Synthetic natural rubbers cyclization

Synthetic polyisoprenes are superior to natural rubber in terms of consistency of properties. The are also freer of contaminants, and are preferred for applications that require lighter color, for personal care items and for derivatization to chlorinated and cyclized rubber products that are used in the adhesives and coatings industries. 

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. 

Solvent washing and abrading are common treatments for most elastomers, but chemical treatment is required for maximum properties. Many synthetic and natural rubbers require cyclizing with concentrated sulfuric acid until hairline fractures are evident on the surface. 

Establishments primarily engaged in manufacturing synthetic rubber by polymerization or copolymerization. An elastomer for the purpose of this classification is a rubber-like material capable of vulcanization, such as copolymers of butadiene and styrene, or butadiene and acrylonitrile, polybutadienes, chloroprene rubbers, and isobutylene-isoprene copolymers. Butadiene copolymers containing less than 50 percent butadiene are classified in Industry 2821. Natural chlorinated rubbers and cyclized rubbers are considered as semifinished products and are classified in Industry 3069. 

Natural and synthetic rubber and synthetic resins are soluble in organic solvents resulting in cements, resin solutions, or lacquers. In addition, there are many cellulose derivatives, such as nitrocellulose, ethyl cellulose, and cellulose acetate butyrate, used in preparing solvent-based adhesives. Solvent-hased adhesives are also prepared from cyclized rubber, polyamide, and polyisobutylene. Low-molecular-weight polyurethane and epoxy compounds can be used with or without solvent. On the other hand, high-molecular-weight types or prepolymers require solvent to make application possible. 

Binders of paints are normally vegetable oils, e.g., - linseed, dehydrated - castor, - soybean, ->tung and - oiticica oils as such (-xlrying oils) or in modified form (->alkyd resins). They are often combined with numerous synthetic resins. Natural resins (- resins, natural) are also applied in special applications where their high price is acceptable. Decorative - casein paints for plaster walls have lost importance. Chlorinated and cyclized - rubber are also in use (swimming pool coatings). 

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