Research On Synthesis And Application Of Novel Benzoxazine

Novel benzoxazine precursors containing polyethers have been developed from the Mannich condensation reaction of phenol, paraformaldehyde, and amino-terminated poly(ether diamine). The benzoxazine precursors were confirmed by proton nuclear magnetic resonance spectroscopy ('H-NMR). The molecular weight of poly(ether diamine)-based benzoxazines were characterized by gel permeation chromatography (GPC) and matrix assisted laser desorption/ionization time of flight mass spectroscopy(MALDI-TOF). The benzoxazine precursors were incorporated with typical monofunctional and difunctional benzoxazine monomers to form processable mixtures, followed by thermal curing. Differential scanning calorimetry (DSC) was used to study cross-linking behavior of these benzoxazines. The curing temperature of the benzoxazine precursor with longer polyether chain length occurs at higher temperature since it has more benzoxazine rings. Thermal properties of the cross-linked benzoxazine mixtures were investigated by dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). The flexibility of the cured phenol-based and bisphenol A-based benzoxazines are increased with incorporating the poly(ether diamine)-based benzoxazines. And the glass transition temperature of the cured mixtures can exceed 200℃. The decomposition temperatures at 5% and 10% loss weight and the char yield at 800℃of the cured polybenzoxazines increase with increase of polyether chain length. The introduction of poly(ether diamine)-based benzoxazine with longer polyether chain compels the dielectric constant of the cured phenol-based and bisphenol A-based benzoxazine polymers to increase.A kind of allylated benzoxazine containing N-substituted m-methyl benzene ring (BA-mt) was synthesized from the Mannich reaction of paraformaldehyde, diallyl bisphenol A and m-toluidine. The structure of BA-mt was confirmed by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance spectroscopy (1H-NMR). The allylated benzoxazine BA-mt was mixed with bis(4-maleimidophenyl) methane (BMI) and diallyl bisphenol A (DABPA) in the different mass ratio. The curing reaction process of modified BMI/DABPA/BA-mt resin was examined by Differential Scanning Calorimeter (DSC). Dynamical thermal mechanical analysis (DMA) and thermogravimetric analysis (TGA) were used to study their thermal properties. The results show that thermal stability of the cured BMI/DABPA resin decreases with addition of BA-mt. However, the loss weight temperature at 10 wt% of the cured resins are still more than 400℃, and the char yield at 800℃increase to 33 wt%. The glass transition temperature of the cured resin with 10 parts of BA-mt in BMI/DABPA reaches at 319℃. The bending property of the cured BMI/DABPA resin increases with addition of BA-mt in the resin. And the bending strength and modulus of the modified BMI/DABPA resin based on 10 parts by weight of BA-mt are 44 MPa and 3760 MPa, respectively. The water absorption of the cured modified resins decreases with addition of BA-mt content.As amine sources,2,6-dimethyl aniline,2,6-diethyl aniline,2-ethyl-6-methyl aniline and 2,6-diisoprothyl aniline were used to react with phenol and paraformaldehyde to form novel benzoxazines under microwave condition. The structure of the benzoxazines have been confirmed by proton nuclear magnetic resonance spectroscopy ('H-NMR), Fourier transform infrared spectroscopy (FTIR) and elemental analysis. The curing behaviors of the benzoxazines were studied using differential scanning calorimetry (DSC). The new benzoxazines were mixed with difunctional benzoxazine (BAF) in the different molar ratio. The DSC,DMA and TGA were used to study on the properties of mixtures of polybenzoxazines. The glass transition temperature of the cured benzoxazines are increased with incorporating the bisphenol A-based benzoxazine. The introduction of new benzoxazine compels the dielectric constant of the cured bisphenol A-based benzoxazine polymers to increase.