Abstract

A novel curing agent containing phosphorus and carboxyl group compound diphenyl(2,3-dicarboxylpropyl)phosphine oxide (DPDCPPO) was synthesized and used as a curing and flame retarding agent for epoxy resins (EP). Its chemical structure was well characterized by Fourier transform infrared (FTIR) spectroscopy, ¹H, ¹³C and ³¹P NMR. The DPDCPPO was mixed with phthalic anhydride (PA) by different weight ratios into epoxy resins to prepare flame retardant EP thermosets. The flame retardant properties, combusting performances, and thermal degradation behaviors of the EP thermosets were investigated by limiting oxygen index (LOI), vertical burning tests (UL-94), cone calorimeter measurement, and thermogravimetric analysis (TGA) tests. The surface morphologies and chemical compositions of the char residues for EP thermosets were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The water resistant properties were evaluated by placing the samples into distilled water at 70°C for 168 h. The results revealed that the flame retardant EP thermosets passed V-0 flammability rating and the LOI value reached 33.2% when the weight ratio of DPDCPPO and PA was 20 : 80. The cone test results revealed that the combustion parameters of the flame retardant EP thermosets including heat release rate (HRR) and total heat release (THR) significantly decreased compared with pure EP thermosets. The TGA results indicated that the incorporation of DPDCPPO promoted the decomposition of epoxy resins matrix ahead of time compared with that of pure EP, and led to a higher char yield and thermal stability at high temperature. The morphological structures and analysis of the XPS of the char residues revealed that DPDCPPO benefited the formation of a sufficient, compact and homogeneous char layer, with rich flame retardant elements on the epoxy resin material surface during combustion. After completing the water resistance tests, the EP/20 wt % DPDCPPO/80 wt % PA thermosets retained excellent flame retardancy, and the moisture absorption of the EP thermosets decreased with the increase of DPDCPPO content in the thermosets, due to the existence of the P–C bonds and the rigid aromatic hydrophobic structure.

中文翻译：

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新型含磷固化剂的合成及其对环氧树脂阻燃性和热稳定性的影响

摘要

合成了一种新型的含磷和羧基的二苯基（2,3-二羧丙基）膦氧化物（DPDCPPO）固化剂，并将其用作环氧树脂（EP）的固化和阻燃剂。通过傅立叶变换红外（FTIR）光谱，¹ H，¹³ C和³¹很好地表征了其化学结构1 H NMR。将DPDCPPO与邻苯二甲酸酐（PA）以不同的重量比混合到环氧树脂中，以制备阻燃EP热固性塑料。通过极限氧指数（LOI），垂直燃烧测试（UL-94），锥形量热仪测量和热重分析（TGA）测试，研究了EP热固性塑料的阻燃性能，燃烧性能和热降解行为。分别通过扫描电子显微镜（SEM）和X射线光电子能谱（XPS）研究了EP热固性炭残留物的表面形态和化学组成。通过将样品置于70°C的蒸馏水中168小时来评估其防水性能。结果表明，阻燃EP热固性材料通过了V-0阻燃等级，LOI值达到了33。当DPDCPPO和PA的重量比为20:80时为2％。锥形测试结果表明，与纯EP相比，阻燃EP热固性塑料的燃烧参数（包括放热率（HRR）和总放热（THR））显着降低。热固性塑料。TGA结果表明，与纯EP相比，DPDCPPO的加入促进了环氧树脂基体的分解，并导致了较高的炭产量和高温下的热稳定性。炭残留物的XPS的形态结构和分析表明，DPDCPPO有利于在燃烧过程中在环氧树脂材料表面上形成足够，致密且均质的炭层，并在环氧树脂材料表面形成丰富的阻燃元素。完成耐水性测试后，