Oxidation mastic

The vulcanization recipe wasi EPDM 100, stearic acid 1.0, zinc oxide 5 0, accelerator M 0.5, TMTD 1.5, HAF 50, sulfur 1.5 phr. Peroxide-curing of E-P copolymers was carried out with a modified procedure of (6) EPR 100, dicumyl peroxide 3, zinc oxide 3, TMTD 0.5, HAF 50, sulfur 0.2 phr, the mixture being masticated for 20 minutes at 0-50°C and cured at lb0°G. 

Dammar resin was introduced into Europe in the nineteenth century, mainly as a paint varnish It is still used today since it has good optical properties and low acidity. It is derived from various species (the genus Hopea and Shorea of the Dipterocarpaceae family). It is characterised by tetracyclic triterpenoids of the dammarane series and contains minor amounts of pentacyclic triterpenoids of the series of olanane, ursane and hopane. It also contains a polymeric fraction named polycadinene or [S-resene. Dammar resin triterpenoids undergo oxidation with ageing, as described for the components of mastic resin. 

Figure 5.7 GALDI mass spectra of mastic. Commercially available mastic (a) in an advanced state of oxidation as can be seen by comparison with really fresh mastic a few days after harvesting (b). As with dammar, oxidation and degradation progress quickly in both light and darkness. The same mastic as in (b) is depicted after natural ageing in the dark after 7 weeks (c), and in a window after 7 weeks (d) and 42 weeks (e)...

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. 

Figure 5.8 GALDI mass spectra of mastic with variable amounts of polymer, artificially aged for 880 h (36] (a) without polymer (b) normal mastic and (c) with added polymer. Oxidation and decomposition is enhanced with lower amounts of polymer, thus the mastic polymer retards oxidation of the triterpenoids...

UV-filtered light, as in a museum, effectively reduces the amount of oxidation to almost the same level that occurs in darkness. The polymer fraction of mastic was found to reduce the degree of oxidation in the material, possibly by acting as a radical scavenger. 

Mastication which is carried out at temperatures exceeding 115 °C. In hot mastication, the plasticising effect results from oxidative reactions. See Cold Mastication. 

Ablative mastics absorb heat as they lose mass through oxidative erosion... 

Solid-state chemical oxidation technology is generally applied using H H Eco Systems, Inc., Microenfractionator technology or using a masticator. According to vendor information... 

There are some facts to support a theory that effective quenching gases can be formed from the high temperature reaction products of the mastic, as, for example, hydrochloric acid and antimony oxide to form antimony oxychloride. The Department of the Army, Office of Quartermaster General (1), reports that combination of antimony oxide and hydrochloric acid at flame temperatures is more efficient in extinguishing a fire than either component alone. 

Blue Stars. Rub fine and mix 20 parts of chlorate of potassium, 11 of sulphur, 14 of cupric oxide, and 1 of mastic. 

Completion of the reaction by transfer of a proton from the solvent to the carbanion will then give a product (3a -f- 3b) of composition corresponding to thermodynamic equilibrium of the anionic species. That this approximates closely to an equilibrated mixture of the alcohols has been confirmed by subjecting some steroid alcohols to equilibration with alkoxide ions, under conditions sufficiently Mastic to allow thermodynamic equilibrium to be attained through a reversible oxidation/reduction process. Reduction of steroidal 20 ketones is of considerable interest in providing a mixture of epimers, each present in considerable proportion. The reduced mixture contains a modest preponderance of the 20a-epimer [34], although recent experiments [34M] confirm indications from molecular models that the 20/ -alcohol is the more stable. Further work is needed to clarifythis situation (see alsop. 139). 

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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