Differential Thermal Analysis (DTA) - Spada UNS

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SIFAT THERMAL POLIMER

(Thermal Properties of Polymers)

Dr. Mohammad Masykuri, M.Si.

PROGRAM STUDI PENDIDIKAN KIMIA FAKULTAS KEGURUAN DAN ILMU PENDIDIKAN

UNIVERSITAS SEBELAS MARET

Kimia Polimer

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Mohammad Masykuri - Universitas Sebelas Maret [email protected]

Thermal Protection System

• Application:

Space Shuttle Orbiter

Fig. 23.0, Callister 5e. (Fig.

23.0 courtesy the National Aeronautics and Space Administration.

reinf C-C (1650°C)

Re-entry T Distribution

silica tiles

(400-1260°C) nylon felt, silicon rubber coating (400°C)

Fig. 19.2W, Callister 6e. (Fig. 19.2W adapted from L.J. Korb, C.A. Morant, R.M. Calland, and C.S.

Thatcher, "The Shuttle Orbiter Thermal Protection System", Ceramic Bulletin, No. 11, Nov. 1981, p.

1189.)

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Thermal Protection System

• Application:

• Silica tiles (400-1260C) :

--large scale application

--microstructure:

100 m

~90% porosity!

Si fibers

bonded to one

another during

heat treatment.

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Physical Properties Measured by Thermal Analysis

Physical Property Derived Technique

Mass Thermogravimetry

Evolved gas analysis

Temperature Differential thermal analysis

Enthalpy Differential scanning calorimetry

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Thermal Analysis Methods

Differential Thermal Analysis (DTA)

• Heat of Transitions

Differential Scanning Calorimetric (DSC)

• Heat flow during Transitions

Thermal Gravimetric Analysis (TGA)

• Weight Loss due to decomposition

• Derivative Thermogravimetric Analysis (DTG) Thermal Mechanical Analysis (TMA)

• Thermal Expansion Coefficient

Dynamic Mechanical Analysis (DMA)

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Basic Principles

• Sample is heated at a constant heating rate

• Sample’s Property Measured

• Wt TGA

• Size TMA

• Heat Flow DSC

• Temp DTA

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Basic Principles

• A group of methods by which the physical & chemical properties of a

substance, mixture &/or reaction mixtures are determined as a function of temperature and/or time, while sample is subjected to a controlled

temperature program.

• Include heating or cooling (dynamic) or holding temperature constant (isothermal), or combination.

• Thermogravimetry Analysis (TGA) – mass of substance against temperature or time.

• Differential Scanning Calorimetry (DSC) – heat flow as a function of temperature or time.

• Thermal Mechanical Analysis (TMA) – deformation under static load vs T or time.

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Thermogravimetri

c Analysis (TGA)

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Thermogravimetric Analysis (TGA)

A technique in which the mass of a substance is measured as a function of temperature while the substance is subjected to a controlled temperature program

M as s

Time/Temperature

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Used to measure changes in weight (mass),  m, of sample as a function of T and/or time.

Commonly used to

• Determine polymer degradation temperature,

• Residual solvent level,

• Absorbed moisture content, and amount of inorganic

(noncombustible) filler in polymer or composite material compositions.

• Decomposition temperature of materials-impurities in

ceramic etc

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Response ;

• Weight gain – adsorption (physical), oxidation (chemical).

• Weight loss – vaporization (physical), desorption (physical), oxidation (physical), decomposition (chemical),

dehydration & desolvation (chemical).

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Application of TGA

• Determines temperature and weight change of decomposition reactions, which often allows quantitative composition analysis. May be used to

determine water content.

• Allows analysis of reactions with air, oxygen, or other reactive gases (see illustration below).

• Helps to identify plastics and organic materials by measuring the

temperature of bond scissions in inert atmospheres or of oxidation in air or oxygen.

• Used to measure the weight of fiberglass and inorganic fill materials in

plastics, laminates, paints, primers, and composite materials by burning off the polymer resin. The fill material can then be identified by XPS and/or

microscopy. The fill material may be carbon black, TiO2, CaCO3, MgCO3,

Al2O3, Al(OH)3, Mg(OH)2, talc, Kaolin clay, or silica, for instance

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Application of TGA

(i) No decomposition with loss of volatile products.

(ii) Rapid initial mass loss characteristic of desorption or drying.

(iii) decomposition in single stage.

(iv) multi-stage decomposition.

(v) multi-stage decomposition but no stable intermediates.

(vi) Gain in mass as a result of sample reaction.

(vii) reaction product decompose again.

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Application of TGA

Depending on polymer composition, reaction upon heating will give their own characteristic TG curve.

Result can give thermal stability of material – desorption, decomposition

& oxidation information.

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TGA Data of Calcium Oxalate

• Constant Heating Rate

• Initial Temp

• Final Temp

• Heating Rate (°C/min)

• Data

• Weight vs Time

• Weight vs Temp.

• Differential This Data

(DTG)

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TGA Data of Calcium Oxalate

Calcium oxalate monohydrate – 3 distinct weight losses.

CaC

₂

O

₄

.H

₂

O  CaC

₂

O

₄

 CaCO

₃

 CaO

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Contoh Lain

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Contoh Lain

• Molded underfill material (flip chip application) – 3

degradation stages ; moisture & volatiles in resin, weakly bonded monomers, then

breakage of cross-

linked monomers

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Contoh Lain

Multiple-stage reaction:

dehydration reaction of hydroxide from

LiOH.H

₂

O (exo).

4LiOH.H

₂

O (solid) + O

₂

 2Li

₂

O + 4H

₂

O Then formation

reaction of Li

₂

SnO

₃

due to reaction between

Li O with SnO in

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Factors Affecting TG curve

• Factors affecting TG curve

• heating rate

• sample size

• particle size of sample

• the way it is packed

• crucible shape

• gas flow rate

• DTG – derivative of TG curve, often useful in revealing extra detail.

• TG also often used with DTA (differential thermal analysis).

• DTA – record difference in T (∆T) between sample and reference material. Each DTA curve should be marked with either endothermic or exothermic direction.

• Curve – peak represent exothermic or endothermic reaction.

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Differential Thermal

Analyzer (DTA)

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Differential Thermal Analyzer (DTA)

• Record temperature difference between sample & reference material.

• If endo event (e.g melting) temperature sample will lower than reference material.

• If exo event (e.g oxidation) response will be in opposite direction.

• Reference material:

• thermally stable at a certain temperature range

• Not react with sample holder or thermocouple

• both thermal conductivity

• heat capacity should be similar to those of sample

• Both solid sample & reference material usually powdered form.

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Differential Thermal Analyzer (DTA)

• Sample and Reference Placed in Heater

• Initial Temp

• Final Temp

• Data

• Temp of Sample vs Time (or Temp)

• Temp of Reference vs Time (or Temp)

• Reference should be inert, e.g. nothing but latent heat

• Measures

•

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TG/DTA of Montmorillonite Clay

TG/DTA scan of montmorillonite clay.

• Large endotherm at 114°C is assigned to loss of interlayer absorbed water.

• 2

^nd

endotherm at 704°C is

dehydroxylation reaction of the mineral.

• Last 2 peaks are attributed to

structural changes, since no

weight loss are evident in TG.

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DTA of Gold

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Differential Scanning

Calorimeter (DSC)

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Differential Scanning Calorimeter (DSC)

• A thermal analysis technique in which the amount of energy absorbed (endothermic) or released (exothermic) by a material is measured.

• Both events are the result of physical and/or chemical changes in a material.

• Normally the weight of sample is 5 – 10 mg,

• Sample can be in solid or liquid form.

• Many of the physical (e.g evaporation) or chemical (e.g

decomposition) transformation are associated with heat absorption

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Features of DSC Curves

• Initial Temp

• Final Temp

• Data

• Heat flow to sample minus Heat flow to reference vs Time (Temp.)

• Measures heat of

crystallization

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Polymer without weight

change in this temperature

range

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Heat is being absorbed by

sample (increase in its heat

capacity). Polymers gone thru

T

_g

, but transition occur over a

temperature range. So T

_g

is

taken as middle of the incline.

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Crystallization point – Tc where at this temperature polymer have enough energy to arrange into ordered arrangements, crystal. Polymers give off heat at this point. Area of peak = latent energy of crystallization.

Heat absorbed in order to melt – additional heat to increase temperature.

Area of dip = heat of melting.

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• Typical DSC curve for polymer (especially thermoplastic), for polymers that don’t crystallize (amorphous), T

_c

& T

_m

will not present.

• Comparing T

_g

with T

_c

& T

_m

, T

_g

only

involve changes in heat capacity.

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DSC curve for typical organic polymer.

Tg – change in heat capacity but no change in enthalpy, ∆H = 0.

DSC directly measures ∆H of

transitions. Also degree of crystallinity,

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DSC Response

Physical changes :

Exothermic – adsorption, crystallization.

Endothermic – desorption, melting, vaporization.

Chemical changes :

Exothermic – oxidation, decomposition, curing.

Endothermic – reduction, decomposition, dehydration.

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Instrumentation DSC

Computer makes sure that the 2 separate pans heat at the same rate (usually

10°C/min or lower) as each other. So if endothermic or exothermic events,

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Instrumentation DSC

2 modes – depending on

method of measurement

used .

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DSC Application

 Identify melting point, glass transition, Curie temperature, energy required to melt material. Evaluation of phase transformation.

 Decomposition, polymerization, gelation, curing.

 Evaluation of processing, thermal & mechanical histories.

 Process modeling, material’s min process temperature (processing condition).

 Determine crystallization temperature upon cooling.

 Perform oxidative stability testing (OIT).

 Compare additive effects on material.

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DSC Application

• DSC have many applications in field of polymer science & engineering.

• Tg, Tc & Tm transitions are characteristic of each polymer  identification.

• Curing conditions for thermoset – heat for curing which allows calculation of degree of curing.

• But, DSC technology is not sensitive to detect Tg in cross-linked or highly crystalline resins. Also for polymer with high filler content.

• Handling liquid also difficult. Interpretation of phase transition requires

further info – XRD, etc.

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DSC for Determine Miscible/Immiscible Blending

Polymer blend – immiscible blend. If fully soluble, Tm peak will be in between Tm each

elements.

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DSC for Determine Miscible/Immiscible Blending

Polymer blend – immiscible blend. If fully soluble, Tm peak will be in between Tm each

elements.

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DSC for Determine Cristallinity

% of crystallinity calculated relative

to 100% crystal material’s Tm peak.

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DSC for Determine Cristallinity

Higher crystallinity gives larger &

higher Tm peak.

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DSC Data of Indium at Multiple Heating

Rates

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DSC Data of Polyethylene Terephtalate (PET)

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DSC Data of PET Glass Transition

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Thermo Gravimetric/Differential

Thermal Analyzer (TG/DTA)

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Thermo Gravimetric/Differential Thermal Analyzer

(TG/DTA)

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TG/DTA Data of Calcium Oxalate

50 to 800°C @10°C/min, Nitrogen

@150ml/min, Sample Weight

0.965mg, Platinum Pans, Data

Interval 0.5sec

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Thermal Stability of Polymers

Chemical structure of thermally stable polymer:

to have aromatic repeating unit.

TABLE 4.3. Representative Thermally Stable Polymers

^a

Type

Poly(p-phenylene)

Polybenzimidazole

Polyquinoxaline

Structure Decomposition

Temperature (

^o

C)

^b

660

650

640

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TABLE 4.3. Representative Thermally Stable Polymers

^a

Type

Polyimide

Poly(phenylene oxide)

Polythiadiazole

Poly(phenylene sulfide)

Decomposition Temperature (

^o

C)

^b

585

^c

570

490

490 Structure

a

Data from Korshak

¹⁷

b

Nitrogen atmosphere unless otherwise indicated.

c

Helium atmosphere.

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Differential Thermal Analysis (DTA) - Spada UNS

SIFAT THERMAL POLIMER

23.0 courtesy the National Aeronautics and Space Administration.

--microstructure:

Enthalpy Differential scanning calorimetry

Basic Principles

temperature program.

Thermogravimetri

Commonly used to

dehydration & desolvation (chemical).

• Helps to identify plastics and organic materials by measuring the

Al2O3, Al(OH)3, Mg(OH)2, talc, Kaolin clay, or silica, for instance

(vii) reaction product decompose again.

TGA Data of Calcium Oxalate

Contoh Lain

dehydration reaction of hydroxide from

• the way it is packed

• Curve – peak represent exothermic or endothermic reaction.

• If exo event (e.g oxidation) response will be in opposite direction.

Differential Thermal Analyzer (DTA)

TG/DTA of Montmorillonite Clay

Differential Scanning

• Many of the physical (e.g evaporation) or chemical (e.g

• Measures heat of

, but transition occur over a

Area of dip = heat of melting.

DSC curve for typical organic polymer.

Chemical changes :

Instrumentation DSC

 Process modeling, material’s min process temperature (processing condition).

• Tg, Tc & Tm transitions are characteristic of each polymer  identification.

DSC for Determine Miscible/Immiscible Blending

elements.

Rates

TG/DTA Data of Calcium Oxalate

Structure Decomposition

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