Processing and performance of aromatic-aliphatic thermotropic polyesters based on vanillic acid
نویسندگان
چکیده
In this work we report on the processing, melt-drawing, and performance of new vanillic acid based aliphatic-aromatic thermotropic polyesters. It is demonstrated that these materials are easily processed from their nematic melts yielding highly oriented products. Furthermore, we demonstrate that a molecular weight (Mw) of roughly 30 kg/mol is required in order to successfully perform spinning on these polymers. The application of a polymer with lower Mw results in poor mechanical performance and fiber breakage during the winding process. Wide-angle X-ray diffraction analysis has been performed on the fibers and it is demonstrated that the orientation parameter increases with increasing draw-ratio of the fiber. Although these polymers are readily processed from their thermotropic melts, the obtained fibers only retain their orientation up to temperatures in the range of 120e130 C, after which they start to melt. In general, these fibers exhibit tensile moduli in the range of ~10 GPa and a tensile strength around ~150e200 MPa. FTIR and solid-state NMR experiments indicate that only the aromatic components are molecularly oriented during the spinning process. In contrast, the aliphatic moieties exhibit a high mobility, normally corresponding to a local isotropic motion. It is expected that the poor molecular orientation of the aliphatic moieties in these aliphatic-aromatic thermotropic polyesters contribute to the relatively low tensile modulus of the fibers, obtained after the extrusion and melt-drawing process. © 2015 Elsevier Ltd. All rights reserved.
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