curso an lisis t rmico 2012 1

5/27/2018 Curso an Lisis T Rmico 2012 1

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Definicin:Constituye un grupo detcnicas en las que una

propiedad de la muestra esmonitoreada en funcin deltiempo o de la temperatura,

mientras la temperatura dela muestra cambia en formaprogramada, en una

atmsfera determinada.

ANALISIS TRMICO


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Campo del Anlisis Trmico

Crioscopa

Ebulloscopa

Calorimetra

Termogravimetra (TGA)

Termogravimetra derivada (DTG)

Anlisis Trmico Diferencial (DTA)

Anlisis Termoelctrico (Cambio de Resistencia Elctrica)

Anlisis Termomecnico (TMA)

Calorimetra diferencial de Barrido (DSC)


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Que podemos determinar por AnlisisTrmico?

Estabilbidad Trmica de una

Sustancia

Agua libre (humedad) Agua ligada (de cristalizacin)

Retencin de solventes

Pureza de una Sustancia

Punto de Ebullicin

Punto de Fusin

Calores de transicin

Calores especficos


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Caracterizacin de Catalizadores

Caracterizacin de minerales

Caracterizacin de fibras

Control de productos cermicos

Transiciones vtreas

Control de la calidad depolmeros

Cristalizacin

Cambios de colorPolimorfismo (Ej. Frmacos)


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Factores que afectan los

resultados en Anlisis Trmico Muestra

Cpsula o contenedor de la

Muestra Velocidad de Calentamiento o

enfriamiento

Atmsfera

Masa de la Muestra y su forma fsica


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Tipos de procedimientos usados

Tcnica Simple: Cuando se usa una sola tcnica (TGA, DTA, DSC, etc.).

Tcnicas Simultneas: Cuando dos tcnicas se aplican a la misma

muestras y al mismo tiempo.

TGA-DTA DSC-TGA

Tcnicas Complementarias: Cuando

dos tcnicas se aplican a distintas

muestras (misma sustancia) o a

diferentes tiempos. DTA+TGA

TGA+DRX

TGA +GC (Anlisis de gases liberados)

- TGA + FTIR


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Anlisis Termogravimtrico (TGA)y

Termogravimetra Derivada

(DTG)


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Anlisis Termogravimtrico (TGA)

Definicin:

Es una tcnica en la que la masa de la muestra esmonitoreada en

funcin del tiempo o de la temperatura, cuando latemperatura de la muestra sigue cierto programa, en unaatmsfera especfica.

Termogravimetra Derivada (DTG)

Definicin:Es cuando se grafica la velocidad de cambio de la masa(dm/dt), en funcin de la temperatura


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Equipos TGA

(TERMOBALANZA)


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La termobalanza TGA 7 est equipada con una

ultramicrobalanza capaz de detectar cambios de peso de hasta

0.1 mg, con una capacidad mxima de 130 mg. Se pueden

alcanzar temperaturas de hasta 1000C, con velocidades de

calentamiento entre 0.1-200C/min. Asimismo, podemos

controlar la atmsfera a la que se lleva a cabo el anlisis.

TGA Perkin-Elmer Modelo

(TGA 7)


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Anlisis Trmico Diferencial y Anlisis

Termogravimtrico simultneos DTG-60El nuevo DTG-60/60H es el instrumento

que permite mediciones simultneas de

anlisis trmico diferencial (DTA) y

termogravimtricas (TG), ahorrando

tiempo de anlisis y de preparacin de

muestras. Como en DSC, el controladorTA-60WS proporciona funciones

avanzadas de adquisicin y anlisis de

datos e informe de resultados.

EspecificacionesDTG-60 DTG-60H

Rango de

temperaturasAmbiente a 1100C Ambiente a 1500C

Rango de TGA 500mg

Lectura mnima 1g

Carga mxima 1g incluyendo tara

Rango de DTA 1000V

Dimensiones 367ANCHOx 650PROF.x 453ALT. mm

Peso aprox. 35 Kg


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Esquema de

un

Termobalanza


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Control de la Temperatura


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Diferentes tipos de Comportamiento Trmicos


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22PerkinElmer


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24PerkinElmer


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Anlisis Trmico Diferencial (DTA)

Definicin:

Es la tcnica en la que la diferencia de

temperatura entre la muestra y un materialde referencia es monitoreada en funcin deltiempo o de la temperatura, mientras latemperatura de la muestra cambia segn un

programa establecido, en una atmsferaespecfica.


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Termograma tpica de DTA

Termograma tpica de DTA, usando la convencin

en que los picos endotrmicos son hacia

abajo. indica la seal diferencia de

temperaturas ( = T = Tr Tm)


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Calorimtria Diferencial de Barrido (DSC)


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La Calorimetra Diferencial de Barrido (DSC) puede ser de flujo

de calor o de potencia compensada (Compensacin).

En el primer caso, se mide la variacin en el flujo de calor entrela muestra y la referencia cuando dicha muestra se somete a un

programa de temperatura en una atmsfera controlada.

En el segundo caso se mide la potencia que hay que aportar o

retirar del sistema para que muestra y referencia se mantengan a

la misma temperatura cuando dicha muestra se somete a un

programa de temperatura en una atmsfera controlada.


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Power Compensated DSC System Design

Sample ReferencePlatinum Alloy

PRT Sensor

PlatinumResistance Heater

Heat Sink


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Caracteristicas del DSC

La DSC es una tcnica cuantitativa que permite

obtener informacin de la temperatura a la cual tiene

lugar el cambio energtico en estudio y del calor

involucrado en el proceso (Cp, Hf, Hc).


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Calormetro Diferencial de Barrido (DSC)

Calormetro Diferencial de Barrido tipo Compensacin

Rango de Temperatura: -170 C 600 C con velocidades de calentamiento

entre 0.1-200C/min. Velocidad de enfriamiento hasta 200 C/min.

Tipo: Compensacin

Permite determinar H, Cp


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Benefits of Power Compensated DSC for

Difficult Characterization Measurements

High sensitivity for the detectionof the weak transitions

Fast heating (High Speed DSC)

for increased sensitivity

StepScan DSC for the separation

of Tg from longer term, kinetic

transitions (crystallization or

enthalpic relaxation)

Outstanding resolution for better

separation of overlapping events


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Resolucin Versus Sensibilidad en (DSC)

Resolucin: se refiere a la habilidad del DSC a

separar transisiones trmicas que ocurren a

temperaturas muy cercanas

Sensibilidad:se refiere a la habilidad del instrument adetectar transiciones dbiles (background noise)

Las condiciones de medidas en DSC pueden ser

optimizadas para aumentar laResolucin y

Sensibilidad

Equipos de DSC del tipo compensacin ofrecen alta

Resolucin y Sensibilidad


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Como se puede mejorar la resolucin en DSC

Utilizar Muestra pequea

Usar Baja velocidad de calentamiento

Usar Helio como gas purgante

Usar muestra en forma de una capa o un film delgada

Usar un equipo de DSC de alta desempeo y

resolucin


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Aplicacin donde la Resolucin es Importante

Polimorfismo de frmacos

Polimorfismo de grasas (mantequilla de cacao,

chocolates, etc.)

Procesamiento de los PolmerosMezclas (Blendas) polimricas

Crystales Lquidos

Determinacin de Pureza de los Frmacos


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Cmo mejorar la Sensibilidad del DSC

- Aumentar el peso de la muestra

- Usar alta velocidad de calentamiento

- Utilizar muestras en forma de una capa o film para

mejorar el contacto con el sensor de la temperaturadel equipo

- Calibrar el equipo para cada medicin

- Mejorar la lnea base y su reproducibilidad- Aplicar la tcnica de StepScan DSC

- Controlar o alterar la historia trmica de la muestra


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Aplicaciones donde la Sensibilidad es Importante

Recubrimientos Recubrimiento Optico Recubrimiento de conservas Recubrimiento de pliculas (transparencias) Recubrimiento magnetico (floppy diskettes, cintas de

video) Pinturas aplicados sobre un sustrato

Deteccon de aditivos de baja concentracin en polmeros,

alimentos, productos farmacuticos Estudio de proteinas Anlisis de pequeas cantidades (microgramos) de

Prototipo de un fmaco nuevo


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Resolution

Pharma Polymorphs

Identification of polymorphism (unstable melting

forms) is very important for pharmaceuticals

Polymorphism is related to:

Drug dissolution times and bio-delivery Shelf lifetimes

Patentability (polymorphs are patentable)

DSC provides excellent means of characterizing

pharmaceuticals for polymorphismRequires high resolution since polymorphic

transitions can severely overlap


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- Estudio de transiciones de primer orden: fusin, solidificacin,

cristalizacin, etc...

- Estudio de polimorfismos.

- Identificacin de polmeros.- Estudios de polmeros: curado, transiciones vtreas, fusin, grado de

cristalinidad.

- Estudio de oxidacin.

- Determinacin de purezas.

- Determinaciones de Cp.

Aplicaciones de la Calorimetra Diferencial de Barrido (DSC):


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RESOLUCIN

DSC de Compensacin

Deteccin de Diferentes Polymorfos de Frmacos La deteccin de Polimorfo de un Frmaco es importante

Los diferentes Polimorfos de un Frmaco es patentable

Asuntos de seguridad (La velocidad de disolucin de un

Polimorfo es diferente que otros)

Tiempo de vida del producto (Los polimorfos inestables

pueden cambiar sus propiedades a travs del tiempo)


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DSC de CompensacinDeteccin de Diferentes Polymorfos de Frmacos

La deteccin de Polimorfismo requiere DSC de alta

resolucin

Las transiciones polimorficos son muy cercanos y dficil

de resolver

El tiempo de respuesta del DSC es muy importante para la

evaluacin de Polimorfismo

Pyris Diamond DSC provee la mejor respuesta y

resolucin


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El Polimorfismo es dficil de

detectar

DSC de compensacin a 10 C/min

aparentemente muestra un solo

pico de Fusin

Ampliando el termograma revela

otra transicin a mayor temperatura


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Esta segunda fusin

(endoterma) se debe al

Polimorfismo de la muestra


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La presencia de Polimorfismo puede ser

demostrado cambiando la escala de tiempo en el

DSC.

Esto se logra disminuyendo la velocidad de

calentamiento de la muestra a 3 C/min

Menor velocidad de calentamiento aumenta la

resolucin del equipo y aumenta la separacin delas transiciones correspondientes a diferentes

Polimorfos.


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A una velocidad vde calentamiento

de 3 C/min, se detecta fusiones de

diferentes Polimorfos

Una fusin inestable, seguido de

cristalizacin y posterior fusinestable

El DSC de compensacin tiene

muy baja inertia trmica


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OTROS EJEMPOLS DE APLICACIONES DE DSCPolymers

Acrylic Resin:

Acrylic resins are a group of related substances derived from acrylic acid ormethacrylic acid noted for their rubbery nature. The

most significant acrylic resin is polymethylacrylate, which is used in anemulsed form for lacquer, textile finishes, adhesives and,

mixed with clay, to gloss paper. One of the main characteristic features ofacrylic resin is its high transparency.

Acrylic resins can be cured by UV or visible light of the proper wavelength,

intensity and duration.


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Results:

The reaction enthalpy was calculated from the signal of the first and second radiation process, each corrected by the third one

(baseline). The exothermic peaks during the measurements are due to curing of the resins and show the influence of the

photoinitiator amount on the reaction. The resin with 4% photoinitiator reacts faster than the one with 1% photoinitiator

during the first exposition (210 J/g to 163 J/g). Both samples finish curing during the second exposure. The total enthalpy is

comparable for both resins (approx. 212 J/g).


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Paints & Coatings

Epoxy Powder Coating

Powder coatings are dry types of coating which are applied as

a free-flowing, dry powder. The main difference between a

convencional liquid paint and a powder coating is that the

powder coating does not require a solvent to keep the binder

and filler parts in a liquid suspension form. The coating is

typically applied electrostatically and is then cured under heat

to allow it to flow and form a "skin."


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The endothermic step detected at 59Cduring the firstheating indicates the glass transitionof the powder coating

befote curing. The exothermal effect between 90 and 240C

results from curing of the sample. It occurs in at least two

steps because a shoulder was detected at 108C, additionally

to the peak at 173C. In the second heating, the glass

transition is shifted to 107C and the step in specific heat is

smaller than in the first heating (0.24 J/(g/*K) to 0.35 J/(g*K))

which is due to cross-linking of the material.

Polymers (Automotive)


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Acrylonitrile butadiene styrene or ABS is a thermoplastic used to make light, rigid,

molded products such as piping, musical instruments, automotive body parts, wheel

covers, toys (like LEGO bricks), etc.

The three endothermic changes (steps) in the specific heat-flow rate curve correspond to the

glass transitions of polybutadiene (at -79C), polystyrene (at 100C) and polyacrylonitrile (at

117C). Additionally, a melting peak was determined at 162C (peak temperature) indicating

melting of a crystalline additive. According to the position of the melting peak, it probably

results from polypropylene. Because of the crystallinity of this material, its presence in the ABS

can lead to embrittlement-induced cracking.

S i i i


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Sensitivity

Detection of Tg of Polypropylene

High level of crystallinity ofpolypropylene yields a weak

Tg

DSC with high sensitivity is

required to detect Tg of thispolymer

Power Compensation DSC

results displayed here show

well-defined Tg of poly-propylene at -8 C


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Benefits of StepScanDSC for Tough

Characterization Problems

- StepScan DSC is a TMDSC approach.

- StepScan DSC applies a repetitive sequence of heat-

hold steps over the temperature range of interest

- StepScan DSC separates out fast (reversible) andslow (irreversible) thermal events

- Thermodynamic Cp signal is free of kinetic effects,

such as evolution of solvents or water, crystallization,

relaxation, etc.

- Provides clearer identification of weak Tgs


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StepScanDSC

Basic DSC heat flow equation is:

heat flow = Cp(dT/dt) + f(T,t)

The Cp term yields the reversible information

The f(T,t) term reflects the kinetic or irreversibleaspects of the sample

With StepScan DSC, the sample is either being

heated at a constantrate

Or, is held under isothermalconditions (dT/dt = 0)


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StepScan DSC

Applies repetitive sequenceof heat-hold cycles

Uses traditional approach to

measure DSC heat

capacities but utilizessmaller temperature steps

Temperature step of 2 C

and hold period of 20 to 30

seconds


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StepScan DSC

StepScan DSC separates outreversible (heating) and

irreversible (isothermal)

thermal events

Makes data interpretationeasier.

Analysis of PET (plastic

Bottels)

StepScan DSC

Results for PET

Cold Crystallization

Tg

St S DSC


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StepScan DSC

Identification of Hidden Tg

Standard DSC results onpolymer blend (ABS -

Amorphous PET-

Polycarbonate)

DSC results show two Tgswhere there should be three

Tg of amorphous PET is

masked by crystallization

exothermic peak

St S DSC


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StepScan DSC

Identification of Hidden Tg

These are the StepScan DSCresults generated on the

polymer blend

The irreversible crystal-

lization event of the PET isseparated out from the

reversible Tg of the

polycarbonate component

The three Tgs of all threecomponents (PET, ABS and

polycarbonate) are now

identified

Detection of S bambient Properties of Sol tions


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Detection of Subambient Properties of Solutions

Freeze-Drying Formulations

Many pharmaceuticals are freeze-dried to produce alonger shelf lifetime

Active drug is placed into solution with other

components including cryo-protector (e.g., sucrose,mannitol, dextran, lactose)

Presence of cryo-protector solute alters solution

chemistry producing small level of amorphous phase

Results in occurrence of Tg(s) and other transition insubambient regions

Transitions related to collapse of formulation



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Freeze-Drying Formulations

Detection of subambient formulation transition(s)canbe difficult by DSC when solutions are dilute (


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StepScan DSC of Freeze Dry Formulations

Dilute (5%) Sucrose Solution

StepScan DSC provides thethermodynamic or reversible heat

capacity data

The Thermodynamic Cp provides

clearer identification of Tg for

materials with accompanyingkinetic transitions (water loss,

crystallization)

This example shows the clearer

identification of the two Tgs of a

5% sucrose formulation



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10% Sucrose Solution

This example shows resultson 10% sucrose formulation

As concentration of solute

increases, magnitudes of

Tgs increaseCrystallization transition at -

30 C is no longer observed

with 10% solution

StepScan DSC of Coatings


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StepScan DSC of Coatings

Floppy Diskette

Floppy diskettes contain athin magnetic, polymeric

coating on a PET substrate

Detection of Tg of magnetic

coating is considereddifficult or impossible using

standard DSC

StepScan DSC results show

the Tg of the coating as wellas of the highly crystalline

PET substrate


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High Speed DSC

Increasing the applied DSC heating rate can provideadditional sensitivity

High Speed DSC entails using heating rates much

faster than normal (50 to 400 C/min)

Detection of Weak Tg by DSC


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Using High Speed DSC

Many polymeric materialsexhibit very weak glass

transition events

Sensitivity can be improved

by using more sample or byincreasing the applied DSC

heating rate

These DSC results show the

detection of the very thincoating on a transparency

film by using a heating rate

of 50 C/min



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Using High Speed DSC

These are High Speed DSCresults obtained on a pharma

material at 200 C/min

Sample did not exhibit Tg

by standard DSCUse of very fast heating

rates allowed for detection

of Tg at 224 C

High Speed DSC approachis valuable for low mass

samples (


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Detection of Weak Transitions by DSC

Counterbalancing

Additional sensitivity can be obtained from a DSCusing counterbalancing

This refers to matching the heat capacity of the

sample and the reference

For samples containing a solvent or a substrate, it is a

good practice to counterbalance with the given

solvent or substrate material


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Detection of Toners on Photocopied Documents

For forensic purposes, it is desired to take a photo-copied document and characterize the properties of

the toner

Toner is difficult to detect by DSC because of high

mass content of paper substrate (92% of sample) and

low thermal conductivity of paper

Paper (where no toner is present) can be used as a

DSC reference counterbalanceProvides enhanced sensitivity of toner properties and

makes detection possible


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These DSC results showphotocopied document #1

Toner yields melting

transitions at 65 and 81 C


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These DSC results showphotocopied document #2

This toner yields Tg at 59 C

DSC toner data is useful for

identifying origin ofphotocopied document


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Detection of Protein Denaturation

Proteins comprise about 1 to3% of the total mass of the

solution

Protein denaturation event is

low energy and requiresDSC with high sensitivity

Water or buffered solution

can be used as

conterbalanceResults here are for

Humulin N insulin solution

with heat of only 0.09 J/g


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Isothermal crytstallization measurements of high density polyethylene

DSC Analysis


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DSC Analysis


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Anlisis Termomecnico (TMA)

El Anlisis Termomecnico (TMA) es una tcnica en la que semide la deformacin de una muestra cuando es sometida a una

fuerza constante y a un programa de temperatura en una

atmsfera controlada. Esta fuerza puede ser de compresin,

flexin o traccin.El Anlisis Termomecnico (TMA) determina cambios

dimensionales de slidos , lquidos y materiales pastosos en

funcin de la temperatura y/o tiempo bajo una fuerza mecnica

definida (DIN 51 005, ASTM E 831, ASTM D 696, ASTM D

3386, ISO 11359Partes 1 a 3). Es cercano a la Dilatometra,

que determina los cambios de longitud de muestras bajo carga

negligible (DIN 51 045).


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Aplicaciones del Anlisis Termomecnico (TMA):

- Ensayos de compresin-dilatacin

- Estudio de transiciones vtreas

- Estudio de reblandecimientos y fusiones.- Coeficiente de dilatacin.