Simultaneous techniques

Table 1. Thermogravimetric methods, simultaneous techniques and experimental...

IPNs can be prepared by either the "sequential" or the "simultaneous" technique. IPNs synthesized to date exhibit varying degrees of phase separation depending primarily on the compatibility of the component polymers (4-7). 

The energy dispersive x-ray fluorescence spectrometer, which had been developed recently as a qualitative analysis instrument, showed promise of meeting the goals of the new laboratory (1). Its unique features, which earned it the name, The Curators Dream Instrument, are The measurements require neither sampling nor alteration of the object in any way. Systems for obtaining quantitative analysis data are now operational (I). Concentrations of up to thirty elements above chlorine (Z = 17) can now be printed out simultaneously. Techniques have been developed that minimize errors caused by sample size, shape, position, overlapping spectral peaks, matrix effects, and baseline compensation. Interpretative procedures have been established that recognize the shallow depth of penetration of the excitation radiation (2). 

Multiple simultaneous techniques—a more complete picture of the phase transition. 

Time resolved diffraction studies Multiple simultaneous techniques-... 

Two- and three-component interpenetrating polymer network (IPN) elastomers composed of polyurethanes (PU), epoxies (E), and unsaturated polyester (UPE) resins were prepared by the simultaneous technique. Fillers and plasticizers were... 

Additionally, simultaneous hot-stage DSC/FTIR studies have been conducted to investigate the different cure characteristics of polymeric materials (95). Using this simultaneous technique, information of the thermal, spectroscopic, and visual properties of the material were collected. 

Perhaps the most commonly used simultaneous technique involving electric conductivity is that with DTA. Burmistrova and Fitzeva (66) used this technique to study the reactions between alkaline earth metal oxides (CaO, SrO, BaO) and selected Pb, Cu, and Ni halides. Electrical conductivity is useful in determining the appearance of a liquid phase at the moment of interaction between the solids. The interaction between BaO and CuBr, as shown in Figure 11.18, is exothermic, as revealed by the DTA curve peak at 360°C. This is accompanied by an increase in electrical conductivity also,... 

The reaction processes of substances cannot be analyzed by simple DTA/DSC or TG when thermal transition and the mass change due to reaction overlap. If DTA/DSC or TG is coupled with an evolved gas detector (EGD) and/or evolved gas analyzer (EGA), the reaction process can clearly be detected. Among various thermal analysis coupled simultaneous techniques [56], DTA/DSC or TG coupled with EGD and/or EGA is extensively used. TA-EGD-EGA coupled... 

An analytical scheme for the TA-EGD-EGA coupled simultaneous technique is shown in Figure 2.32. The evolved gas from TA (DTA/DSC or TG) is introduced into the EGA system after passing through the EGD system. The evolved gas is directly introduced to a thermal conductivity detector (TCD), avoiding second reactions. Two methods are used for the TA and EGA coupled simultaneous technique (1) on-line coupled simultaneous technique in series and (2) off-line combined method. In technique (1), TA is connected serially with a Gas chromatograph (GC) [61-65], mass spectrometer (MS) [57, 64, 65], Fourier transform infrared (FTIR) spectrometer [66, 67], non-dispersive IR (NDIR) spectrometer [68, 69] or thermo-gas-titrimetric... 

Figure 2.32 Analytical scheme for the TA-HGD-EGA coupled simultaneous technique...

The DTA/DSC-EGD coupled simultaneous technique and relevant equipment have been investigated since 1979 [62, 74, 75]. The Model CDR-1 power compensation DSC analyzer (ambient temperature ca 720 C) was developed by the Tian Ping Instrumental Factory (Shanghai, China). The EGD detector is a thermal conductivity detector (TCD) in the GC analyzer. The CDR-1 DSC analyzer coupled with GC was constructed using a specially designed gas conduit. A schematic diagram of the on-line coupled simultaneous DTA/DSC-EGD apparatus is shown in Figure 2.33. 

For extended applications, a DTA/DSC-EGD-GC on-line coupled simultaneous technique and relevant apparatus were established in the 1980s [63]. The CDR-1 E>SC analyzer was replaced by the Model CRY-1 DTA (ambient temperature ca 1200 C) for the purpose of high-temperature measurements. The scheme of the DTA-EGD-GC on-line coupled simultaneous apparatus is shown in Figure 2.37. DTA and a EGD-GC... 

For the quantitative analysis of a certain component in mixed gases, an automatic titration technique for evolved gases from TA connected with the process of continuous titration was developed [58, 70- 72, 94], This technique is known as thermo-gas titration (TGT). Detected curves (TGT curve) and derivative curves (DTGT curve) can be obtained. The TG-DTA-TGT coupled simultaneous technique and relevant equipment were also established in the 1980s [70]. This technique is based on the direct determination of CO2 and SO, (SO,) and on the indirect determination of HjO. A schematic diagram of the TG-DTG-DTA-TGT-DTGT coupled simultaneous apparatus [71] is shown in Figure 2.42. 

Evaluation of Catalysts in the Solid State by the DTA-EGD-GC On-line Coupled Simultaneous Technique... 

DTA-EGD-GC on-line coupled simultaneous technique and relevant equipment (see section 2.4) arc effective tools for evaluating catalysts [14-17],... 

The DTA-EGD-GC on-line coupled simultaneous technique provides a microscale experimental method that is precise and rapid for the investigation of the reaction processes involved in the thermal decomposition of samples. The variations of the composition of reaction gases evolved can be traced and the mechanism of gas-solid phase and gas-gas phase thermal reactions in an inert gas or reactant gas can be studied. 

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