Polymeric materials are composed of monomer units of extremely diverse chemical nature and size. Moreover, they can take several forms, linear, branched, or cross-linked. Each of these characteristics will induce different properties on the final material. In order to ensure the conformity of polymers to customer specifications, their characterization is necessary. To define a polymer, the following criteria must be known:
- Chemical nature :
- Analysis of the chemical functions present on the polymer chain: alcohol, urethane, amine, acrylic …
- Definition of the polymer structure: homopolymer, copolymer, tri-block etc…
- Identification of the polymer chain end
- Polymer chain :
- Determination of the molar mass distribution, the population number, the polydispersity index
- Observation of the cross-linking density
- Measurement of the branching rate
- Thermal data :
- Characterization of specific temperatures (melting, glass transition, crystallization and degradation temperatures)
- Mechanical and rheological properties:
- Analysis of mechanical properties in tension, compression and dynamics
- Determination of viscoelastic properties
- Measurement of thixotropy index
To obtain this information, various analytical equipment can be used. It may be necessary to correlate several results to determine all the expected information.
First, a FTIR (Fourier Transform Infrared Spectroscopy) analysis can be used to trace the chemical functions present on the polymer. This spectroscopic technique measures the amount of light absorbed by the polymer in the infrared region of the electromagnetic spectrum.
Chemical bonds between atoms absorb light differently depending on the wavelength at which they are stressed. Thus, an infrared spectrum with characteristic peaks is obtained. The operator then uses correlation tables to determine which chemical functions are visible in this spectrum.
Then a nuclear magnetic resonance (NMR) analysis is performed. This spectroscopic technique is based on the magnetic properties of atomic nuclei. This analysis is mainly performed on hydrogen atoms (1H proton NMR) and on carbon atoms (13C NMR).
These atoms are composed of particles, some of which are sensitive to magnetic fields. Indeed, when these particles are subjected to a magnetic field, they will go into an excited state causing a resonance. This resonance frequency is specific to each atom that is identically linked to another