2. Better Characterization of Multi-Component Materials. Using
Auto Stepwise TGA Thermogravimetric analysis(TGA) is a powerful
technique 2 for the characterization of the decomposition or weight
loss properties of materials. The technique provides the following
useful information: Decomposition temperatures Thermal degradation
properties Oxidative degradation characteristics Quantitative
weight losses PerkinEl Compositional analysis mer Pyris 1
Assessment of inert fillers TGA Long term stabilities Flammability
properties Rates of degradation
3. Figure 1. TGA results on cigarette tobacco sample A
Displayed in Figure 1 are the TGA results obtained by heating a
sample of cigarette tobacco A at a constant ramp rate of 40 C/min.
The sample was analyzed using an air purge (40 mL/min), which helps
to simulate the real-life thermooxidatve degradation properties of
the cigarette tobacco 3
4. Figure 2. Comparison of standard TGA results and auto
stepwise isothermal data on tobacco sample A. The sample
(approximate mass of 14 mg) was heated at a rate of 40 C/min under
an air purge (40 mL/min) and with an auto stepwise entrance
threshold value of 3.5 %/min and an exit threshold value of 1.0
%/min. Shown in Figure 2 are the TGA results obtained for the
tobacco sample A using the auto stepwise mode of 4 operation and
directly compared with standard
5. The TGA Noack Test for the Assessment of Engine Oil
Volatility Researchers in the automotive and petrochemical 5
industries have studied the effects of oil volatility on engine
emissions and oil consumption over the past decade. It is generally
accepted that reducing oil volatility should have a positive impact
on emissions and consumption TGA Noack Test Procedure The TGA Noack
test offers the precision and safety of the GC test while
simultaneously providing real life conditions (exposure to air at
an elevated temperature) of the traditional Noack test. In
addition, the TGA Noack method is fast and easy to perform
6. The recommended conditions for the TGA Noack test are:
Sample mass of 36 to 40 mg placed in 6 aluminum liner using
injection pipette Air purge at a flow rate of 150 mL/min Heat
sample from 50 to 249 C at 65C/min Hold sample at 249 C for 15
minute isothermal period Measure mass loss (%) at certain time
interval, Noack Reference Time, as specified by analyzing a Noack
reference oil (RL-N)
7. The Noack reference time is determined by analyzing a sample
of the reference oil, RL-N, under the conditions specified above.
The time that it takes for the reference oil to reach a specified
mass loss (14.2% for oil RL-N) then becomes the Noack reference
time that is used as the standardized reference time for the
assessment of mass losses during subsequent 7 measurements
8. The TGA instrument should be burned out periodically (e.g.,
every 10 runs) by heating the instrument (no sample present) to
1000 C and holding for a 10 minute period under an air purge. Shown
in the following figure are the TGA results obtained on a series of
three motor oils with different volatilities. The oil with the
higher degree of volatility exhibits the greatest loss in weight
after the Noack reference time interval at 249 C. 8
9. Measurement of Waters of Hydration with Pyris 6 TGA The
Pyris 6 TGA offers the following desirable 9 features and benefits:
High sensitivity for the detection of small weight loss transitions
High resolution for the better separation of overlapping
transitions Top loading balance design for ruggedness and
durability Robust design for reliable, long term use Built in gas
switching accessory and purge gas flow regulator for convenience
and ease of use 45 position autosampler for reliable, unattended
operation Pyris Player software for user friendliness and ease
10. 10
11. The TGA instrument was calibrated for temperature response
using the Curie points of alumel, perkalloy and iron 11
12. Characterizing Polymer Lifetimes Using TGA Decomposition
Kinetics: TGA Decomposition Kinetics The assessment of product
lifetimes is easily performed using the PerkinElmer TGA
Decomposition Kinetics Software (N5370669).The TGA kinetics
approach uses the wellknown variable heating method developed by
Flynn and Wall . The kinetics approach starts with the following
general expression: da/dt = Aexp(-E/RT)(1-a)n 12
13. Under the application of a constant heating rate, f, and
assuming a first order reaction (n = 1), the rate expression
becomes: da/(1-a) = {A/f} exp(-E/RT) dT With the TGA decomposition
kinetics approach, the sample is heated at several different
heating rates ranging between 40 and 1 C/min. Typically, 3 to 6
different heating rate experiments are performed to assess the TGA
decomposition kinetics. A constant decomposition level is selected
(ranging between 1 and 10%) and the corresponding temperature is
determined for each different heating rate. The measured values of
temperature and TGA heating 13 rate are then used to calculate the
activation energy
14. Displayed in Figure 1 are the TGA results generated on the
HDPE resin at an applied heating rate of 10 C/min. The plot shows
the percent mass as a function of sample temperature. A single
well-defined weight loss event is obtained with an onset
temperature of 459.8 C 14
15. As the heating rate is increased, the onset of
decomposition is pushed to higher temperatures, reflecting the time
temperature dependency of the decomposition reaction. Similarly, as
the heating rate is decreased, the onset temperature is moved to
increasingly lower temperatures. This is shown in Figure 2 for the
HDPE resin at 15 heating rates of 1, 2.5, 5, 10, 20 and 40
C/min.
16. Displayed in Figure 3 is the log rate constant versus
inverse temperature plot obtained from the TGA kinetics software
for the HDPE resin. The plot shows the results generated at
constant conversion levels of 3%, 5% and 8%. The activation
energies are assessed to be 162, 173 and 184 kJ/mole at the 3, 5
and 8% conversion levels. The change in activation energy reflects
differences in the decomposition kinetics due to 16 factors such as
anti-
17. Displayed in Figure 4 are the isothermal conversion curves
for the HDPE resin based on the kinetic parameters calculated by
the software. These curves show the percent conversion
(decomposition) versus time at different temperatures providing
useful predictive information on the relative thermal stabilities
of the polymer under isothermal conditions. 17
18. Figure 5 shows another useful predictive series of curves.
This plot shows the percent conversion versus temperature for the
HDPE resin. This shows the temperature required to achieve a given
level of decomposition at different holding times. 18
19. Displayed in Figure 6 are the isoconversion curves which
presents the time to achieve a particular level of conversion as a
function of temperature. These are particularly useful for product
lifetime assessments. If the desired level of critical conversion
is known, then the time to achieve this critical level at a
particular operating or end use temperature can be predicted
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