Para rubber

Hevea rubber from uncultivated trees growing in the Amazon Valley of Brazil and exported from Para, a town at the mouth of the river. Para rubber was the best variety of all wild rubber but the advent of plantation rubber steadily reduced its importance until it is now of no significance in world rubber production. 

Weir, J. R., Pathological Survey of the Para Rubber Tree (Hevea brasiliensis)... 

Gramiccioni et al. [187] reported the determination of residual ethylene oxide in sterilized polypropylene syringes and in materials such as plasticized PVC, polyurethane, and para rubber. The sterilized object was cut into small pieces, weighed, and placed into a flask containing N,N-dimethylacetamide (DMA). The flask was capped and shaken to make the sample homogeneous. After 24 hr it was shaken again and a sample was... 

Properties A translucent material with an elastic texture like para rubber. Strongest, quickest, and most waterproof explosive. It has an extremely high velocity and is rated at 100 per cent strength. It is sometimes sold under the name, Torpedo Explosive No. 1. Rate of detonation 7800 m/sec. (d = 1.63). 

Coagulation of the Latex.—Pure rubber or caoutchouc is an emulsion colloid and in most cases is held in emulsion by the protective action of other colloids, principally proteins. The breaking up of the emulsion with the coagulation of the caoutchouc depends thus upon the removal or destruction of the protective colloids. This is accomplished by different means. The latex of the para rubber from the Amazon is coagulated by heat and smoke, while the latex from the same species of tree on the plantations of the Malay States is usually coagulated by treatment with acid. Boiling of the latex, the addition of formaldehyde, and simple dilution with water are other methods in use. Enzymes are also present associated with the protective colloid proteins but their function seems not to be connected with the coagulation of the caoutchouc. 

Ramsay grease 25 6 pts. vaseline 1 pt. paraffin wax 6 pts. Para rubber General work... 

Assun9ao, F.P., Bentes, M.H.S., and Serruya, H., A comparison of the stability of oils from Brazil nut, Para rubber and passion fruit seeds (Bertholletia excelsa, Hevea brasiliensis, Passiflora edulis), J. Am. Oil Chem. Soc., 61, 1031-1036, 1984. 

R. are systematically classified into "natural rubber and synthetic rubber. In 1994, the world market for R. amounted to a production volume of ca. 14500000 t, of which ca. 9 000 0001 were synthetic R. and 5 400000 t natural R. from the para rubber tree (Hevea brasilien-sis) . 

Assuming that the parabolic dififusion law (Q IQ oof = DtlnP applies, the slope of the curve log Q 20) versus 1/T (T denotes °K.) gives an activation energy of 6900 cal./moL, a figure which may be compared with 6300 caL/atom for He-rubber to 11,900 cal./moL for Ng-neoprene. Smoked rubber, para-rubber, and pale crepe rubber similarly gave values of the activation energy of 7000, 9800 and 9600 cal./mol. of water respectively. 

Ravindran, V. and Ravindran, G. (1988) Some nutritional and anti-nutritional characteristics of para-rubber Hevea brasiliensis) seeds. Food Chem. 30, 93-102. 

An elastomer may be defined as a natural or synthetic material that exhibits the rubberlike properties of high extensibility and flexibility. Although the term rubber originally meant the TS elastomeric material obtained from the para rubber tree (Hevea braziliensis) it now identifies any thermoset elastomer (TSE) or thermoplastic elastomeric (TPE) material. Such synthetics as neoprene, nitrile, styrene butadiene, and butadiene are now grouped with natural rubber. 

Nakayama K, Usui T, Hiraishi S, Onosato K 1972 Pulping of para rubber tree. Jpn Tappi 26 323-326... 

Heat and smoking employed by the natives for preparing Para rubber. 

The objections to be raised against the first and third methods, viz, heating and smoking, and evaporation, are that many of the undesirable constituents such as dirt, bark, resin, protective colloids, etc., are left in the coagulant, caoutchouc. Some of these substances can be removed, of course, by subsequent treatment such as grinding and washing, drying in air or vacuo, but mineral matter, resins, and proteins still remain and cannot be eliminated except by expensive processes. It must be confessed, however, that Para rubber obtained by the natives of Brazil is superior to that made by the most scientific methods yet devised on plantations. It is a matter not yet decided whether the superiority of Para rubber is due to the method, or to the inherent qualities of the latex. 

Parakautschuk Hevea brasiliensisi Euphorbiaceae) para rubber... 

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