Mastic solutions

Msstix, m. mastic (the resin), gum mastic, -braontwein, m. mastic (the liquor), -firnis, m. mastic varnish, -harz, n. mastic (resin). -Idtt, m. mastic (cement), -lack, m. mastic varnish, -losimg,/. mastic solution, mastizieren, v.t. masticate. 

The resin composition was indeed found to influence the ageing processes in mastic, the polymer fraction was shown to reduce the oxidation of triterpenoids (Figure 5.8). This was found for both natural ageing [33, 36] and artificial ageing. Because the polymer, a polymyrcene, contains many double bonds that can easily be oxidised [42], it might act as a radical stabiliser. The mastic samples shown in Figure 5.8 were obtained from three aliquots of the same mastic solution, the polymer part of the first aliquot was removed and added to the third. 

In a later article Zunz f has pointed out that there is no relation between the effect of the albumoses on mastic solutions and the effect on gold solutions. Heteroalbumoses and sjmalbumoses precipitate mastic turbidities, while other albumoses do not. On the other hand heteroalbumoses have a protective action on gold solutions. 

From what has been said it will be seen that the electric charge on the particles is not the only factor involved. For if this were the case both gold and mastic solutions should be affected in a similar manner, as they are both negative. Rather must the action be attributed to specific properties that have not yet been clearly explained. 

Another major area of use is in the field of adhesives. The main attractions of the material are the absence of a need for mastication, easy solvation of the polymer, which is supplied in a crumb form, the production of low-viscosity solutions and high joint strength. In conjunction with aromatic resins they are used for contact adhesives whilst with aliphatic resin additives they are used for permanently tacky pressure-sensitive adhesives. In addition to being applied from solution they may be applied as a hot melt. 

The hydrohalide is usually prepared by passing hydrogen chloride into a solution of masticated high-grade raw rubber in benzene at 10°C for about six hours. Excess acid is then neutralised and plasticisers and stabilisers are added. The benzene is removed by steam distillation and the product washed and dried. Alternatively the solution is cast on to a polychloroprene rubber belt, leaving a tough film after evaporation of the solvent. 

Chlorinated rubber is usually prepared by bubbling chlorine into a solution of masticated rubber in a chlorinated hydrocarbon solvent such as carbon tetrachloride. Hydrochloric acid is removed during the reaction. The solvent may be removed by vacuum or steam distillation or by precipitation of the derivative by a non-solvent such as petroleum. 

These polymers are very sensitive to mastication. Mastication decreases the solution viscosity and increases the ease of solution. Because the reactive sulphur linkages, rapid vulcanizing properties are obtained. On the other hand, the presence of thiuram disulphide improves the resistance of CR to dehydrochlorination. 

The most commonly observed effect of current flow is the development of alkaline conditions at the cathode. On bare metal this alkaline zone may exist only at the metal surface and may often reach pH values of 10 to 12. When the soil solution contains appreciable calcium or magnesium these cations usually form a layer of carbonate or hydroxide at the cathodic area. On coated lines the cations usually move to holidays or breaks in the coating. On failing asphalt or asphalt mastic type coatings, masses of precipitated calcium and magnesium often form nodules or tubercles several centimetres in diameter. 

In some cases adsorption of the ion resulting in precipitation may promote apparent hydrolysis, as instanced in the case of Fuller s earth (p. 187), thus if gum mastic suspension in water, a negative colloid, be floated on a solution of copper sulphate the copper ions will be adsorbed and the solution will be left feebly acid—a phenomenon noted by Spring (Bee. d. Trav. Ghim. d. Pavs-Bas, ly. 215, 1900). 

Fig. IS. Separation of the polymeric products obtained after masticating natural rubber containing 38.5% methyl methacrylate to 97% conversion (O) fractional precipitation by methanol from iOml of 1% benzene solutions (Q) fractional precipitation by acetone ...

Example 1. A dilute solution of gum mastic in alcohol is poured slowly into a large volume of water. A saturated solution of sulfur in alcohol is poured into water. 

Its only use in the arts, says Ure, is in the formation of a cement for joining broken china and glass, and which is prepared as followsTake isinglass, one ounce distilled water, six ounces boil these together down to three ounces add half that quantity of strong alcohol, seethe the mixture for. two or tliree minutes, and then strain it next add, while hot, first, half an ounce of milky emulsion of ammoniacum, and then five drachms of an alcoholic solution of resin mastic. This resembles an article sold as diamond oement. 

Thus, macroradicals have been obtained by stretching fibers (20), deforming plastics by compression (37), ball mill grinding (11), freezing and grinding of polymer solutions (10), ultrasonic irradiation (I), mastication (19), dispersion in a microblender (25), and other mechanical techniques (36). Many reviews on the formation of macroradicals by degradative processes have also been published (5, 12,13,16, 33). 

P roblem 3 How will you prepare the colloidal solutions of the following Arsenic sulphide, ferric hydroxide, gold, sulphur, silicic acid, carbon, iodine, mastic. (Meerut 2000)... 

Mastic sol It is a resin type hydrophilic colloid. Its colloidal solution is obtained when it is dispersed in only pure distilled water. As such it carries a very little charge, but when dispersed in acidic solution and alkaline solution, a positively charged and negatively charged sol, respectively is obtained. 

Rubber as the Disperse Phase. In polyblend systems, a rubber is masticated mechanically with a polymer or dissolved in a polymer solution. At the conclusion of blending, a rubber is dispersed in a resin as particles of spherical or irregular shape. We can further subdivide this system into three classes according to the major intermolecular forces governing adhesion (a) by dispersion forces—e.g., the polyblend of two incompatible polymers, (b) by dipole interaction—e.g., the polyblend of polyvinyl chloride and an acrylonitrile rubber (56), and (c) by covalent bond—e.g., an epoxy resin reinforced with an acid-containing elastomer reported by McGarry (43). 

In sulfuric acid production, acid brick lining of membrane coated mild steel tanks and reaction vessels is considered the most durable and versatile construction material for the sulfuric acid plant. Such linings wiil reduce the steel shell temperature and prevent erosion of the normally protective iron sulfate film that forms in stagnant, concentrated (oxidizing) sulfuric acid. Dilute (red uC ing) sulfuric acid solutions are very corrosive to carbon steel, which must be protected by impermeable (e.g., elastomeric) membranes and acid brick lining systems. Such acid brick linings often employ membranes comprising a thin film of Teflon or Kynar sandwiched between layers of asphalt mastic. 

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