Li Qian, Li Yujie, Chen Yifan, Wu Qiang, Wang Siqun
School of Engineering, Zhejiang A&F University, Hangzhou 311300, China.
Center for Renewable Carbon, University of Tennessee, Knoxville, TN 37996, USA.
Materials (Basel). 2021 Apr 25;14(9):2205. doi: 10.3390/ma14092205.
A novel liquid phosphorous-containing flame retardant anhydride (LPFA) with low viscosity was synthesized from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and methyl tetrahydrophthalic anhydride (MeTHPA) and further cured with bisphenol-A epoxy resin E-51 for the preparation of the flame retardant epoxy resins. Both Fourier transform infrared spectroscopy (FT-IR), mass spectrometry (MS) and nuclear magnetic resonance (NMR) measurements revealed the successful incorporation of DOPO on the molecular chains of MeTHPA through chemical reaction. The oxygen index analysis showed that the LPFA-cured epoxy resin exhibited excellent flame retardant performance, and the corresponding limiting oxygen index (LOI) value could reach 31.2%. The UL-94V-0 rating was achieved for the flame retardant epoxy resin with the phosphorus content of 2.7%. With the addition of LPFA, the impact strength of the cured epoxy resins remained almost unchanged, but the flexural strength gradually increased. Meanwhile, all the epoxy resins showed good thermal stability. The glass transition temperature () and thermal decomposition temperature () of epoxy resin cured by LPFA decreased slightly compared with that of MeTHPA-cured epoxy resin. Based on such excellent flame retardancy, low viscosity at room temperature and ease of use, LPFA showed potential as an appropriate curing agent in the field of electrical insulation materials.
由9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物（DOPO）和甲基四氢苯酐（MeTHPA）合成了一种新型低粘度含磷液体阻燃酸酐（LPFA），并进一步与双酚A环氧树脂E-51固化以制备阻燃环氧树脂。傅里叶变换红外光谱（FT-IR）、质谱（MS）和核磁共振（NMR）测量均表明DOPO通过化学反应成功地引入到MeTHPA的分子链中。氧指数分析表明，LPFA固化的环氧树脂表现出优异的阻燃性能，相应的极限氧指数（LOI）值可达31.2%。含磷量为2.7%的阻燃环氧树脂达到了UL-94V-0等级。随着LPFA的加入，固化环氧树脂的冲击强度几乎保持不变，但弯曲强度逐渐增加。同时，所有环氧树脂均表现出良好的热稳定性。与MeTHPA固化的环氧树脂相比，LPFA固化的环氧树脂的玻璃化转变温度（）和热分解温度（）略有下降。基于如此优异的阻燃性、室温下的低粘度和易于使用的特点，LPFA在电气绝缘材料领域显示出作为一种合适固化剂的潜力。
