Thermodynamic data for decomposition reactions studied by differential scanning calorimetry: a cautionary note

1969 ◽  
pp. 266 ◽  
Author(s):  
T. A. Clarke ◽  
E. L. Evans ◽  
K. G. Robbins ◽  
J. M. Thomas
Keyword(s):  
Differential Scanning Calorimetry ◽  
Thermodynamic Data ◽  
Cautionary Note ◽  
Scanning Calorimetry ◽  
Decomposition Reactions

scholarly journals Enthalpies of Combustion and Formation of Histidine Stereoisomers

2018 ◽  
Vol 2018 ◽  
pp. 1-6
Author(s):  
A. Neacsu ◽  
D. Gheorghe ◽  
I. Contineanu ◽  
A. M. Sofronia ◽  
F. Teodorescu ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Crystalline State ◽  
Enthalpies Of Formation ◽  
Racemic Mixture ◽  
Group Additivity ◽  
Scanning Calorimetry ◽  
Combustion Energy ◽  
Temperature Range ◽  
Decomposition Reactions ◽  
The Stability

The combustion energy of histidine enantiomers (L and D) and of their racemic mixture was measured experimentally. The following values for the enthalpies of formation corresponding to the crystalline state were derived (L = −451.7, D = −448.7, DL = −451.5 kJ·mol−1), and information concerning their stability was obtained by correlating the values of the above thermochemical quantity with the structure of the molecules by using the group additivity scheme. The samples were characterized using a simultaneous thermogravimetry (TG) coupled with differential scanning calorimetry (DSC) techniques in the temperature range between ambient and beyond melting-decomposition, and the corresponding parameters were calculated. The high values of the decomposition temperatures highlight the stability of the compounds. The decomposition reactions are discussed in terms of DSC and TG data, obtained by us and other researchers.

scholarly journals Misuse of pre-exponential factor in the kinetic and thermodynamic studies using thermogravimetric analysis and its implications

2018 ◽  
Author(s):  
Imtiaz Ali
Keyword(s):  
Differential Scanning Calorimetry ◽  
Thermogravimetric Analysis ◽  
Thermodynamic Data ◽  
Standard Test ◽  
Test Method ◽  
Scanning Calorimetry ◽  
Exponential Factor ◽  
Thermodynamic Studies ◽  
Exponential Factors ◽  
Kinetic And Thermodynamic Studies

This paper describes the misuse of Arrhenius pre-exponential factor in the kinetic and thermodynamic studies using thermogravimetry. Standard test method (ASTM E698) has been used recently by many researchers to calculate the pre-exponential factor. ASTM E698 is reserved for differential scanning calorimetry (DSC) and impose many restrictions which have being overlooked by many recently. The obtained pre-exponential factors have been used to describe the thermodynamic behavior during the course of thermal conversions. The objective of this paper is to inform the readers that the pre-exponential factor obtained from the restricted equation can mislead and generate some false thermodynamic data.

Thermal Stability of N-Heterocycle-Stabilized Iodanes – A Systematic Investigation

2019 ◽  
Author(s):  
Andreas Boelke ◽  
Yulia A. Vlasenko ◽  
Mekhman S. Yusubov ◽  
Boris Nachtsheim ◽  
Pavel Postnikov
Keyword(s):  
Thermal Stability ◽  
Differential Scanning Calorimetry ◽  
Thermogravimetric Analysis ◽  
Systematic Investigation ◽  
Scanning Calorimetry ◽  
Thermal Stability Of

<p>The thermal stability of pseudocyclic and cyclic <i>N</i>-heterocycle-stabilized (hydroxy)aryl- and mesityl(aryl)-l<sup>3</sup>-iodanes (NHIs) through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) is investigated. NHIs bearing <i>N</i>-heterocycles with a high N/C-ratio such as triazoles show among the lowest descomposition temperatures and the highest decomposition energies. A comparison of NHIs with known (pseudo)cyclic benziodoxolones is made and we further correlated their thermal stability with reactivity in a model oxygenation. </p>

Optimasi Proses Pembuatan dan Karakterisasi Fisik Niosom Sinkonin

2019 ◽  
Vol 16 (2) ◽  
pp. 178
Author(s):  
Hariyanti Hariyanti ◽  
Sophi Damayanti ◽  
Sasanti Tarini
Keyword(s):  
Differential Scanning Calorimetry ◽  
Particle Size ◽  
Hair Follicle ◽  
Scanning Calorimetry ◽  
Span 60

Sinkonin praktis tidak larut dalam air, sedikit larut dalam kloroform dan alkohol. Hal ini berdampak pada rendahnya penetrasi transfollicular sinkonin, karena hanya bahan aktif hidrofilik yang mampu melewati hair follicle. Dengan demikian dibutuhkan satu sistem penghantaran yang mampu menurunkan hidrofobisitas sinkonin untuk meningkatkan penetrasi sinkonin ke follicle. Niosom merupakan vesikel ampifilik dengan struktur lapisan rangkap yang terbentuk dari hidrasi kombinasi surfaktan nonionik dan kolesterol yang mampu menurunkan hidrofobisitas sinkonin. Penelitian ini bertujuan untuk menentukan proses pembuatan niosom sinkonin yang optimum. Pembuatan niosom sinkonin diawali dengan menentukan temperatur gelasi (Tg) dari span 60 dengan Differential Scanning Calorimetry (DSC), kemudian dilanjutkan dengan optimasi proses meliputi: optimasi kecepatan rotavapor pembentukan film lapis tipis, temperatur hidrasi, kecepatan rotavapor hidrasi, waktu hidrasi, dan waktu sonikasi. Karakteristik vesikel niosom yang optimal meliputi: ukuran partikel dan indeks polidispersitas dengan menggunakan Particle Size Analized (PSA) serta efisiensi penjeratan sinkonin dengan menggunakan KCKT. Temperatur gelasi (Tg) span 60 45±2 oC, kecepatan rotavapor pembentukan film lapis tipis niosom 210 rpm, temperatur hidrasi 55±2 oC, kecepatan rotavapor hidrasi 210 rpm, waktu hidrasi 20 menit, waktu sonikasi suspensi niosom 1 menit. Ukuran vesikel yang diperoleh adalah 100–200 nm, indeks polidispersitas 0,2–0,4 dan efisiensi penjeratan niosom sinkonin 84,49±0,0025%. Proses pembuatan niosom sinkonin memiliki pengaruh besar terhadap hasil ukuran vesikel dan efisiensi penjeratan niosom sinkonin.

Improving Wire Sweep Performance by Measuring Degree of Cure of Epoxy Mold Compounds

2011 ◽  
Author(s):  
Sheila Liza B. Dal
Keyword(s):  
Differential Scanning Calorimetry ◽  
Shelf Life ◽  
Trial And Error ◽  
Active Components ◽  
Scanning Calorimetry ◽  
Degree Of Cure ◽  
Electronic Package ◽  
Viscosity Changes ◽  
Epoxy Mold Compounds

Abstract The choice of epoxy mold compound (EMC) for an electronic package is based mostly on how much protection it provides to the active components in the package. But the choice is not a straightforward process. Rather it is mostly trial and error using different assembly parameters to find the most robust material while assembly defects are monitored. One such defect associated to EMC processing is wire sweep, and many studies have shown that it is mainly caused by viscosity changes in the EMC. In this study, samples of EMC in various stages of shelf life and staging times were analyzed for degree of cure using a method called differential scanning calorimetry (DSC). Samples are then processed at assembly for wire sweep measurement. It was found out that degree of cure increases with staging time at different rates for each shelf life. It was also found out that wire sweep did not only increase with degree of cure but it was also found to be predictable with respect to the latter. Using this information, the age and staging limit for each material was identified that would not cause wire sweep issues.

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