction of sulfur with the adhesive principle whereby the adhesive characteristics are suppressed or eliminated. 

An isomeric derivative of natural rubber produced by a variety of chemical treatments. The products are resinous and find application as reinforcing agents in natural rubber compounds (particularly in shoe soles) and as rubber-to-metal adhesives. 

A hard resinous thermoplastic substance of the same chemical composition as rubber hydrocarbon but having the ftvms-structure. See Cis-trans Isomerism. Formerly extensively used for the insulation of submarine cables (now superseded by polyethylene) and in the early manufacture of golf balls (now superseded by... 

A solvent for natural and most synthetic rubbers except nitrile. It is a petroleum spirit existing in five isomeric forms normal hexane has a boiling point of 69 °C. 

Xylol (dimethylbenzene), used as a rubber solvent. Xylene exists in three isomeric forms, commercial xylol being a mixture of all three. Xylyl Mercaptan... 

The reactions of intramolecular isomerization occur and are important in the oxidation of natural and synthetic rubbers. The peroxyl radical addition to the double bond occurs very rapidly. For example, the peroxyl radical adds to the double bond of 2-methylpropene by 25 times more rapidly than abstraction of hydrogen atom from this hydrocarbon (see Chapter 4). Therefore, the oxidation of polymers having double bonds proceeds as a chain process with parallel reactions of P02 with double and C—H bonds including the intramolecular isomerization of the type [12] ... 

Saturable dye absorber, 14 677 Saturated aqueous salt solution, 9 34 Saturated calomel electrode (SCE), 9 571 Saturated fatty acids, 10 829, 830 Saturated hydrocarbons adsorbent affinity, 1 674 adsorption by zeolites, 1 624 fluorine reactivity with, 11 831 isomerization of, 12 172—173 Saturated polyester resins, based on trimethylpentanediol, 12 673 Saturated polyesters, 10 7 Saturated synthetic rubber, 10 705 Saturation and coating processes, 10 12-13 Saturation bonding, 17 509-510 Saturation color, 19 262 Saturation concentration, 15 677 Saturation index... 

Another alteration process is alkylation which is used to produce higher octane aviation gasoline and petrochemical feedstock for explosives and synthetic rubber. An isomerization process is also used to produce more material as an alkylation feedstock. 

Golub, M. A., Cyclized and Isomerized Rubber, Chap. 10A in Polymer Chemistry of Synthetic Elastomers, Part II, J. P. Kennedy and E. G. Tornqvist, eds., Wiley-Interscience, New York, 1969. 

Necklace models represent the chain as a connected sequence ctf segments, preserving in some sense the correlation between the spatial relationships among segments and their positions along the chain contour. Simplified versions laid the basis for the kinetic theory of rubber elasticity and were used to evaluate configurational entropy in concentrated polymer solutions. A refined version, the rotational isomeric model, is used to calculate the equilibrium configurational... 

Curro and Mark 38) have proposed a new non-Gaussian theory of rubber elasticity based on rotational isomeric state simulations of network chain configurations. Specifically, Monte Carlo calculations were used to determine the distribution functions for end-to-end dimensions of the network chains. The utilization of these distribution functions instead of the Gaussian function yields a large decreases in the entropy of the network chains. 

---