Polyisoprenes latex

This product is an ultraviolet light absorber for use in polystyrene, unsaturated polyesters, coatings, varnishes, lacquers, and coatings based on epoxy or phenolic alkyds. It is also used in pressure sensitive adhesives, polymethylacrylate (fdm or sheeting), thermoplastic rubbers, polyisoprene latex and alcohol based cosmetics. 

FROM ISOPRENE MONOMER TO SYNTHETIC POLYISOPRENE LATEX AND ITS USES Henderson P Kraton Polymers (Rapra Technology Ltd.)... 

Latex mbber foams are generally prepared in slab or molded forms in the density range 64—128 kg/m (4—8 lbs/fT). Synthetic SBR latexes have replaced natural mbber latexes as the largest volume raw material for latex foam mbber. Other elastomers used in significant quantities are polychloroprene, nitrile mbbers, and synthetic i j -polyisoprene (115). 

A number of high molecular weight polyisoprenes occur in nature which differ from natural rubber in that they are essentially non-elastic. As with natural rubber they are obtained from the latex of certain plants but they differ in that they are either frani-l,4-polyisoprenes and/or are associated with large quantities of resinous matter. 

An alternative source of the frani-1,4-polyisoprene is balata, obtained from Mimosups balata, occurring in Venezuela, Barbados and Guyana. The latex is thin and may be tapped in the same way as natural rubber. 

The latex of the Sapota achras yields a thermoplastic material, chicle, consisting of about 17.4% hydrocarbon, 40% acetone soluble resin and 35% occluded water. The hydrocarbon appears to contain both trans- and c/s-polyisoprene. Although originally introduced as gutta pereha and natural rubber substitutes, deresinated chicle has become important as the base for chewing gum. Like other polyisoprenes, it is meeting competition from synthetic polymers. 

An alternative chewing gum base is obtained from jelutong, a mixture of polyisoprene and resin obtained from latex of the Dyera costulata. This tree is found in many countries but Borneo is the principal commercial source. At one time jelutong was an important rubber substitute and 40000 tons were produeed in 1910. Production in recent years has been of the order of 5000 tons per annum, mainly for chewing gum. 

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. 

Since 1960, the inner core has been made from c/5-poly-butadiene by the compression moulding technique. This replaced the earlier material made from a suspension of barytes or bentonite clay in water and glycerine or the winding of rubber threads made from t /5-polyisoprene, either from latex or a dry rubber compound. A typical thread recipe is given Table 4. 

The use of polyisoprene or butadiene-styrene latex with bentonite or chalk filler and polyoxypropylene as an additive has been used in a plugging solution for oil and gas wells [1042]. The solution can be pumped but coagulates within the formation at temperatures of 100° C within 2 hours. This causes a reduction in permeability. The formulation is particularly useful in deep oil deposits. 

Other polymeric binders, natural and synthetic, may be found as paints or varnishes in modern artworks and installations. Artists very easily adopt resins developed as industrial coatings or for specialized applications, and use them according to their creative needs. Natural rubber latex is a water dispersion of 1,4-ds-polyisoprene particles where pigments can be added to give coloured paints. By means of Py-GC/MS the presence of these paints can be easily assessed. As shown in Figure 12.13, the principal marker peaks in the pyrogram are those of isoprene, limonene and other cyclic dimers. 

The hard thermoplastic hydrocarbon obtained from the latex of Mimusops globosa. Balata has the same molecular formula as natural rubber (C5H8)n but has the tram polyisoprene structure whereas natural rubber has c/ s-structure. 

Improvement in the processing and vulcanized qualities of a range of systems have been reported over the past decades. Modification of natural rubber, due to work in the British Rubber Producers Research Association, yields some of the most striking applications of microgel. A detailed study at the MV Lomonosov Institute of Fine Chemical Technology, in Moscow, on the effect of microgels on mechanical properties of cis-polyisoprene and butadiene-styrene rubbers extensively illustrates the properties of blends from latex combination of microgel and conventional or linear systems.(31)... 

The formation of coagulum is observed in all types of emulsion polymers (i) synthetic rubber latexes such as butadiene-styrene, acrylonitrile-butadiene, and butadiene-styrene-vinyl pyridine copolymers as well as polybutadiene, polychloroprene, and polyisoprene (ii) coatings latexes such as styrene-butadiene, acrylate ester, vinyl acetate, vinyl chloride, and ethylene copolymers (iii) plastisol resins such as polyvinyl chloride (iv) specialty latexes such as polyethylene, polytetrafluoroethylene, and other fluorinated polymers (v) inverse latexes of polyacrylamide and other water-soluble polymers prepared by inverse emulsion polymerization. There are no major latex classes produced by emulsion polymerization that are completely free of coagulum formation during or after polymerization. 

Rubbers rely on fillers (both reinforcing and nonreinforcing) to obtain their properties. The curing system also produces a dirty-colored material. To color a rubber is difficult, and only a few basic colors are used. To obtain a transparent rubber, special latex or synthetic cis-polyisoprene must be used, and the use of a peroxide cure is normal. Polyurethanes can be colored any color, but the yellowing of aromatic systems must be taken into account. Aliphatic systems can give transparent nonyellowing systems. 

A number of plants and some trees contain a white, milky liquid that is released when the stem or bark is cut. The liquid is called a latex from the Latin meaning liquid. Common sources include dandelions, milkweed, goldenrod, and potted rubber plants. Rubber trees, from which substantial quantities of latex can be harvested, grow in some tropical areas of the world. A major constituent of this latex is a homopolymer of isoprene (2-methyl-1,3-butadiene), called polyisoprene. Polyisoprene, as well as a number of other elastomers, has a carbon-carbon double bond in every repeat unit. The properties of polyisoprene are the result of the presence of these double bonds. Just as stereochemistry plays a critical role in both proteins and polysaccharides, we will see its importance here. 

IP-PP and DMA-PP can yield volatile C3 hemiterpenes. At the other extreme, extensive polymerization of the C3-pyrophosphates (with release of pyrophosphate, PP ) yields the formation of the plant latex polymers such as eis-polyisoprenes (rubber) and trans-polyisoprenes (gutta-percha). In between these extremes, a variety of monoterpenes, sesquiterpenes, triterpenes and C3() carotenes derive from these C3-pyrophosphate precursors. 

NOTE Ibtals for plastics are for those products listed and exclude some small-volume plastics. Synthetic rubber data include Canada. Dry-weight basis unless otherwise specified Density 0.940 and below " Data include Canada from 2001 Density above 0.940 Data include Canada from 1995 Data include Canada from 2000 Data include Canada from 1994 Includes styrene-butadiene copolymers and othm styrene-based polymers Unmodified Includes butyl styrene-butadiene rubber latex, nitrile latex, polyisoprene, and miscellaneous others. SOURCES American Plastics Council, International Institute of Synthetic Rubber Producers. 

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