磷氮复合阻燃环氧树脂的制备及其阻燃性能

为改善环氧树脂的阻燃性,成功合成了一种含苯砜基和磷杂菲杂环的阻燃添加剂(FRASP)。采用傅里叶变换衰减全反射红外光谱法(ATR-FTIR)、核磁共振(NMR)和元素分析等手段对FRASP的化学结构进行表征。将FRASP添加到双酚A型环氧树脂(DGEBA)中,经4,4’-二氨基二苯甲烷(DDM)固化后,制备出DGEBA-FRASP复合树脂。FRASP质量分数为9wt%的DGEBA-FRASP复合树脂的极限氧指数(LOI)达到35.9%,垂直燃烧(UL94)的等级为V-0级。残炭的形貌和激光拉曼光谱(LRS)分析显示,FRASP促进膨胀、致密、高石墨化程度的多孔炭层的生成。热重分析表明,FRASP改变了DGEBA-FRASP复合树脂的热降解过程,促进了DGEBA-FRASP复合树脂提前热分解,使最大失重率降低,并提高了残炭量。热裂解分析显示,DGEBA-FRASP复合树脂裂解过程中产生了含磷分子和不可燃气体,可稀释O₂并抑制燃烧过程中自由基链式反应。FRASP分子中P、N和S的协同作用,改善了DGEBA-FRASP复合树脂的阻燃性能。 

Preparation and performance of flame-retardant epoxy resin composite containing phosphorus and nitrogen

A flame retardant additive with sulfone and phosphaphenanthrene groups (FRASP) was successfully synthesized for improving the flame retardancy of diglycidyl ether of bisphenol A type epoxy resins (DGEBA). The chemical structure of FRASP was characterized by attenuated total internal reflectance Fourier transform infrared spectroscopy (ATR-FTIR), nuclear magnetic resonance (NMR) and elemental analysis. FRASP was added into DGEBA, and the flame-retardant DGEBA-FRASP composite resins were prepared via thermal curing reaction between 4,4’-diaminodiphenyl methane (DDM) and the mixed DGEBA. When the mass fraction of FRASP is 9wt%, the limiting oxygen index (LOI) reaches 35.9%, and V-0 rating under the vertical combustion (UL94) test is achieved. The morphology and Laser Raman spectroscopy (LRS) analysis of char residues after UL94 test indicate that the addition of FRASP favor the generation of an intumescent, tight and high-graphitization degree char layer with porous structure inside. The thermosgravimetric analysis results reveal that FRASP changes the thermal degradation process of DGEBA-FRASP composite resins and the maximum mass loss rate decreases, which results in a higher residual char. Pyrolysis-gas chromatography/mass spectrometry analysis shows that the phosphorus fragments and nonflammable gas release during DGEBA-FRASP composite resins thermal decomposition, which can dilute the O₂ and act as free radical inhibitors in combustion. Owing to the synergistic effect of P, N and S in condensed and gas phase, the DGEBA-FRASP composite resins display improved flame-retardancy.