Authors:Javier Tarrío-Saavedra, Carlos Gracia-Fernández, Jorge López-Beceiro, Salvador Naya, and Ramón Artiaga
temperature modulated differential scanning calorimetry (TMDSC) technique, is suggested for identifying and characterizing the organic–inorganic interphase produced in nanomaterials such as fumed silica-filled epoxy and thermoplastic polyurethane (TPU
Authors:H. Dantas, R. Mendes, R. Pinho, L. Soledade, C. Paskocimas, B. Lira, M. Schwartz, A. Souza, and Iêda Santos
Gypsum is a dihydrated calcium sulfate, with
the composition of CaSO4⋅2H2O,
with large application interest in ceramic industry, odontology, sulfuric
acid production, cement, paints, etc. During calcination, a phase transformation
is observed associated to the loss of water, leading to the formation of gypsum
or anhydrite, which may present different phases. The identification of the
phases is not so easy since their infrared spectra and their X-ray diffraction
patterns are quite similar. Thus, in this work, temperature modulated differential
scanning calorimetry (TMDSC) was used to identify the different gypsum phases,
which can be recognized by their different profiles.
The non-equilibrium process due to irreversible heat exchanges occurring during a temperature modulated differential scanning
calorimetry (TMDSC) experiment is investigated in detail. This enables us to define an experimental frequency dependent complex
heat capacity from this calorimetric method. The physical meaning of this dynamic heat capacity is discussed. A relationship
is clearly established between the imaginary part of this complex quantity and the net entropy created during the experimental
The response of a chemical reaction to temperature modulation has been examined experimentally in an epoxy thermosetting system.
The kinetic response appears in the imaginary part of the complex heat capacity determined by TMDSC. From the imaginary part
and the ‘non-reversing’ heat flow of reaction, the activation energy has been determined. The value of the activation energy
obtained is in good agreement with the value determined from Kissinger's plot utilizing the peak temperatures of the exothermic
reaction with different heating rates.
Authors:C. A. Gracia-Fernández, P. Davies, S. Gómez-Barreiro, Beceiro J. López, J. Tarrío-Saavedra, and R. Artiaga
, 2 ]. Differential scanning calorimetry (DSC) and modulated temperature DSC (TMDSC) are extensively used to monitor the curing reaction of these materials [ 3 ]. Most of the curing reactions are thermally induced, but there are important applications
Authors:F. Cser, M. Jollands, P. White, and S. Bhattacharya
Cross-linked polymers have particular rheological responses during reprocessing, e. g. if the material is recycled, special
processing conditions are required. Other virgin polymers can be used as a blending component to enhance rheological properties.
Bi-layer film of EVA/LLDPE was produced on a blown film line and cross-linked by high-energy radiation. This film was ‘agglomerated’
then reprocessed in a twin-screw extruder with virgin LLDPE and blown into film. The miscibility of the blend components was
then studied using a TA Instruments temperature modulated differential scanning calorimeter (TMDSC).
It was found that the cross-linked EVA/LLDPE scrap and the LLDPE have a slight miscibility in the liquid state. A bigger portion
of LLDPE was miscible (dissolved) in EVA in low LLDPE blends. A positive deviation in the heat capacity of the LLDPE component
compared to the additivity rule indicated melting to be more reversible in the first heating cycle. This initial miscibility
was attributed to being induced by high shear during processing. A smaller positive deviation also occurred in the second
heating cycle. This was attributed to intrinsic miscibility.
Authors:F. Cser, J. Hopewell, K. Tajne, and R. Shanks
Polyethylene samples prepared by thermal fractionation (TF) were annealed in several consecutive cycles in a temperature modulated
DSC (TMDSC) at a temperatures one C below the peak temperatures, increased from cycle to cycle relative to these peaks. The
transition enthalpy of each cooling cycle was greater or equal to that of the preceding heating cycle. The total heat-flows
of each heating cycle corresponded to those of the samples in the reference state up until the vicinity of the annealing temperature.
During the annealing, the heat capacities decreased to a lower value over a one minute period. The thermal memory effect caused
by the thermal fractionation was eliminated by a small overheating of the material for a short time. The fast disappearance
of the thermal memory by a relatively very small degree of heating above their melting temperature denies a long range physical
separation of macromolecules by TF.
Authors:N. Santos, J. Santos, F. Sinfrônio, T. Bicudo, I. Santos, N. Antoniosi Filho, V. Fernandes, and A. Souza
The babassu (Orbignya Phalerata Mart.) biodiesel has lauric esters as main constituents, resulting in high oxidative stability and low cloud and freezing
points. In order to reduce these side effects, the saturated ethyl esters content was reduced by means of winterization process.
The TMDSC and PDSC techniques were used to verify the thermal and oxidative stabilities of the ethyl babassu biodiesel. During
the heating stage, the winterized solid phase of ethyl esters presented an endothermic transition associated to the solidification
process. This behavior was not observed for the liquid winterized FAEE, confirming the efficiency of the winterization process.
Authors:I. Bravo-Osuna, A. Muńoz-Ruiz, M. Jiménez-Castellanos, J. Ford, and M. Whelan
The use of modulated temperature differential scanning calorimetry (TMDSC) and differential scanning calorimetry (DSC) in the measurement of the glass transition temperature (Tg) in polymer-water systems presents several important problems. These include the presence of water evaporation endotherms, partial water evaporation during scanning, changes in pan integrity due to vapour pressure developing in the pan headspace during analysis, and possible interaction between water and polymer at high temperatures. As a result, in most of the cases, only apparent Tg values can be obtained. In this study, TMDSC and DSC were used to determinate the thermal behaviour of methylmethacrylate copolymer-water systems. The samples were previously equilibrated at different relative humidities (RH) from 0 to 97% RH. Three different pan arrangements were used. In addition, thermogravimetric analysis (TG) was carried out to determine the initial amount of water in the sample. None of the pan arrangements was entirely suitable for the study of these systems. When sealed pans were used, the plastification effect of water was observed. Some evidence of degradation was also observed in which water and methylmethacrylate appeared to play roles.
Authors:B. Sauer, W. Kampert, R. McLean, and P. Carcia
The thermal and crystal morphological properties of poly[ethylene teraphthalate] (PET) and poly(ethylene-2,6-naphthalenedicarboxylate) (PEN) biaxially oriented films were compared to amorphous and other isotropic semi-crystalline samples. Crystal melting as a function of temperature was characterized by temperature modulated DSC (TMDSC) and found to begin just above the glass transition for both oriented films. About 75°C above the glass transitions, substantial exothermic recrystallization begins and continues through the final melting region in oriented films. The maximum in the non-reversing TMDSC signal for the oriented films signifies the maximum recrystallization exothermic activity with peaks at 248°C and 258°C for PET and PEN, respectively. The final melting endotherm detected was 260°C and 270°C for PET and PEN, and is shown by the TMDSC data and by independent rapid heating rate melting point determinations to be due to the melting of species recrystallized during the heating scan. The results are compared with TMDSC data for initially amorphous and melt crystallized samples. The volume fraction of rigid species (Frigid=total crystal fraction plus rigid amorphous or non-crystalline species) were measured by TMDSC glass transition data, and contrasted with the area fraction of rigid species at the oriented film surface characterized with very high resolution atomic force microscopy (AFM) phase data. The data suggest that the 11 nm wide hard domains in PET, and 21 nm wide domains in PEN film detected by AFM consist of both crystal and high stiffness interphase species.