Ceramification of Composites of MgO-Al_(2)O_(3)-SiO_(2)/Boron Phenolic Resin with Different Calcine Time

The ceramifiable polymer composite of MgO-Al_(2)O_(3)-SiO_(2)/boron phenolic resin(MAS/BPF)with 40wt%of inorganic fillers was calcined at 1200℃for different time to promote ceramification of ceramifiable composite and improve heat resistance.The effects of different calcine time on the macroscopical morphology,mass loss,phase evolution,microstructure and chemical bond evolution of MAS/BPF composites were characterized by XRD,XPS,and SEM analyses.The experimental results reveal that the increase of calcine time result in the fewer holes,relatively denser and smoother top layer of MAS/BPF composites and protect the interior from deeper decomposition.The final residues of composites are amorphous carbon and C-O-Si-Al-Mg ceramic.And MAS/BPF composites show excellent mass stability,low shrinkage and self-supporting features after 2 h holding compared with BPF composites without 40wt%of inorganic fillers.

Fluxing Agents on Ceramification of Composites of MgO-Al2O3-SiO2/Boron Phenolic Resin

Fluxing agents of zinc borate, antimony oxide, galss frit A and glass frit B, with different melting or softening point temperatures, were added into MgO-Al_2O_3-SiO_2/boron phenol formaldehyde resin（MAS/BPF） composites to lower the formation temperature of eutectic liquid phase and promote the ceramification of ceramifiable composites. The effects of fluxing agents on the thermogravimetric properties, phase evolution, and microstructure evolution of MAS/BPF composites were characterized by TG-DSC, XRD and SEM analyses. The results reveal that the addition of a fluxing agent highly reduces the decomposition rate of MAS/BPF composites. Fluxing agents lower the formation temperatures of liquid phases of ceramifiable MAS/BPF composites obviously, and then promote the ceramification and densification process. The final residues of composites are ceramic surrounded by large amount of glass phases.

Enhanced Thermal Resistance of Boron Phenolic Composites by Addition of TiSi_(2) Particles

TiSi_(2) reinforced boron phenolic composites(TP)and Vitreous silica fabric reinforced TiSi_(2)/boron phenolic composites(VTP)were prepared by compression molding,and their thermal,mechanical,ablation properties were studied.TG results show that thermal stabilities and residual carbon rate of boron phenolic are improved after introducing TiSi_(2) particles.Compared with VTP-0(containing 0 phr TiSi_(2)),flexural strength of VTP-60(containing 60 phr TiSi_(2))pyrolysis product increases by 29.5%at 1200℃.Raman spectrum shows that TiSi_(2) particles promote the ordering of the glass carbon structure of VTP pyrolysis product.Compared to VTP-0,the linear and mass ablation rates of VTP-60 reduce by 32.1%and 77.5%,respectively.XRD and SEM indicate the formation of an oxide coating layer,TiO_(2)-SiO_(2),integrates the bulk and protects the underlying materials from damage under high temperature oxygen-containing airstream.All these results prove that mechanical properties of pyrolysis product,thermal,and ablation resistance are improved by addition of TiSi_(2) particles.

Synthesis and Characterization of Carborane Bisphenol Resol Phenolic Resins with Ultrahigh Char Yield

Two carborane-containing resol phenolic resins（P1 and P2） with high boron content were synthesized via the reaction of carborane bisphenols（1 and 2） with formaldehyde in the presence of alkaline. HRMS results indicate that P1 is mainly composed of hydroxymethylated o-carborane bisphenols, the Mw of which was restrained around 500 due to the strong steric hindrance of o-carborane bisphenol. In contrast, the molecular weight of P2 was well regulated under various reaction conditions. The obtained resins were characterized with spectroscopic techniques including FTIR, 1H-NMR, ^13C-NMR, and 11B-NMR, which gave satisfactory results. TGA studies show that P2 shows char yield of 88.9% and 92.9% at 900 ℃ under nitrogen and air respectively. The imported carborane cage endows phenolic resin with ultrahigh char yield. Particularly, the char yield of the obtained carborane-containing phenolic resin under air is higher than that under nitrogen. FTIR and XRD confirm that the carborane cage could react with oxygen to form B2O3 at elevated temperatures, which postpones the thermal decomposition of phenolic resin and accounts for the high char yield.

耐高温酚醛树脂研究进展

酚醛树脂在胶粘剂领域是--种非常重要的材料,但是由于普通酚醛树脂分子链中存在大量的酚羟基和亚甲基.使酚醛树脂的耐热性受到影响。因此.要想提高酚醛树脂的耐高温性能.就需要改善酚醛树脂的分子结构。详细对硅改性酚醛树脂、钼改性酚醛树脂,硼改性酚醛树脂和硼硅改性酚醛树脂进行了综述.旨在为制备耐高温酚醛树脂提供参考。