Natural rubber INDEX

Another term for plasticity retention index. Viscosity-Stabilised Natural Rubber... 

ISO 4660, Rubber, Raw Natural—Color Index Test, International Organization for Standardization, Geneva, Switzedand, 1991. 

Most ageing tests are carried out on vulcanised or thermoplastic compounds, but there has been a need to assess the oxidative effects of storage on natural rubber. Various accelerated procedures using ovens or infra-red lamps have been used with visual assessment of deterioration. A more satisfactory procedure based on the measurement of plasticity after oven ageing has been standardised as ISO 293033 and the result is known as the plasticity retention index. 

BS 903 Part A59.2, 1995. Methods using plastimeters - Determination of the plasticity retention index (PRI) of raw natural rubber. 

The choice of date range is arbitrary. The number of journal articles for each year was obtained from a search of electronic version of English-based polymer and polymer-related journals using the keywords polyolefin and blends. Within polyolefin keyword, the subkeywords used in the search were polyethylene (PE, LLDPE, LDPE, HDPE, UHMWPE, PE, etc.), polypropylene (PP, iPP, sPP, aPP, etc.), polybutene-1, poly-4-methylpentene-l, ethylene-diene monomer, ethylene-propylene-diene terpolymer, ethylene propylene rubber, thermoplastic olefins, natural rubber (NR), polybutadiene, polyisobutylene (PIB), polyisoprene, and polyolefin elastomer. For the polyolefin blends patent search, polymer indexing codes and manual codes were used to search for the patents in Derwent World Patent Index based on the above keywords listed in the search strategy. 

Solution adhesive is obtained from solid rubber obtained by coagulation of latex as acquired from the tree. The coagulation is effected by dilute aqueous solution of organic acids. The solid rubber can be graded in terms of dirt content, ash content, nitrogen content, and volatile matter. It can also be categorized by plasticity retention index and Mooney viscosity. To maintain uniformity it is necessary to choose solid natural rubber of known characteristics. 

Malaysian Rubber Producers Research Association, 1984. The Natural Rubber Formulary and Property Index. Imprint of Luton, England. 

Parth, M. Aust, N. Lederer, K. Distribution of molar mass and branching index of natural rubber from Hevea brasiliensis trees of different ages by SEC coupled with online viscometry. Macromol. Symp. 

Fig. 188. Dependence of the index of abrasion (v) of tread rubbers made from natural rubber with various antiaging agents on the testing temperature, a) Air b) nitrogen. 1) Without antiaging agents 2) neozone D 3) neozone D + flectol N 4) neozone D + MV 5) neozone D + 4010 6) santoflex AW.

Furthermore, the C=C bonds in the natural rubber structure might induce poor thermal and oxidative resistance in the natural rubber blends. Thus, Thawornwisit and coworkersproposed the preparation of hydrogenated natural rubber, which is one of the chemical modifications available to improve the oxidation and thermal resistance of diene-based natural rubber before blending with poly(methyl methacrylate-co-styrene). The poly(methyl methacrylate-co-styrene) was resistant to the outdoor environment and had excellent optical properties with a high refractive index, but it was extremely brittle and had low impact strength. Hydrogenated natural rubber could, however, be used as an impact modifier, as well as to improve its thermal and oxidative resistance for these acrylic plastics. 

Many years later Weber indicated that the natural rubber molecule was unsaturated since it reacted with bromine to give a material of empirical formula C5H8Br2. This clearly implied an addition reaction to a double bond. This was borne out by the more accurate and reliable iodine chloride method of Kemp in 1927 and the refractive index technique of Macallum and Whitby in 1924. 

V in a large range of velocities. The powCT index 0.55 is a characteristic of the natural rubber. 

Figure 7. Master curve, in log-log coordinates, regrouping all tfie adhesive rebound critical heights (balls and projectiles), which allows one to determine, firom its slope P, the index n characterizing the viscoelastic behavior of the natural rubber sample tested.

The phase contrast microscope is invaluable for examining other junctions formed between rubbers differing only in refractive indices. Figure 3 shows the junction between natural rubber and SBR. There is enough refractive index difference to show the bond line in the phase contrast microscope. Bond lines can be observed even when identical rubbers are used if they have been cured differently. For instance, one can see the bond between peroxide and sulfur cured natural rubbers. 

The effect is examined of tetramethyl thiuram disulphide (TMTD) on the heat ageing and oxidation of clay-filled NR, with reference to the plasticity retention index of NR, using thermal analysis and scanning electron microscopy test methods. The results showed that heat and oxygen resistant properties could be obtained when the clay-filled natural rubber compound was cured by semi-effective or effective curing systems, with 1.5 phr or 3.0 phr of TMTD. 3 refs. 

There is also a fourth division of Beilstein (systems 4721 -4877) that covers natural products of uncertain structure rubbers, sugars, and so on. These are treated in vols. 30 and 31, which do not go beyond 1935 and which are covered in the collective indexes. These volumes will not be updated. All such compounds are now included in the regular Beilstein volumes. 

---