dsc & tga
DESCRIPTION
Thermal analysis-DSA-TGATRANSCRIPT
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%