ICTA temperature standards

Clark and Garlik (133) compared the TS peak temperatures with the DTA peak temperatures for the NBS-ICTA temperature standards. However, the precise relationship between the TS peak and the DTA peak for a given thermal event was not established. 

Table 3. DTA-Temperature Standards NBS-ICTA standard reference material...

Accurate temperature calibration using the ASTM temperature standards [131, 132] is common practice for DSC and DTA. Calibration of thermobalances is more cumbersome. The key to proper use of TGA is to recognise that the decomposition temperatures measured are procedural and dependent on both sample and instrument related parameters [30]. Considerable experimental control must be exercised at all stages of the technique to ensure adequate reproducibility on a comparative basis. For (intralaboratory) standardisation purposes it is absolutely required to respect and report a number of measurement variables. ICTA recommendations should be followed [133-135] and should accompany the TG record. During the course of experiments the optimum conditions should be standardised and maintained within a given series of samples. Affolter and coworkers [136] have described interlaboratory tests on thermal analysis of polymers. 

Numetal (386°C), Permanorm 5 (459°C), Trafoperm (754°C). The method does not permit the temperature measurement with high precision. These standards have been studied by several authors. The ICTA temperatures are within 5-10°C. McGhie et al. proposed a calibration technique in which a small inert platinum weight is suspended by a fusible link composed of a calibration standard that releases the platinum weight at the temperature of melting. The Mettler instrument TGA 850 is constructed so that the melting curve of standards can be measured and used as calibration, as demonstrated in Table 4. 

As with many other analytical techniques, the temperature axis used in differential thermal analysis (and DSC) must be calibrated with materials having known transition temperatures. The International Confederation of Thermal Analysis (ICTA) has been very active in developing a set of standard materials for this purpose (19) and has worked with the U.S. National Bureau of Standards to have these materials made commercially available (20). The U.S. National Bureau of Standards GM 754-GM 760 DTA temperature standards are listed in Table 6.2. They cover the temperature range from —83 to 925 C. The results of an ICTA round-robin study with 24 cooperating laboratories have been reported by Menis and Sterling (20). 

The extrapolated onset temperatures for the NBS-ICTA standard materials are given in Table 11.9 (133). Three sets of data are presented, the 1CTA (134) temperature the DTA (model 673-4 DTA apparatus) temperature and the TS-DTA apparatus temperature. Standard deviations between these onset temperatures and the ICTA mean extrapolated onset values (7iCTA) are —1.5 and — 6-5°C, respectively. The deviation of the DTA 673-4 is negligible... 

In contrast to calorimetric standards, there exists an official set of temperature standards for DTA and DSC measurements (Table 2). They were developed by the International Confederation for Thermal Analysis (ICTA). The materials can be obtained from this organization. These standards were created several years ago, when accurate T and AH measurements were still not possible to be made simultaneously. Unfortunately some of them are not suitable for calorimetric calibration, indicated by in... 

To establish a common basis for thermal analysis experiments, a series of ICTA (International Confederation for Thermal Analysis)-NBS (National Bureau of Standards) Standard Reference Materials were proposed via common experiments. These Standard Reference Materials have now been re-named ICTA Certified Reference Materials (CRM) and catalogued by the NBS (now NIST) as GM-758, GM-759 and GM-760 (see Table 1.4). The temperature standards of CRM are not the true transition temperatures of these materials, e.g. the difference between the extrapolated onset of a CRM and the equilibrium transition temperature is usually 3 "C. 

McAdie, H. G., 1972. Requirements and realization of thermal analysis standards. Temperature standards for DTA. In Thermal Analysis. Proc. Third ICTA Davos 1971. H. G. Wiedemann, ed. Basel and Stuttgart Birkhauser Verlag, 1 591. 

Since there is no contact between pan and furnace, the thermal lag is higher than in DSC. The standards recommended by ICTA and distributed by NBS are ferromagnetic standards exhibiting loss of ferromagnetism at their curie point temperature within a magnetic field Nickel (354°C), Permanorm 3 (266°C),... 

Blaine and Fair (55) determined new estimates for the true magnetic transition temperatures of the ICTA Certified Magnetic Reference Materials GM761, using a six-point calibration method. The results of the magnetic transition temperatures obtained are presented in Table 3.2. Experimental measurement precision varied from 0.81°C for nickel to 3.2°C for Permanorm 3. The narrowest magnetic transition temperature was 3.0°C for nickel, whereas the widest was 13.1°C for Permanorm 3. A pooled standard deviation of 2.0°C could be calculated from these data. The experi-... 

Accurate temperature calibration using NIST-ICTA melting point standards (indium, tin, lead, aluminium, zinc of purity >99.999% accuracy to O.DC or better [59]) is essential. Richardson [60] has critically described standardisation and quality assurance of DSC. Much work has been done to implement peak separation software techniques. 

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