Sulfur polymer

Sulfur Polymer Cement. SPC has been proven effective in reducing leach rates of reactive heavy metals to the extent that some wastes can be managed solely as low level waste (LLW). When SPC is combined with mercury and lead oxides (both toxic metals), it interacts chemically to form mercury sulfide, HgS, and lead sulfide, PbS, both of which are insoluble in water. A dried sulfur residue from petroleum refining that contained 600-ppm vanadium (a carcinogen) was chemically modified using dicyclopentadiene and oligomer of cyclopentadiene and used to make SC (58). This material was examined by the California Department of Health Services (Cal EPA) and the leachable level of vanadium had been reduced to 8.3 ppm, well below the soluble threshold limit concentration of 24 ppm (59). 

Sulfur polymer cement shows promise as an encapsulation and stabilization agent for use with low level radioactive and mixed wastes. Use of SPC allows accommodation of larger percentages of waste than PCC. As of this writing (1997), SPC-treated waste forms have met requirements of both the Nuclear Regulatory Commission (NRC) and the Environmental Protection Agency (EPA). 

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 ... 

BNL claims the following advantages of sulfur polymer cement ... 

In some well-known transformations involving inorganic ring systems, biradicals act as reaction intermediates that are sufficiently persistent to be detected by EPR spectroscopy (see Section 3.6). For example, the polymerisation of cyclo-Sg to form the helical sulfur polymer Soo (plastic sulfur) occurs via the... 

Asphaltene Structure by Chemical Methods. The concept of asphaltenes being a sulfur polymer of the type ... 

Figure 2 Partial pressure of sulfur polymers as a function of temperature. The numbers refer to the number of atoms in the polymer.

Since selenium shares to a certain extent similar chemical properties with sulfur, polymers containing selenium in the backbone are conceivable. The formation and thermal properties of poly(selenoformaldehyde) have been reported in literature [3]. 

Oxybis(benzene-sulfonyl hydr azide) OBSH 155-160 125 N2 Water, aromatic sulfur polymer Azocel (Fairmount) OBSH (Dong Jin) Celogen OT (Uniroyal) Unicel OT (Dong Jin) Santechem (Santech)... 

Polymeric sulfur is produced commercially as insoluble sulfur (IS) and is used in the rubber industry [56] for the vulcanization of natural and synthetic rubbers since it avoids the blooming out of sulfur from the rubber mixture as is observed if Ss is used. The polymeric sulfur (trade-name Crys-tex [57]) is produced by quenching hot sulfur vapor in liquid carbon disulfide under pressure, followed by stabilization of the polymer (against spontaneous depolymerization), filtration, and drying in nitrogen gas. Common stabilizers [58] are certain olefins R2C=CH2 like a-methylstyrene which obviously react with the chain-ends (probably -SH) of the sulfur polymer and in this way hinder the formation of rings by a tail-bites-head reaction. In this industrial process the polymer forms from reactive small sulfur molecules present in sulfur vapor [59] which are unstable at ambient temperatures and react to a mixture of Ss and on quenching. 

The main chemical characteristic of tire chips and tire shreds is their nonreactivity under normal environmental conditions. The principal chemical component of tires is a blend of natural and synthetic rubber, but additional components include carbon black, sulfur, polymers, oil, paraffins, pigments, fabrics, and bead or belt materials. 

Dodgson K, Heath BT, Semlyen JA. Equilibrium ring concentrations and the statistical conformations of polymer chains part 15. Large cycHcs in liquid sulfur. Polymer. 1999 40 3995-3999. 

Ciassification Organo-sulfur polymer Uses Precipitant for removal of heavy metals from process wastewater, ground waters, and other polar soivs. stabilizer for detoxification and stabilization of heavy metals in contaminated solids, such as soils, sludges, ash and sediments... 

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