Thermal behavior

The thermal decomposition of the sulfur allotropes has been studied extensively by Steudel et al. [55]. 

S7 cycZo-heptasulfur is the least stable of all sulfur allotropes. After 2 h at 20 °C a sample of y-S7 had decomposed to a mixture of Sg and S containing only trace amounts of S7. After 4 days at 20 °C (in the dark) the decomposition was complete and yielded 81% S and 19% Sg [106]. The melting of y-Sj at 39 °C is reversible, but on further heating the melt polymerizes exothermically at 70-110 °C followed by the exothermic depolymerization of Sqo to the equilibrium melt in the region above 115 °C [55]. 

Sg below 96 °C, cycZo-octasulfur is stable as orthorhombic a-Sg. However, the conversion to monoclinic j8-Sg at temperatures just above the triple point of 96 °C is kinetically hindered and requires lattice defects or imperfections as present in a powder but usually not in a single-crystal [158]. Therefore, single-crystals of a-Sg usually melt at 115 °C without prior conversion to the j8-form. For the same reason the temperature at which the transition a fi is observed by DSC measurements depends on the heating rate and is often found well above 100 °C, even if a powder-like sample is used. The activation energy for the a fi transition is approximately identical to the enthalpy of sublimation of a-Sg (100 kj mor ) [158]. Heating of Sg to 90-110 °C, just be- 

Sg if solid a-Sg is heated with a rate of 2-20 K min to the melting point of 63 °C and the melt is rapidly cooled to room temperature, it consists mainly of Sg with traces of S7 and Ss. At 25 °C S9 is about as stable as Se [33]. 

Siq if Sio is heated at a rate of 5 K min in a DSC apparatus one observes the melting at 92 °C and an exothermic polymerization reaction in the temperature range 95-119 °C followed by depolymerization to mainly Ss and some S7 together with traces of other sulfm rings. If rapidly heated to 

The degree of randomness (5) can be defined as the sum of the two probabilities (Pnt + Ptn). For random copolymers, 5 = 1, for alternative copolymers, 5=2, while for block copolymers or physical blends, 5 is close to zero. 

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The variation of Cp for crystalline thiazole between 145 and 175°K reveals a marked inflection that has been attributed to a gain in molecular freedom within the crystal lattice. The heat capacity of the liquid phase varies nearly linearly with temperature to 310°K, at which temperature it rises more rapidly. This thermal behavior, which is not uncommon for nitrogen compounds, has been attributed to weak intermolecular association. The remarkable agreement of the third-law ideal-gas entropy at... 

Noncrystalline domains in fibers are not stmctureless, but the stmctural organization of the polymer chains or chain segments is difficult to evaluate, just as it is difficult to evaluate the stmcture of Hquids. No direct methods are available, but various combinations of physicochemical methods such as x-ray diffraction, birefringence, density, mechanical response, and thermal behavior, have been used to deduce physical quantities that can be used to describe the stmcture of the noncrystalline domains. Among these quantities are the amorphous orientation function and the amorphous density, which can be related to some of the important physical properties of fibers. 

Thermal Analyses. Thermal analysis often complements x-ray data in providing information on phase composition. The thermal behavior of aluminum hydroxides is particularly important in filler type appHcations. 

The thermal behavior of the closely related homoallyl-substituted azirine (182) has also been studied (77JA1871). Heating a solution of (182) in toluene gave 2-methylbiphenyl (183)... 

The thermal behavior of A and B above 150°C has been studied. Both in the gas phase and in solution, each compound yields a 3 5 mixture of ,Z-l,5-cyclooctadiene (C) and Z,Z-l,5-cyclooctadiene (D). When hexachlorocyclopentadiene is present, compound E is found in place of C, but the amount of D formed is about the same as in its absence. Formulate a description of the thermolysis mechanism that is consistent with these facts and the general theory of thermal electrolytic reactions. 

Normally, the heat storage capacity of the air in the space can be neglected. Machines, tools, equipment, etc. situated in the room may have a significant influence on the thermal behavior of the room and must be considered in the simulation. 

To describe rhe dynamic thermal behavior of the envelope and internal structural elements, the following two methods are most often used In thermal building simulation codes ... 

Moisture-transport simulation includes transport as well as storage phenomena, quite similar to the thermal dynamic analysis, where heat transfer and heat storage in the building elements are modeled. The moisture content in the building construction can influence the thermal behavior, because material properties like conductance or specific heat depend on moisture content. In thermal building-dynamics simulation codes, however, these... 

The thermal behavior of a zone is affected by the presence of internal heat sources and by HVAC operating features, which are dealt in the next sections. 

This section deals mainly with the interaction of thermal models as outlined in Section J 1.3 and airflow models as described in Section 11.4 for the purpose of integrated modeling of thermally induced (stack-driven) natural ventilation, governed by the thermal behavior of the building. For the integrated analysis ol air velocity fields and radiative and thermal effects in the building using CFD codes, see also Section 11.2 and Ott and Schild.-... 

Ott F. Numerical coupling of airflow, radiation and thermal behavior of the building [in German]. Thesis No. 11805, Federal Institute of Technology, Zurich, 1996. 

The major reasons for the beluu ior of vertical temperature in water bodies are the low thermal condnctii ity and the absorption of heat in the first few meters. As tlie surface waters begin to heat, transfer to low er layers is reduced and a stability condition develops. The prediction of thermal behavior in lakes and reser oirs is an important power plant siting consideration and also is a major factor in preienting e.xcessive thermal effects on sensitive ecosystems. Furthermore, the extent of thermal stratification influences the vertical dissolved ox)gen (DO) profiles where reduced DO often results from minimal exchiuige with aerated water. ... 

Diethylamino-4-(4-methoxyphenyl)-isothiazole 5,5-dioxide 6 is (95T(51)2455) a highly reactive partner in 1,3-dipolar cycloadditions with several dipoles. Azomethine yhdes, such as oxazolones 7 and miinchnones 8, afforded with 6 bicychc pyrrolo[3,4-d]isothiazole 5,5-dioxides 9, 10, 11 in satisfactory yield. The regioselectivity of the reaction was excellent. The thermal behavior of these new bicychc systems was investigated. When heated at their melting point or shghtly above, triarylpyrroles 12, 13 were obtained through SOj and AtiV-diethylcyanamide ehmination. 

The thermal behavior of many ionic liquids is relatively complex. For a typical IL, cooling from the liquid state causes glass formation at low temperatures solidifica-... 

In contrast to two-phase physical blends, the two-phase block and graft copolymer systems have covalent bonds between the phases, which considerably improve their mechanical strengths. If the domains of the dispersed phase are small enough, such products can be transparent. The thermal behavior of both block and graft two-phase systems is similar to that of physical blends. They can act as emulsifiers for mixtures of the two polymers from which they have been formed. 

Recently, various polyesters such as poly(ethylene adipate), poly(tetramethylene adipate), poly(caprolac-tone), and poly(aliphatic carbonate), having terminal hydroxyl groups, were reacted with ACPC to give corresponding macroazoesters and their thermal behaviors were observed by DSC [14]. The block copolymers of these polycondensation polymers with addition polymers such as PSt and PMMA were synthesized [14]. 

The mechanical and thermal behaviors depend partly on the degree of crystallinity. For example, highly disordered (dominantly amorphous) polymers make good elastomeric materials, while highly crystalline polymers, such as polyamides, have the rigidity needed for fibers. Crystallinity of polymers correlates with their melting points. 

The above decomposition mechanism is very important for the understanding of the hydrolysis, at elevated temperatures, of potassium heptafluoroniobate, K2NbF7, and of the thermal behavior of K2NbOF5. 

The thermal behavior of Li, Ni02 in relation to safety is another key factor when in considering materials for lithium-ion batteries. LiNi02 is stable even when it is heated with an organic electrolyte. However, partially or fully oxidized LiNi02 is quite active toward organic electrolyte oxidation and this reaction is exothermic. 

Steady state models of the automobile catalytic converter have been reported in the literature 138), but only a dynamic model can do justice to the demands of an urban car. The central importance of the transient thermal behavior of the reactor was pointed out by Vardi and Biller, who made a model of the pellet bed without chemical reactions as a onedimensional continuum 139). The gas and the solid are assumed to have different temperatures, with heat transfer between the phases. The equations of heat balance are ... 

The two-dimensional energy equation simulating the thermal behavior of the solid propellant ... 

Polyethylene s simplicity of structure has made it one of the most thoroughly studied polymeric materials. With an estimated demand of close to 109 billion pounds in 2000 of the homopolymer and various copolymers of polyethylene,24 it is by far the world s highest volume synthetic macromolecule. Therefore, it is still pertinent to study its structure-property relationships, thermal behavior, morphology, and effects of adding branches and functional groups to the polymer backbone. 

Thermal Behavior of Precisely Placed Branches in ADMET Polymer Microstructures... 

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