Effects of pure and intercalated halloysites on thermal properties of phthalonitrile resin nanocomposites

In this work, composite materials with different halloysite nanotubes (HNTs) content as fillers were prepared by using phthalonitrile resin with alkyl center as matrix. In order to improve the dispersibility of HNTs in the polymers, phenylphosphonic acid (PPA) was used to treat HNTs. The results of Wide-angle X-ray Diffraction (WAXD), Fourier Transform Infrared spectroscopy (FTIR), Thermogravimetric Analysis (TGA) and Scanning Electron Microscope (SEM) showed that when the mass ratio of PPA to HNTs was 2:1, the intercalation rate of HNTs was the highest. The thermomechanical properties, thermal stability and thermal oxidation stability of the composite were tested by Dynamic Mechanical Analysis (DMA) and Thermogravimetric analysis (TGA). The results indicated that the polymers with intercalated HNTs as fillers have better thermomechanical properties than those with pure HNTs as fillers. When the modified HNTs content was 7%, the storage modulus of the polymer increased by 16.52% and 15.43% at 30 °C and 380 °C, respectively. With the increase of fillers, the thermal stability of polymers with pure HNTs as fillers increased, while that of polymers with modified HNTs as fillers increased first and then decreased. On the other hand, the limit oxygen index (LOI) of the polymers also increased to some extent. The degradation and control of the nanocomposites at high temperature were discussed. SEM was used to observe the cross-section morphology and found that pure HNTs would agglomerate in the polymer. The thermal properties of the phthalonitrile resin were improved by using the wide source HNTs as fillers.