The well-known divergence between the present ‘state of the art’ of thermogravimetry and industrial requirements is discussed.
Sources of errors are analyzed and the optimization of measuring conditions is discussed regarding the problems associated
with static and dynamic (flow) atmospheres, and interactions between materials and gases or vapors. Recommendations for gas-flow
control systems and vapor sources are given. Thermal stability and the kinetics of gas-evolving, reversible, thermal decompositions
of solids are discussed. The scope of TG-derived kinetics for practical use is examined. Some new characteristic points of
TG curves are proposed and defined, e.g. ‘procedure-independent decomposition temperature’ and ‘augmented decomposition temperature’
(obtained at pseudo-equilibrium conditions).
E37 on Thermal Measurements published a new test method 'Standard Test
Method for Volatility Rate by Thermogravimetry' in June 1999 with the
designation E 2008. This approach to assessing volatility utilizes an extension
of the pinhole technology previously employed by E37 for vapor pressure determinations
using differential scanning calorimetry (ASTM E 1782). After publication of
the test method E 2008, an Interlaboratory Study was undertaken to develop
a 'Precision and Bias' statement to be assigned with the test
method. This paper provides some background data that supports the claim that
E 2008 is generally insensitive to experimental conditions other than temperature.
The Interlaboratory Study showing the statistical review is also discussed.
Authors:J May, A Del Grosso, N Etz, R Wheeler, and L Rey
(TG), thermogravimetry/mass spectrometry (TG/MS), and loss-on-drying methodology
are used to provide residual moisture results for freeze-dried biological
products regulated by the US Food and Drug Administration. Residual moisture
specifications must be met in order to ensure freeze-dried biological product
potency and stability throughout the licensed product's shelf life.
TG, TG/MS, loss-on-drying and vapor pressure moisture measurements are compared
for a BCG Vaccine. Comparisons are made between residual moisture data for
the freeze-dried cake and vapor pressure moisture determinations in the space
above the freeze-dried cake in the final container. Vapor pressure moisture
precision data is presented for α-interferon and BCG vaccine. Impact
of residual moisture and vapor pressure moisture upon product stability is
A new technique, called modulated thermogravimetry, is introduced as a tool for obtaining continuous kinetic information for
decomposition and volatilization reactions. The approach makes use of an oscillatory temperature program to obtain kinetic
parameters during a mass loss. MTGA™ may be used under quasi-isothermal conditions to observe a single mass loss or may be
combined with linear heating rate or Hi-Res™ controlled rate thermogravimetry to scan from one mass loss region to another.
Results obtained are in agreement with those obtained by other kinetic methods.
A possible deduction is proposed of channel length distribution in one-dimensional porous materials from the kinetic data
obtained in isothermal thermogravimetry (TG). The method utilizes the absorption/desorption of small molecules into one-dimensional
nano-channel. In the surface-controlled absorption/desorption, the second derivative with respect to time is directly proportional
to the channel-length distribution function. Even in the diffusion-controlled case, the second derivative with respect to
the square root of time gives rough information on the distribution function.
Authors:A. Araujo, V. Fernandes, A. Silva, and J. Diniz
The evaluation of the crystallinity of several samples of ALPO-11 was performed by X-ray diffraction and thermogravimetry.
Through XRD, the degrees of crystallinity of the samples were determined by the measurement of the area of the peaks at 2γ
ranging from 20.7 to 24.1 degrees. The sample that presented the largest area was considered as 100% crystalline and the areas
of the other samples were normalized in relation to this. From TG, the degree of crystallinity was determined considering
the mass loss in the temperature range from 453 to 653 K that is related to remotion of di-isopropylamine molecules used during
the synthesis procedure. The quantity of diisopropylamine on the material is proportional to the degree of crystallinity.
Authors:Ana Carla S. L. S. Coutinho, Solange A. Quintella, A. S. Araujo, Joana M. F. Barros, Anne M. G. Pedrosa, V. J. Fernandes Jr., and M. J. B. Souza
Nanoporous silica with narrow pore size distribution has attracted increasing attention as a novel material for separations and reactions involving large molecules. SBA-15 has been synthesized in an acidic medium using a triblock copolymer as template. In this work, the SBA-15 was synthesized by the hydrothermal treatment at 373 K for 48 h, of a gel with the following overall molar composition: 1.0TEOS:0.017P123:5.7HCl:193H2O, where TEOS is tetraethyl orthosilicate and P123 is poly(ethylene oxide, propylene oxide and 1,4-dioxane). The obtained material was characterized by thermogravimetry, X-ray diffraction, infrared spectroscopy and BET surface area. A kinetic study using the model free model was accomplished in the stage of decomposition of the template (P123). The obtained value of the apparent activation energy was ca. 131 kJ mol−1.
used and demonstrate that thermogravimetry (TG) can be a good replacement for these methods.
Sampling and current analysis techniques
As CFR sect. 211.67 states, “Equipment and utensils shall be cleaned, maintained, and
Authors:T. Kleps, M. Piaskiewicz, and W. Parasiewicz
Thermogravimetry was employed to study the changes occurring in rubber vulcanizates during devulcanization carried out by
microwave treatment, a new promising method of recycling rubber waste. The thermogravimetric parameters Ti , T5 and Tp and the compositions of devulcanizates in comparison with vulcanizates were determined. The results obtained allowed estimation
of the degree of destruction of the polymer chains in response to microwave treatment and permitted establishment of the most
advantageous conditions of devulcanization in order to obtain the best properties of rubber devulcanizates for reuse in rubber
The results demonstrated that thermogravimetry is a very useful method for investigation and control of the microwave devulcanization
Water states and displacements can be investigated with thermogravimetry (TG) either in its classical or in the Knudsen version (where standard pans are replaced with Knudsen cells). The case of wheat flour dough is considered in various steps of bread making, namely, mixing, proofing, baking, staling. The split of DTG signals into various components (gaussian functions) support the assumption that the overall dough water is partitioned into various fractions. Few comments are devoted to water displacements during freezing.