Coral rubber

A sample of milled pale crepe hevea was reported to have 0.18% head-to-head and 1.7% tail-to-tail while Coral Rubber contains approximately 0.3 to 0.5% head-to-head and as much as 4.8 to 6.8% tail-to-tail. Coral Rubber thus contains a quite appreciable amount of tail-to-tail structure. 

It is noteworthy that the lithium-catalyzed polyisoprene—known as Coral rubber (13)—is the only one of the rubbers investigated which has more of the cis structure than the trans structure. The great predominance of the cis structure in Coral rubber, therefore, places this rubber in a class by itself compared to all other metal-catalyzed, or even free radical-catalyzed, polymers in Tables I and II. 

Lithium metal-catalyzed polyisoprene and polybutadiene have unusual microstructures compared to the analogous polymers made with the other alkali metals. The lithium metal-catalyzed polyisoprene, named Coral rubber, has a microstructure almost identical to that of Hevea rubber. The unusual microstructure of the lithium metal-catalyzed polybutadiene, or butadiene-styrene copolymer, probably accounts for its superior rubberlike properties at low temperatures. 

Lithium metal dispersions form polymers of isoprene that are high in cis-1,4 contents as shown in Table 5.8. These polymers form in hydrocarbon solvents. This is done industrially and the products are called Coral rubbers. They contain only a small percent of 3,4 structures and no tmns-U4 or 1,2 units. The materials strongly resemble Hevea rubber. 

Coral rubber Cis-l,4-poly(isoprene). Manufactured by Goodrich, USA. 

RUBBER (Synthetic). Any of a group of manufactured elastomers that approximate one or more of the properties of natural rubber. Some of these aie sodium polysulfide ( Thiokol ). polychloiopiene (neoprene), butadiene-styrene copolymers (SBR), acrylonitrilebutadiene copolymers (nitril rubber), ethvlenepropylene-diene (EPDM) rubbers, synthetic poly-isoprene ( Coral, Natsyn ), butyl rubber (copolymer of isobutylene and isoprene), polyacrylonitrile ( Hycar ). silicone (polysiloranei. epichlorohy-drin, polyurethane ( Vulkollan ). 

Coral [B. F. Goodrich]. TM for a stereospecific, polyisoprene rubber consisting essentially... 

Naturally, the more complex the composition of the substances to be pyrolysed, the more characteristics are needed for identification. For example, in identifying isoprene rubbers (NK, SKN-3, SKIL, Natsyn, Coral, Cariflex IR), the characteristic pyrolysis products are isoprene and dipentene, whereas with butadiene rubbers (SKB, SKD, Budene, Diene NF, Buna CB, Asadene NF, Cariflex BR, Ameripol CB) they are butadiene and vinylcyclohexane. With copolymer rubbers, the number of characteristic products necessary for identification increases to three, viz., butadiene, vinylcyclohexene and styrene are used for butadiene -styrene rubbers (SKS-10, SKS-30, Buna S. Europrene-1500, Solprene) and butadiene, vinylcyclohexene and methylstyrene are used for butadiene-methylstyrene rubbers (SKMS-10, SKMS-30) [139, 140]. Fig. 3.12 [139, 140] shows as an example pyrograms of individual general-purpose rubbers and a four-component mixture of rubbers. The shaded peaks correspond to those components in the pyrolysis products which are used for identification. The ratio of the pyrolysis products changes depending on the composition of the copolymer and the structure of the polymer. 

Resin, Alkyd (Glycerol - Phthalic Acid) Rubber, Coral ... 

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