Preparation and properties of polybenzoxazine blends and their glass fabric-reinforced composites

p-aminophenyl propargyl ether (APPE) was synthesized by amino-protection and deprotection process. Phenol, APPE and paraformaldehyde were used to prepare the propargyl ether-based monofunctional benzoxazine (P-APPE) by Mannich condensation. P-APPE, phenol/aniline-based benzoxazine (PAF) and silicon-containing arylacetylene (PSA) were blended to obtain the modified benzoxazines in solution. Differential scanning calorimeter, dynamic mechanical analysis, thermal gravimetric analysis and broadband dielectric spectrometer were used to study the thermal and dielectrical properties of the blend resins. The results show that the thermal properties of the benzoxazine blends are improved with addition of PSA, and the dielectrical constant and dissipation factor of the benzoxazine blends decrease with the increase of PSA content in the blends. With the addition of 14.3% mass fraction of PSA, the glass transition temperature and the temperature at 5% mass loss of the cured blend resin can increase from 195℃ to 235℃, and from 355℃ to 399℃, respectively. However, more than 50% of the inter-layer shear strength (ILSS) and bending strength of the glass fabric-reinforced composites decrease with the addition of 5.3% mass fraction of PSA in the blends.