DSC & TGA

DSC & TGA

Differential Scanning Calorimetry and Thermal Gravimetric Analysis

Pashaie.mokhtar7@gmail.com

Different Techniques• Thermometric Titration (TT)

• Heat of mixing• Thermal Mechanical Analysis (TMA)

• Thermal Expansion Coefficient• Dynamic Mechanical Analysis (DMA)

• Viscoelastic Properties• Differential Scanning Calorimetric (DSC)

• Heat flow during Transitions• Thermal Gravimetric Analysis (TGA)

• Weight Loss due to decomposition• Derivative Thermogravimetric Analysis (DTG)

• Differential Thermal Analysis (DTA)• Heat of Transitions

• Temperature Programmed Desorption (TPD)• Temperature at which gas is desorbed from (catalyst) surface• Emission gas Thermoanalysis (EGT)

Basic Principle

• Sample is heated at a constant heating rate

• Sample’s Property Measured

• Wt TGA• Size TMA• Heat Flow DSC• Temp DTA• Gas evolved TPD

The adsorption of heat will be different in the two pans due to the different composition in the pan. In order to keep the temperature of the two pans constant during the experiment, the system needs to provide more or less heat to one of the two pans.

What is DSC?

DSC looks at how a material’s heat capacity (Cp) is changed by temperature.

This allows the detection of transitions like melts, glass transitions, phase changes, and curing.

Thermal properties of a polymer

Heat Capacity The heat capacity (Cp) of a system is the quantity of heat needed to raise the temperature of the system of 1 °C. It is usually given in units of Joules/°C. It can be derived introducing two parameters, namely the heat flow and heating rate.

Glass Transition

In the two regimes, before and after the Tg, the polymers have different heat capacities: Usually polymers have a higher Cp above the Tg. Due to this difference in Cp, the DSC is a valuable method to determine the Tg.

Temperature in the middle of the inclined part of the graph is by definition the Tg.

T

V

Tm

Totally crystalline

T

V

Tg

Totally glassy

T

V

TmTg

Semi-crystalline

Crystallization

When polymers fall into these crystalline arrangements, they give off heat to the system, thus the process is exothermic.

1. have confirmation of the occurrence of the crystallization; 2. determine the polymer's crystallization temperature (Tc) as the lowest point of the dip; 3. gain insight into the latent energy of crystallization for the polymer by observing the area of the dip.

Melting

melting is an endothermic transition. The melting is a first order transition since when the melting temperature is reached; the polymer's temperature does not rise until all the crystals have completely melted.

the latent heat of melting can be measured from the area of the peak

Melting of Indium

157.01°C

156.60°C28.50J/g

Indium5.7mg10°C/min

-25

-20

-15

-10

-5

0

Hea

t Flo

w (m

W)

150 155 160 165

Temperature (°C)

Exo Up Universal V4.0B TA Instruments

Peak Temperature

Extrapolated Onset

TemperatureHeat of Fusion

Glass Transition vs. Melting

Melting occurs only in a crystalline polymer, while the glass transition takes place to just to polymers in the amorphous state.

DSC Instruments

Two types of DSC instrument have been widely used:

The heat flux DSC (e.g., TA DSC and Mettler DSC)

The power compensational DSC (Perkin-Elmer system)

Heat flux DSC:

Power compensated DSC

Modulated DSC

the same heat flux DSC cell is used, but a sinusoidal temperature oscillation (modulation) is overlaid on the conventional linear temperature ramp, resulting heating rate is sometimes faster than the underlying linear heating rate, and sometimes slower than the underlying rate

Experiment : Thermal behavior of PET

Determine on the PET sample a. The glass transition, melting and crystallization temperature; b. The heat of crystrallization and melting.

Preparing sample: • Cut a piece of PET film from the plastic bottle, clean it with water and dry it. • Make a thin film with the weight 5-15 mg, (this is the normal sample weight in DSC experiment). • Keep the film flat enough and with suitable size for Aluminum pan.

Glass transition sensitivity

Tg is reversible

TGA

Thermal Gravimetric Analysis

continuous measurement

of weight on a

sensitive thermobalance

as sample temperature

is increased in air or in an inert atmosphere.

Photodiodes

Infrared LED

Meter movement

Balance arm

Tare pan

Sample platform

Thermocouple

Sample pan

Furnace assembly

Purge gas outlet

Heater

Elevator base

Purge gas inlet

Sample pan holder

Quartz Liner

Off-Gases

Balance Purge

Sample Thermocouple

SamplePan

Furnace Core

Purge Gas In

Data are recorded as a thermogram of weight versus temperature

evaporation of residual moisture or solvent

polymer decomposition

Thermal stability studies

characterize polymers through loss of a known entity such as HCl from poly(vinylchloride) Thus weight loss can be correlated with percent vinylchloride in a copolymer.

determining volatilities of plasticizers and other additives

Some applications

• Heating a sample of Calcium oxalate

• Ca(C204)*xH2O Ca(C204) *H2O + x-1 H2O• Ca(C204)*H2O Ca(C204) + H2O • Ca(C204) CaCO3 + CO• CaCO3 CaO + CO2

Thermal Degradation of Polyhydroxylated Nylon 6,6

0 100 200 300 400 500 600

-100

-80

-60

-40

-20

0

100oC -6.3%150oC -6.9%200oC -19.0%235oC -50.0%

205oC

425oC

DTG

TG

DT

G

Wei

ght L

oss

(TG

), %

Temperature, oC

0.0

5.0k

10.0k

15.0k

Poly (4-dodecyl-1-4-aza heptamethylene-D-glucaramide) Thermal decomposition.

0 100 200 300 400 500 600

-100

-80

-60

-40

-20

0

TG (%

Wei

ght L

oss)

Temperature, oC

TGpercent

0

2

-97.5%@400oC

-1.3%@150oC

188oC0.6%/oC

372oC1.3%/oC

166oC

DTG

(%/o C

)

Thermogravimetric analysis of a polymeric blend containing HDPE and an inorganic filler (phosphogypsum)

0 100 200 300 400 500 600 700 800

-60

-50

-40

-30

-20

-10

0

-62.8%

% w

eigh

t los

s

Temperature, oC

TGpercentL

Precipitated Zr5O8(SO4)2*15 H2O

Analysis of Filtrate from Precipitation

• Precipitation

• 5ZrOCl2 + 2H2SO4 + xH2O Zr5O8(SO4)2*15 H2O (s) + 10 HCl

• Decomposition• Zr5O8(SO4)2*15 H2O (s) Zr5O8(SO4)2*14 H2O (s) + H2O (v)

• Zr5O8(SO4)2 5 ZrO2 (s) +2 SO2 (v)

15 H2O Water Loss Wt. Loss % loss1 18.0152 1.7215732 36.0304 3.4431463 54.0456 5.1647194 72.0608 6.8862925 90.076 8.6078656 108.0912 10.329447 126.1064 12.051018 144.1216 13.772589 162.1368 15.49416

10 180.152 17.2157311 198.1672 18.937312 216.1824 20.6588713 234.1976 22.3804514 252.2128 24.1020215 270.228 25.82359

SO2 1 64.0588 31.94522 128.1176 38.0668

% Polymer = 64.4%% Carbon Black = 3.4%% Glass Fibre = 32.2%