新型生物基苯并嗪的合成及性能

以生物基糠胺、 酚酞和多聚甲醛为原料, 制备了一种新型生物基苯并噁嗪树脂——酚酞糠胺型苯并噁嗪树脂(PPTL-F-BOZ), 采用FTIR, ¹H NMR和 ¹³C NMR等手段对其单体PTL-F-BOZ的结构进行了表征, 并对其固化反应、 耐热和阻燃性能进行分析. 结果表明, 与传统的化石基双酚型苯并噁嗪——双酚A苯胺型苯并噁嗪(BPA-A-BOZ)相比, PTL-F-BOZ显示出较低的固化反应温度, 且糠胺中呋喃环的存在会增加聚合物的交联密度, 并减缓苯氧结构向苯酚结构的重排反应, 致使其在DSC曲线中出现了2个固化峰. PPTL-F-BOZ树脂具有较高的T_5%(质量损失5%的温度)和800 ℃的残炭率, 其极限氧指数(LOI)高达36.2%, 在垂直燃烧中达到V-0等级, 表现出优异的热稳定性和阻燃性能.

Synthesis and Properties of a Novel Bio-based Benzoxazine†

A novel bio-based benzoxazine resin(phenolphthalein-furfuramine-benzoxazine, PTL-F-BOZ), used bio-based furfurylamine, phenolphthalein, and paraformaldehyde as raw materials, was synthesized and characterized by Fourier transform infrared spectroscopy(FTIR), nuclear magnetic resonance(¹H NMR and ¹³C NMR). The curing, thermal and flame retardant properties were analyzed by differential scanning calorimetric(DSC), thermogravimetric analyzer(TG), limiting oxygen index(LOI), vertical burning test, microscale combustion calorimetry(MCC), cone calorimeter(Cone) and scanning electron microscope(SEM). The DSC curve of PTL-F-BOZ showed a two-stage curing with two maxima at 224 and 251 ℃ respectively, and had lower curing temperature than that of the traditional fossil-based bisphenol benzoxazine bisphenol A-aniline benzoxazine(bisphenol A-aniline-benzoxazine, BPA-A-BOZ). The presence of the furan ring in the furfurylamine increased the cross-linking density of polymer, retarded the rearrangement reaction from the phenoxy structure to the phenol structure, and resulted in two curing peaks in the DSC curve of PTL-F-BOZ. Under nitrogen and air atmospheres, the temperatures of 5% mass loss(T_5%) for PPTL-F-BOZ resin were 380 and 370 ℃, respectively and the residual chars at 800 ℃ were 63.0% and 10.5%, respectively. Compared with PBPA-A-BOZ resin, PPTL-F-BOZ resin both possessed higher T_5% and residual char of 800 ℃. From the DTG curve, the maximum mass loss rates of two decomposition stage(Peak 1 and Peak 2 values) of PPTL-F-BOZ resin were 0.67%/min and 3.28%/min, which were only 7.38% and 63.44% of PBPA-A-BOZ(9.07%/min and 5.17%/min) under nitrogen atmosphere, and those were also the same under air atmosphere. LOI of PPTL-F-BOZ resin was 36.2%, which was higher than that of PBPA-A-BOZ resin. Meanwhile, in the UL-94 test, PPTL-F-BOZ resin extinguished quickly and released less smoke during combustion process, and the original morphology was kept well and a stable carbon layer was formed after burning. Its first ignition time(t₁) and second ignition time(t₂) were 1.4 and 8.5 s, respectively, far smaller than the maximum permissible values of 10 s, and a UL94 V-0 rating was also achieved. Hence, PPTL-F-BOZ resin showed excellent thermal and flame retardant properties.