The issue?
In an effort to improve the sustainability of its polymer parts, an industrial player called on the FILAB laboratory to evaluate the thermal behavior of two PVCs intended for the manufacture of 3D-printed parts.
The client requested FILAB's assistance with this quality initiative.
To address this issue and determine the activation energy, the FILAB laboratory used ATG as a simulation and analysis tool to anticipate the aging of PVC-printed parts.
Context of the analysis
Approach :
The objective of this study is to determine the activation energy, i.e., the energy required to initiate the decomposition of two polymer materials of different chemical nature (black sample and white sample).
The standard used to conduct this study is ASTM E1641. This standard describes a standardized method for determining the activation energy (Ea) of a thermal decomposition process based on data obtained by thermogravimetric analysis (TGA).
Principle of the method :
Several ATG analysis are performed on the same sample at different heating rates (here: 1, 2, 5, 10 °C/min). For a given conversion rate (10%), the characteristic degradation temperatures are recorded for each ramp.
Methodology and technique used
Thermogravimetric Analysis (TGA) :
Thermogravimetric analysis (TGA) is a technique used to monitor the mass change of a sample subjected to a gradual increase in temperature in a controlled atmosphere.
As part of the study, it was used to observe the thermal degradation behavior of the polymers tested, identify critical mass loss temperatures, and model the degradation kinetics in order to extract an activation energy (Ea) associated with the phenomenon.
This method is applied to both samples in order to compare them. For each sample, four curves are obtained with different temperature ramps.
Conclusion of the comparative study
The four analysis carried out with different ramps on the two PVC samples intended for 3D printing show that, for the same conversion rate of 10%, the two materials analyzed have significantly different activation energies :
The black sample has a rate of 139.91 kJ/mol, while the white sample has a rate of 206.76 kJ/mol.
This difference indicates that the white polymer requires more energy to initiate thermal degradation than the black material. In other words, it is more thermally stable and therefore more suitable for 3D printing.
Black sample White sample
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Frequently asked questions
How can TGA be used to compare the thermal behavior of two PVC materials?
Thermogravimetric analysis monitors changes in the mass of a sample during a temperature program under a controlled atmosphere. FILAB compared two PVC materials intended for 3D-printed parts to characterize their thermal decomposition. The resulting curves were then used to study the kinetics of the phenomenon according to the selected protocol. Discover TGA.
Why perform TGA analysis at several heating rates?
The kinetic study compares the temperatures associated with the same conversion rate for several heating ramps. FILAB used heating rates of 1, 2, 5, and 10 °C/min for each PVC. This series of measurements made it possible to estimate the decomposition activation energy within the framework of the method presented, based on ASTM E1641.
What does the 10% conversion rate used in this study represent?
The conversion rate establishes the same level of progress of the decomposition process in order to compare analysis performed at different heating rates. FILAB selected 10% for the case presented. The activation energies obtained must therefore be interpreted in relation to this conversion level and the kinetic model used.
What activation energies were obtained for the two PVC samples?
The study reports 139.91 kJ/mol for the black sample and 206.76 kJ/mol for the white sample, at the selected conversion rate. These results show a difference in decomposition kinetics between the two materials under the protocol studied. They provide a basis for thermal comparison, to be considered alongside other manufacturing and part-use requirements.
Is activation energy sufficient to predict the service life of a pvc-printed part?
Activation energy characterizes the thermal phenomenon studied under the selected conditions and according to the chosen model. Using it to anticipate aging must be considered in relation to the temperatures, environment and actual stresses experienced by the part. The article presents a comparison of thermal decomposition; on its own, it does not provide a guaranteed service life.