Authors:O. P. Mchedlov-Petrossyan, V. L. Chernyavski, and V. Y. Dubnitski
The paper describes the results of statistical analysis of DTA diagrams. A connection is found between the second and third endothermal effects. An analysis of geometrical characteristics of theT, S andh values of DTA diagrams confirms the absence of reliable connections. The rank correlation coefficients are determined according to Spearman. Non-linear programming is formulated to obtain the kinetic dependencies of the process of hydration of cement studied by DTA.
Some of the materials used as chromatography packings, adsorbents or catalyst supports are glasses of controlled porosity (CPGs). The chemical structure of these materials can easily be changed by heating the porous glass. Such thermal modification leads to the enrichment of the CPG surface in boron atoms. The long exposure of CPGs to thermal treatment can even cause the formation of borate crystals in the pores of the glasses. This paper considers the application of thermal analysis to the investigation of porous glasses heated for different periods of time.
The hydration kinetics of C3S pastes can be easily evaluated by DTA using the most intense and reversible transition of C3S. Some modifications are proposed to Ramachandran's method concerning the measurement of this effect, the weight of the sample used for each experiment and the heating rate. The results of the hydration degree versus times of C3S agree reasonably with those reported by Ramachandran, while still better agreement is observed with those of Locher who used X-ray quantitative analysis.
Attempts were made to apply DTA together with TG for the investigation of asphalt-poly(methyl methacrylate) systems. Compositions were made by photopolymerization of methyl methacrylate in the presence of asphalt or asphalt components.
Thermogravimetric analysis in conjunction with evolved gas analysis are discussed for powder PMMA, particle diameter of 0.1
mm. Furthermore, differential thermal analysis measurements were performed in both pure nitrogen and oxidative environment.
These measurements are conducted to assess major differences associated with particle size. The results indicated for powder
PMMA, in pure nitrogen the degradation can be described as three-step reactions, while in oxidative environment it is two-step
reactions. Furthermore the reaction in both environments are mainly endothermic. This in contrast to results reported for
industrial-grade PMMA with relatively larger particle size of 0.5 mm.
Authors:V Vinciguerra1, R Bucci, F Marini, and A Napoli
The thermal decomposition
of iminodiacetic, oxydiacetic, and thiodiacetic acids in helium atmosphere
has been studied by means of thermogravimetry (TG), differential thermal analysis
(DTA) and temperature-programmed pyrolysis directly coupled with mass spectrometry
(TPPy-MS). Evolved gas analysis (EGA) profiles of iminodiacetic and oxydiacetic
acids were obtained and compared with TG and DTA profiles.
of iminodiacetic acid forms water, CO, CO2, CH3CN,
HCN and some hydrocarbons. After water evolution a cyclic anhydride is formed,
as well as for oxydiacetic acid. Thiodiacetic acid vaporizes without decomposition.
The aim of this study was to correlate the results of experimental data using DTA method and predictions of artificial neural
network (ANN) and multivariate linear regression (MLR). Thermal decomposition of polymers was analyzed by simultaneous DTA
method, and kinetic parameters (critical points, the change of enthalpy and entropy) of polymers were investigated. A computer
model based on multilayer feed forwarding back propagation and multilayer linear regression model were used for the prediction
of critical points, phase transitions of low-density polyethylene (LDPE) and mid-density polyethylene. As a result of our
study, we concluded that ANN model is more suitable than MLR about prediction of experimental data.