Due to the high surface-to-volume ratio of nano-sized fillers, studying of the polymer/nanoparticle interfacial region in polymer nanocomposites (PNCs) is essential to understand their structure-property relationship. It is commonly discussed that in this region a so-called rigid amorphous fraction (RAF) is formed by adsorption of polymer segments onto the nanoparticles. The properties of RAF differ from the bulk matrix, as for instance the segmental mobility is restricted, sometimes percolating through the whole system, which can affect the overall nanocomposite behavior. Here, by a combination of calorimetric, X-ray scattering and TEM techniques the structure and mobility of an epoxy-based PNC with layered double hydroxide (LDH) as a nanofiller is studied. Small angle X-Ray scattering (SAXS) proved that well defined interfaces are present in the system with a dense fractal structure. The presence of RAF was further confirmed and investigated by a combination of temperature modulated DSC (TMDSC) and Flash DSC. The former method enables quantifying the amount of the immobilized fraction. It was found that for high filler content (ca. 15 wt%) RAF is approximately 40 wt% of the polymer matrix, which was never shown before for epoxy-based PNCs and emphasizes the importance of interfaces. The latter one is a novel technique, where high heating rates (up to 10 000 K/s) are applied. This method was employed for the first time to a thermosetting system to investigate the glass transition behavior of the PNCs. It confirmed the presence of RAF and its impact on the overall PNC properties. Lastly, the relaxation rates from both calorimetric techniques were used to construct an activation plot, showing the effect of nanoparticles on the glassy dynamics.

Calorimetric study on the rigid amorphous fraction in an epoxy-based nanocomposite

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.