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TOPEM, a new temperature modulated DSC technique

Application to the glass transition of polymers

Journal of Thermal Analysis and Calorimetry
Authors: Iria Fraga, S. Montserrat, and J. Hutchinson

Abstract  

TOPEM is a new temperature modulated DSC technique, introduced by Mettler-Toledo in late 2005, in which stochastic temperature modulations are superimposed on the underlying rate of a conventional DSC scan. These modulations consist of temperature pulses, of fixed magnitude and alternating sign, with random durations within limits specified by the user. The resulting heat flow signal is analysed by a parameter estimation method which yields a so-called ‘quasi-static’ specific heat capacity and a ‘dynamic’ specific heat capacity over a range of frequencies. In a single scan it is thus possible to distinguish frequency-dependent phenomena from frequency-independent phenomena. Its application to the glass transition is examined here.

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Vitrification during the isothermal cure of thermosets

Part I. An investigation using TOPEM, a new temperature modulated technique

Journal of Thermal Analysis and Calorimetry
Authors: I. Fraga, S. Montserrat, and J. Hutchinson

Abstract  

The process of vitrification that occurs during the isothermal cure of a cross-linking system at temperatures below T g∞, the glass transition temperature of the fully cured resin, has been studied by TOPEM, a new temperature modulated DSC (TMDSC) technique based upon the use of stochastic temperature pulses. A comparison is made between TOPEM and another TMDSC technique, and some advantages of TOPEM are considered. The TOPEM technique is used to show that the mobility factor is not always a reliable approach to predicting the cure rate during vitrification, in view of its frequency dependence. Also, the dependence of the apparent vitrification time on frequency is examined. There appears to be a non-linear relationship between the apparent vitrification time and log(frequency), which is further discussed in the second part of this series.

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Abstract  

The processes of vitrification and devitrification that occur in an epoxy resin when it cures non-isothermally with a hardener are studied in terms of their frequency dependence and as a function of the heating rate. A novel modulated DSC technique, TOPEM, has been used which permits the evaluation of the frequency dependence for a single sample in a scan at constant underlying heating rate, thus avoiding errors arising from the composition of the sample. The effects of both frequency and heating rate on vitrification and devitrification are investigated. Some advantages of this technique are observed and discussed.

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Journal of Thermal Analysis and Calorimetry
Authors: C. A. Gracia-Fernández, P. Davies, S. Gómez-Barreiro, Beceiro J. López, J. Tarrío-Saavedra, and R. Artiaga

thermosets. Part I. An investigation using TOPEM, a new temperature modulated technique . J Therm Anal Calorim 91 : 687 – 695 10.1007/s10973-007-8613-7 . 29. Itota , T , Carrick , TE

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