Melting point of SPS

Rgure 17.5 shows the dynamic storage moduli E of SPS and APS. The E of SPS and APS are equivalent below Tg. The E of APS steeply drops at Tg due to the start of the molecular motion, but the E of SPS is kept above Tg up to near the melting point of SPS, although E drops to about one-tenth of E of that below Tg. This thermal resistance is given by the crystallization of SPS the formation of crystallinity works as physical linkage, and the physical linkage prevents the mobilization of molecules above Tg. 

Sulfur crystallizes in at least two distinct systems the rhombic and the monoclinic forms. Rhombic sulfur, Sa, is stable at atmospheric pressures up to 95.5°C, at which transition to monoclinic sulfur, SP, takes place. Monoclinic sulfur is then stable up to its natural melting point of 114.5°C. The basic molecular unit of both of these crystalline forms of sulfur is the octatomic sulfur ring Other forms of sohd sulfur include hexatomic sulfur as well as... 

A product of still higher purity may be prepared by washing with sulphuric acid. 100 parts of dinitrophenol and 120 parts of sulphuric acid (sp. gr. 1.84) are agitated for 12 hr at room temperature. Then the sulphuric acid is filtered off and the dinitrophenol is washed with a small quantity of fresh sulphuric acid and finally several times with water. In this way the melting point of the product can be raised to 108.5°C. 

Ten milliliters of fuming nitric acid (sp. gr. 1.5) is added dropwise to a solution of 10 g. (0.054 mole) of dibenzothiophene (p. 101), in 80 ml. of glacial acetic acid at room temperature. The mixture is stirred for an hour and then poured into water. The precipitated solid is removed and extracted with hot ethanol until the melting point of the residue is about 180°. This residue is then recrystallized from benzene to give a 40% yield of product melting at 186°. The ethanol extraction removes dibenzothiophene sulfoxide also formed in 40% yield. 

Although the sp-hybridized carbon atoms are commonly found in acetylenes, nitriles, allenes, carbon dioxide, etc., heavy group-14 element analogs of these compounds are very rare [16, 17]. The first silicon compound with a formal s/i-silicon atom, trisilaallene 12, was synthesized as a dark green solid using two-step reactions from stable dialkylsilylene 13 [18] in overall 42% yield (Scheme 5) [19]. Trisilaallene 12 is sensitive to air but thermally rather stable, with a melting point of 198-200 °C. 

Figure 1. Rate of the hydrolysis of different aliphatic polyesters with a lipase from Pseudomonas sp. at different degradation temperatures. Left side correlation with the melting point of the polyesters right side correlation with the difference between melting temperature and degradation temperature...

The present paper is concerned with the melting points of covalent semiconductors with the tetrahedral coordination of atoms, in which the bonds are formed by electrons in the sp hybrid states. This extensive class of semiconductors can be divided into three groups normal ( filled up ), defect, and excess semiconductor phases [1]. The first group of confounds is characterized by the same number of atoms in the cation and the anion sublattices... 

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