Thermoanalytical method that allows to measure the energy exchanges and therefore determine the thermal characteristics and phase changes of the material, in addition to the % crystallinity of the semi-crystalline polymers.
Differential scanning calorimetry, as can be guessed from the name, exploits the energy exchanges between the tested polymer and the external environment to evaluate the thermal characteristics and phase changes, such as melting temperature, glass transition temperature and associated enthalpies, as well as crystallization.
To do this, the test is essentially conducted in inert gas (nitrogen) through 3 distinct phases:
FIRST HEATING: The sample is initially heated up to a temperature at which it does not degrade, to identify the melting temperature and glass transition of the sample as it appears. In the event that a comparison is made between components and virgin material, this phase could bring to light hot crystallization phenomena, internal tensions or molding problems;
COOLING: After the first heating phase, the sample is completely melted and available to be cooled, then recrystallization is induced, in order to allow it to “rearrange” the polymer chains and crystallize, canceling the so-called “thermal history”.
SECOND HEATING: In this phase, the material, having returned to thermodynamically favorable conditions, presents the thermal characteristics of melting and/or glass transition of the polymeric matrix, eliminating the “thermal history”.
In addition to all this, the DSC technique is also able to evaluate the percentage of crystallinity derived from the melting of a semi-crystalline polymer and also the polymerization and vulcanization residues.
With the OIT (Oxidation Induction Time) technique, the sample is placed under a flow of oxygen at a constant temperature and it is possible to evaluate the time necessary for an oxidation reaction to be triggered. The shorter the time, the lower the oxidation stability. Commonly used to determine the efficiency of antioxidants and stabilizers in polymeric matrices and to study aging processes.
The advantage of the DSC technique is that of being able to investigate the thermal history of a component from the birth of the material to the molding compared to the virgin material, with limited costs and times (the analysis can last from a few minutes to a few hours) and allows a small amount of sample, in fact only about ten milligrams are used.
This test can be easily coupled to the FT-IR and TGA analysis technique, in order to have a complete drawing on the polymeric matrix of the material and on its characteristics and behavior under temperature.
The laboratory is able to perform the test according to the requirements of the international ISO 11357-1/2/3 standards and thanks to the experience acquired over years of testing, it also has a polymer library for which it is possible to compare the curves of different samples.
