Uncertainty evaluation for the adiabatic temperature rise in isoperibol calorimetry

This article describes a practical approach for evaluating the uncertainty of results for determinations of the adiabatic (corrected) temperature rise in isoperibol calorimetry. The methodology is firmly based on the recommendations of the Guide to the expression of uncertainty in measurement (GUM). Although developed for a specific modification of the Regnault?CPfaundler method, the approach is sufficiently general to make it applicable to virtually any other scheme for the evaluation of temperature?Ctime curves in temperature-rise calorimetry.     

Recent Progress in Low Temperature Calorimetry

The paper gives a review on recent progress on new methods, instrumental innovations and new trends in low temperature calorimetry as reported in the last five years in the literature. The paper refers to establishing strictly adiabatic conditions, improved analysis of quasi-adiabatic experiments, high resolution adiabatic and isoperibol scanning calorimeters and microcalorimeters for the study of μ-samples. This revised version was published online in August 2006 with corrections to the Cover Date.     

Modeling the heat flow and heat capacity of modulated differential scanning calorimetry

Modulated differential scanning calorimetry (MDSC) uses an abbreviated Fourier transformation ?r the data analysis and separation of the reversing component of the heat flow and temperature signals. In this paper a simple spread-sheet analysis will be presented that can be used to better understand and explore the effects observed in MDSC and their link to actual changes in the instrument and sample. The analysis assumes that instrument lags and other kinetic effects are either avoided or corrected for.     

The art of calorimetry

An introduction to the various types of calorimeters is given. The requirements for precise temperature measurements with thermistors are derived. Methods and equations for accurate heat exchange corrections for isoperibol temperature-change calorimetry under various conditions are derived. The characteristics and design principles for constant temperature baths are discussed. The construction of devices for addition of reagents, of stirrers, and of calibration heaters is described.     

Monte Carlo model of the temperature rise at a GaAs surface under an electron beam

Scanning electron microscopy (SEM) has frequently been used to study semiconductor materials. It offers the possibility of obtaining reliable qualitative and quantitative information on relevant local material parameters. The temperature rise due to electron‐beam bombardment can influence some semiconductor parameters, which then will influence the SEM information. In this work we propose a model calculation based on the Monte Carlo (MC) method to calculate the temperature rise due to electron‐beam heating. The results show that the temperature rise increases with increasing numbers of electrons (electron‐beam current), and the inverse behavior is observed with respect to the electron energy (electron‐beam voltage). The decrease in temperature rise with depth is also obtained. Copyright © 2006 John Wiley & Sons, Ltd.     

The Effect of the Pressure Pulse on Solution Temperature in Stopped-Flow Calorimetry

Abstract

The pressure pulse effect, which exhibits itself by a step conductance rise on the response curves of thermistors in the stopped-flow microcalorimeter, is shown theoretically and experimentally to be due to the temperature rise of the solution caused by its adiabatic compression. Thermocouples respond similarly to thermistors in the range of 1 to 400 bars.     

Enthalpy relaxation of an epoxy–anhydride resin by temperature‐modulated differential scanning calorimetry

The enthalpy relaxation of an epoxy–anhydride resin was studied by physical aging and frequency‐dependence experiments with alternating differential scanning calorimetry (ADSC), which is a temperature‐modulated differential scanning calorimetry technique. The samples were aged at 80 °C, about 26 K below the glass‐transition temperature, for periods up to 3800 h and then scanned under the following modulation conditions: underlying heating rate of 1 K min⁻¹, amplitude of 0.5 K, and period of 1 min. The enthalpy loss was calculated by the total heat‐flow signal, and its variation with the log (aging time) gives a relaxation rate (per decade), this value being in good agreement with that calculated by conventional DSC. The enthalpy loss was also analyzed in terms of the nonreversing heat flow, revealing that this property is not suitable for calculating enthalpy loss. The effect of aging on the modulus of the complex heat capacity, |Cp*|, is shown by a sharper variation on the low side of the glass transition and an increase in the inflexional slope of |Cp*|. Likewise, the phase angle also becomes sharper in the low‐temperature side of the relaxation. The area under the corrected out‐phase heat capacity remains fairly constant with aging. The dependence of the dynamic glass transition, measured at the midpoint of the variation of |Cp*|, on ln(frequency) allows one to determine an apparent activation energy, Δh*, which gives information about the temperature dependence of the relaxation times in equilibrium over a range close to the glass transition. The values of Δh*, determined from ADSC experiments in a range of frequencies between 4.2 and 33 mHz and at an amplitude of 0.5 K, and an underlying heating rate of 1 K min⁻¹, were analyzed and compared with that obtained by conventional DSC from the dependence of the fictive temperature on the cooling rate. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2272–2284, 2000     

Using the Transfer Function of an Isoperibolic Reaction Calorimeter for Thermo-kinetic Analysis

It is an aim of the present work to determine the chemical heat flow rate of a reaction without explicitly solving the heat balance equations. Therefore, it is necessary to calculate the heat flow rate directly from the temperature course of an experimentally determined reaction. For this transformation the transfer function of the calorimeter is needed 1 . An isoperibol reaction calorimeter was used for the experiments. With different calibrations and gained transfer functions, it is shown that the chemical heat flow rate can be determined from the temperature course of a reaction. The evaluation is fast and easy to use, which improves automation and prevents possible input errors.     

Determination of the heatsetting temperature of polyester by TMA

The determination of the effective temperature of the thermal treatment applied to polyester substrates in the textile process has been broadly studied by differential scanning calorimetry (DSC). In this investigation, the authors have studied the possibilities of the thermomechanical analysis (TMA) as a method for the determination of this temperature. For this purpose, fabrics of polyester heatset in an industrial plant between 160 and 210°C, have been analyzed by DSC and TMA. The good results obtained show the possibilities of this technique for the determination of the effective temperature of a thermal treatment. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Use of Adiabatic Calorimetry for the Process Analysis and Safety Evaluation in Free Radical Polymerization

Adiabatic calorimetry is a technique that has been introduced as an important approach to hazard evaluation of exothermically reactive systems. In this paper the free radical polymerization of methyl methacrylate (MMA) has been studied. One of the most important aspects of MMA polymerization is its exothermicity and autoaccelerating behaviour, these characteristics can generate the occurrence of a runaway reaction.In a runaway situation the reacting system is close to adiabatic behaviour because it is unable to eliminate the heat that is being generated. An even worse situation can be reproduced in the laboratory with the Phi-Tec pseudo-adiabatic calorimeter. Process design parameters that are usually calculated from thermodynamic data or using semiempirical rules, such as adiabatic temperature rise or maximum attainable pressure, can be directly determined.The existence of the ceiling temperature has been experimentally demonstrated.This revised version was published online in November 2005 with corrections to the Cover Date.     

Potential applications of microcalorimetry for the study of physical processes in pharmaceuticals

In calorimetry, the heat-flow to or from a sample is measured as a function of time (isothermal calorimetry) or temperature (scanning calorimetry). The technique is not dependent on the physical form of the sample and is usually non-destructive (exceptions include temperature-induced irreversible phase transitions and thermal decomposition). The inherent sensitivity of modern instruments allows measurements on the micro-Watt scale. Calorimetry is highly suited to the study of pharmaceutical systems because small sample masses are usually required and the technique is very sensitive to changes induced by, for instance, formulation or processing. It is the purpose of this review to show applications of both isothermal and scanning calorimetry in the field of physical and bio-physical pharmacy. Potential applications include studies of physical stability, excipient compatibility, chemical stability and the study of the potential interactions of and between macromolecules such as lipids, surfactants, and nucleic acids.     

The advantages and disadvantages of direct and indirect calorimetry

Kleiber's definitions of what constitutes direct and indirect calorimetry are accepted as the beginning of a commentary on the advantages and disadvantages of direct and indirect calorimetry in which calorimetry is divided into a number of categories based on the kind of calorimetric measurement. For non-reaction calorimetry such as entropy determinations and differential scanning calorimetry, the only means of measurement is by direct calorimetry. For reaction calorimetry, a preference of direct over indirect calorimetry depends on the accuracy needed and the ability of the experimenter to define the system. The data necessary to correct the observed heat loss in direct calorimetry are often all that are needed to make an indirect calculation of the true heat loss. In general, because they are convenient and inexpensive to use, indirect calorimetric methods are preferable to direct methods. However, when possible, one method can be used to verify the results of the other.     

Study of temperature distribution of sliding block with asperity surface

In this study, a numerical thermal model is developed for sliding block contact under various loads, sliding velocities and surface roughness. The temperature distributions are shown for perfectly insulated thermal conditions along noncontact surfaces. For a particular five‐peaks contact model, the maximum temperature at the central peak is slightly lhigher than the others. The temperature profile decreases as the distance to the symmetry axis increases, and then decreases dramatically at the noncontact area. It is clear to see that the maximum temperature locates at the symmetry central peak of the asperity contact area instead of the leading head of the smooth surface. The maximum temperature rise parameter increases as the pressure, sliding velocity and asperity roughness increased or conductivity decreased. This phenomenon becomes obvious for cases at high pressure, velocity and roughness and low conductivity. Particularly, the influence of roughness is not significant for low velocity. Similar results are found for the maximum temperature rise parameter difference between peaks or peaks/valleys. The simulation results of this asperity surface sliding block contact model are able to provide essential information for the components of microelectro—mechanical systems (MEMS) and biochemical reaction mechanism. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermochemical properties of 1-butyl-3-methylimidazolium nitrate

Heat capacity for 1-butyl-3-methylimidazolium nitrate [C₄mim][NO₃] in the temperature range (5–370) K has been measured by adiabatic calorimetry. Temperatures and enthalpies of its phase transitions have been determined. Thermodynamic functions have been calculated for the crystalline and the liquid states. Phase transition temperatures for set of nitrate salts have been compared. Enthalpy of combustion and enthalpy of formation for crystalline [C₄mim][NO₃] have been determined using a static-bomb isoperibol combustion calorimeter. A correlation scheme for the estimation of C_p of ionic liquids has been developed.     

The heat capacity of polymers

The long path to an understanding of heat capacity is traced from isothermal and adiabatic calorimetries to the most recent three methods of isoperibol, scanning, and temperature-modulated calorimetry (TMDSC). These latter three methods are: the traditional method of scanning thermal analysis; the quasi-isothermal method of finding the maximum amplitude of the periodic heat flow in response to a temperature modulation at a constant base temperature; and the pseudo-isothermal analysis of a temperature-modulated scanning experiment by subtracting the effect due to the underlying constant heating rate. In parallel, the development of the knowledge about phases and molecules is traced from its beginning to present-day nanophases and macromolecules.     

Reversibility of the low‐temperature transitions of polytetrafluoroethylene as revealed by temperature‐modulated differential scanning calorimetry

Temperature‐modulated differential scanning calorimetry reveals distinct differences in the kinetics of the low‐temperature phase transitions of polytetrafluoroethylene. The triclinic to trigonal transition at 292 K is partially reversible as long it is not complete. As soon as the total sample is converted, supercooling is required to nucleate the reversal of the helical untwisting involved in the transition. The trigonal phase can be annealed in the early stages after transformation with a relaxtion time of about 5 minutes. The dependence of the reversing heat capacity on the modulation amplitude, after a metastable equilibrium has been reached, is explained by a non‐linear, time‐independent increase of the heat‐flow rate, perhaps caused by an increased true heat capacity. The order‐disorder‐transition at 303 K from the trigonal to a hexagonal condis phase is completely reversible and time‐independent. It extends to temperatures as low as the transition at 292 K or even lower. Qualitatively, the thermal history and crystallization conditions of polytetrafluoroethylene do not affect the transition kinetics, that is, melt‐crystallized film and as‐polymerized powders show similar transition behaviors, despite largely different crystallinities. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 750–756, 2001     

Combined use of adiabatic calorimetry and heat conduction calorimetry for quantifying propellant cook-off hazards

Recent work performed at DERA (now QinetiQ) has shown how accelerating rate calorimetry (ARC) can be used to obtain time to maximum rate curves using larger samples of energetic materials. The use of larger samples reduces the influence of thermal inertia, permitting experimental data to be gathered at temperatures closer to those likely to be encountered during manufacture, transportation or storage of an explosive device. However, in many cases, extrapolation of the time to maximum rate curve will still be necessary. Because of its low detection limit compared to the ARC, heat conduction calorimetry can be used to obtain data points at, or below, the region where an explosive system might exceed its temperature of no return and undergo a thermal explosion.Paired ARC and heat conduction calorimetry experiments have been conducted on some energetic material samples to explore this possibility further. Examples of where both agreement and disagreement are found between the two techniques are reported and the significance of these discussed. Ways in which combining ARC and heat conduction calorimetry experiments can enhance, complement and validate the results obtained from each technique are examined.