Thermogravimetric experiments

The copolymers have a remarkably improved thermostability with respect to the polysiloxanediols. While the polysiloxane homopolymers undergo 15% weight loss at 350-360°C, as determined by the thermogravimetric experiments, the same percent weight loss is observed at 430-510°C for various samples of... 

Based on thermogravimetric experiments on the compound Fe2Si04 at various T and conditions, Nakamura and Schmalzried (1983) established that the extrinsic disorder of fayalite is conveniently represented by the equihbrium... 

The schematic set-up for a thermogravimetric experiment is shown in Figure 16-2. The device is a combination of a sophisticated high temperature furnace (with temperature and gas atmosphere control) and a micro-balance. Since it is meant to... 

As was demonstrated in thermogravimetric experiments, PBI and PBI-Mo are stable at temperature up to 673 K in an oxygen atmosphere. Immobilization of the Mo catalyst occurs by ligand exchange between Mo02(acac)2 and the polymer refluxed in toluene for 72 h. The activity of the catalyst was first tested for the epoxidation of propylene with /-BuOOI I (242) ... 

These points respectively define the temperature at which, on reheating, a cooled or quenched pyrolysis residue begins to soften and develop fluidity and the temperature at which the liquid residue begins to change its chemical composition, i.e., when pyrolysis recommences. This latter point is more ambiguous since it is determined from a thermogravimetric experiment which is subject to the effects of experimental procedure, as discussed earlier. Therefore, it is essential to use a fixed heating rate, etc., in the determination of the decomposition temperature. The volatile content can be determined in the same experiment. 

The kinetic parameters given are derived from the thermogravimetric experiments. The mechanisms of pyrolysis, as discussed by this team, are too complex and varied to be treated here in more detail. 

Diffraction data Table 4.6) were collected from a powder containing fluorine. Using the Mineral Database and 3 strongest of the 15 observed peaks identify the material. Additional information about the powder no weight loss has been detected during a thermogravimetric experiment carried out between 25 and 500°C. 

The thermogravimetric experiments were performed under purified hydrogen flow on a Sartorius balance. 

Firstly the influence of water vapour on the catalytic properties of the equilibrated (V0)2P207 catalyst is reported. Afterwards the effect of water vapour on the enrichment in phosphorus of the catalyst surface and the reversibility of this effect is described using thermogravimetric experiments in the presence and absence of water vapour and XPS as well as ISS measurements of the respective catalyst samples. 

The data collected in each thermogravimetric experiment is a set of measured (m, t, T) values resulting from the chemical changes undergone by a reactant sample heated under constant or programmed temperature conditions. These are discussed as follows ... 

A further important interaction, namely, that between an active substance and water, can be studied by DSC and TSC (28). To illustrate this case, we will present results obtained with a drug manufactured in three states labeled hydrated hemihydrate (HEMI), monohydrate (MONO), and freeze-dried (FD) forms. The last is mostly amorphous and absorbs water in nonstoichiometric quantities. The other two forms are highly crystalline and contain specific ratios of water per active molecule. Thermogravimetric experiments have shown that water is linked between two active molecules for the hemihydrate, whereas the distribution is homogeneous and the ratio unimolecular for the monohydrate. Moreover, two different hemihydrate batches obtained by two different industrial processes have been analyzed. Complementary studies have shown that the batch labeled PR, is more crystalline and more stable than the PR2 batch in terms of the transition to the monohydrate form. 

The thermogravimetric experiments showed that the catalyst reduced most efficiently at 400 °C. At 400 °C, the degree of reduction exceeded 10 %, whereas the degree of reduction was only 6 % at 170 °C. 

Whereas the oxidation behaviour of 0-NiAl has been investigated under various conditions [1-5], the oxidation behaviour of the related 0-FeAl phase is entirely unknown. Therefore, as a comparison, the oxidation of 0-FeAl was studied by means of thermogravimetrical experiments in the temperature range from 800°C to 1100°C. Similar phenomena as for NiAl have been observed concerning formation and conversion of A1203 modifications and occurrence of porosity beneath the scale. 

The thermogravimetrical experiments with Fefi0Al40 yielded corresponding results within the experimental error, so they are not presented in detail. 

An alternate technique is to carry out a thermogravimetric experiment and measure the weight gain of the material for which the oxidation resistance is to be measured as a function of time (Fig. 7.17). In this case, the weight change per unit area Aw is related to time by ° ... 

In contrast with exposure tests, thermogravimetric experiments are useful to study short-term kinetics regarding possible incubation times or the influence of gas phase composition. Evidence must show that the overall mass change is not influenced by reactions of the salt itself, by significant evaporation, or by reaction with the gas phase. 

Figures la and lb show the TGA-mass spectrometry data for water and NMP on the as-received poly(amide-imide), indicating that neither liquid was removed until five minutes into the run, which corresponded to approximately 220 C. The thermogravimetry showed that there was a total of approximately 2 weight percent of water and NMP in the polymer. Isothermal thermogravimetric experiments were conducted on the as-received sample between 145 and 165 C. Temperatures above 155X were enough to dry the sample in 3 hours. Although, further drying of the samples were done at 190 C, an intermediate value between 155 and 220°C. Even this simple experiment showed that there were strong associations of the water and NMP to the poly(amide-imide).

The thermogravimetric experiments are run using open platinum sample pans. Pans made from aluminium, platinum, quartz, glass, stainless steel ete. were also available. The... 

The residue of a visbreaker (sample 19) exhibits a distillable fraction. The corresponding boiling point is 420 °C. The residue therefrom pyrolyzes between 450 °C and 490 "C. In the thermogravimetric experiment no DTG maximum was found in the distillation range. 

Thermogravimetric experiments on oxidation of oil shale in oxygen with kinetic evaluation according to Doyle and Gorbatchev [4-52, 4-53] resulted in considerably varied activation energies for the LTO region (Table 4-157). 

Figure 10.43. Temperature to 50% of weight loss during thermogravimetric experiment eonducted for pure plasticizer and plasticizer mixed with PVC (plasticizer - 65 phr) vs. boiling temperature of plasticizer. [Data fiom Marcilla A Beltran M, Polym. Deg. Sab., 53, No.2, 1996, p.261-8.]...

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