Thermal analysis studies

It is convenient to classify here the decompositions of metal salts of the various oxyhalogen acids on the basis of the oxygen content of the anion, with subsections devoted to the metals of a particular sub-group of the Periodic Table. Again, consideration of the ammonium salts is deferred to Sect. 4. As noted elsewhere in this review, some reports are not explicit as to whether or not melting accompanies reaction thermal analysis studies can be valuable [843]. 

These thermal analysis studies serve to establish a direct relationship between a heat-induced AR method and the reversal of formalin-induced intra- and intermolecular protein cross-links.10 2831 Further, while formalin-treatment provides thermal stability to RNase A, this stabilization is not sufficient to prevent thermally induced protein denaturation at temperatures (>100°C) typically used in heat-induced AR methods.32 34 The implications of this finding for the mechanism of AR will be discussed further in Section 15.6. 

Previous thermal analysis studies had indicated that while Sb203 did not react directly with DBDPO, there was some evidence that the reaction of a polymer substrate with the Sb203 generated a species which was very reactive (23), and that this product was antimony metal (Sb°). Therefore, simple mixtures of DBDPO with powdered antimony, bismuth and zinc metals (mole ratio of bromine to metal of 3 1) were pyrolyzed and the extent of reaction determined by CGC. 

Sealants obtained by curing polysulfide liquid polymers with aryl bis(nitrile oxides) possess stmctural feature of thiohydroximic acid ester. These materials exhibit poor thermal stability when heated at 60°C they soften within days and liquefy in 3 weeks. Products obtained with excess nitrile oxide degrade faster than those produced with equimolar amounts of reagents. Spectroscopic studies demonstrate that, after an initial rapid addition between nitrile oxide and thiol, a second slower reaction occurs which consumes additional nitrile oxide. Thiohydroximic acid derivatives have been shown to react with nitrile oxides at ambient temperature to form 1,2,4-oxadiazole 4-oxides and alkyl thiol. In the case of a polysulfide sealant, the rupture of a C-S bond to form the thiol involves cleavage of the polymer backbone. Continuation of the process leads to degradation of the sealant. These observations have been supported by thermal analysis studies on the poly sulfide sealants and model polymers (511). 

For example, amorphous clarithromycin was prepared by grind and spray-drying processes, and XRPD was used to follow changes in crystallinity upon exposure to elevated temperature and relative humidity [59]. Exposure of either substance to a 40°C/82% RH environment for seven days led to the formation of the crystalline form, but the spray-dried material yielded more crystalline product than did the ground material. This finding, when supported with thermal analysis studies, led to the conclusion that the amorphous substances produced by the different processing methods were not equivalent. 

Cheng, Y.-Y., Brillhart, M., Cebe, P. and Capel, M., X-ray scattering and thermal analysis study of the effects of molecular weight on phase structure in blends of polybutylene terephthalate with polycarbonate, J. Poly. Sci., Polym. Phys., 34, 2953-2965 (1996). 

David, D.J. Determination of specific heat and heat of fusion by differential thermal analysis. Study of theory and operating parameters, Aural Chem., 36(11) 2162-2166, 1964. 

Lynch, L.J. Sakurovs, R. Barton, W.A. Webster, D.S. Bacon, N.A. Parks, T. Reactive Inertlnlte and Coal Carbonization -NMR Thermal Analysis Studies NERDDP End of Grant Report, Project No. 662, l5o7 Chapter5. 

Vamell, D. F., Runt, J. P., Coleman, M. M. FT-IR and Thermal Analysis Studies of Blends of Poly(Caprolactone) and Homo- and Copolymers of Poly(vinylidene chloride). Preprint submitted to CARBON... 

H. Tanojo, J. A. Bouwstra, H. E. Junginger, and H. E. Bodde, In vitro human skin barrier modulation by fatty acids skin permeation and thermal analysis studies, Pharm Res. 14 42-49 (1997). 

Van Den Berg, J., A. Broersma, A.J. Van Dillen, and J.W. Geus. 1983. A thermal analysis study of vanadium pentoxide and silver vanadate (Ag035V2O5). Thermochim. Acta. 63 123-128. 

The above thermal analysis studies demonstrated the enhanced thermal stability of POSS materials, and suggested that there is potential to improve the flammability properties of polymers when compounded with these macromers. In a typical example of their application as flame retardants, a U.S. patent39 described the use of preceramic materials, namely, polycarbosilanes (PCS), polysilanes (PS), polysilsesquioxane (PSS) resins, and POSS (structures are shown in Figure 8.6) to improve the flammability properties of thermoplastic polymers such as, polypropylene and thermoplastic elastomers such as Kraton (polystyrene-polybutadiene-polystyrene, SBS) and Pebax (polyether block-polyamide copolymer). 

Grafting a pre-formed HMS support is also a useful method for introducing organic functionality however NMR and thermal analysis studies reveal that the organic group is... 

M. Tomassetti, A. Catalan , V. Rossi, and S. Vecchio, Thermal analysis study of the interactions between acetaminophen and excipients in solid dosage forms in some binary mixtures, J. Pharm. Biochem. Anal. 37 (2005), 949-955. 

Stefanithis, I.D. and Mauritz, K.A., Microstructural evolution of a silicon oxide phase in a perfluorosulfonic acid ionomer by an in situ sol-gel reaction. 3. Thermal analysis studies, Macromolecules, 23, 2397, 1990. 

Product temperature is a principal dependent variable that reflects the progression throughout the lyophilization process. During freezing, the product is chilled to a final temperature for sufficient time to achieve the necessary solidification. The appropriate temperature required is determined by the character of the formulation and measured during thermal analysis studies completed as part of development. It is also prudent to verify the physicochemical properties if the product formulation is altered when the product progresses through clinical trials. 

The thermal analysis studies of different forms of sorbitol, mannitol, glucose, magnesium stearate are reviewed in Ref. l Mono-, di-, and trihydrate of magnesium stearate as well as the amorphous form may be found. According to Wada and Matsubyara ° thermal analysis is the most appropriate method for characterization of magnesium stearate. 

More pyrolysis oil was produced from treated than untreated wood at 400 °C at 200 s. of pyrolysis time. CCA showed a significant influence on the thermal behavior of wood. The metals may have a catalytic effect on the thermal decomposition of the wood, resulting in more pyrolysis oil [6]. According to the thermal analysis study, thermal decomposition of hemicellulose is shifted to lower temperatures in the presence of CCA resulting in a higher release of volatile compounds [7],... 

The phase transition of lipid bilayers which comprise phospholipid mixtures, or phospholipids with different lengths of acyl chains, are of great importance due to their similarities with biomembranes or with lipid drug carriers such as liposomes, it is important to study the phase transitions and to detennine the exact crystalline mesophases of the mixed system. Thermal analysis studies indicated that the mi.xed lipids provide higher melting temperatures compared to those of pure lipids. This phenomenon occurrs w hen the lengths of the acyl chains are substantially different. 

Evolved gas applications are widespread and diverse. Coordination chemistry has been considerably enhanced by thermal analysis studies of a wide range of metal complexes. The emphasis of these studies has been to derive thermal decomposition mechanisms for such metal complexes. Prior to the development of EGA, such reported mechanisms were suspect because the volatile decomposition products and the solid intermediates were, in general, not identified directly but characterized indirectly on the basis of mass loss data. This procedure is flawed when multiple gaseous decomposition products and nonstoichiometiic intermediates are involved. The thermal analysis of one such group of metal complexes, the metal dithiocarbamates, has been extensively studied and reviewed by Hill and Magee and these are definitive studies in this field. 

Lafferty SV, Newton JM, Podczeck F. Dynamic mechanical thermal analysis studies of polymer films prepared from aqueous dispersion, frit J Pharm 2002 235 107-111. 

Smith A. Pharmaceutical and biological applications of thermal analysis studies in polymorphism and hydration. Anal Proc 1986 23 338-389. 

A number of companion techniques have been shown to be useful and merit further use. These include NMR, IR, MS, GC-MS, AA, X-ray microscopy, and GPC. ESR has not been appreciably utilized as a companion technique but may be considered, particularly with polymers containing ESR-sensitive metals. Gel permeation chromatography (GPC) should be considered as a companion tool for thermal degradation evaluations where depolymerization is suspected. There is a need for a number of well-chosen thermal analysis studies of both the volatile products by TG-MS, etc. (for both chemical and toxicological purposes) and the residue. Such studies should occur throughout the studied temperature range rather than just at the room and final temperatures. 

It is also necessary for us to define the limits of what this text is intended to cover. In the first instance, we have not attempted to provide a comprehensive review of all pharmaceutical thermal analysis studies but have instead focused on including examples that illustrate a particular point. Secondly, we have not gone into coupled... 

These results, together with die thermal analysis studies, illustrate the chain confinement and reductions in chain mobility induced by the tin phase. The concerns are that these species can therefore potentially influence the important stress relaxation or compression set properties of the elastomer, thus influencing material reliability. 

A differential thermal analysis study has been made of these complexes and also of a 1-chloronaphthalene adduct (195). The complexes decompose above 560°C in vacuo with the formation of unmetallated phthalocyanine and stannous phthalocyanine. The infrared spectrum of (XLVI) is not greatly different from that of other phthalocyanines, suggesting very little distortion in the phthalocyanine rings (195). Stannic phthalocyanine (XLVI) may have a sandwich structure in which the tin atoms lie between the two phthalocyanine units in an eight-coordinate environment (109). An X-ray structural determination is in progress (307). 

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