Crystalline orientation assessment in transversely isotropic semicrystalline polymer: Application to oedometric compaction of PTFE

Gabriel Guenoun (1, 2, 3) , Nicolas Schmitt (3) , Stéphane Roux (3) , Gilles Regnier (2)

1 SGR - Saint-Gobain Recherche
2 PIMM - Laboratoire Procédés et Ingénierie en Mécanique et Matériaux
3 LMPS - Laboratoire de Mécanique Paris-Saclay

The Hermans orientation factor is a scalar giving a simple assessment of molecular or crystal orientation in a polymer. It is usually determined from X-ray diffraction measurements. The evaluation of the Hermans orientation factor is proposed from the diffraction analysis of only a single diffracting plane. The estimation relies on (a) the assumption that the polymer crystals possess a cylindrical symmetry with respect to the chain direction and (b) that the processing conditions induce a transverse isotropy of the polymer chains. A practical consequence of the proposed analysis is that the Hermans orientation factor can be computed from a single 1D diffractogram. This enables fast evaluations since even low signal-to-noise ratio signals can be processed with optimal noise reduction. An illustration of this method for uniaxially compacted polytetrafluoroethylene (PTFE) powder is presented. The crystalline orientation is followed during in situ crystallization experiments with a fine time resolution.

Mots clés: Materials Chemistry; General Chemistry; Polymers and Plastics; crystalline orientation; transverse isotropy; X-ray diffraction; PTFE

Domaines: Matériaux

Gabriel Guenoun, Nicolas Schmitt, Stéphane Roux, Gilles Regnier. Crystalline orientation assessment in transversely isotropic semicrystalline polymer: Application to oedometric compaction of PTFE. Polymer Engineering and Science, 2021, 61 (1), pp.107-114. ⟨10.1002/pen.25561⟩. ⟨hal-03158759⟩