Natural rubber depolymerization

Fig 9 Density effect of stretched and unstretched explosives curves 1—3 refer to unstressed sheets 1 = 15% natural rubber, 2 = 15% depolymerized rubber, 3 = 20% depolymerized rubber. Curve 4 refers to a stretched 15% rubber containing explosive of 1,4g/cc initial density (Ref 45)... 

Explosive, Flexible of Kegler. It may be prepd by mixing an expl with an elastometer (depolymerized natural or synthetic rubber) and a vulcanizing agent. Vulcanization is cmried out simultaneously with formation of the product. For example, 500g dry PETN of particle size natural rubber(such as... 

Hydroxy-terminated natural rubber (HTNR) It is a honey-colored viscous liquid and is prepared by the depolymerization of masticated natural rubber (NR) in the presence of H202 in toluene. Similar to other polyols, it is curable with TDI/MDI. Some important attributes of HTNR are ... 

Natural rubber, chemically speaking poly(W.v-1,4-isoprene), is a natural polymer derived from Hevea brasiliensis and various other tropical plants like Castilloa elastica [147]. This natural polymer is mainly produced in Asia and the tropics in high, industrially relevant, amounts (e.g., 9.7 Mio mto in 2007). Apart from its usual use as an elastomeric material, some research was devoted onto the metathesis degradation (depolymerization) of natural rubber with ethylene in a CM fashion. It was believed that metathesis of natural rubber is impossible, until a pioneering... 

Scheme 22 Synthesis of telechelic acetoxy-terminated cis- 1,4-polyisoprene by olefin metathesis depolymerization of natural rubber [144]...

Natural rubber oligomers with (i-pinene terminal units have been synthesized by Gutierrez and Tlenkopatchev via metathesis depolymerization [151]. The bulk degradation of natural rubber in the presence of (i-pinene, as chain-transfer agent, and C4 (0.1 mol% related to polymers with Mn between 490 and 1,700 kDa) produced monoterpene-terminated oligomers in yields between 80% and 90%. The results were further confirmed with model CM reactions using (i-pinene and (Z)-3-methyl-2-pentene. 

There are very few examples of direct hydroxylation of olefins using hydrogen peroxide, since these methods are limited to polymer applications or derivatization of natural products. Vinyl monomers have been hydroxy-lated in an alcoholic medium using acidic hydrogen peroxide 111 normally the acid is methanesulfonic. Natural rubber has also been hydroxylated, and simultaneously depolymerized by employing a hydrogen peroxide/UV system.112 The product distribution can be altered by varying the irradiation time. 

Only up to 58% of natural rubber can be practically depolymerized to isoprene during pyrolysis. A random chain scission may also take place along the polymeric chain. The result is the formation of molecules of lower molecular weight. However, in order to be volatile enough to be analyzed by typical analytical techniques associated with analytical pyrolysis, these fragments have to be relatively small. The formation of monomers as a final step in the random chain scission is not uncommon, and sometimes it is difficult to decide if a depolymerization or a random chain scission was the first step in pyrolysis. 

Liquid natural rubber, SBR, acrylonitrile elastomers, neoprene, and chlorosulfonated polyethylene are also used as sealant compositions. Filled depolymerized natural rubber and SBR latex are readily cured at room temperature by the incorporation of ultraaccelerators. 

Supercritical water and carbon dioxide have been used for controlled depolymerization of natural rubber and automotive tires at 380 and 276 bar. It is shown that the extent of... 

Chen, D. T., Perman, C. A., Riechert, M. E., and Hoven, J. (1995) Depolymerization of tire and natural rubber using supercritical fluids, / Hazardous Materials, 44, 53-60. 

C -l,4-polyisoprenes are produced by depolymerizing polyisoprene or natural rubber. The material is used as a reactive plasticizer for adhesive tape, abrasive and friction products such as grinding wheels, and automobile brake linings, wire and cable sealants, and hot melt adhesives. The natural rubber product serves as a base for cold molding compounds for arts and crafts, asphalt modifier, as potting, or in molds. 

Maleated natural rubber/poly(methyl methacrylate) Maleated depolymerized natural rubber/epoxy resin Natural rubber/poly(methyl methacrylate)... 

Contact Adhesives. Nowadays, rubber solutions based on natural rubber or styrene-butadiene rubber, optionally in conjunction with regenerate and depolymerized rubber, are used for large-area bonding where adhesion does not have to meet stringent requirements, as is the case, for example, with the lining of vessels, containers, etc. with rubber. 

Experimental work has shown that a chemically depolymerized latex exhibits the characteristics of a pressure-sensitive adhesive." Good peel strength was found without the addition of resin, and as the low glass transition temperature of natural rubber was not affected by the reaction, these materials may be of interest in low temperature applications. Blends... 

Natural mbber, the other natural hydrocarbon polymer, consisting mainly of cfr-l,4-polyisoprene is relatively resistant to microbial attack in comparison to other natural polymers. A number of micro-organisms have been reported to degrade natural rubber. An enzyme which degrades the mbber was isolated from the extracellular culture medium of Xanthomonas sp., and the erude fractions which are capable of depolymerizing natural mbber in the latex state have been reported.The same authors " reported on a Nocardia strain that used natural mbber as its sole carbon source. 

Polymeric sulfur is produced commercially as insoluble sulfur (IS) and is used in the rubber industry [56] for the vulcanization of natural and synthetic rubbers since it avoids the blooming out of sulfur from the rubber mixture as is observed if Ss is used. The polymeric sulfur (trade-name Crys-tex [57]) is produced by quenching hot sulfur vapor in liquid carbon disulfide under pressure, followed by stabilization of the polymer (against spontaneous depolymerization), filtration, and drying in nitrogen gas. Common stabilizers [58] are certain olefins R2C=CH2 like a-methylstyrene which obviously react with the chain-ends (probably -SH) of the sulfur polymer and in this way hinder the formation of rings by a tail-bites-head reaction. In this industrial process the polymer forms from reactive small sulfur molecules present in sulfur vapor [59] which are unstable at ambient temperatures and react to a mixture of Ss and on quenching. 

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