Thermal Stability Studies

TCA has been used to study degradation kinetics and various factors affecting thermal stability of polymers, such as crystallinity, molecular weight, orientation, tacticity, substitution of hydrogen atoms, grafting, co-polymerisation, addition of stabilisers, and so on. 

Libiszowski and co-workers [9] used TCA and thermal volatilisation analysis to investigate the thermal stability of a-ester (o-hydroxy terminated poly-L-lactides (PLA) i.e., [C HjOC(0)-PLA-OH] and its esterified counterpart [C H 0C(0)-PLA-OCfOlCHfC HjlC Hj]. Thermogravimetric measurements versus number average 

The introduction of bromine and trifluoromethyl groups into these polymers in an attempt to increase their flame retardency does not affect the onset decomposition temperature of the first stage (around 260-290 °C), but it does greatly reduce the thermal stability of the second stage (around 500-510 °C), which suggests that the halogenated polybenzoxazole is less stable in the non-halogenated polybenzoxazole. 

Thermal stability measurements have been carried out on numerous other polymers including polyethylene ethylene vinyl-alcohol copolymer [12], polyaniline [13], ) 3 s-stilbene-N-substituted maleimides [14], cellulose [15-20], polystyrene [14, 16], ethylene-styrene copolymers [21,22], ST-DVB-based ion exchangers [23], vinyl chloride-acrylonitrile copolymers [24], polyethylene terephthalate [25], polyesters such as polyisopropylene carboxylate [26], polyglycollate [27-29], Nylon 6 [30], polypyromellitimides, poly-N-a-naphthylmaleimides [26,31], polybenzo-bis(amino-imino pyrolenes) [32], polyvinyl chloride [33-35], acrylamide-acrylate copolymers and polyacrylic anhydride [36-38], polyamides [39], amine-based polybenzo-oxazines [40], polyester hydrazides [41], poly-a-methyl styrene tricarbonyl chromimn [42], polytetrahydrofuran [43], polyhexylisocyanate [44], polyurethanes [45], ethylene- 

Determination of the values of the kinetic parameters for simple one-stage processes are derived from the rate of mass change with time and are as described by the 

---

G. M. Graham, M. M. Jordan, K. S. Sorbie, J. Bunney, G. C. Graham, W. SableroUe, and P. HiU. The implication of HP/HT (high pressure/high temperature) reservoir conditions on the selection and application of conventional scale inhibitors Thermal stability studies. In Proceedings Volume, pages 627-640. SPE Oilfield Chem Int Symp (Houston, TX, 2/18-2/21), 1997. 

From the discussion presented of reactions in solids, it should be apparent that it is not practical in most cases to determine the concentration of some species during a kinetic study. In fact, it may be necessary to perform the analysis in a continuous way as the sample reacts with no separation necessary or even possible. Experimental methods that allow measurement of the progress of the reaction, especially as the temperature is increased, are particularly valuable. Two such techniques are thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). These techniques have become widely used to characterize solids, determine thermal stability, study phase changes, and so forth. Because they are so versatile in studies on solids, these techniques will be described briefly. 

A thermal stability study was first carried out to determine the following information (1) the solidification temperature as a function of the concentration of the sulfonate (2) the enthalpy of decomposition by DTA (3) the autocatalytic nature of the decomposition by Dewar flask (4) kinetic data for decomposition by Dewar flask (5) the time to maximum rate by ARC, and (6) the heat generation as a function of temperature, also by ARC. In addition, the enthalpy of dilution was determined for various potential water leak rates. These data were useful in defining emergency response times. 

G. Zeng, W.-L. Yu, S.-J. Chua, and W. Huang, Spectral and thermal stability study for fluorene-based conjugated polymers, Macromolecules, 35 6907-6914, 2002. 

M. Fournier, C. Fuemi-Jantou, C. Rabia, G. Herve, and S. Launay, Polyoxometalates Catalyst Materials X-Ray Thermal Stability Study of Phosphorus-containing Heteropolyacids Hj xPMi2. xVx04o13-14H20 (M = Mo, W x = 0-1), J. Mater. Chem., 2, 971-978 (1992). 

J. Campos-Delgado, Y.A. Kim, T. Hayashi, A. Morelos-Gomez, M. Hofmann, H. Muramatsu, M. Endo, H. Terrones, R.D. Shull, M.S. Dresselhaus, M. Terrones, Thermal stability studies of CVD-grown graphene nanoribbons Defect annealing and loop formation, Chemical Physics Letters, vol. 469, pp. 177-182, 2009. 

Tris(dimethyl sulfoxide)indium(III) chloride is a white crystalline nonhygro-scopic compound, soluble in alcohols, ethyl acetate, and nitromethane. Decomposition occurs at 130°. The infrared spectrum and the results of thermal stability studies have been reported.6 The presence of dmso can be verified from the infrared spectrum,6 which shows C—H vibrations, and =0 at 945, 960, and 995 cm. ... 

Srinivasulu, S. and Rao, A.G.A. 1995. Structure and kinetic thermal stability studies of the interaction of monohydric alcohols with lipoxygenase 1 from soybeans (Glycine max). J. Agric. Food Chem. 43 562-567. ... 

Materials for a batch of ammonium perchlorate castable propellant were charged into a mechanical mixer. A metal spatula was left in accidentally, and the contents ignited when the mixer was started, owing to local friction caused by the spatula. A toollisting safety procedure was instituted [1], The literature on the kinetics of thermal decomposition has been reviewed critically [2]. More refined thermal stability studies show some large differences from earlier ones [4]. 

R. L. Bolduc, P. R. Thermal stability studies on a homologous series of nitroarenes. /. Phys. Chem. 1995, 99, 9593-9602. 

Meaningful thermal stability studies on heteropoly compounds must be accompanied by solubility studies of the heated materials to ascertain actual decomposition. In addition, the length of heating must also be specified since such decomposition may be rate dependent in view of the fact that both 12-molybdophosphoric and 12-molybdosilicic acids decompose slowly with time even at room temperature5. ... 

Gilman, J. W., Flammability and thermal stability studies of polymer layered-silicate (clay) nanocompos-... 

THE SYNTHESIS AND THERMAL STABILITY STUDY OF MESOPOROUS CERIUM (IV) OXIDE POWDERS... 

The use of bidentate chelating carbene has also been investigated (Scheme 16) however, in thermal stability studies of the organoindium carbene hydride derivative, the... 

In thermal stability studies, accelerated testing at elevated temperatures is used to minimize the time needed to assess the thermal stability of the substance/ product. From the Arrhenius plot, one can predict the shelf life of the product at a proposed storage temperature. 

BNA (also known as LNA) has been used in TFOs in a pyrimidine motif at neutral pH. The binding constant of the BNA TFO was about 20 times larger than that of DNA as a result of a large decrease in the dissociation rate constant. A 3 -amino-2, 4 -BNA nucleotide has been prepared to introduce N3 -P5 phosphoramidate linkages. It is introduced as a dinucleotide unit (61), and in thermal stability studies was shown to exhibit superior duplex and triplex stability compared to either BNA or DNA, and shows enhanced resistance to digestion by SVPDE. These properties have previously been observed for N3 -P5 phosphoramidate linkages in DNA. ... 

Thermal stability of vinyl chloride copolymers is usually better than that of the homopolymer [27]. Some pyrolysis studies on PVC copolymers are reported in literature [28-32], A summary of several thermal stability studies of poiy(vinyl chloride) copolymers are indicated in Table 6.3.3. 

Figure 1 - Diagram of the calorimeter used in the adiabatic thermal stability studies.

Figure 2 - The experimental differential temperature curve obtained from the adiabatic thermal stability study.

Thermal stability studies on pharmaceutical formulations have been formalized for many years. Specific protocols have been developed to provide data from which a shelf-life determination can be made (Carstensen, 1995). Thus, procedures followed in one laboratory are readily reproduced in another, and shelf-life is a consistent estimation for the product, independent of the laboratory in which the data were gathered. In thermal stability studies, the principal consideration is how long the drug substance or formulation is exposed to a particular temperature. The nature of the apparatus to be used is not important as long as the temperature of the sample is uniform. Thus, the sample may be contained in a flask, bottle, or tube, or held in a water thermostat or an air incubator — whatever is most convenient for the study. Also, the concentration of the drug studied is not crucial because a thermal degradation usually proceeds by first-order kinetics for which the half-life is independent of the starting concentration. 

---