Complexes of cell–THPC–urea–ADP with transition metal ion Co2+ and lanthanide metal ions such as La3+, Ce4+, Nd3+ and Sm3+ have been prepared. The thermal behavior and smoke suspension of the samples are determined by TG, DTA, DTG and cone calorimetry.
The activation energies for the second stage of thermal degradation have been obtained by following Broido equation. Experimental
data show that for the complexes of cell–THPC–urea–ADP with the metal ions, the activation energies and thermal decomposition
temperatures are higher than those of cell–THPC–urea–ADP, which shows these metal ions can increase the thermal stability
of cell–THPC–urea–ADP. Moreover, these lanthanide metal ions can more increase thermal stability of samples than do the transition
metal ion Co2+. The cone calorimetry data indicate that the lanthanide metal ions, similar to transition metal Co2+, greatly decrease the smoke, CO and CO2 generation of cell–THPC–urea–ADP, which can be used as smoke suppressants.
A method combining prior collection of gaseous products with subsequent neutron activation analysis has been developed for simultaneous determination of traces of arsenic, mercury, antimony and selenium in biological materials. The generation of hydrides of arsenic, antimony and selenium and cold vapor of mercury in the vapor generaion and collection system was investigated by the use of radiotracers of the respective elements. The result indicates that selenium and mercury can be completely evaporated from the digested sample solution in 5M HCl with the addition of 5% sodium tetrahydroborate solution, while additional reduction proces by potassium iodide and ascorbic acid is needed for complete evaporation of arsenic and antimony. The gaseous products were collected in a quartz tube for neutron irradiation. The detection limits of these elements were fount to be in the range of 10–7 to 10–8 g under the present experimental conditions. The reliability was checked with NBS standard reference materials.
Pentaerythritol diphosphonate melamine-urea-formaldehyde resin salt, a novel cheap macromolecular intumescent flame retardants
(IFR), was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus characterized by IR. Epoxy
resins (EP) were modified with IFR to get the flame retardant EP, whose flammability and burning behavior were characterized
by UL 94 and limiting oxygen index (LOI). 25 mass% of IFR were doped into EP to get 27.2 of LOI and UL 94 V-0.
The thermal properties of epoxy resins containing IFR were investigated with thermogravimetry (TG) and differential thermogravimetry
(DTG). Activation energy for the decomposition of samples was obtained using Kissinger equation. The resultant data show that
for EP containing IFR, compared with EP, IFR decreased mass loss, thermal stability and Rmax, increased the char yield. The activation energy for the decomposition of EP is 230.4 kJ mol−1 while it becomes 193.8 kJ mol−1 for EP containing IFR, decreased by 36.6 kJ mol−1, which shows that IFR can catalyze decomposition and carbonization of EP.
Authors:D. Lin, H. Wang, M. Lin, M. Lin, and Y. Wu
Adding a magnetic field gradient to the conventional TG system constructs the magnetic thermogravimetry analysis (TG(M) i.e. Faraday methods) and the magnetic derivative thermogravimetry (DTG(M)) techniques. We used the techniques to study the nanocrystalline processes of the FeCuNbSiB and FeCuNbCoSiB amorphous alloys. Some problems of their applications such as the characteristic temperature Tmin and TC are also discussed in detail.
In the present study, the effect of primary processing route on the dissolution and precipitation reactions in a commercial
Al−Si alloy (designated as A390) is investigated using differential scanning calorimetry (DSC). The Al−Si alloy selected for
the present investigation was processed using conventional casting and spray atomization and deposition routes. The results
of differential scanning calorimetry conducted on the as-processed samples indicated no significant dissolution reaction for
the as-cast A390 alloy when compared to the similar results obtained for as-spray atomized and deposited samples. However,
the thermal analysis conducted on the solutionized cast and spray deposited samples exhibited no significant difference in
the kinetics of precipitation reactions. The results of the differential thermal analyses were finally rationalized in terms
of observed microstructural features.
Authors:S. Lin, J. Tseng, M. Lee, T. Wu, and C. Shu
Styrene is an important chemical in the petrochemical industry. In recent years, there have been sporadic releases, runaway
reactions, fires, and thermal explosion accidents incurred by styrene and its derivatives worldwide. The purpose of this study
was to estimate the impact of styrene and its derivatives of α-methylstyrene (AMS) and trans-β-methylstyrene (TBMS) contacting with benzaldehyde. Experiments were carried out to evaluate the thermokinetic parameters
estimated by differential scanning calorimetry (DSC) and thermal activity monitor III (TAM III). TAM III was used to determine
the fundamental thermokinetics under various isothermal temperatures, 80, 90 and 100°C. This autocatalytic reaction was demonstrated
in thermal curves. After styrene was contacted with benzaldehyde, the exothermic onset temperature (T0) and the total heat of reaction (Qtotal) were altered by DSC tests. When benzaldehyde is mixed with AMS and TBMS, the reaction time will be shorter but the enthalpy
reduced, as revealed by TAM III tests.
As AMS and TBMS, respectively, were contacted with benzaldehyde, both exothermic phenomena were changed during the reaction
excursion. According to the results of this research, an operator should dictate the oxygen concentration in order to avoid
any potential hazards during handling and transportation.
Authors:C. Liao, S. Wu, T. Su, M. Shyu, and C. Shu
is an important commodity chemical that is globally applied in various polymerization
processes. The aim of this study was to obtain integrated thermokinetics and
safety parameters for polymerization of styrene. We mainly used differential
scanning calorimetry (DSC), thermal activity monitor (TAM), and simulative
methods to investigate thermal polymerization of styrene and styrene containing
various levels of 4-tertiary-butylcatechol
(TBC). The results obtained included the rate constant (k),
reaction order (n), apparent activation
energy (Ea), frequency
factor (A), and so on, from various DSC
curves and simulative methods. From DSC curves, the exothermic onset temperature
(T0) was about 105
and 132C for styrene and styrene containing 10 ppm TBC. On the other
hand, the test results from TAM indicated that styrene polymerization displays
an autocatalytic phenomenon from 50–85C. By means of this study,
the intrinsic safety of a system for styrene during transportation and storage
could be established.
Authors:M. Deibel, S. Landsberger, D. Wu, and W. Ehmann
Copper (Cu) is an essential element and is incorporated in many biomolecules that are involved in protecting the brain from oxidative damage. Many brain regions strongly affected by neurodegene rative diseases are small. A sensitive nondestructive procedure to determine Cu is desirable to preserve samples for additional studies. Copper is not easily determined by instrumental neutron activation analysis (INAA) due to high activity levels produced by major abundance elements such as sodium (Na) and chlorine (Cl), which produce a high Compton background. An INAA method involving a short epithermal neutron irradiation and counting with a Compton suppression system was developed to determine Cu in brain, via 5.1-min66Cu. These short irradiation results are compared to those based on coincidence spectrometry of annihilation photons from positron emitting 12.7-h64Cu after a long irradiation.