Natural rubber derivatives

With the exception of some of the natural rubber derivatives these materials were available during the first deeade of this eentury and, together with celluloid, aetually completed the range of plastics materials then in eommercial use. In spite of being ousted from important markets they have continued to find use in specialised applications, details of which will be given in subsequent sections of this chapter. The historical significance of these materials was dealt with in the first chapter of this book. 

A number of other natural rubber derivatives may be prepared by addition reaction at the double bond. 

Leblanc JL (2010) Non-linear viscoelasticity of (unvulcanized) natural rubber, derived materials and compounds through large amplitude oscillatory strain (LAOS) testing. Rubb Chem Technol 83 65-96... 

Figure 11.15. Typical chemical groupings in a sulphur-vulcanised natural rubber network, (a) Monosulphide cross-link (b) disulphide cross-link (c) polysulphide cross-link (j = 3-6) (d) parallel vicinal cross-link (n = 1-6) attached to adjacent main-chain atoms and which have the same influence as a single cross-link (e) cross-links attached to common or adjacent carbon atom (f) intra-chain cyclic monosulphide (g) intra-chain cyclic disulphide (h) pendent sulphide group terminated by moiety X derived from accelerator (i) conjugated diene (j) conjugated triene (k) extra-network material (1) carbon-carbon cross-links (probably absent)...

Natural rubber displays the phenomenon known as natural tack. When two clean surfaces of masticated rubber (rubber whose molecular weight has been reduced by mechanical shearing) are brought into contact the two surfaces become strongly attached to each other. This is a consequence of interpenetration of molecular ends followed by crystallisation. Amorphous rubbers such as SBR do not exhibit such tack and it is necessary to add tackifiers such as rosin derivatives and polyterpenes. Several other miscellaneous materials such as factice, pine tar, coumarone-indene resins (see Chapter 17) and bitumens (see Chapter 30) are also used as processing aids. 

Non-elastomeric chemical derivatives of natural rubber are discussed in Chapter 30 in which chemically related naturally occurring materials such as gutta percha and balata are briefly considered. 

The chemistry and technology of natural rubber were considered briefly in Chapter 11. In this chapter some non-elastomeric derivatives will be reviewed. 

Mention may finally be made of graft polymers derived from natural rubber which have been the subject of intensive investigation but which have not achieved commercial significance. It has been found that natural rubber is an efficient chain transfer agent for free-radical polymerisation and that grafting appears to occur by the mechanism shown in Figure 30.8. 

DAVIES, B. L., and glazer, j., Plastics derived from Natural Rubber, Plastics Institute Monograph No. C8, London (1955)... 

Chemical nature Isolation of casein from milk Production of casein plastics Properties of casein Applications Miscellaneous Protein Plastics Derivatives of Natural Rubber Gutta Percha and Related Materials Shellac... 

Many other polymers compete with cellophane such as polyethylene which is extruded as a tough film or in greater thickness as a nonbreakable bottles. Vinyl products used in films are polystyrene, polyesters, and nylon. A chemical derivative from nature rubber, chlorinated rubber, gives films of extraordinary stretch ability. 

An example of a nonlinear polymer derived by cross-linking an initially linear polymer is afforded by vulcanized natural rubber. In the usual vulcanization procedure involving the use of sulfur and accelerators, various types of cross-linkages may be introduced between occasional units (about one in a hundred) of the polyisoprene chains. Some of these bonds are indicated to be of the following type ... 

An isomeric derivative of natural rubber produced by a variety of chemical treatments. The products are resinous and find application as reinforcing agents in natural rubber compounds (particularly in shoe soles) and as rubber-to-metal adhesives. 

An obsolete term for natural rubber. The India is not the present-day India but derives from the West Indies since some of the first commercial rubber was obtained from there in the eighteenth century. 

Quinone and some of its derivatives may be used in the non-sulphur vulcanisation of natural rubber. The best-known derivative is para-quinone dioxime used as a curing agent for butyl rubbers. 

This derivative of natural rubber produced by the action of hydrogen chloride (liquid or gaseous) found application as a transparent food packaging film, but has now been superseded by modem packaging materials such as PET. 

Synthetic rubber(s), 1 693, 21 761. See Ethylene-propylene polymers. See also Butyl rubber acetylene-derived sources, 1 228 synthesis of first butyl rubber after disruption of natural rubber supply in WW II, 4 433... 

Renewable raw materials are made or derived from short-term renewable sources (one to a few years or a few tens of years) such as plants, trees, wood wastes and other agricultural products. Not all these materials are necessarily biodegradable. Natural rubber, for example, comes from the latex of a tree (Hevea brasiliensis) and is not biodegradable. Renewable materials are often considered as opposites to fossil sources such as petroleum that are not renewable on a human timescale. On the other hand, some synthesized plastics such as certain polyesters are biodegradable. 

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