Сверхтермостойкие полимерные нанокомпозиты на основе гетероциклических сеток: структура и свойства

Nanocomposites based on heterocyclic polymer network, obtained from bisphthalonitrile and different (0.03-5.0 wt. %) contents of modified silicate montmorillonite (MMT) nanolayers, were studied. Their nanostructure, thermal, relaxation and elastic properties were characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDXS), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). DMA and TGA measurements were performed in both air and nitrogen mediums at temperatures from 20° to 600–900°C. Depending on MMT content, different extents of its exfoliation in the matrix, from single nanolayers to thin and “thick” MMT stacks were observed in the nanocomposites. The pronounced effects of constraining dynamics by nanoparticles and dynamic heterogeneity in the glass transition are shown. The possibilities for total suppression of glass transition and invariable elastic properties of nanocomposites within the temperature range from 20° to 600°C were shown. The studied nanocomposites manifest unique (for polymers) thermal properties, with glass transition temperature up to 570°С and satisfactory thermal stability, with retaining the material integrity, up to ~500°C in air and to ~900°C in N2 medium.

Study of the Properties of Poly-P-Phenylene-Benzimidazole-Terephthalamide Fiber Material

The properties of the fiber material, which prepared from the high-performance heterocyclic polymer poly-p-phenylene-benzimidazole-terephthalamide (PBIA), were investigated. Poly-m-phenylene isophthalamide (PMIA) and poly-p-phenylene terephthalamide (PPTA) fibers were also studied, for comparison, under the same experimental conditions. Thermogravimetry(TG) and thermogravimetry coupled to Fourier transform infrared spectroscopy(TG-FTIR) were used to study the properties of these fibers. The results show that PBIA fiber has better tensile properties, thermal stability than that of PMIA and PPTA fibers. The onset degradation temperature of PBIA is the highest, namely 421°C in nitrogen. TG-FTIR provides information on the compositions of the pyrolyzates as well as their relationship to the structures of the polyamides. Analysis of the results indicates that a hydrolytic mechanism plays a leading role at lower temperature, and a homolytic mechanism is dominant at higher temperature.