Talalay process

The earhest frothing process developed was the Dunlop process, which made use of chemical gelling agents, eg, sodium fluorosiUcate, to coagulate the mbber particles and deactivate the soaps. The Talalay process, developed later, employs freeze-coagulation of the mbber followed by deactivation of the soaps with carbon dioxide. The basic processes and a multitude of improvements are discussed extensively in Reference 3. A discussion more oriented to current use of these processes is given in Reference 115. 

Many different processes are patented for preparing latex foam but only two are of commercial interest for preparing molded cushioning stock the Dunlop, which is most widely used, and the Talalay processes. Some producers have developed variations, which are combinations of the two processes. 

In the Talalay process, the froth is produced by chemical rather than mechanical means. Hydrogen peroxide and an enzyme decomposition catalyst are mixed iato the latex and the mixture placed ia the mold. Decomposition of the peroxide by the added enzyme results ia the Hberation of oxygen which causes the latex mix to foam and fill the mold. The foam is then rapidly chilled and CO2 is iatroduced to gel the latex. The gelled foam is then handled ia a manner similar to that used ia the Dunlop process. 

A method of manufacturing latex foam. Compounded latex is foamed and gelling agent added the mould is filled and the gelled foam vulcanised by steam at 100 °C the product is stripped from the mould, washed and dried. See Talalay Process. 

Monodisperse silica sols are important in the previously mentioned Talalay process for making foam rubber pillows. If a 4-nm silica sol is normally used, then a substitution of a 3.5-nm particle at the same silica dosage would theoretically increase the strength of the rubber by 14.3%. If, however, the particle size is changed from 4.5 to 5.0 nm, the strength of the rubber would decrease by 11 to 20% at the same silica dosage. Under these conditions, the crumbling effect of the foam rubber would return. 

A typical rubber formulation, for example, that demonstrates the surface area properties of silica sol can be seen in the Talalay process for making foam rubber [24] the elastomer foam is in a latex form, to which is added an accelerator, an antioxidant, a vulcanizing agent, and carbon black. The mixture is then foamed, either mechanically or chemically, gelled, vulcanized to... 

Dunlop A process for making foam rubber which uses sodium fluorosilicate to coagulate the rubber particles and deactivate the surfactants. See also Talalay. 

The oxidation-reduction process for the conversion of hydroxysteroids to keto-steroids (and the reverse reaction) has been studied in detail by T dalay and his collaborators with induced enzymes isolated from Pseudomonas testosterord. They purified one enzyme system which oxidized the 3o -hydroxyl group and another which oxidized both 3j3- and 17/3-hydroxyl groups. Talalay has characterized the oxidation-reduction reaction with these enzymes as NAD-linked and illustrated the general reaction as ... 

Currently, most of the foams found on the market based on NR are produeed from the eolloidal suspension eommonly ealled latex. Two methods have been traditionally used to produee latex foams Dunlop and Talalay. Mattresses and pillows are eommon examples of products obtained through these processes. Nevertheless, foams produced by dry natural rubber are unlikely to be found in the market and it is a topic which has not been studied in depth yet. Only few studies concerning dry natural rubber foams are found in the literature. Also, prices of dry natural rubber ( 6 /kg) are extremely high in comparison with synthetic rubber materials such as styrene butadiene rubber ( 2.3 /kg). 

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