Natural rubber chemical modification

Forms of BR and polyisobutylene. The properties of butyl rubber and polyisobutylene depend on their moleeular weight, degree of unsaturation, nature of the stabilizer incorporated during manufacture and, in some cases, chemical modification. It is common to produce halogenated forms of butyl rubber to increase polarity and to provide a reactive site for alternate cure mechanisms [6],... 

Improvement in the processing and vulcanized qualities of a range of systems have been reported over the past decades. Modification of natural rubber, due to work in the British Rubber Producers Research Association, yields some of the most striking applications of microgel. A detailed study at the MV Lomonosov Institute of Fine Chemical Technology, in Moscow, on the effect of microgels on mechanical properties of cis-polyisoprene and butadiene-styrene rubbers extensively illustrates the properties of blends from latex combination of microgel and conventional or linear systems.(31)... 

By using this method, the chemical shifts of the resonances in the spectra of a sulfur vulcanized natural rubber (Fig. 32 expanded aliphatic region in shown in Fig. 33 [top]) are assigned to various units of the polymer network, which arise from structural modifications induced by the vulcanization 194,196 200). Different sulfidic structures are found for unaccelerated and accelerated sulfur vulcanizations, respectively. With increasing amount of accelerator (as compared to the sulfur), the network structure exhibits less crosslinking, fewer main chain structural modifications, and fewer cyclic sulfide structures 197). 

The ability of a soap or surfactant to enhance the chemical stability of natural rubber latex was assessed by ascertaining its effect upon the mechanical stability of natural rubber latices whose stabilities had been reduced by various chemical modifications. Natural rubber latices of reduced stability were produced in three different ways as follows ... 

With the war years, polyvinyl chloride (PVC) resins came under study, and plasticized PVC compounds, based on these resins, became available as calendered sheet lining materials-the material of choice for stainless steel pickling and for chrome plating and other exposure employing mixtures of chemicals including such strong oxidants as nitric and chromic acid which rapidly attack natural rubber. (A higher temperature limit modification now seldom seen is PVDC, for which the continuous temperature limit is said to be 170°-180°F.)... 

In practice, the most important chemical modification of natural rubber is vulcanization. Vulcanization is applied for the modification of mechanical properties of natural rubber, mainly regarding the temperature range of elasticity, which is considerably extended. The process consists of a chemical reaction with sulfur (1-3%), which takes place at 130-145° C. Besides sulfur, a reaction at room temperature with S2CI2 is sometimes used for vulcanization. The reaction takes place as follows ... 

Polymer forming began with the chemical modification of natural polymers such as natural rubber vulcanization and cellulose acetylation. The first efforts to shape natural polymers and early synthetic ones into useful products such as textile fibers and films for packaging date from the middle of the 19 century. 

In the 1960s, carbon black-elastomer interaction was considered as the result of a chemical bonding (Bueche, 1961, 1960) between acidic surface functions and natural rubber alkaline moieties (Donnet and Heinrich, 1960 Le Bras and Papirer, 1983). So many studies have been conducted to increase carbon black activity by surface oxidation (Le Bras and Papirer, 1983) oxygen at high temperatures, H2O2, ozone, nitric acid. The type of oxidation used determines the number and the type of functions obtained it is interesting to underline that such chemical modifications are used at industrial scale for specialty carbon blacks (inks, pigments). 

Gopalan, N.K., Dufresne, A., Gandini, A., Belgacem, M.N. Crab shell chitin whisker reinforced natural rubber nanocomposites. 3. Effect of chemical modification of chitin whiskers. Biomacromolecules 4, 1835-1842 (2003)... 

The earliest applications of polymer chemistry involved chemical modification designed to improve the physical properties of naturally occurring polymers. In 1839, Charles Goodyear transformed natural rubber, which is brittle when cold and tacky when warm, to a substance that maintains its elasticity over a wider temperature range by heating it with sulfur (vulcanization). The first synthetic fibers— called rayons—were made by chemical modification of cellulose near the end of the nineteenth century. 

Nature already produces the desired structures, and isolation of these components mostly requires only physical methods without chemical modification. Examples comprise polysaccharides (cellulose, starch, alginate, pectin, agar, chitin, and inuUn), disaccharides (sucrose and lactose), and triglycerides, lecithin, natural rubber, gelatin, flavors and fragrances, etc. 

Recently, a patent application was filed on a method of chemical modifications of natural rubber and epoxidized natural rabber by alkyds made from palm... 

The progress of chemistry, associated with the industrial revolution, created a new scope for the preparation of novel polymeric materials based on renewable resources, first through the chemical modification of natural polymers from the mid-nineteenth century, which gave rise to the first commercial thermoplastic materials, like cellulose acetate and nitrate and the first elastomers, through the vulcanization of natural rubber. Later, these processes were complemented by approaches based on the controlled polymerization of a variety of natural monomers and oligomers, including terpenes, polyphenols and rosins. A further development called upon chemical technologies which transformed renewable resources to produce novel monomeric species like furfuryl alcohol. 

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