Sulfur plastic

Amorphous or "plastic" sulfur is obtained by fast cooling of the crystalline form. X-ray studies indicate that amorphous sulfur may have a helical structure with eight atoms per spiral. Crystalline sulfur seems to be made of rings, each containing eight sulfur atoms, which fit together to give a normal X-ray pattern. 

Sulfur has a striking ability to catenate, or form chains of atoms. Oxygen s ability to form chains is very limited, with H202, 03, and the anions 02, 022-, and OG the only examples. Sulfur s ability is much more pronounced. It appears, for instance, in the existence of Ss rings, their fragments, and the long strands of plastic sulfur that form when sulfur is heated to about 200°C and suddenly... 

Because of the conversion of orthorhombic sulfur to monoclinic form, the above values of melting points are difficult to observe, as the resulting allotropic mixture melts at only 115 C. Amorphous or plastic sulfur can be produced through the rapid cooling of molten sulfur. X-ray crystallographic studies show that the amorphous form may have a helical structure with eight atoms per turn. This form is metastable at room temperature and gradually reverts back to crystalline within hours to days but this conversion can be rapidly catalyzed. 

Some elements also exist in amorphous forms. For example, charcoal is an impure, amorphous form of carbon. When sulfur is heated to its boiling point and cooled quickly, an amorphous form called plastic sulfur forms. It has the formula S, and is often called polymeric sulfur. ... 

Thermodynamically stable sulfur forms deep yellow, nonodorous orthorhombic crystals with a space group Fddd-D, containing 16 molecules, i.e., 128 atoms in the unit cell. It has a density of 2.069 gm/cm and is well soluble in CS2. Its molecular unit is Sg, cyclooctasulfur, a crown-shaped molecule with a symmetry of i>4d. The pale flowers of sulfur, prepared by alchemist by distillation, are insoluble in CS2, and the structure is not yet fully understood. Another form, plastic sulfur, is obtained by melting sulfur to about 180°C, where it forms as highly... 

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... 

Long chains which are polymers of small molecules, e.g. plastic sulfur composed of polymers of S8 units with variable chain lengths, and red phosphorus which is a P4 polymer. 

Test Road Paved with Plasticized Sulfur", Chemical and Engineering News, (1980), 58 (35), 25. 

Rapidly quenched, pure elemental sulfur is extremely plastic (6) This plastic sulfur with its polymeric structure has tensile qualities lacking in the crystalline form, but... 

Bordoloi, . K. Pearce, E. M. "Plastic Sulfur Stabilization by Copolymerization of Sulfur with Dicyclopenta-diene" ADV. CHEM. SER. 1978, 165, 31. 

In some systems, the same polymer may be produced from different monomers, e.g., plastic sulfur can be formed by polymerizing SB as well as S8 molecules. In such systems, a polymer may be stable with respect to one monomer but labile with respect to another one. For example, linear siloxane (-Me2SiO-) , which could be formed from the cyclic tetramer (-Me2SiO-)4, decomposes into the cyclic trimer (-Me2SiO-)3 and the reaction 3 (-MegSiO-)4-> 4 (-Me2SiO-)3 proceeds, therefore, through a polymer intermediate. 

Lee R. Summerlin, Christie L. Borgford, and Julie B. Ealy, "Plastic Sulfur," Chemical Demonstrations, A Sourcebook for Teachers, Vol. 2 (American Chemical Society, Washington, DC, 1988), p. 53. 

A FIGURE 19.11 Effect of temperature on the properties of sulfur, (a) Fluid, straw-colored liquid sulfur at about 120°C. (b) Viscous, reddish brown liquid sulfur at about 180°C. (c) Plastic sulfur, obtained by pouring liquid sulfur into water. Plastic sulfur is unstable and reverts to rhombic sulfur on standing at room temperature. 

Rhombic sulfur is yellow and quite stable. Monoclinic sulfur is orange and less stable than rhombic sulfur. Plastic sulfur is almost black and slowly reverts to rhombic sulfur. 

Sulfur has three solid allotropes, two different crystalline forms based on small Ss molecules called rhombic and monoclinic sulfur and a 3rd form of long chain (-S-S-S- etc.) molecules called plastic sulfur. 

Sulfur, modified in its structure so as to become plastic, presents other problems as it can be a very ductile material. Reinforcement in the sense of load sharing may be effected by incorporating relatively ductile thermoplastic fibers. There is a commercial interest in using polypropylene fibers, and Bennett (10,11) has patented a process whereby woven polypropylene fibers are impregnated with asphalt or bitumen and then are coated on at least one side with a sulfur composition. The plasticized sulfur coating sticks to the base and makes the laminate flexible, weather resistant, and light reflecting. 

Plastic Sulfur Stabilization by Copolymerization of Sulfur with Dicyclopentadiene... 

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