was carried out using a Thermogravimetric Analyzer Q500, TA Instruments.
Dynamic heating at a heating rate of 10 °C/min to 600 °C
was performed to study the thermal stability of PN samples in air
(60 mL/min). A JEOL JSM 7600-F field-emission scanning electron microscope
(FESEM) was used for morphology examination. Fourier transform infrared
(FTIR) spectra from 400 to 4000 cm–1 with spectral
resolution of 4 cm–1 were collected using a PerkinElmer
Instruments Spectrum GX FTIR spectrometer to study the chemical interaction
between alumina and phthalonitrile. X-ray photoelectron spectroscopy
(XPS) measurements were conducted using Kratos AXIS Supra to investigate
the chemical bonding present in the samples. TA Instrument Discovery
Hybrid Rheometer (HR-3) was used to determine the time taken for cross-linked
networks to form in alumina-filled PN without APB. Differential scanning
calorimetry (DSC) was used for curing studies of the filler-containing
PN systems. Samples were weighed and sealed in hermetic pans. Dynamic
heating scans were carried out using Discovery DSC, TA Instruments,
from 40 to 380 °C at a heating rate of 10 °C/min under flowing
N2 (40 mL/min).