Modified Natural Rubber

Over the years, natural rubber has been modified in many ways. One of these was constant viscosity rubber, described earlier. Some of these modifications, such as chlorinated rubber, have been successful for a while but were then superseded by other materials. Others are produced in small volumes and, at times, stocks may be non-existent. A number of modified natural rubbers have been produced in the last decade, and the presumption is they may still be obtained. 

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Gazeley. K.F. and Mente, P.G., Pressure-sensitive adhesives from modified natural rubber latex. Adhesives, Sealants and Encapsulants Conference, Kensington, London, 5th November, 1985. 

The third and newest modified natural rubber available is epoxidized natural rubber (ENR). This modification was actually discovered as early as 1922 (50), although the elimination of ring opening and side reactions to give a purely epoxidized material took another 50 years or so to achieve (51). The resulting polymer is a new material, with properties totally different from natural rubber, as indicated in Table 5. 

Polystyrene-modified natural rubber PP/natural rubber (288)... 

As natural rubber is a product of nature, its properties are determined by the biochemical pathway by which the polymer is synthesized in the plant. In the case of natural rubber the polymerization process cannot be tailored like that of synthetic rubbers. The only option to modify natural rubber is after it has been harvested from the tree. The important modified forms of natural rubber include hydrogenated natural rubber, chlorinated natural rubber, hydro-halogenated natural rubber, cyclized natural rubber, depolymerised liquid natural rubber, resin modified natural rubber, poly(methyl methacrylate) grafted natural rubber, poly(styrene) grafted natural rubber, and epoxidized natural rubber [33,34]. Thermoplastic natural rubber prepared by blending natural rubber and PP is considered as a physically modified form of natural rubber. 

C.S.L.Baker, Modified natural rubber, in Anil K. Bhowmick and Howard L. Stephens eds.. Handbook of Elastomers - New Developments and Technology, Marcel Dekker Inc., New York, pp.31 - 33,1988. 

Among the particulate organic fillers, wood meal is the most important material for use in thermoplastics, in particular PP. For curable molding compounds, powdered cellulose is also in this category. These finely powdered materials are actually fibrous, finely ground and specially conditioned products based on spruce or beech wood or cotton. Others include wood granulate, sawdust, shell and seed meal and, already mentioned in relation to impact modifiers, natural rubber. 

When a modified natural rubber is compounded, an amount of a modified natural rubber is preferably more than 30% by weight in order to obtain significant effect of improvement in grip performance. On the other hand, an amount of a modified natural rabber is preferably 15-85% by weight when used for a sidewall in order to allow the formation of an appropriate sea-island structure with other rabber as NR, and thereby improve crack resistance properly of the tire compound. 

RouUly A., Rigal L., Gilbert R.G., Synthesis and properties of composites of starch and chemically modified natural rubber, Polymer, 45, 2004, 7813-7820. 

Strength and Durability of Natural Rubber and Chemically Modified Natural Rubber... 

Strength and Durability of Natural Rubber and Chemically Modified Natural Rubber 169 Tearing Energy atdc/dN 2 x 10 cm/ vs Strain... 

S. Chitrattha, T. Phaechamud, Oxygen transmission of modified natural rubber, poly (lactic acid) and chitosan porous structures for wound dressing, Asian Journal of Pharmaceutical Sciences, ISSN 1818-0876 (November 24, 2015). Available online http //dx.doi. org/10.1016/j.ajps.2015.11.064. 

The influence of dichlorocarbene modified natural rubber (DCNR) on the rheological behaviour of blends based on NR and hydrogenated nitrile rubber (HNBR) was studied.The NR used in this study was ISNR 5 grade from India. The HNBR used was a Zetpol 2010 grade (Nippon Zeon, Japan) with... 

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