Mixtures differential scanning calorimetry

Time domain reflectometry has been used to study the hydration of L-xylo- and D-orohuto-ascorbic add solutions in water and water ethanol mixtures, differential scanning calorimetry and thermogravimetric analysis have been used to study hydration of a-maltose and amylose, a new physical chemical model describes the thermodynamic properties of binary water-carbohydrate... 

Most hydrocarbon resins are composed of a mixture of monomers and are rather difficult to hiUy characterize on a molecular level. The characteristics of resins are typically defined by physical properties such as softening point, color, molecular weight, melt viscosity, and solubiHty parameter. These properties predict performance characteristics and are essential in designing resins for specific appHcations. Actual characterization techniques used to define the broad molecular properties of hydrocarbon resins are Fourier transform infrared spectroscopy (ftir), nuclear magnetic resonance spectroscopy (nmr), and differential scanning calorimetry (dsc). 

Figure 10.7 The phase diagram (a) and the glass transition temperatures (b) of a PSC/PVME mixture obtained, respectively, by light scattering and differential scanning calorimetry (DSC). Irradiation experiments were performed in the miscible region at 127 C indicated by (X) in the figure of trans-cinnamic acid-labeled polystyrene/poly(vinyl methyl ether) blends.

Nakazawa, E., Noguchi, S., and Takahashi, J. (1984). Thermal equilibrium state of starch-water mixture studied by differential scanning calorimetry. Agric. Biol. Chem. 48, 2647-2653. 

Thermal analytical techniques such as thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) have all been successfully employed in studying the pyrotechnic reactions of energetic materials such as black powder, as well as of binary mixtures of the constituents. 

A study of benzocyclobutene polymerization kinetics and thermodynamics by differential scanning calorimetry (DSC) methods has also been reported in the literature [1]. This study examined a series of benzocyclobutene monomers containing one or two benzocyclobutene groups per molecule, both with and without reactive unsaturation. The study provided a measurement of the thermodynamics of the reaction between two benzocyclobutene groups and compared it with the thermodynamics of the reaction of a benzocyclobutene with a reactive double bond (Diels-Alder reaction). Differential scanning calorimetry was chosen for this work since it allowed for the study of the reaction mixture throughout its entire polymerization and not just prior to or after its gel point. The monomers used in this study are shown in Table 3. The polymerization exotherms were analyzed by the method of Borchardt and Daniels to obtain the reaction order n, the Arrhenius activation energy Ea and the pre-exponential factor log Z. Tables 4 and 5 show the results of these measurements and related calculations. 

Equimolar mixtures of 41 separately and independently with each of the dieneophiles 42, 43, and 44 were examined by differential scanning calorimetry (DSC). The thermograms obtained from these experiments are shown in... 

Oxidation of mixtures of 2,6-disubstituted phenols leads to linear poly(arylene oxides). Random copolymers are obtained by oxidizing mixtures of phenols. Block copolymers can be obtained only when redistribution of the first polymer by the second monomer is slower than polymerization of the second monomer. Oxidation of a mixture of 2,6-di-methylphenol (DM ) and 2fi-diphenylphenol (DPP) yields a random copolymer. Oxidation of DPP in the presence of preformed blocks of polymer from DMP produces either a random copolymer or a mixture of DMP homopolymer and extensively randomized copolymer. Oxidation of DMP in the presence of polymer from DPP yields the block copolymer. Polymer structure is determined by a combination of differential scanning calorimetry, selective precipitation from methylene chloride, and NMR spectroscopy. 

Differential scanning calorimetry has been utilized by many to investigate inclusion complexes in solid-state. The melting endotherm of the substrate typically is changed as a result of complexation. The complex formed may have a different melting point, or no melting endotherm because of its amorphous nature. The physical mixture in most cases will still exhibit the melting endotherms of the substrate and the CD (if it is crystalline). 

Figure 1. Differential scanning calorimetry curves for 50 wt% dispersions of 1,2-dipalmitoylphosphatidy1-choline-cholesterol mixtures in water containing (a) 0 (b) 5.0 (c) 12.5 (d) 20.0 (e) 32.0 and (f) 50.0 mol% cholesterol. (Reproduced with permission from Ref. 11. Copyright 1968 Elsevier Science Publishing Company, Inc.)...

Differential scanning calorimetry was used for evaluating the interaction between model mixtures of stratum corneum lipids and gel-state PC. The mixing of the systems was complete in about 24 h.21 The slow interaction of gel-state PC may also apply to its topical application in vivo. 

Differential Scanning Calorimetry (DSC) is a sensitive way of detecting phase transformations of a bulk material [85,86]. Monitoring the thermal behavior of a crystal or a powder as a function of its conversion to product can give important information. This technique can verify whether a reaction occurs in a purely solid phase or whether there may be liquid phases involved at a given temperature. Melting point depression can be monitored as product appears, and the characteristic melting of a new phase can be detected if one is formed. DSC can reveal whether or not a eutectic transition attributable to a mixture of phases is present. We have also used DSC in our lab to monitor the thermal stability of reactive crystals. 

Extremely important for the safe handling of such pyrotechnic mixtures are, in addition to the chemical stability (compatability with the binder and other additional compounds) particular the thermal stability and the lowest possible impact, friction and electrostatic sensitivities. Figure 2.18 shows an example of a DSC ther-mogramm (Differential Scanning Calorimetry), which shows that the new environmentally friendly red mixture (colorant components from Figure 2.17) is thermally... 

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