Four forms of calcium sulfate are known : dihydrate CaSO4, 2H2O (gypsum), hemihydrate CaSO4, ½ H2O (plaster) and two anhydrites CaSO4 : natural and insoluble anhydrite and soluble anhydrite III (obtained by heating plaster to 200°C) .
Plaster and anhydrite III, which are soluble in water , are used in the building industry, because of their setting properties.
Calorimetry is an interesting method for studying the setting of calcium sulfates.
The influence of temperature on the hydration of plaster is well known to plasterers in view of the differences they observe between the behaviour of their material in winter and summer.
Also it appears that, above a well defined temperature, the water-plaster mixture gives a paste which does not set for several hours.
The calorimeter C80 is used for studying the influence of temperature on plaster setting.
The setting time of a cement has to be well known in order to determine its industrial applications Tricalcic silicate (C3S) is the active component of cements, giving a high resistance which obtained rapidly. A thermal investigation of C3S hydration by means of calorimetry allows us to determine the setting time and the kinetics of hydration, and also the influence of temperature on the parameters.
Many elastomers are used as seals, adhesives and flexible parts. Their resistance to heat, solvents and pressure especially make them excellent candidates to manufacture gaskets and o-rings. Three different o-rings are investigated by thermogravimetry with the Labsys TG 1150°C to compare their resistance to temperature: NBR (Nitrile butadiene rubber), EPDM (ethylene propylene diene monomer) and Viton (fluoropolymer).
Elastomers are often employed in severe conditions of use, particularly of temperature (joints, pipes, ..). Optimal conditions of use must be well defined in order to know when to make replacement. Isothermal thermogravimetry gives information on the resistance of elastomer to a given temperature and determines its decomposition kinetics.
The investigation is run on cis-polybutadiene.
Cement is obtained from the baking of mixture of clays and limestones in which silica is one of the main components. Mineral salts are numerous in the initial compound, and sometimes traces of nitrates.
A controlled amount of gypsum can be added to the manufactured cement in order to retard its setting rate.
The thermal behaviour of the three different salts (silica, nitrate, gypsum) is investigated by DSC .
Shows the neutralization of HCl solution by a NaOH solution
Heat capacity is a very important thermodynamic parameter, when determining the heat balance of a reaction. The specific heats of the different components, before and after the reaction, have to be known in order to define the correct heating of the system.
The heat capacity of crude cement and clinker is measured according to the stepwise method.
An increment of temperature is scanned, and the calorimetric peak, corresponding to the sample heated is integrated, as shown below.
Presents the determination of the heat of decomposition of H2O2 in presence of FeCl3
Gypsum is used to prepare plaster products. Small amounts of gypsum are also contained in cements. Because of the characteristic nature of the gypsum peaks, the dehydration studies can be employed for the quantitative and qualitative determination of the components in any mixtures (dihydrate, hemihydrate).
Dehydration of gypsum occurs in two stages :
CaSO4, 2 H2O –> CaSO4, ½ H2O (plaster) –> CaSO4 (anhydrite)
Elastomers are frequently used for applications at low temperatures. Their point of brittleness or glass transition must be determined with precision in order to define the minimal temperature of use. The glass transition of an elastomer can be characterized by a variation of heat capacity, which makes thermal analysis a very useful method for detecting this phenomenon.
The control of polymerization assumes the knowledge of the reaction rates. It is essential to know the quantities of heat which must be removed by the cooling systems to obtain maximum productivity. The isothermal calorimetric test gives the curve for the conversion of monomer into polymer versus time. Its analysis determines the kinetics of polymerization necessary for the previous previsions. An example is given for the polymerization of a mixture of styren and butadien (7%) at different temperatures (130,140,150°C).
Presents the vulcanization of rubber
Elastomers show an important variation of their heat capacity near the glass transition. The knowledge of the heat capacity before and after transition is of a great utility for the uses and applications of the compounds. In DSC methods, heat capacity (Cp) is proportional to thermal power evolved when the sample is heated. Two runs are necessary in order to determine precisely Cp : the first one with empty cells (sample and reference), the second one using the same cells, with the sample. The difference between the two curves characterizes the heat capacity of the sample.
Reticulated polyurethan is obtained through the reaction of a glycol and a diisocyanate, according to the following reaction :
X (O = C = N – R – N = C = O) + x (OH – R ‘ – OH) – –> X (O – C = NH .. R – HN – C = O)
The reaction is calorimetrically followed by using the mixing cell with a metallic menbrane (see description in C80 chapter).
Uses of natural rubber are numerous and well known (tires, pipes, shoes, ..). In some cases, synthetic rubbers are prefered due to their specific properties and their lower cost importance. Thermogravimetry allows to compare their resistance to temperature. The investigation is run on the following elastomers : natural rubber, butyl rubber, cis-polybutadien, polychloropren (Neoprene).
Shows the determination of heat of reaction by DRC
Oxidation induction time (OIT) is defined as the time that takes oxidation of a sample to occur under oxygen at a given temperature. Applied to polymers, this measurement enables the evaluation of its oxidative stability. As an example, the process of aging of water pipes submitted to chlorinated water could be forecasted by performing OIT analysis. The OIT measurement is defined in the ISO11357-6 standard.
Shows the dissolution of NaCl in water
PolyEthylene Terephtalate (PET) is a polyester widely employed in daily life (e.g. in water bottles, textile fibers, credit cards). The crystallinity is a very important characteristic because it is directly related to the properties of the polymer (e.g. toughness, clarity, stability). It is defined as the ratio between the crystalline and amorphous phases in the polymer. DSC is one of the main analytical techniques to determine the crystallinity ratio in a semicristalline polymer.
Shows the dissolution of KCl in water
Presents the cristallization of paraffin which is in solution in gas-oil
Presents the curve of melting and cristallization of water which is in a gas-oil water emulsion
Shows the heating curve of iron : different phase transitions ansd melting are observed
Shows the titration curve of a suspension of zeolite by a solution of n-butylamine
Shows the possibilities of DRC
Shows the calibration of DRC
Shows the determination of Cp by DRC
Presents the measurement of the energy dissipated during storage of a battery
Shows the determination of Qdos by DRC
Freeze-drying of a solution consists in first cristallyzing it totally, then sublimating the formed ice on installing vacuum. In order to obtain a final product of good quality, it is necessary to install vacuum at a temperature lower than the glass temperature (Tg) of the frozen solution.
Presents the heating curve of a stalled bread
Presents the decomposition of ditertbutyl peroxide
Presents the melting curve of a Pb-Sn alloy
Explains how to determine a phase diagram from a melting curve of an alloy
Presents the decomposition of NBR rubber by thermogravimetry : enables to determine the content in oil+wax, elastomer, carbon black and ash
Presents the curve of denaturation + aggregation of a solution of interleukin
Presents the proximate analysis of a coal
Presents the curve of denaturation of a solution of lysozyme
Presents the decomposition of calcium oxalate
Presents the curve of denaturation + aggregation of a solution of amylase
Presents the different transformations during heating of kaolinite
Presents the cristallization of palm oil at avery low cooling rate (8 K/h)
Presents the formation of hydrate of hydrocarbide on operating with BT215 at high pressure
Presents the gelatinization of a wheat flour suspension
Presents the retrogradation of a wheat flour suspension after gelatinization
Presents the set-up to determine the heat of solubility of n-paraffines by supercritical CO2
Clathrate hydrates are non-stoichiometric solid compounds in which individual « guest » atoms or molecules of suitable size and shape are held in the cavities provided by the hydrogen-bonded lattice of the « host » water molecules. Recent reports that large reserves of natural gas are present as clathrate hydrates in permafrost regions and beneath the oceans have generated interest in the study of their thermophysical properties such as heat capacity and thermal conductivity. An understanding of such properties will be required regardless of the production scheme used to recover natural gas from these deposits.
Presents the curves of melting and gelification obtained on mixed konjac mannan and xanthan gum
The main objective of the present investigation is the completion of the thermochemical data base for the Na2O- GeO2 system as well as the provision of systematic experimental data on the thermochemical behavior of oxide liquids.
Presents the method to determine the heta exchange during the clinkering reaction by drop method
A composite ceramic-salt packed bed configuration is being developed for high-temperature thermal storage. The thermophysical properties of the more particular hybrid system SiO2/ Na2SO4 have been investigated in the range from room temperature above the melting point of the salt, 884°C. The Na 2SO4 fraction in the composite materials was varied between 20 and 50 %. The following properties were measured: specific enthalpy, coefficient of thermal expansion and thermal diffusivity.
Direct measurement of the heat of mixing (interaction) of polymers is not feasible due to their high viscosity. The indirect approach described here is a heat of solution method, in which a
Hess’s Law cycle is used to determine the heat of mixing from the individual heats of solution of the alloy and its constituent polymers in a common solvent.
Presents an example of determination of pore size distribution of a resin
The acidity of synthetic HY samples dealuminated with silicon tetrachloride vapour at various temperatures is investigated using microcalorimetry. The work covers sample preparation, characterization, and acidic properties. The differential heats of ammonia adsorption versus coverage and the acidity spectra are described. The catalytic performance is measured in the hydrogen transfer reaction.
Presents the reduction of zirconia when heated under wet helium at different levels of humidity
Presents the decomposition of calcium oxalate at constant heating rate and constant DTG
Presents the decomposition of copper sulfate at constant heating rate and constant DTG
Presents the decomposition of calcium sulfate at constant heating rate and constant DTG
Amorphous sucrose is generally obtained by freeze-drying or by spray drying of sucrose solution. Due to an important mechanical friction and to quick cooling, a thin amorphous
layer could be formed at the surface of the sucrose particles. By calorimetry method, it has been possible to evaluate low level amorphism of solid sucrose.
Presents the decomposition of tyre
Presents the influence of KCl or NaCl salts on the thermal properties of gellan gum gels
Presents the isothermal crystallization of a solution of lysozyme (13,4%)
Presents the determination of the heat of dissolution of iron in aluminium on using the drop method
Presents the expansion of zirconia in the heating ans cooling modes : a rapid length variation is observed during the phase transitions
Presents the expansion of cast iron : a sudden shrinkage is observed during a transition
Presents the melting curve of steel
Presents the growth of the batcteruia contained in yoghurt when more milk is provided
Pasta cooking conditions were simulated in a differential flux calorimeter. The profile of the endothermic starch gelatinization peak was observed to directly describe the process
according the first-order kinetics. Isothermal calorimetry provide much more reliable results than do other traditional approaches allowing here assessment of the gelatinization kinetics and simple thermodynamic treatment.
heat production of male frogs was measured in a microcalorimeter through which continuous flow of gas was passed in order to generate constant normoxic, hypoxic or anoxic conditions.
Presents different transitions obtained in MBBA (liquid crystal)
The molar heat capacities of two synthetic Sr and Ba compounds were measured by differential scanning calorimetry between 312 and 712 K. In addition, heat capacities were calculated from a model of the vibrational spectra using optical frequencies measured by IR spectroscopy.
Presents the decomposition of PVC
Heat capacity of crystalline and amorphous gelatins at different concentration have been here studied in a wide range of temperature
Presents the denaturation of several collagen solutions containing different hyaluronic acid concentrations
Presents the melting curve of benzocaine by DSC
Presents the denaturation of ribonuclease using the MicroDSC3
Presents the behaviour of hydrochloride dihydraye salt
Presents the interaction of glucoamylase with a maltose solution
Presents the melting curve + Solid fat index of the fatty fraction of a suppository
Presents the melting curve of the fatty fraction of a suppository
Presents the denaturation curve of human growth hormone
Presents the DSC curve obtained during the growth of e.coli
Presents different transitions obtained in cholesteryl myristate (liquid crystal)
Presents the DSC curve obtained when a yest dough grows
Presents the determination of the heat of dissolution of steroid in methanol
Carrageenans are linear sulfated polysaccharides extracted from Red Algae and used in food processing for their gelation properties. Three types of carrageenan exist: iota, kappa and lambda. Gelation is only obtained with the kappa and iota forms. Iota carrageenan produces soft gels whereas the gels obtained with the kappa form are strong. The MicroDSC technique is well adapted to investigate the formation and the melting of such gels
Presents the behaviour of SiC when hold at 1150°C under O2 during 1150°C
Presents the reduction of a plate of steel by hydrogene after previous oxidation
Presents the melting curve of an intermetallic CuTi
Presents the sintering of MoSi2 while heated
Presents the denaturation curve of soy solution
Presents he decomposition of black powder while heated
Presents the denaturation curve of egg white solution
Presents the TMA curve of a polycarbonate sample : two shrinkages are observed : one due to TG one to the softening
Presents the expansion of a sample of PET
Presents the decomposition of a solution of ammonium perchlorate
Presents the expansion of a sample of polyester
Presents the expansion of a sample of polyethylene : the Tg is determined : Tg is generally hardly determined by DSC but easily by TMA
Dehydration of gypsum presents two endothermic peaks : they make possible the quantification of gypsum and plaster