Authors:Christelle Herman, Tom Leyssens, Valérie Vermylen, Véronique Halloin, and Benoît Haut
with metastable forms [ 2 ].
DifferentialScanningCalorimetry (DSC) is commonly used to evaluate most of the thermal properties of solid states, such as melting temperatures and enthalpies or specific heat capacities [ 3 ]. Whilst recent
Being a reliable analysis method for the determination of caloric effects, power compensated differentialscanningcalorimetry (DSC) was applied to determine the heat of reaction of hydrothermal carbonization (HTC
This study examines the polymerization of dental monomers catalyzed by synthesized acylphosphine oxides in a differential
scanning calorimetry (DSC) cell. This research focuses on establishing a relationship between radicals generated by the acylphosphine
oxide photoinitiators and the kinetic reaction rates of methyl methacrylate (MMA) and acrylamide (ACM), a model monomer. The
thermal stability of mono- and di-acylphosphine oxides was examined by DSC. Endothermic melting and exothermic polymerization
reactions initiated with the two initiators were recorded. The acrylamide model system laid the ground work for the critical
evaluation of the synthesized new initiators of mono (2,4,6-trimethylbenzoyl) diphenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)
phenylphosphine oxide. The bis(acyl) phosphine oxide photoinitiator was more reactive than the mono-(acyl) phosphine oxide
with methyl methacrylates under laboratory conditions. In exothermic reactions, temperatures rose higher and more rapidly
for bis(acyl) phosphine oxide initiated reactions than mono-(acyl) phosphine oxide initiated reactions.
Authors:D. Hourston, M. Song, H. Pollock, and A. Hammiche
Modulated-temperature differential scanning calorimetry was used to measure the glass transition temperature,Tg, the heat capacity relaxation in the glassy state and the increment of heat capacity, δCp, in the glass transition region for several polymers. The differential of heat capacity with respect to temperature was used
to analyseTg and δCp simply and accurately. These measurements are not affected by complex thermal histories.
Differentialscanningcalorimetry (DSC) is extensively used in chemistry and physics to analyze, e.g. phase transitions of different compounds [ 1 , 2 ]. Recently this technique has been used with increasing
Authors:A. Samuni, D. Crommelin, N. Zuidam, and Y. Barenholz
This study was aimed to investigate the physicochemical changes induced in 200 nm extruded oligolamellar DPPC:DPPG (10:1)
liposomes by freezing, followed by γ-irradiation, in the absence and presence of 5 mM stable cyclic nitroxide radicals, 2,2,6,6-tetramethylpiperidine-1-oxyl
(Tempo) and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (Tempol). The characterization is based on the use of differential
scanning calorimetry (DSC) and was aimed to differentiate the contribution of freezing and γ-irradiation in the presence and
absence of nitroxides. Liposomal preparations of DPPC/DPPG which have sub-, pre- and main-phase transitions in the temperature
range (0�C<Tm<50�C) were used.
Our results show that: (1) freezing modified and induced fusion to MLV as well as fission to SUV, (2) freezing did not fully
prevent the radiation-induced changes in the thermotropic characteristics of the liposomes, and (3) Tempo and Tempol did not
prevent the changes in thermotropic behavior caused as a result of freezing of the liposomal dispersion. These results demonstrate
that DSC is a powerful and sensitive tool in both physical and chemical studies of lipid assemblies.
Authors:E. Marti, E. Kaisersberger, and E. Füglein
Multicycle Differential Scanning Calorimetry (MCDSC) is a procedure where repeated temperature cycles are executed and the
measured data are superimposed for a selected number of cycles. Temperature cycles with a single sample are executed under
selected experimental conditions in one of these procedures, namely, the MCDSCs. The second one, MCDSCm is a procedure in which every identical temperature cycle starts with a new sample of the same substance of a similar mass.
The procedure MCDSCs using the same sample for a number of cycles is only applicable for substances and materials which are chemically and physically
stable under the selected experimental conditions. The application of MCDSC enhances two extremely important qualities of
a DSC measurement, namely, the sensitivity and the statistical base, both qualities with respect to the final data elucidated.
Another possibility by MCDSC also related to the enhanced sensitivity can lead the discovery of a phenomenon which hitherto
has not been observed. The most important result of any MCDSC application is the determination of the mean DSC curve within
the temperature interval of interest by superimposing the single curves point by point and by the division of the calorimetric
values obtained with the number of scans evaluated. The signal-to-noise-ratio (SNR) for the mean curve can be compared with
the value determined for one or even for all the single curves measured yielding the improvement factor achieved with a MCDSC
measurement. This experimentally determined improvement of the SNR can be compared with the value given on a statistical consideration
by Gauss as the square root of the number of cycles evaluated. The main aims of this article are to prove the practical application
of the procedure and the efficiency in case of rather small sample masses. Substances were selected with known enthalpy transitions
and, in addition, polystyrene was taken for a determination of the data for the glass transition by MCDSC. Rather small sample
masses in the order of micrograms as well as the experimental conditions have been selected for the measurements with 4,4′-azoxyanisole
and n-hexatriacontane with the expectation to get a value of SNR for the single curves of about unity or even below. Two aims should
be achieved with these experiments. First, the multicycle procedures and the data evaluation developed should be capable of
establishing, after performing of a certain number of cycles, a mean curve showing an improvement over the SNR with respect
to the single curves. Second, we should be able to get a rough estimation of the lower limit of the SNR for a single curve,
below the instrumental noise level of the DSC used, necessary to achieve with a MCDSC experiment a mean curve with a clearly
Authors:L. Delbreilh, M. Negahban, M. Benzohra, C. Lacabanne, and J. Saiter
Relaxation times of bisphenol A polycarbonate around the glass transition temperature are estimated using the combination
of differential scanning calorimetry (DSC) and thermostimulated depolarization currents (TSDC). These measurements are performed
using samples with different thermal histories below and above the vitrification transformation. This protocol enables the
extension of the range of equilibrium relaxation times measured by dielectric spectroscopy. By this mean we may recalculate
the values of the Kauzmann temperature and fragility index.
Authors:I. Chakarska, S. Todinova, and K. Idakieva
The process of cross-linking of collagen phosphoric acid hydrolysates (CH) with cyanuric chloride (CY) was studied by the
increase in the denaturation temperature using differential scanning calorimetry (DSC). This measurement gave indications
concerning the efficiency of the treatment, i.e., the extent of cross-linking of the collagen hydrolysates. The optimal conditions
for cross-linking were determined: CH/CY in a ratio 1:1, reaction time 1 h at temperature 50 °C. At these conditions cross-linked
structural units with higher thermal stability were formed.
Modulated temperature differential scanning calorimetry (MTDSC) is used to study simultaneously the evolution of heat flow
and heat capacity for the isothermal and non-isothermal cure of an epoxy-anhydride thermosetting system. Modelling of the
(heat flow related) chemical kinetics and the (heat capacity related) mobility factor contributes to a quantitative construction
of Temperature-Time-Transformation (TTT) and Continuous-Heating-Transformation (CHT) diagrams for the thermosetting system.