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Interpreting DSC curves;Part 2: Isothermal measurementsJ. Widmann

Dear CustomerUserCom is becoming more and more popular. In the last edition, we made a number ofimprovements to the layout and have now decided to print a Spanish version in additionto the English, German and French editions.On the last page, we would like to introduce the METTLER TOLEDO editorial team. Thename of the author is now noted along with the title of each article.

Information for users ofMETTLER TOLEDO thermal analysis systems

2/2000

Contents

TA TIP– Interpreting DSC curves; – Part 2: Isothermal measurements

New– Crucible brochure– Automatic liquid nitrogen refilling

system

Applications– Characterization of petroleum products

with DSC– Applications of Differential Scanning

Calorimetry to thermosetting materials– Measurement of pore size distribution

with DSC– Measurement of low concentrations of

PE-LD in PE-HD– OIT of polyethylene with the TMA/

SDTA840

TIP– Effect of sample mass on TG results

12

Isothermal DSC measurements are used for the following applications:• crystallization processes including polymorphism,• desorption, vaporization and drying,• chemical reactions such as autoxidation, polymerization or thermal decomposition.

Isothermal DSC measurement curves are usually easier to interpret than dynamic mea-surements curves (UserCom11):• an important advantage of isothermal measurements is that an effect can be observed

almost in isolation (other effects occur at other temperatures).• changes in the heat capacity of the sample of course remain undetected, and the

baselines are exactly horizontal (except in the transition range). The heat capacitycan however be measured with quasi-isothermal methods such as the isothermal stepmethod [1], or temperature modulated DSC (ADSC), in which the temperature is var-ied slightly around the mean value [2].

• All isothermal DSC curves flatten off asymptotically to 0 mW at the end of the reaction.

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Strictly speaking, only the DSC furnace isisothermal. The sample itself is howeverisoperibolic, i.e. measured at constant fur-nace temperature, because it is not coupleddirectly to the isothermal furnace, but indi-rectly via the thermal resistance of the DSCsensor. For instance, with a heat flow of10 mW and a thermal resistance of ca.0.04 K.mW-1, the temperature of the samplediffers by about 0.4 K from the temperature

then introduce the sample pan with theautomatic sample robot. With this tech-nique, the sample reproducibly reachesthe programmed temperature withinhalf a minute to an accuracy of 0.1 K.This applies to the low mass Al pans andto the standard Al pans; with heavierpans, e.g. high pressure crucibles, tem-perature equilibration naturally takeslonger.If a sample robot is not available, youcan, with a bit of practice, introduce thepan manually even more rapidly. If theautomatic furnace lid is not installed,hold the manual furnace lid with asecond pair of tweezers in one handwhile you introduce the sample with theother hand. Make sure that the lid coolsdown as little as possible. The manualmethod allows a defined thermalpretreatment of the sample.Examples are:• A sample is shock-cooled in liquid

nitrogen and then allowed to crystal-lize in the DSC at 0 °C.

• A sample is melted at 200 °C andthen allowed to crystallize in the DSCat 130 °C.

In our laboratory we use an old DSC20measuring cell as an accurate furnacefor thermal pretreatment.

2. Insert the sample and heat the measur-ing cell to the desired temperature at alinear rate. The advantage of thismethod is that the sample can be repro-ducibly subjected to (almost) anypreprogrammed thermal history (an ad-vantage for routine measurements). Thedisadvantage is that it can take minutesuntil the desired temperature is reachedand has stabilized (longer transition pe-riod). In addition, you are limited to themaximum heating and cooling rates ofthe measuring cell.

You may want to evaluate the measured re-action free of any disturbances caused bythe transition from the dynamic to isother-mal state. You can do this by correcting themeasurement curve, either by deconvolu-tion, or better still, by subtracting the mea-surement curve of an inert sample with thesame heat capacity measured with thesame method (possibly a second measure-ment of the reacted sample, see Fig. 5).

of the furnace. If the DSC signal decreasesto zero during the course of the effect, thenthe sample temperature is exactly the sameas the furnace temperature.There are two ways to raise the sample asrapidly as possible to the temperature re-quired for the isothermal measurement:

1. Preheat the measuring cell for severalminutes at the desired temperature and

Fig. 2. The indium sample was put in the measuring cell that had been preheated to 157.0 °C. The sampleimmediately began to melt. Afterward it was cooled to 155.9 °C at 0.5 K/min. Isothermal crystallizationbegins after about 4 minutes. The sample temperature is displayed below. Because of the slight thermalresistance between the DSC sensor and the indium sample, the measured melting temperature is 0.06 Khigher than the crystallization temperature.

Fig. 1. Isothermal physical transitions; a: crystallization of a polymer, e.g. polypropylene cooled from themelt, Tiso = 130 °C (often with a shoulder, as shown); b: crystallization of a pure metal; c: enantiotropicreverse transition of the high temperature form to the low temperature modification (the crystallization of themelt of a pure substance consisting of individual droplets would look similar); d: evaporation of a solvent ca.10 °C below the boiling point in a sample pan with a 1 mm hole in the lid. At constant temperature, the rateof crystallization of a substance that crystallizes well (b), and the evaporation rate of the solvent (d) remainpractically constant until the end of the transition.

a c

b d

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Fig. 3. The enantiotropic reverse transition of the high temperature form of potassium perchlorate at 7 K belowthe equilibrium temperature. The kinetics shown by the large number of fine crystals (above) is completelydifferent to that of the small number of coarse crystals (below). Particularly fine crystals have an inductionperiod of almost an hour. Samples of extremely fine crystals exhibit an almost smooth bell-shaped curvebecause of the very large number of individual particles (statistics).

Fig. 4. Above: the ”normal” course of the decomposition reaction of dibenzoyl peroxide dissolved in dibutylphthalate measured in an Al pan with a 50 µm hole in the lid. The reaction rate is greatest at the beginning ofthe reaction when the concentration of unreacted material is highest. Afterward, the reaction falls offasymptotically to zero.Below: an example of a reaction at 110 °C with an induction period of more than 7 hours. During theinduction period, nothing appears to happen to the ethyl acrylate (in fact a stabilizer is used up). After this, thepolymerization reaction then rapidly reaches the maximum rate.

Physical transitions• Isothermal crystallization below the

melting point (Fig. 1a: polypropylene at130 °C, Fig. 2 above: indium at155.9 °C). In comparison to dynamiccooling with relatively rapid coolingrates, larger crystals with fewer flaws areformed.

• Isothermal melting (Fig. 2, above left).With several isothermal steps, you cancarefully approach the temperature ofthe thermodynamic equilibrium of theliquid and solid phases (melting andcrystallization rate = 0, i.e. heatflow =0).

• Isothermal monotropic transition belowthe melting point of the metastablemodification. In this way, you can trans-form the sample completely to the stableform, for example in order to determineits heat of fusion.

• Isothermal enantiotropic reverse transi-tion below the equilibrium temperature,thereby gaining an insight into the bi-zarre kinetic behavior of the sample(Fig. 3).

• Isothermal evaporation (Fig. 1d) belowthe boiling point or sublimation belowthe melting temperature. This allowsyou to completely remove a volatilecomponent and afterward measure theresidue dynamically.

Chemical reactionsA so-called “normal” chemical reaction be-gins as soon as the reaction temperature isreached. It becomes slower and slower asthe concentration of the starting materialsdecreases (Fig. 4, above). Autoacceleratingreactions, i.e. autocatalytic reactions, orreactions inhibited by the addition of stabi-lizers, have a significant induction period(Fig. 4, below) in which nothing appears tohappen (the DSC signal is certainly lessthan about 0.1 mW). Afterward, the reac-tion rate increases rapidly to its maximumvalue, after which it decreases just like in a“normal” reaction.

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Fig. 5. Above left: the curing reaction of an epoxy resin at 190 °C is shown. The heat of reaction is 69.6 J/gusing a horizontal baseline. The second measurement run afterward has an area of –1.5 J/g. The total area(i.e. the difference) is therefore 71.1 J/g. Below right: the difference curve (1st run – 2nd run) is displayed.The curve corrected in this way has an area of 71.2 J/g.

Fig. 6. Determination of the oxidative stability according to standards such as ASTM D3895-80, EN 728-97,ISO 11357-6. The sample is heated dynamically to the desired temperature in an inert atmosphere (N2).There then follows a stabilization period of 2 minutes after which the measuring cell is purged with oxygenand measurement of the induction period begins.Sample: polyethylene, Hostalen GM 5040 T12, ca. 12 mg. Measurement temperature: 220 °CIn the case of electrical insulation material, which is of course in contact with copper, the induction time of17.4 minutes obtained with an aluminum pan is compared with the result using a copper pan. The value of7.91 minutes demonstrates the unfavorable influence of the redox catalyst copper on the oxidative degradationof polyethylene.

Isothermal measurements are excellent forthe detection of autoaccelerating processes.From the safety point of view, these are im-portant to investigate but are otherwise dif-ficult to measure. They can hardly be de-tected with a dynamic temperature pro-gram. For the initial isothermal measure-ments, we recommend a temperature thatis about 40 K below the onset of the dynam-ic measurement.The OIT (Oxidation Induction Time) is oneof the most frequently performed isother-mal measurements. It is used to comparethe oxidative stability of polyolefines(Fig. 6) or petroleum in the presence of ox-ygen. The measurement is very often termi-nated on reaching a threshold value of5 mW since usually only the inductiontime, i.e. the onset, is of interest. Vaporiza-tion of part of the sample at the measure-ment temperature of around 200 °C can beprevented by performing the measurementunder increased pressure, e.g. at 3 MPa in apressure DSC.Thermosetting resins are often cured iso-thermally and the resulting glass transitiontemperature determined afterward.Compared with dynamic measurements,isothermally measured reaction peaks pro-vide a direct and clear insight into the ki-netics of processes.

Literature[1] H. Staub und W. Perron, Analytical Chem-

istry 46 (1974) p 128[2] METTLER TOLEDO ADSC software data-

sheet

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New in our sales program

The new “Crucibles for Thermal Analysis”brochure describes the entire range of MET-TLER TOLEDO crucibles. The aim is to helpyou find the best crucible for your applica-tion as quickly and easily as possible.

You can work around the clock with thenew automatic liquid nitrogen refilling sys-tem. This has advantages when used withthe automatic sample robot, and is alsouseful for measurements performed over anextended period of time, e.g. with tempera-ture modulated DSC (ADSC).The automatic refilling system consists of amodified standard liquid nitrogen Dewar

Example: The light aluminum crucible, 20 µlThe light aluminum crucible has the shortest signal time constant, especiallywhen using helium as a purge gas. It is particularly suitable for measuringpolymer films, disks and powders - the samples are pressed down tightlyagainst the base of the crucible.It is less suitable for liquid samples because the liquids might be squeezed outof the crucible on sealing.The narrow space between the crucible and the lid leads to the formation of aself-generated atmosphere. Piercing the lid beforehand allows contact with theatmosphere.A special die set is required for the sealing press.

(English: 51 724 175, German: 51 724 174, , French: 51 724 176,Spanish: 51 724 177, Italian: 51 724 178)

with an integrated filling level sensor, sev-eral magnetic valves and a new electronicscontrol system. The automatic refilling sys-tem is connected directly to the liquid ni-trogen valve (3) of the DSC module. Thestandard liquid nitrogen Dewar is installedon the inlet side of the refilling system.As soon as the filling level sensor (1) of theautomatic refilling system senses that the

liquid nitrogen level is too low, it opens thevalve on the inlet side (2) and pumps inliquid nitrogen until a predefined level isagain reached.Because this filling operation is also per-formed under pressure, the DSC modulecontinues to work without interruption,and no measurement data is ever lost.

Crucible brochure

Automatic liquid nitrogen refilling system

There is a detailed description of eachcrucible together with information aboutits specific use and application. A com-prehensive table helps you choose theright crucible.

12

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Standardliquid

nitrogen Dewar

Automatic liquidnitrogen

refilling system DSC module

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Applications

IntroductionConventional fuel is obtained exclusivelyfrom petroleum or crude oil. Petroleum isprimarily a mixture of 6 different classes ofsubstances. The composition of the mixtureis specific to the region where the oil occursand consists of• straight-chain n-alkanes (CnH2n+2) with

molar masses between 16 and300 g/mol

• branched-chain alkanes (iso-alkanes)• cycloalkanes• aromatics• sulfur-containing compounds• polycyclic and heterocyclic resins as well

as bitumens with molar masses of about1000 g/mol.

Distillation of the crude oil yields variousfractions, which are classified as follows:low boiling fractions, e.g. gasoline (petrol),aviation gasoline, naphtha; higher boilingfractions, e.g. fuel or heating oil and diesel;and high boiling fractions (heavy oil andlubricating oils). The residue after distilla-tion is known as bitumen (or asphalt).

In the liquid state, the distillate appearsmacroscopically as a single-phase mixture.On cooling, crystals are formed, i.e. a mul-tiphase mixture is obtained. The separationof crystalline material is undesirable andleads to a number of problems:

1. Crystallized material separates out form-ing a sediment. This is often a problem,especially for the storage of diesel andheating oils.

2. Crystallized material is retained in fil-ters, which can lead to blockages.

3. Bitumen (asphalt) products are mainlyused for surfacing roads. Crystallizationcauses the surface to become brittle andresults in the formation of cracks.

Hydrocarbon distillates consist primarily ofcomplex hydrocarbon compounds and crys-tallizable fractions. The former are partial-ly liquid at room temperature and exhibit aglass transition at low temperatures. Theglass transition temperatures of the liquidconstituents depend on the petroleum dis-tillate. Typical values are -30 °C for bitu-men, -130 °C for diesel and -150 °C forgasoline. The proportion of the crystalliz-able fractions is between 0% and 10% forbitumen, between 5% and 25% for fuel oiland up to 40% for crude oil. The chemicalstructure of the crystals depends on the dis-tillate. With fuel oils, n-alkanes with 10 to28 carbon atoms crystallize out, with bitu-men n-alkanes with 20 to 60 carbon atoms;and with crude oil n-alkanes with 5 to 60carbon atoms. Lightly branched iso-al-kanes and cycloalkanes are also present.

Characterization of petroleumproducts with DSCPetroleum products are usually character-ized by their glass transition temperatureand their melting behavior. The measure-ment of these parameters is easily per-formed by DSC. A typical temperature pro-gram for the analysis of petroleum deriva-tives begins by cooling the sample at10 K/min from room temperature to-100 °C (for heavy hydrocarbon com-pounds) or to -150 °C (for light hydrocar-bon compounds, e.g. kerosene, gasoline).Afterward the sample is heated linearly at5 K/min up to final temperatures of typi-cally 50 °C (for fuel oils such as light heat-ing oil or diesel), 80 °C (crude oil), 100 °C(heavy oil) and 120 °C (bitumen). Figure 1shows the corresponding heating curves fordifferent samples. Various effects can be ob-

Characterization of petroleum products with DSCJ.M. Létoffé. Laboratoire de Thermodynamique Appliquée. INSA 69621. Villeurbanne Cedex. France

Fig. 1. DSC curves of different petroleum distillates

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served. The marked increase of the heat ca-pacity at low temperatures (step in the heatflow curve) is caused by the glass transi-tion. Very often, part of the sample thencrystallizes out (usually iso-alkanes), caus-ing an exothermic peak. The melting of thevarious crystals can lead to several relative-ly broad, endothermic peaks. The shape ofthe peak mirrors the size and weight distri-bution of the crystals and is characteristic ofa particular distillate or particular crude oil.

For medium distillates (gasoline, heatingoil), ∆H(T) can be described by a third or-der polynomial [1]. It is sufficient to use aconstant value of 160 J/g. With bitumen,the melting enthalpy is larger. In practice,a value of 200 J/g is has proven best. Withcrude oils and heavy oils, a value of 160 J/gis recommended below 30 °C anda value of 200 J/g above 30 °C.For a number of practical reasons, theproblems mentioned at the beginning in

connection with crystals separating out oncooling are particularly important. Withcrude oils and heavy oils, it is best to mea-sure the crystallization in the temperaturerange 80 °C to -20 °C at a cooling rate of2 K/min; and with medium heavy fuel oils,between 25 °C to -30 °C at a cooling rate of0.5 K/min. In such experiments, a more orless pronounced exothermic peak is ob-served that shows the course of the crystalli-zation. For the evaluation of the correspond-ing DSC curve, one distinguishes between thefollowing characteristic temperatures:

• the turbidity (cloud) point, with crudeand heavy oils often also called the waxappearance temperature (WAT), corre-sponds to the temperature at which crys-tallization begins (ASTM D2500).

• the CFPP, Cold Filter Plugging Point,corresponds to the temperature belowwhich all crystallizable material hascrystallized (EN 116).

• the flow point (FP) is the temperature atwhich the viscosity of the sample is sohigh that it no longer flows (ASTM D97).

To evaluate the crystallization peak, a hori-zontal or tangential baseline is drawn onthe left side of the curve. A value of 200 J/gis assumed for the crystallization enthalpy.

Evaluation of DSC curves ofpetroleum productsThe crystalline components are embeddedin the liquid matrix. The matrix is charac-terized by the glass transition temperatureTg and the step height of the change of thespecific heat. The glass transition tempera-ture correlates well with the average molemass of the matrix. The percentage amountof the crystallized fractions can be calculat-ed by dividing the measured heat of fusionby the (in principle temperature-depen-dent) melting enthalpy ∆H(T) of a fictive,fully crystallized sample.For the compounds considered here, a lin-ear baseline can be used for the determina-tion of the peak area. This begins at aboutTg +30 K (Ti) and ends at about 10 K afterthe end of the melting process (Tf). Themelting enthalpy of the crystallized materi-al can be estimated in the following way.

Fig. 2. Evaluation of a DSC curve of diesel oil

Fig. 3. Typical crystallization behavior of diesel oil

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Example 1: light petroleumdistillate (Fig. 3)The turbidity point is taken to be the onsettemperature of the crystallization peak(Tonset). The turbidity point defined in thisway can be reproducibly measured with anaccuracy of ±0.5 K. The values obtainedwith this method are slightly lower thanthose determined using the ASTM standardmethod (TASTM). The measurement of 50different light distillates led to the follow-ing correlation:

WAT = Tonset = 0.98·TASTM -3.6

For the determination of the CFPP value,the analysis of 40 light petroleum products

gave the following correlation between thetemperature at which 0.45% of the crystal-lizable material has crystallized out(Tc(0.45%)) and the CFPP determined ac-cording to EN 116:

Tc(0.45%) = 1.01⋅TCFPP EN 106 - 0.85.

For the determination of the flow point wefound the optimum correlation to be:

Tc(1%) = 1.02·Tflow point ASTM - 0.28

[2]. Here, Tc(1%) is the temperature atwhich 1% of the crystallizable fractions hascrystallized out.

Fig. 4. Typical crystallization behavior of diesel oil

Example 2: heavy and crude oils(Fig. 4)The determination of the turbidity point forheavy and crude oils is performed in a sim-ilar way to the light petroleum products. Ifthe flow point is below 0 °C, the crystallinecontent after cooling is only about 2 mass%.The behavior of the sample is therefore forthe most part determined by the noncrys-talline matrix [3].

ConclusionsDSC measurements allow a rapid and reli-able characterization of extremely differenttypes of petroleum products. The glasstransition temperature and melting behav-ior provide important information on thequality of petroleum derivatives. In addi-tion, the origin of a sample of unknownpetroleum can be determined because themeasured curves are characteristic of thepetroleum, i.e. they are “fingerprints”.Cooling experiments yield important prac-tical information on the crystallization be-havior of petroleum derivatives.

Literature[1] F. Bosselet, Thèse Saint Etienne n°008

(1984)[2] P. Claudy, J.M. Létoffé, B. Neff, B. Damin,

FUEL, 65 (1986) 861-864[3] J.M. Létoffé, P. Claudy, M.V. Kok,

M. Garcin, J.L. Volle, FUEL, 74 (6) (1995)810-817

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Applications of Differential Scanning Calorimetry to thermosettingmaterialsDr. B. Benzler, Applikationslabor Mettler-Toledo, Giessen

IntroductionDifferential Scanning Calorimetry (DSC)allows endothermic or exothermic enthalpychanges in a sample to be quantitativelymeasured. Melting processes in partiallycrystalline plastics, glass transitions andchemical reactions such as the curing ofthermosetting resins can all be routinelyanalyzed [1].The heat capacity increases on heatingabove the glass transition. The glass transi-tion temperature, Tg, and the change of thespecific heat capacity at the transition,∆cp, are characteristic of the state of aplastic. If intramolecular and intermolecu-lar mobility become restricted, for exampleas a result of increased crosslinking, thenthe glass transition temperature increases.∆cp allows certain conclusions to be drawnabout molecular interactions.

Prepregs are semi-finished products madefrom fabric impregnated with resin harden-er mixtures. They are used to manufacturethermosetting molded materials throughthe action of pressure and temperature [2].During the course of the development of aresin system for SMC prepregs (Sheet Mold-ing Compounds) on the basis of unsaturat-ed polyester resins (UP resins), the follow-ing questions arose concerning:• the control of reactivity, e.g. whether the

desired degree of cure is achieved even ifthe formulation is varied,

• the optimum duration of the compres-sion (i.e. molding) and curing opera-tions, and

• how long the prepregs can be stored, i.e.their storage stability.

Investigating the reactivity, keepingto the formulationFigure 1 shows the DSC curves of three dif-ferent resin/hardener formulations. Thecuring reaction is observed as an exother-mic peak. The value Delta H (∆H) corre-sponds to the normalized peak area injoules per gram of sample and therefore tothe heat of reaction.For a resin/hardener system, the larger the

heat of reaction, the higher the degree ofcure of the material. The standard formu-lation (“Standard system”) contains theresin and hardener (curing agent) in a ra-tio that had proven to be good empirically.The temperature normally used for the si-

multaneous curing and molding processwas 120 °C. The middle curve (“Standardsystem”) shows the dynamic DSC curingreaction of a sample of this material mea-sured at a heating rate of 3 K/min. On oneoccasion, when a curing agent was by mis-

Fig. 1. DSC curves of different formulations measured at a heating rate of 3 K/min. Samples of 50 to 70 mgprepreg were weighed into the medium pressure crucible. Besides the usual formulation (”Standard system“),a formulation with a different hardener (”Different curing agent“), and a formulation in which one of theconstituents had been left out (”Wrong mixture“) were measured.

Fig. 2. With increasing curing time at 120 °C, the glass temperature increases while at the same time the heatof the postcuring reaction decreases. The heating rate used was 20 K/min.

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take omitted, a faulty batch (“Wrong mix-ture”) was produced. The curing reactionof this material took place at a significantlyhigher temperature, and the heat of reac-tion was noticeably smaller. This meansthat curing at the usual processing temper-ature (i.e. 120 °C) would either not be pos-sible or would at best be very unsatisfactory.The third curve (“Different curing agent”)is a formulation with a different hardener.

Investigation of the influence ofmolding timeMolding and curing of this SMC prepreg isdone at 120 °C under pressure in a mold-ing press. DSC can also determine the time

required for this process. To do this, anumber of test plates of the same composi-tion were subjected to different moldingtimes. The postcuring reaction of each ofthe plates was then investigated with DSC.The resulting curves are shown in Figure 2.The glass temperature increases during thecourse of curing. At the same time, the stepheight at the transition decreases, which istypical for these UP resins. The postcuringreaction gives rise to exothermic peaks thatbecome successively smaller because thedegree of cure increases with increasingmolding time. The relationship between theenthalpy change of the postcuring reaction∆Hr and the molding time is given by the

following equation:ln ∆(Hr) = a - b · t

For a first order reaction, “a” is equal tothe logarithm of the heat of reaction and“b” is equal to the rate constant of the cur-ing reaction at the molding temperature.From Figure 3 it can be seen that no fur-ther significant postcuring takes place(< 1 J/g) when the molding time is 210 sor longer, i.e. the resin is effectively cured(ea = 12.9 and b = 0.0054 s-1).

In Fig. 1 (heating rate 3 K/min) the DSCcurve of the curing reaction begins to devi-ate from the baseline at about 100 °C. Acorrespondingly slower reaction is howeverexpected at lower temperatures. In particu-lar, the reaction proceeds slowly even atroom temperature, which makes prepregsunusable after a certain storage time. Toinvestigate the storage stability, severalprepregs were stored for different periods oftime at 30 °C and then measured with DSCat 10 K/min. The results are summarized inFigure 4. The positions of the peaks on thetemperature axis do not differ to any greatextent. However, it is clear that the heat ofthe curing reaction decreases with increas-ing storage time. Experience shows that adegree of cure of up to about 30% can be tol-erated. The storage time of this prepregshould therefore not exceed 6 days at 30 °C.

ConclusionsThese practical examples show that simpleinvestigations with Differential ScanningCalorimetry provide an enormous amountof information and allow many questionsof a practical nature to be answered. Apartfrom establishing, optimizing and check-ing the formulation, the molding time forthe curing and molding process and thestorage stability of the prepregs can also bedetermined. The main experimental quanti-ties used for the evaluation are the exother-mic heats of the curing and postcuring reac-tions. The glass transition temperature alsoyields useful additional information.

Literature[1] B. Benzler: Dynamische Differenzkalo-

rimetrie - Hohe ReproduzierbarkeitPlastverarbeiter 47 (1996) 9, Seite 66

[2] B. Benzler: Vollständig vernetzt ? Dyna-mische Differenzkalorimetrie an EP-HarzenPlastverarbeiter 47 (1996) 11, Seite 58

Fig. 3. The heat of postcuring (logarithmic) measured by DSC as a function of molding time.

Fig. 4. After storing for 7 days at 30 °C, the remaining heat of reaction decreases from the initial value of167 J/g to 110 J/g, and after 42 days to just 88 J/g. These DSC curves were measured at 10 K/min.

Time in s

∆Hr

in J/

g

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Measurement of pore size distribution with DSCThad C. Maloney, Helsinki University of Technology, P.O. Box 6300, FIN-02015 HUT, Finland, e-mail: Thad.Maloney@hut.fi

IntroductionPore size distribution (PSD) is a criticalproperty of many materials. Ceramics, cat-alysts, pharmaceuticals, and the author’sown special area of interest namely cellulo-sic pulp fibers, are examples of such mate-rials. The classical methods for measuringpore size distribution are gas sorption andmercury porosimetry. An interesting alter-native technique is based on DSC and iscommonly known as thermoporosimetry.In this article, thermoporosimetry refers tothe measurement of pore size density basedon the determination of the melting pointdepression of an absorbate held in a porousmaterial. The relationship between the porediameter (D) and the melting temperaturedepression (∆Tm) is described by the well-known Gibbs-Thomson equation:

4 VT σlSD = (1)

∆Hm ∆Tm

where V is the molar volume, T the meltingpoint of large crystals of the selected adsor-bate, ∆Hm the heat of fusion, and σls thesurface energy at the liquid-solid interface.Although almost any substance can be usedas the adsorbate, water is one of the mostattractive substances to fill the pores,because the melting point lies in a temper-ature range that can easily be measured.For water, V = 19.6 10-6 m3/mol,T = 273.14 K, ∆Hm = 6.02 kJ/mol. The val-ue of σls was determined by measuring themelting point depression of water in a se-ries of controlled porous glass (CPG) stan-dards of known pore diameter by DSC. Theresult obtained from these measurementswas 12.1 mN/m. The relationship betweenpore size and melting point depression istherefore:

D = 40.3 nm K / ∆Tm (2)

A basic problem in thermoporosimetry isthat the equilibrium melting temperatureTm must be determined as accurately as

perature by the equation:V = Hl / (ρ · 334.5 J/g) (3)

where ρ is the density of the water at thecorresponding temperature, and 334.5 J/gis the specific heat of fusion of water.

In this case, the temperature dependence ofthe heat of fusion and the heat capacity isneglected.

ExperimentalThe measurements were performed with aDSC821e equipped with an IntraCooler. Thepurge gas was nitrogen at 50 ml/min. Theresults were evaluated with the STARe soft-ware package.For thermoporosimetry, accurate tempera-ture calibration in the range around 0 °C isessential. A two-point calibration with mer-cury and water gives good results and isrecommended. The pan used for mercuryshould be treated beforehand to prevent themercury reacting with the aluminum toform an amalgam (and thereby possiblymaking a hole in the pan). The treatmentconsists of subjecting the pan to watervapor in an autoclave at about 120 °C forseveral minutes, or by storing the pan forseveral days at 25 °C in air at 95% relativehumidity, e.g. in a desiccator over water.Under these conditions, an inert film ofaluminum hydroxide-oxide is formed onthe surface of the pan.The following isothermal step method wasused for temperature calibration:∆tiso = 5 min, ∆T = 0.02 K andβ = 0.05 K/min. The melting point is takento be the temperature at which the entiresample has melted. The temperature cali-bration obtained in this way is slightly dif-ferent from that based on dynamic mea-surements.

∆Tm/K 40 20 10 5 2 1 0.5 0.2 0.1 0.05

D/nm 1 2 4 8 20 40 80 200 400 800

Table 1. Melting point depression and pore size

possible in order to calculate the difference∆Tm between it and the melting point T. Infact, even slow heating rates can give riseto temperature gradients that affect the re-sults. One way to overcome this problem isto use a temperature program with isother-mal steps in the melting range. The tem-perature is held constant until the sampleand reference temperatures are in equilib-rium with the furnace temperature, i.e.Ts ≈ Tr ≈ Tc. An isothermal step program isshown schematically in Figure 1. Three pa-rameters are required to define such a tem-perature program:1. The duration of the isothermal segment

∆tiso must be long enough for meltingto reach an equilibrium state.

2. The temperature step, ∆T, determines theresolution of the measurement. Materi-als with a narrow pore size distributionneed a correspondingly small ∆T.

3. The heating rate, β, of the dynamic seg-ment between two steps should be suffi-ciently slow to avoid large fluctuationsof the DSC signal as the DSC switchesfrom the heating mode to the isother-mal mode and vice versa, but fastenough to facilitate a rapid measure-ment. The optimum parameters aresample dependent.

One important advantage of the isothermalstep method is that it allows very smallmelting temperature depressions to be ac-curately measured. This, however, requiresextremely high temperature stability in thisstep mode type of operation. The value forthe DSC 821e is about 0.02 K. This enablespores sizes of up to about 430 nm to bemeasured.The total volume V of the pores with therelevant diameter for an isothermal stepcan be determined from the peak area(heat of fusion Hl) measured at this tem-

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Although tau lag is not important for theisothermal steps, it does have an effect onthe dynamic segments in the measurementprogram. It was therefore adjusted in theusual way at various heating rates usingthe onset temperatures of the melting peaksof mercury and water. Heat flow calibrationis performed on the melting peak of ice at5 K/min. (NB Water can supercool to amarked degree; it does not usually crystal-lize until below -15 °C). Experiments per-formed beforehand showed good agreementbetween the peak areas of the isothermaland dynamic measurements. This meansthat dynamic calibration can be used forthe isothermal step method.For the determination of pore size distribu-tion, water-saturated samples of 2 mg to4 mg were hermetically sealed in standard40 µl aluminum pans. The water must bepresent in excess, i.e. more than to just fillthe pores. The sample used to determinethe pore size should be washed well withpure water to avoid any additional meltingpoint depression through the presence ofimpurities.

MeasurementsThe sample is first measured dynamicallyat a relatively slow heating rate (5 K/min)to determine the parameters for the stepprogram. If the pores are sufficiently small,two peaks are obtained, one for the porewater and the other for the bulk (excess)water. Samples with large pores give rise topeaks that overlap (Fig. 2). If the maxi-mum pore diameter is less than100-200 nm, the step method can separatethe peaks. If the samples have larger pores,a partial pore size distribution can still beobtained up to about 430 nm. This corre-sponds to a ∆Tm of 0.1 K.The total water content of the sample is de-termined by drying after the experiment.The proportion of freezable pore water andthe excess water is calculated from the cor-responding peak areas by integration anddivision by 334.5 mJ/mg (equation 3). Ad-sorbed water does not freeze; the proportioncan be obtained by subtracting the calcu-lated freezable water from the total water.The following parameters were used for themeasurement of silica gel with isothermalsteps (Fig. 3): ∆tiso = 5 min, ∆T = 0.3 °Cand β = 0.5 K/min.

Evaluation1. Draw a baseline across the isothermal

segment from the left to the right of themelting peak.

2. Subtract the baseline from the measure-ment curve. The curve corrected in thisway now begins at zero (see Fig. 3, up-per diagram).

3. Calculate the integral of the step curve(see Fig. 3, lower diagram).

4. Draw in the line of the sensible heat, Hs,(tangent from the left in Fig. 3, lowerdiagram).

5. Subtract the line of the sensible heatfrom the integral to obtain the (latent)heat of melting (Hl).

6. Set up a table of values for heat of melt-ing versus temperature.

7. Import the values or table into a spread-sheet program.

Fig. 2. Dynamic DSC curves of water-saturated porous glasses with average pore sizes (Dav) of 15 nm and100 nm. β = 5 K/min. With a pore size of 15 nm, two melting peaks are observed - that of the pore water andthat of the free (bulk) water.

Fig. 1. Conventional DSC temperature program (dashed line) and an isothermal step program with therelevant parameters indicated.

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The pore size distribution of silica gel eval-uated in this way agrees very well with theresults obtained by mercury porosimetry(Fig. 4).To reduce measurement time, it is some-times advantageous to use a temperatureprogram in which the size of the tempera-ture step varies with temperature. Initially,at the beginning of the measurement, rela-tively large temperature steps are used.Smaller steps are then used where neces-sary in order to obtain better resolution(usually in the range of larger pores). This,however, complicates the evaluation ofsuch nonequidistant isothermal stepcurves.

ConclusionsDSC isothermal step melting is a good wayto determine pore size distribution. Temper-ature gradients are avoided and excellenttemperature resolution is obtained. Poreswith diameters of up to 430 nm can be de-termined with this method.The measurement is easy to perform and issuitable for many different types of sam-ples. The method can easily be optimizedfor maximum resolution or shortest mea-surement time by setting the size of thetemperature increments accordingly.DSC allows the measurement of moist sam-ples, which is very advantageous for the in-vestigation of hydrogels such as cellulosefibers. The pores of these materials existonly in the swollen state. By varying thewater content, it is possible to observe howthe pores disappear on drying. This type ofmeasurement is not possible with gassorption or mercury porosimetry becausethese methods require dry samples.

8. The amount of pore water and hence thepore volume is calculated from the heatof melting according to equation 3. Thespecific pore volume in ml/g up to therelevant pore size is obtained by dividingthe pore volume by the dry mass of theporous sample (cumulative distribution).

9. The pore size follows from ∆Tm accord-ing to equation 2.

10. To obtain the pore size distribution, thedifference between neighboring valuesof the cumulative distribution is dividedby the difference of neighboring valuesof the pore size.

Fig. 3. Thermoporosimetry of a water-saturated porous glass. Upper diagram: isothermal step DSC measurementof a water-saturated porous glass with an average pore size (Dav) of 15 nm.Lower diagram: result of the evaluation, points 1 to 4 (see text).

Fig. 4. The pore size distribution based on the measurement in Figure 3 (filled black squares). The resultsfrom mercury porosimetry (blank white squares) are presented for comparison purposes.

0.0

0.1

0.2

0.3

0.4

1 10 100

D (nm)

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Measurement of low concentrations of PE-LD in PE-HDDr. M. Schubnell

IntroductionSmall amounts of PE-LD are often added toPE-HD to modify its mechanical properties.The following experiments describe the useof DSC to determine the detection limit forsuch additions, and to investigate the ex-

tent to which these additions can be quan-titatively determined in polymer mixtures.Four samples of different (known) PE-LDcontent were used for these experiments.The samples of pure PE were first mea-sured. Figure 1 shows that the melting be-

havior of PE-LD differs clearly from that ofPE-HD. Assuming at least a partial incom-patibility of the two materials, one can ex-pect the DSC melting curve of mixture ofPE-LD and PE-HD to exhibit two clearmelting peaks, as shown in Figure 1.

ExperimentalSamples: PE-LD and PE-HD mixtures withPE-LD concentrations of 3%, 1.97%, 1.06%and 0.5%Measuring cell: DSC821e with IntraCoolerSample preparation: pellets of about 10 mgin 20 µl aluminum pansHeating rate: 10 K/min

ResultsFigure 2 shows the DSC curves of the differ-ent samples. The broad melting peak of PE-HD of course predominates. The muchsmaller melting peak (shoulder) of PE-LDis superimposed on the low temperatureside of PE-HD melting peak and is not veryclearly defined because the PE-LD contentof the samples is so low. Careful analysis ofthe PE-LD melting region shows that PE-LD concentrations of less than 1% can beclearly identified on the melting curve. Thearea of the superimposed PE-LD peak wasintegrated using the baseline type “Spline”.The evaluation of the series of samples us-ing identical parameters (such as baselineand temperature range) allowed an evensmaller peak with a PE-LD content of 0.5%to be measured. The results show that thedetection limit for PE-LD in a PE-HD ma-trix is about 0.5% PE-LD. The PE-LD con-tent cannot of course be directly inferredfrom the peak areas. If the ratio of the par-tial areas to the total area is plotted as afunction of the PE-LD content (see Fig. 3),then to a good approximation a straightline is obtained. In practice this means thatthe PE-LD content of an unknown samplecan be estimated using a calibration mea-surement in which a sample of knownPE-LD content is evaluated. This procedureof course assumes that the chemical struc-ture (such as length and distribution ofside chains) and physical structure (such

Fig. 1. Melting curves of PE-LD and PE-HD. The peak maximum of the PE-LD melting curve is appreciablylower. The crystallinity of PE-LD and PE-HD is also different; typically the degree of crystallinity of PE-HD isabout 65%, and PE-LD about 25%.

Fig. 2. DSC curves of mixtures of PE-HD/PE-LD of different PE-LD content. The curves on the right showsections of the curves from the left that have been greatly expanded

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as degree of crystallinity) of all the compo-nents used and the preparation conditions(e.g. temperature and mixing technique)are identical.

ConclusionsThe results show that concentrations ofconstituents in the percent range can bedetected in polymer mixtures and, in cer-tain circumstances, even quantified. Forthe PE-LD/PE-HD system investigated, thedetection limit was found to be between0.5% and 1%.Fig. 3. Ratios of the PE-LD melting peak (baseline type Spline“) to the total peak area as a function of the PE-

LD content.

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OIT of polyethylene with the TMA/SDTA840J. Widmann, Ph. Larbanois

Sample Crosslinked PE from a plastic pipe (PE-X)

Information expected OIT, Oxidative Induction Time at 210 °C in oxygen

Measuring conditions Measuring cell TMA/SDTA840 with Gas Controller at the reactive gas inletProbe Negative load of -0.01 N, raised, (no changes in length can be measured with the probe

raised)Sample preparation A piece of ca.15 mg was cut off with a knifeCrucible Light aluminum pan, 20 µl, with no lidTMA measurement Heating from 50 °C to 210 °C at 20 K/min, then isothermal for 5 min under nitrogen.

Afterward, switched to oxygen (gas inlet: reactive gas)

Atmosphere N2 and O2 50 ml/min, purge gas N2, 20 ml/min

Interpretation The Oxidative Induction Time evaluated with TA/Onset is 38.5 min (time from switching over to oxygen to theonset). A DSC measurement made for comparison purposes gave a result of 43.4 min.The melting point on the left of the diagram confirms the identity of the sample as PE.

Conclusions TMA with simultaneous SDTA can easily measure all the relatively strong thermal effects, including the aboveoxidation reaction. The difference between the values of OIT measured with SDTA and DSC is within the limits ofreproducibility of such measurements.It would also be possible to simultaneously perform TMA measurements in the same experiment, e.g. to measurethe plastic deformation above the crystallite melting point in order to assess the degree of crosslinking (seeCollected Applications, Thermoplastics).

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IntroductionThermogravimetric Analysis (TGA) mea-sures the change in weight of a sample as afunction of temperature. For example, toassess the thermal stability of a sample onewould like to know the temperature atwhich 10% weight loss occurs, or at whatrate evaporation or sublimation takesplace. To obtain the best possible reproduc-ibility and accuracy in such experiments, itis important to know the effect of measure-ment parameters such as the type of purgegas and flow rate, the heating rate, and thesample preparation.One parameter that is very often underesti-mated in TGA measurements is the effect ofsample weight. This parameter has, aboveall, to do with heat transfer from the fur-nace to the sample. All evaporation and(endothermic) decomposition processes re-quire a supply of energy. In the TG furnace,heat is transferred to the sample throughconvection (which predominates at lowtemperatures) and radiation (which pre-dominates at high temperatures). A smallsample therefore decomposes much morerapidly than a large sample, which meansthat the end of the TG step is reached earli-er and therefore at lower temperatures. Be-sides this, larger samples generate moregas. This has to escape through pores inthe sample and from the crucible, therebyprolonging the effect.The effects described above are illustratedin the following example, without goinginto other effects such as sample geometryor sample density.

ExperimentalDecabromodiphenyloxide DECA (C12Br10O,molecular weight 959.2, density3.0 g/ml) melts between 300 °C to 305 °C,followed by evaporation (vapor pressure6.5·102 Pa at 360 °C) and decompositionabove 400 °C. The substance is used as aflame retardant in plastics and fibers.The TG measurements were performed with

a TGA/SDTA851e (small furnace) using ni-trogen at 50 ml/min as purge gas. Thefinely powdered samples were heated from200 °C to 510 °C at 10 K/min in a 70 µlalumina crucible. Whenever other parame-ters were used, this is mentioned in thetext.The DTG curves are calculated as deriva-tives of the TG curves. The SDTA curveswere determined as the temperature differ-ence between the measured sample temper-ature and the program temperature.

Results

Effect of sample massOn heating, the sample of DECA first meltsand then immediately begins to lose weightbefore evaporating completely. The rate atwhich this takes place depends primarilyon the amount of sample. Figure 1 showsthe TG curves of five different samples. Theweight loss for all five samples, measuredin milligrams, begins at the same tempera-ture and with similar rates. The evapora-tion rates (in mg/min) of the large samples

Tips

Effect of sample mass on TG resultsDr. R. Riesen

do not become faster until about 380 °C(see also Fig. 2). It is apparent that thesmallest sample has already completelyevaporated at 400 °C. If the weight losscurves are compared in a normalizedpresentation (i.e. in % as a function of °C),then the evaporation rates look quitedifferent. For example, a weight loss of 10%occurs for the smallest sample at 337 °Cbut for the largest not until 8 minutes later(at 403 °C). This time difference occursbecause much more heat is needed tovaporize 3.3 mg than 0.2 mg.With small sample weights, the TG curveslie exactly on top of each other. Weight lossis however to some extent accelerated withlarger sample weights. This can be ex-plained as being the result of surface trans-port and gas transport properties. It couldalso be caused by the decomposition reac-tion beginning to take effect (see below).The SDTA curves in Figure 2 show thatlarger samples also take longer to meltthan smaller samples (melting at 310 °C).The beginning is, however, in agreementwith the TG curve, practically independent

Fig. 1. TG curves of DECA with different sample weights in an open 70 µl alumina crucible. The fivemeasurements are shown in two different presentations: with the ordinate absolute in milligrams (uppercurves), and normalized in % with respect to the initial sample weight.

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of the sample mass:onset (8 mg) 304.2 °C,onset (33 mg) 304.0 °C;peak (8 mg) 307.9  °C,peak (33 mg) 309.5 °C.The SDTA curves in the evaporation rangeare similar to the DTG curves because theloss of weight is directly related to the up-take of energy.With large samples, the long evaporationtime and the relatively rapid heating rateof 10 K/min means that temperatures are

reached at which decomposition begins.This is particularly clear in the DTG curvesin Figure 2. The curve shape typical of anevaporation process is visible in the twosmallest samples. With larger samples, thiscurve shape is overlapped by the decompo-sition reaction, i.e. there is an additionalloss of weight, which is indicated by thepeak on the evaporation curve. As can beseen in Figure 1 (mg versus °C), the de-composition of the substance already be-gins at temperatures below 400 °C and

is correspondingly stronger with largersamples.

Effect of gas exchangeSample size and the quantity of energy re-quired for evaporation or decompositionare however not the only factors responsiblefor a “shift” of the TG curves. Gas ex-change and the diffusion of gaseous prod-ucts also have a large effect. This is illus-trated in Figure 3, which shows the mea-surement of samples of similar (medium)weight using different crucibles. In an opencrucible, evaporation is relatively rapid butthe delayed removal of vapor from the deepcrucible causes the liquid-vapor equilibri-um to shift to higher temperatures. Thisresults in the TG curve being recorded atabout 20 K higher. If gas exchange is evenmore restricted (with a lid), the equilibri-um is shifted to even higher temperaturesby the self-generated atmosphere; the evap-oration is therefore overlapped by signifi-cant decomposition.

ConclusionsIn thermogravimetry, it is essential to keepnot only the temperature, but also all theother experimental parameters under pre-cise control. To achieve the best possiblereproducibility, it is important to know howthese parameters affect the measurementresults. As has previously been shown[UserCom 9, p.22], the type of crucibleused has a major influence on the rate ofgas exchange and hence on the weight loss.For the same reason, the sample weightalso influences the temperature observedfor an effect, and the rate of weight loss.Even when sample weights are practicallyidentical, a small degree of measurementuncertainty is still to be expected. A seriesof measurements on samples of the sameweight, for example, showed that a temper-ature deviation of ±1 °C at 10% weight lossis possible because other less important pa-rameters such as sample geometry of thecrucible, particle size, packing density, etc.all affect reproducibility. The degree of un-certainty is however much less than theshift of 60 K caused by widely differentsample weights.

Fig. 3. Evaporation of DECA in different crucibles. Dotted curve: 30 µl crucible with low rim; dashed curve:crucible with high rim (70 µl alumina crucible); continuous curve: 70 µl crucible with lid (and small hole).

Fig. 2. The DTG curves (calculated from the absolute sample weight, see the TG curves in Fig. 1) show theevaporation rates for various sample weights in a standard open crucible. SDTA curves are also shown forsample weights of 8 mg and 33 mg.

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Exhibitions, Conferences and Seminars - Veranstaltungen, Konferenzen und Seminare14. Ulm-Freiberger Kalorimetrietage 21 - 23. März 2001 Freiberg, GermanyPittsburgh Conference March 4-9, 2001 New Orleans, LA221st American Chemical Society National Exposition April 2-4, 2001 San Diego, CA222nd American Chemical Society National Exposition Aug. 27-29, 2001 Chicago, ILMEDICTA 2001 Sept. 2-7, 2001 Jerusalem, Israel29th Annual North American Thermal Analysis Society Meeting Sept. 24-26, 2001 St. Louis, MOESTAC 8 Aug. 25-29, 2002 Barcelona, Spain

TA Customer Courses and Seminars in Switzerland - Information and Course Registration:TA Kundenkurse und Seminare in der Schweiz - Auskunft und Anmeldung bei:Helga Judex, METTLER TOLEDO GmbH, Schwerzenbach, Tel.: ++41-1 806 72 65, Fax: ++41-1 806 72 40, e-mail: helga.judex@mt.comTMA/DMA (Deutsch) 26. Februar 2001 Greifensee TMA/DMA (English) March 5, 2001 GreifenseeSTARe SW Workshop Basic (D) 26. Februar 2001 Greifensee STARe SW Workshop Basic (E) March 5, 2001 GreifenseeTGA (Deutsch) 27. Februar 2001 Greifensee TGA (English) March 6, 2001 GreifenseeDSC Basic (Deutsch) 28. Februar 2001 Greifensee DSC Basic (English) March 7, 2001 GreifenseeDSC Advanced (Deutsch) 1. März 2001 Greifensee DSC Advanced (English) March 8, 2001 GreifenseeSTARe SW Workshop Adv. (D) 2. März 2001 Greifensee STARe SW Workshop Adv. (E) March 9, 2001 Greifensee

TMA/DMA (Deutsch) 10. September 2001 Greifensee TMA/DMA (English) September 17, 2001 GreifenseeSTARe SW Workshop Basic (D) 10. September 2001 Greifensee STARe SW Workshop Basic (E) September 17, 2001 GreifenseeTGA (Deutsch) 11. September 2001 Greifensee TGA (English) September 18, 2001 GreifenseeDSC Basic (Deutsch) 12. September 2001 Greifensee DSC Basic (English) September 19, 2001 GreifenseeDSC Advanced (Deutsch) 13. September 2001 Greifensee DSC Advanced (English) September 20, 2001 GreifenseeSTARe SW Workshop Adv. (D) 14. September 2001 Greifensee STARe SW Workshop Adv. (E) September 21, 2001 Greifensee

TA-Kundenkurse und Seminare (Deutschland)Für nähere Informationen wenden Sie sich bitte an METTLER TOLEDO GmbH, Giessen: Frau Ina Wolf, Tel.: ++49-641 507 404.DSC-Kundenkurs 12/13.März 2001 Giessen/D ADSC-Kundenkurs 14. März 2001 Giessen/DWorkshop Pharma: "TA-Methoden zur QS/QC in der pharmazeutischen F&E und Produktion" 15/16. März 2001 Giessen/DSeminar "Thermoanalytische -und spektroskopische Methoden an Kunststoffen" 13. September 2001 Darmstadt/DWorkshop Kurveninterpretation 24.Oktober 2001 Giessen/D DSC-Kundenkurs 22/23. Oktober 2001 Giessen/DInformations-Tage: Wien(A) 07.03.2001 Nürnberg (D) 27.03.2001 München(D) 03.04.2001

Stuttgart (D) 05.04.2001 Greifensee (CH) 05.04.2001

Cours et séminaires d’Analyse Thermique en France et en BelgiqueFrance: Renseignements et inscriptions par Christine Fauvarque, METTLER TOLEDO S.A.,Viroflay: Tél.: ++33-1 30 97 16 89, Fax: ++33-1 30 97 16 60.Belgique: Renseignements et inscriptions par Pat Hoogeras, N.V. METTLER TOLEDO S.A., Lot, Tél.: ++32-2 334 02 09, Fax: ++32 2 334 02 10.Cours clients:TGA et logiciel STARe 27 mars 2001 Viroflay (France) TG et logiciel STARe 16 octobre 2001Viroflay (France)DSC et logiciel STARe 28 mars 2001 Viroflay (France) DSC et logiciel STARe 17 octobre 2001Viroflay (France)DSC avancé et logiciel STARe 29 mars 2001 Viroflay (France) DSC avancé et logiciel STARe 18 octobre 2001Viroflay (France)TMA et logiciel STARe 30 mars 2001 Viroflay (France) TMA et logiciel STARe 19 octobre 2001Viroflay (France)Journées d’information :Journée d’information 13 février 2001 Tours (France) Journée d’information, 19 juin 2001 Aix (France)Journée d’information, 3 avril 2001 Amiens (France) Journée d’information, 25 septembre 2001 Nancy (France)Journée d’information, 29 mai 2001 Pau (France) Journée d’information, 20 novembre 2001 Nantes (France)Séminaires:Aspects de Cinétique en Thermo-Analyse 16 janvier 2001 Toulouse (France)avec la participation du Prof. N. Sbirrazzuoli, Laboratoire de thermodynamique Expérimentale, Université de Nice/Sophia-Antipolis.Analyse Thermique, principes de base et méthodes d'investigation sur des échantillons inconnus 13 mars 2001 Lyon (France)avec la participation de Mr Létoffé, Ingénieur INSA, Laboratoire de Thermodynamique Appliquée, INSA de Lyon.DSC Alternative et ses applications 23 octobre 2001 Paris La Défense (France)avec la participation de Dr. M. Ribeiro, Laboratoire de Thermodynamique et Génie Chimique du Prof. Grolier, LTGC de Clermont-Ferrand.TA Information Day 10 Octobre 2001 Bruxelles (Belgique)STARe User Forum 11 Octobre 2001 Bruxelles (Belgique)

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Corsi e Seminari di Analisi Termica per Clienti in ItaliaPer ulteriori informazioni prego contattare: Simona FerrariMETTLER TOLEDO S.p.A., Novate Milanese, Tel.: ++39-2 333 321, Fax: ++39-2 356 2973.Corsi per Clienti:DSC base 6 Marzo, 5 Giugno, 18 Settembre 2001 Novate MilaneseDSC avanzato 7 Marzo, 6 Giugno, 19 Settembre 2001 Novate MilaneseTGA 8 Marzo, 7 Giugno, 20 Settembre 2001 Novate MilaneseTMA 9 Marzo, 8 Giugno, 21 Settembre 2001 Novate MilaneseGiornate di informazione (Caratterizzazione dei Materiali)Milano 1 Marzo 2001 Bologna 27 Marzo 2001Napoli 20 Marzo 2001 Venezia 28 Marzo 2001Roma 21 Marzo 2001 Torino 29 Marzo 2001Firenze 22 Marzo 2001Seminario di Analisi Termica (Polimeri) 11 Aprile 2001 Milano

Cursos y Seminarios de TA en EspañaPara detalles acerca de los cursos y seminarios, por favor, contacte con: Francesc Catala en Mettler-Toleo S.A.E., Tel: ++34 93 223 76 00E-mail: francesc.catala@mt.comJornadas de Análisis TérmicoSevilla 13-feb-01 Granada 15-feb-01 Zaragoza 3-abr-01Valencia 5-abr-01 Bilbao 5-jun-01 Santiago de Compostela 7-jun-01Seminarios de Análisis TérmicoJornada TA de aplicationes a Polimeros 16-oct-01 Madrid 23-oct-01 BarcelonaJornada TA para Usuarios del Sistema STARe 17-oct-01 Madrid 24-oct-01 BarcelonaJornada TA de applicaciones a Farmacia y Quimica 18-oct-01 Madrid 25-oct-01 Barcelona

TA Customer Courses and Seminars in the USA and CanadaBasic Thermal Analysis Training based upon the STARe System version 6 is being offered in California and at Columbus, Ohio Headquarters. Trai-ning will include lectures and hands-on workshops.For information contact Jon Foreman at 1-800-638-8537 extension 4687 or by e-mail jon.foreman@mt.comTA course April 17 - 18, 2001 Columbus (OH)TA course October 10 - 11, 2001 Columbus (OH)

TA Customer Courses and Seminars in JapanFor details of training courses and seminars please contact:Yasushi Ikeda at METTLER TOLEDO Japan, Tel.: +81-3-5762-0606; Facsimile: +81-3-5762-0756Basic course STARe February 22, 2001 Tokyo Basic course STARe May 25, 2001 OsakaAdvanced course STARe September 14, 2001 Tokyo Advanced course STARe November 15, 2001 OsakaTA information day February 24, 2001 Tokyo TA information day October 25, 2001 Osaka

For further information regarding meetings, products or applications please contact your local METTLER TOLEDO representative.Bei Fragen zu weiteren Tagungen, den Produkten oder Applikationen wenden Sie sich bitte an Ihre lokale METTLER TOLEDO Vertretung.Internet: http:/www.mt.com

Editorial teamMETTLER TOLEDO GmbH, Analytical, Sonnenbergstrasse 74, CH-8603 Schwerzenbach, Schweiz

Dr. M. Schubnell, Dr. R. Riesen, J. Widmann, Dr. J. Schawe, C. Darribère, U. Jörimann

Physicist Chemical Engineer Chemical Engineer Physicist Chemical Engineer Electrical Engineer

e-mail: urs.joerimann@mt.com, Tel.: ++41 1 806 73 87, Fax: ++41 1 806 72 60

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