Natural Latexes

Most synthetic latices contain 5—10 wt % of nonelastomeric components, of which more than half is an emulsifier or mixture of emulsifiers. One reason for this relatively high emulsifier concentration as compared with natural latex is that emulsifier micelles containing solubiHzed monomer play a principle role in the polymerization process. A high emulsifier concentration is usually necessary to achieve a sufficiently rapid rate of polymerization. Secondly, a considerable fraction of the surface of the polymer particles must be covered by adsorbed soap or equivalent stabilizer to prevent flocculation... 

Dry basis natural mbber compound recipe, in part by wt high ammonia natural latex mbber concentrate, 100.0 potassium hydroxide, 0.5 Nacconal 90F (alkylarenesulfonate (AHied Chemical Co.)), 1.0 zinc oxide, 3.0 sulfur, 1.0 ZMBT, 1.0 zinc diethyldithiocarbamate (ZEDC) (trade names Ethazate (Uniroyal, Inc.), Ethyl Zimate (R. T. Vanderbilt), 0.3 antioxidant, as indicated. Wet-basis natural mbber compound recipe, in parts by wt natural latex (NC 356), 167.9 potassium hydroxide, 2.5 Nacconal 90F, 5.0 zinc oxide, 5.45 sulfur, 1.65 ZMBT, 2.0 ZEDC, 2.0 antioxidant, as indicated. AH films poured from freshly mixed compounds, dried overnight in place, then lifted and dried 1 h in air at 50°C before curing. 

The latex may consist entirely of natural latex or synthetic SBR latex or maybe a mixture of both. In the Dunlop process, natural mbber foams shrink more than SBR foams duriag washing and dryiag. The load-beariag capacity of the foams at a given density falls significantly as SBR is used ia place of natural mbber. 

Natural latex is polydisperse (size of individual particles may vary from 0.01 to 5 p.m). Flowever, synthetic latex has a relatively narrow particle size, and therefore the viscosity at a given rubber content is higher in synthetic rubber (polyisoprene) solutions. The average molecular weight is typically about I million g/mol, although it depends on the gel content. 

Natural rubber latex, obtained from rubber trees, is converted to its final form by a process known as vulcanization, first discovered by Charles Goodyear in 1839. Vulcaiuzation is basically a crosslinking reaction of double bonds in the latex structure with sulfur. The polymerization of butadiene with itself or with other vinyl monomers results in a material that like natural latex, still contains double bonds. Thus, synthetic rubber made from butadiene can be processed and vulcanized just like natural rubber. 

Natural latex is concentrated by three main methods centrifuging, evaporation and creaming electrodecantation once showed promise, but the output of latex concentrated by this method is now negligible. 

Synonyms Natural latex—milky fluid that consists of extremely small particles of rubber obtained from plants, principally from the Hevea brasiliensis (rubber) tree, dispersed in an aqueous medium. It contains a variety of naturally occurring substances in a colloidal suspension, including about 1% proteins (e.g., a-globulins, hevein), which are the allergenic fraction. ... 

Dry basis natural mbber compound recipe, in part by wt high ammonia natural latex mbber concentrate, 100.0 potassium hydroxide, 0.5 Nacconal 90F (alkylarenesulfonate (Allied Chemical Co.)), 1.0 zinc oxide, 3.0 sulfur, 1.0 ZMBT, 1.0 zinc die thyldithio c arb am ate (ZEDC) (trade names Ethazate... 

The first modem polyurethanes were developed in Germany in the late 1930s as attempts to produce polymer systems that would be useful as substitutes for natural latex rubber in automobile and truck tires, clearly in preparation for war. 

As for the mattress core, natural latex is the environmentally preferred stuffing, a rubber-tree product that can be sustainably sourced. Some mattresses are stuffed with a mix of natural and synthetic latex, as the latter substance is cheaper (although chemicals are added in the manufacturing process). Both choices are better than the polyurethane foam found in most conventional mattresses. Still other mattress cores have an innerspring system and batting, often cotton. In-nerspring mattresses are a popular crib choice some people think their firmness prevents SIDS. 

A condition of flow in which all elements of a fluid passing a certain point follow the same path, or streamline there is no turbulence. Also referred to as streamline flow . A dispersion (suspension or emulsion) of polymer in water. Latex rubber, a heavily cross-linked polymer solid, is produced either by coagulating natural latex or by synthetic means through emulsion polymerization. Example Latex paint is a latex containing pigments and filling additives. 

General comments on Protocols 1-7. A thick wall, natural latex rubber balloon (ca. 2 L) is used. A cryocool system is used for cooling. Commercial anhydrous ZnCI2 is dried under high vacuum at 100°C for 10 h over P205. This can be stored for use for at least ten days. 

Latex An emulsion of rubber or resin particles dispersed in an aqueous medium. Latex can be used to make plastic films and adhesives. Natural latex is derived from the sap of a rubber tree. Synthetic latex is manufactured in a number of different varieties from basic chemicals. 

There are two main types of coldseal adhesive and these are based on natural latex or synthetic polymers. They differ from pressure-sensitive adhesives in that they stick only to themselves. They are applied to form dry but gummy adhesive layers on flexible plastic films or paper and can be subsequently sealed together by pressure alone to form wrappers for food items and especially for confectionery. 

Frothing agent for adhesives based on natural latex, to be used in fabric/fabric lamination (shoe material). 

---