Authors:Wenwen Huang, Sreevidhya Krishnaji, David Kaplan, and Peggy Cebe
transition of alanine-rich A-block which is similar to the “crystalline module,” glycine rich B-block which is similar to the “elastic module” and their block copolymer BA using temperature-modulateddifferentialscanningcalorimetry (TMDSC). In the present
Temperature modulated differential scanning calorimetry (TMDSC), the most recent development that adds periodic modulation to the conventional DSC, has recently seen a fast growth due to availability of commercial instrumentation. The use of the technique necessitates a total control of all of the experimental parameters. The paper focuses on recent applications to investigate polymers .
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
Polyaniline/multi-walled carbon nanotube (PANI/MWNT) composites were prepared by in situ polymerization. Transmission electron
microscope (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) were used to characterize the PANI/MWNT composites.
Thermal stability and glass transition temperature (Tg) were measured by thermogravimetry (TG) and temperature modulated differential scanning calorimetry (TMDSC), respectively.
The TG and derivative thermogravimetry (DTG) curves indicated that with augment of MWNTs content, the thermal stability of
PANI/MWNT composites increased continuously. While, Tg increased and then decreased with the MWNTs content increasing from 0 to 20 mass%.
Authors:B. Wunderlich, A. Boller, I. Okazaki, and S. Kreitmeier
Temperature-modulated differential scanning calorimetry (TMDSC) is based on heat flow and represents a linear system for the measurement of heat capacity. As long as the measurements are carried out close to steady state and only a negligible temperature gradient exists within the sample, quantitative data can be gathered as a function of modulation frequency. Applied to the glass transition, such measurements permit the determination the kinetic parameters of the material. Based on either the hole theory of liquids or irreversible thermodynamics, the necessary equations are derived to describe the apparent heat capacity as a function of frequency.
differential scanning calorimetry, the melting behaviour of poly(oxytetramethylene)-alt-(aromatic oligoamide) (POTM-alt-AOA)
has been studied in comparison with that of polyoxytetramethylene glycohols
(POTMGs). The apparent melting temperature of the block copolymers is found
to be less than that of the corresponding POTMGs by approximately 30°C.
The relaxation time of melting of a POTM segment has been estimated and compared
with that of POTMG. The relaxation time of POTM-alt-AOA
is slightly shorter than that of POTMG when the molar mass of the POTM segment
is 2900; however, it is longer when the molar mass is 1400.
Authors:N. Delpouve, C. Lixon, A. Saiter, E. Dargent, and J. Grenet
Temperature modulated differential scanning calorimetry (TMDSC) and dynamic mechanical analysis (DMA) are used to calculate
cooperative rearranging region (CRR) average sizes for drawn poly(ethylene terephthalate) (PET) with different draw ratios
(λ) ranging from λ=1 to 4, according to Donth’s approach. It is shown for both studies that the CRR size decreases when increases,
due to the amorphous phase confinement by the crystals generated during the drawing. However, differences observed between
the values calculated from TMDSC and DMA investigations are explained by the differences between a mechanical uniaxial dynamic
solicitation (DMA) or a thermal solicitation (TMDSC) in terms of cooperative rearrangements at the glass transition.
We report a thermal analysis study of the effect of molecular weight on the amorphous phase structure of poly(phenylene sulfide),
PPS, crystallized at temperatures just above the glass transition temperature. Thermal properties of Fortron PPS, having viscosity
average molecular weights of 30000 to 91000, were characterized using temperature modulated differential scanning calorimetry
(MDSC). We find that while crystallinity varies little with molecular weight, the heat capacity increment at the glass transition
decreases as molecular weight decreases. This leads to a smaller liquid-like amorphous phase, and a larger rigid amorphous
fraction, in the lower molecular weight PPS. For all molecular weights, constrained fraction decreases as the scan rate decreases.
Authors:G. Van Assche, E. Verdonck, and B. Van Mele
The free radical cross-linking copolymerization of an unsaturated polyester resin with styrene is studied in isothermal conditions using temperature modulated differential scanning calorimetry (TMDSC) and dynamic rheometry. The dynamic rheometry measurements show that gelation occurs at a conversion below 5%, while TMDSC measurements show that an important autoacceleration starts near 60% conversion, giving rise to a maximum cure rate closely before the (partial) vitrification of the system near 80%. This indicates that the autoacceleration is not due to the sharp increase in bulk viscosity at gelation, but rather to a change in molecular mobilities at higher conversion.
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.