Guttapercha

Analysis of ebonite is more difficult than that of ordinary vulcanised rubber, as it is less readily attacked by solvents the sample for analysis should be finely powdered. The determinations of moisture, ash, sulphur, etc., are made as in manufactured rubber the extraction with acetone should be prolonged, sometimes to 1-2 days, to be complete. The residue insoluble in acetone is extracted first with epichlorhydrin for 3 hours to remove resins insoluble, or almost so, in acetone (copal, mastic, amber) and then with pyridine as indicated for manufactured rubber next comes the treatment with alcoholic potash to dissolve any brown factis present. The residue from this last treatment comprises the pure rubber, the sulphur combined therewith and the mineral matter in one part of it the ash and the sulphur of the ash are determined, and in another the total sulphur, the sulphur united with the rubber being obtained by difference the pure rubber is then calculated by difference. 

Guttapercha consists essentially of solid hydrocarbons (gutta) and resinous matters (fluavil, albane) and may contain also various impurities. In the raw state it is in masses or loaves of different shapes and sizes its colour is from dirty white to reddish brown and it has a peculiar odour D -= 0 96-1 it is not elastic, but is flexible and plastic, its plasticity increasing at about 60-70° C. it melts at about 120° and decomposes at a higher temperature. It is an excellent electrical insulator. 

It is insoluble in water and partially soluble in anhydrous alcohol or ether it dissolves in benzene, carbon disulphide or chloroform and, less easily, in petroleum ether. 

Insoluble Impurities.—From 1 to 2 grams of the substance, previously dried, are heated with about 100 c.c. of chloroform in a reflux apparatus on a water-bath, the liquid being afterwards filtered—preferably through a glass-wool filter, previously tared—and the insoluble residue washed with chloroform, dried and weighed. 

Resins.—The solvent is distilled from the filtered solution of the preceding determination, the residue—consisting of the resins—being dried and weighed. 

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Examine structures of the different forms of rubber provided. Which is natural rubber and which is guttapercha How many monomers are in each strand ... 

The infrared spectra of hevea (natural rubber), balata (or guttapercha), the latter both in the crystalline (a) and the amorphous forms, and of synthetic polyisoprene are compared in Fig. 32. The hevea and balata (amorphous) spectra offer calibrations for cfs-1,4 and irans-1,4 structures, respectively, in the synthetic polymer. Owing to the presence of the methyl substituent, however, the spectral difference between the as and trans forms is slight both absorb at about 840... 

Unlike polybutadiene, polyisoprene prepared at low temperatures shows little or no inclination to crystallize either on stretching or cooling. This may seem surprising in view of the even greater preponderance of trans-1 4 units in polyisoprene than in poly butadiene. The explanation for the contrasting behavior in this respect between low temperature synthetic polyisoprene, on the one hand, and guttapercha and low temperature polybutadiene, on the other, probably is to be found in the appreciable occurrence of head-to-head and tail-to-tail sequences of 1,4 units of the former. 

When we compared the viscosities of solutions of natural rubber and of guttapercha and of other elastomers and later of polyethylene vs.(poly)cis-butadiene, with such bulk properties as moduli, densities, X-ray structures, and adhesiveness, we were greatly helped in understanding these behavioral differences by the studies of Wood (6) on the temperature and stress dependent, melting and freezing,hysteresis of natural rubber, and by the work of Treloar (7) and of Flory (8) on the elasticity and crystallinity of elastomers on stretching. Molecular symmetry and stiffness among closely similar chemical structures, as they affect the enthalpy, the entropy, and phase transitions (perhaps best expressed by AHm and by Clapeyron s... 

Safety Fuse invented by W. Bickford (See Vol 2 of Encycl, p B112-L) and in 1840 the Bickford fuse was adopted by the English military authorities. In 1836 a factory was started in US, in 1839 in France, and in 1844 in Germany. Before 1840 guttapercha-covered fuse had been adopted for blasting under water. Various modifications have since been invented, including fuse cased in metal Colliery Fuse (patented in 1886 by Sir G. Smith), which... 

Goodyear Powder. Black Powder, patented in England in 1865, contd saltpeter, sulfur, charcoal, and a small quantity of caoutchouc or guttapercha... 

Guttapercha (Gummi plasticum or Isonandra gutta), (C10H10)2. A group of hydrocarbons (such as fluavil,. alban) with volatile oil. It consists of purified and coagulated milky exudates of various trees of Palaquium species, native to S. America Asia, colorless rubber-like masses, sticks or sheets,... 

Natural rubber and guttapercha consist essentially of polyisoprene in a s-1,4 and trans-1,4 isomers, respectively. Commercially produced synthetic polyisoprenes have more or less identical structures but reduced chain regularity, although... 

Natural rubber (NR) and guttapercha consist essentially of polyisoprene in cis-l, 4 and trans-1,4 isomers, respectively. Commercially produced synthetic polyisoprenes have more or less identical structure but reduced chain regularity, although some may contain certain proportions of 1,2- and 3,4-isomers. Microstructure differences not only cause the polymers to have different physical properties but also affect their response to radiation. The most apparent change in microstructure on irradiation is the decrease in unsaturation. It is further promoted by the addition of thiols and other compounds.130 On the other hand, antioxidants and sulfur were found to reduce the rate of decay of unsaturation.131 A significant loss in unsaturation was found, particularly in polyisoprenes composed primarily of 1,2- and 3,4-isomers.132,133... 

Anhydrous hydrofluoric acid is so hygroscopic that H. Moissan said that he found it could be kept in the anhydrous condition only with the greatest difficulty. G. Gore, and T. E. Thorpe and F. J. Hambly recommended keeping anhydrous acid in platinum bottles with a ground platinum plate sealed with paraffin wax, and held in place by a elamp. This plan is too expensive for ordinary work, and ceresine wax bottles are generally used. For transport, the commercial acid is bottled and sealed in lead, guttapercha, paraffin, or ceresine wax vessels. The acid attacks vulcanized caoutchouc.5... 

Cord and thread are likewise manufactured by means of a stamp, bearing a number of close parallel sharp edges, which are brought down upon a sheet of guttapercha so as to out it nearly through in a series of corresponding parallel lines. The. narrow slips are then severally tom off, and polished up by hand for ubs,... 

By mixing only two per cent, of chloride of sulphur, or ouly fifteen per cent, of the other substances, with the sirupy solution of gutta-percha, a compound is obtained which does not materially differ from guttapercha in Ite properties. 

Fig. 4.18. Proton-decoupled 13C NMR spectra (22.63 MHz 100-150 mg/ mL deuteriochloroform) of guttapercha (trans-) (a) and natural rubber (m-polyisoprene) (b) [73 i].

The members of this family are mostly tropical with a few temperate representatives. Several economic products come from the family the latex is used in chewing gum edible fruits, oils, guttapercha, and timber are also produced. A proteinaceous sweetener several times sweeter than sugar is also known from the family. 

A whole loaf is weighed, coated with either molten butter or a guttapercha varnish and immersed in a vessel full of water the water... 

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