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Solid Rheological Properties of PBT-Based Vitrimers

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journal contribution
posted on 02.02.2021, 17:08 by L. Farge, S. Hoppe, V. Daujat, F. Tournilhac, S. André
We present an experimental investigation of the mechanical properties of solid vitrimer samples obtained by incorporating a diepoxide into commercial poly­(butylene terephthalate) (PBT) in the presence of a Zn­(II) catalyst using batch compounder and injection-molding machines. Tensile experiments were carried out at different temperatures (80, 120, and 160 °C) below the melting point (220 °C) and with various diepoxide concentrations (0, 1, and 2 wt %). We found that vitrimer plastic deformation mechanisms differ drastically from those of the PBT precursor and more generally from the regular behavior of other semi-crystalline polymers. In PBT vitrimers, strain localization (necking) is very weak and can even be suppressed. This type of behavior is due to the increase in strain hardening caused by vitrimer cross-linking. The creep resistance and stiffness of PBT vitrimers are significantly higher than those of pristine PBT. We found that vitrimer modification of PBT at moderate levels improves dimensional stability without inducing brittleness. These promising results highlight the need to find processes which enable significant production levels of these new materials. In the Perspective section, we briefly present a method to produce PBT-based vitrimers using continuous reactive extrusion.