Natural rubber smoked sheet

Natural rubber (smoked sheet) Carbon black (HAF)... 

Neoprene W to steel Neoprene W to brass Neoprene W to stainless steel Neoprene W to aluminum Neoprene W to copper Natural rubber (smoked sheet) to steel... 

Natural rubber is a constituent of the latex of Hevea brasiliensis a tree grown in the tropics. The latex is present in laticiferous vessels and can be collected after incision of the bark. It contains about 30 % of rubber in form of small droplets and coagulates after the addition of acids. The coagulate is processed to bandlike sheets of raw" rubber (smoked sheets, crepes) which in the industry are heated with sulfur (vulcanization) to harden it. At present time about half of the rubber used in the industry is prepared from Hevea latex, the other half is of synthetic origin. 

Under different deformation conditions, natural rubber (NR) may exhibit predominant viscous flow, elastic or viscoelastic behaviour. Thus, the time for the movement of the NR molecular chains, i.e. relaxation time, is vastly affected by those deformation rate and NR types. The variation of NR types such as smoked rubber sheet, rubber blocks such as skim block, STR 5L and STR 20, is another factor that influences rheological properties and processing of NR due to their different Mooney viscosity, molecular weight distribution and gel content. Types of NRs are based on the different production processes of NR in which rubber smoked sheets are produced from NR in the latex form whereas block types are produced from various types of NR sources such as from latex in the case of STR 5L, from rubber scrap in the case of STR 20 and from skim latex in the case of skim block. 

In solid form, the natural rubber is graded according to the content of dirt remaining from the precipitation of latex at the plantation. Eight basic NR types have been traditionally recognized internationally. Only the so-called ribbed smoked sheets and the pale crepes are normally used for adhesives. The predominant grade system, the Standard Malaysian Rubber system, has been used since 1965. 

A grade of natural rubber inferior to estate brown crepe and formerly known as thick remilled brown crepe cuttings removed in the inspection of smoked sheet rubber are washed, creped and designated smoked blanket crepe . 

Raw rubber can be either natural or synthetic. The standard grades of natural rubber are smoked sheets and pale crepe. For high grade products, first grade smoked sheets, namely RMAIX or Pale Crepe, is used. Pale Crepe is practically colourless and is preferred in products where delicate colour, extreme whiteness or transparency... 

Natural Rubbers (NR). The chemical name for NR is polyisoprene, which is a homopolymer of isoprene. It has the cis-1,4 configuration. In addition, the polymer contains small amounts of non-rubber substances, notably fatty acids, proteins, and resinous materials that function as mild accelerators and activators for vulcanization. Raw materials for the production of NR must be derived from trees of the Hevea Brasiliensis species. NR is available in a variety of types and grades, including smoked sheets, air-dried sheets, and pale crepes. 

RSS Ribbed Smoked Sheet DPNR Deproteinized Natural Rubber. 

Resin, Phenoxy, P R D A 8060 Natural Rubber, Natural [Smoked Sheet, Series Of Additives) r, 631-1715... 

Creep rubber n. Natural rubber of a pale- to dark amber color prepared by coagulating natural-rubber latex with acid, then milling this coagulum into sheets. The other basic form of solid natural rubber (i.e., ribbed sheet) is prepared by drying the latex on rolls in the presence of smoke. 

The radiation cross-linking of natural rubber latex has been studied by a number of workers, and again it was found that the addition of carbon black appreciably reduces the dose required for cross-linking. A feature of the vulcanizates obtained using carbon black was that the electrical conductivity was 10,000 times lower than that of smoked sheet rubber... 

In Figure 8, the viscoelastic properties of natural rubber latex (Hartex 103 from Firestone Co.) and milled smoked sheet natural rubber were examined. Both natural rubbers have tan 8 peak maximum temperature at -58°C. However, the latex has higher room-temperature modulus than the milled natural rubber. Natural rubber latex based pressure-sensitive adhesives offer an advantage over solvent-based systems (milled smoked sheet) because of the molecular-weight difference between the two systems. The high-molecular-weight portion of natural rubber is insoluble in solvent and therefore cannot be used in solvent-based adhesives. Natural... 

In the case of the purified rubber the trisulphide retarded oxidation but with the smoked sheet (which because of the natural antioxidants present oxidized at a lower rate) the trisulphide was a pro-oxidant. A similar pro-oxidant effect was obtained with a peroxide-cured vulcanizate from purified natural rubber but this contained both a trisulphide and a fairly conventional amine antioxidant (N-isopropyl N -phenyl-p-phenylene diamine—actually better known as an anti-ozonant). Monosulphides (e.g. AiSAi) were less antagonistic in their effect. 

Further evidence that polysulphides reduce the efficiency of conventional antioxidants was obtained by studying the oxidation behaviour of a CBS-accelerated sulphur vulcanizate of RSSl smoked sheet natural rubber (Cunneen, 1968). As prepared the vulcanizate contained disulphide and polysulphide linkages. Treatment of the vulcanizate with triphenyl phosphine converted these linkages to the... 

A major dry natural rubber type is ribbed smoked sheet. For this the coagulum is passed between pairs of even-speed steel rollers that squeeze the water out. The final set of rollers has channels cut in them so that the sheet emerging from them has a ribbed surface. The ribbed surface facilitates drying. This rubber is dried in smokehouses. The ribbed sheets are hung over poles mounted on trolleys. Rubber tree wood fires produce the smoke, which dries the rubber and gives the rubber some age resistance from its components such as cresols. Drying takes 48 to 96 hours, with entrance temperatures at about 40 °C and exit temperatures at about 60 °C. Some ribbed sheet rubber is dried in hot air out of contact with smoke. This produces a lighter colored rubber, which commands a premium and is referred to as air-dried sheets. 

The process used to make rubber separators involves mixing precipitated silica, water, and natural rubber to create a thin film. The natural rubber is received in smoked sheets or slabs, and it is normally worked in various pieces of equipment so that the silica, laden with water, can be incorporated. This rubber, silica, and water mixture is then fed to an extruder to create a thin, uniform layer that is sufficiently malleable to be fed into a calendar stack, which has grooved voids in the roll that will create the rib structure. 

Natural Rubber. Natural rubber (NR), all cw-1,4-polyisoprene, is available as the natural latex, but the major raw material for PSAs is the recovered solid, or baled gum rubber. The principal types of NR used for PSAs are pale crepe or ribbed smoked sheet, which is less expensive but of darker color. The baled rubber must be masticated to lower its molecular weight before use. 

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