Vulcanized gutta percha

Gutta percha objects were created from raw, untreated latex that was melted and molded, or from vulcanized gutta percha, which has most of the same properties as hard rubber. Molded gutta-percha was made into a staggering diversity of objects, including golf balls, jewelry, thread, tool and weapon handles, condoms, water pipes, buttons, and in dentistry as a base for dentures, as fillings, and as artificial teeth. The thread was woven into waterproof blankets, tents, and other fabrics, mosdy for use by the military. 

Meyer returned to sound thermodynamic analysis in the discussion of the dependence of the melting point on tension for lightly vulcanized gutta-percha. The classic curve is shown in Fig. 3.12. 

Rubber used in practical applications is crosslinked through disulfide (-S-S-) bonds, and is known as vulcanized rubber. Can you name another important class of polymers which are crosslinked through disulfide bonds Examine vulcanized rubber. How many individual strands does it comprise Are these strands of natural rubber or of gutta-percha What is the percentage (by weight) of sulfur incorporated into the polymer (The molecular weight of the sample is 1701 amu.) Does this classify as a low-sulfur polymer (<3%), a high-sulfur polymer (>10%) or in between ... 

Before 1800 Cotton, flax, wool, and silk fibers bitumens caulking materials glass and hydraulic cements leather and cellulose sheet (paper) natural rubber Hevea brasiliensis), gutta percha, balata, and shellac 1839 Vulcanization of rubber (Charles Goodyear)... 

These various operations, together with the vulcanization of gutta-percha, will now be described successively and in detail—premising that in this country tho manufacture is confined to two or three companies, which work the various patents secured from time to time by Mr, Hancock and others. A simple description of the manufacture,1 as conducted by the London Gutta-Percha Gompany, will, therefore, embrace all that is really important in the different operations. 1 ... 

In December, 1306, a patent was taken by Mr. Emory Rider of London, for improvements in the method of vulcanizing gulte-percba the principal novelty of which consists in the addition of one part of sulphur, or an equivalent thereof in some of its compounds, and one pari of litharge, to sixty-six parte of the gutta-percha, prior to the exposure of the latter to... 

Natural rubber is a polymer of isoprene- most often cis-l,4-polyiso-prene - with a molecular weight of 100,000 to 1,000,000. Typically, a few percent of other materials, such as proteins, fatty acids, resins and inorganic materials is found in natural rubber. Polyisoprene is also created synthetically, producing what is sometimes referred to as "synthetic natural rubber". Owing to the presence of a double bond in each and every repeat unit, natural rubber is sensitive to ozone cracking. Some natural rubber sources called gutta percha are composed of trans-1,4-poly isoprene, a structural isomer which has similar, but not identical properties. Natural rubber is an elastomer and a thermoplastic. However, it should be noted that as the rubber is vulcanized it will turn into a thermoset. Most rubber in everyday use is vulcanized to a point where it shares properties of both, i.e., if it is heated and cooled, it is degraded but not destroyed. 

Vulcanization of soft or India rubber was discovered by Charles Goodyear in 1839. He was followed by Nelson Goodyear, who patented the vulcanization of hard rubber in 1851. These processes involve the treatment of natural rubber with heat, sulfur, and various metallic compounds. The resultant material is stronger and more stable than raw rubber, while still retaining the desirable properties of elasticity and flexibility. It is also resistant to heat and does not melt like raw rubber or gutta percha. 

Gutta-percha (with or without the hyphen) is the hardened latex from a number of different trees found in Borneo, Sri Lanka, and Malaya. The name comes from the Malayan words for juice (gutta) and tree (percha). This viscous plant sap hardens quickly and, after vulcanization, looks and behaves like hard rubber. The term gutta percha has also been used to describe unvulcanized hard rubber, regardless of its origin. 

Polymers with unsaturated carbon chain backbone form another important class of macromolecules, many of the compounds from this class having properties of elastomers. The most common polymers from this class are obtained from 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene) and their derivatives. Natural rubber, which is poly(c/s-isoprene), as well as the natural polymers gutta-percha and balata also have an unsaturated carbon chain backbone. For many practical applications, the polymers from this class are subject to a process known as vulcanization, which consists of a reaction with sulfur or S2CI2, and leads to the formation of bridges between the molecular chains of the polymer. This process significantly improves certain physical properties of practical interest. A separate subclass of polymers with unsaturated carbon chain backbone is formed by polyacetylene. 

The polymer industry traces its beginning to the early modifications of shellac, natural rubber (NR — an amorphous c -l,4-polyisoprene), gutta-percha (GP — a semi-crystalline trfl i-l,4-polyisoprene), and cellulose. In 1846, Parkes patented the first polymer blend NR with GP partially co-dissolved in CSj. Blending these two isomers resulted in partially crosslinked (co-vulcanized) materials whose rigidity was controllable by composition. The blends had many apphcations ranging from picture frames, table-ware, ear-trumpets, to sheathing the first submarine cables. 

Fiber, vulcanized There are natural plastics such as gutta percha and shellac the synthetics include many such as nylon and phenolics. There has been, patented in 1871, one that seems to be between the two and is known as vulcanized fiber which is processed regenerated cellulose fibers, viscose rayon, etc. In the past, this material was popular but now it is almost obsolete. 

Chapter 8 deals with various reactions of polymers including those of natural and synthetic rubber. That includes vulcanization of rubber. While there are very many commercial applications of the cis isomer, gutta-percha utilization is limited to wire coatings, impregnation of textile belting, and as a component of some varnishes. Its use is limited, because it is considerably harder than natural rubber. 

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