Preparation of Poly(phosphoric acid piperazine) and Its Application as an Effective Flame Retardant for Epoxy Resin
Preparation of Poly(phosphoric acid piperazine) and Its Application as an Effective Flame Retardant for Epoxy Resin
复制标题
聚磷酸哌嗪的制备及其作为环氧树脂高效阻燃剂的应用
DOI：
10.1007/s10118-018-2036-8
复制
发表时间：
2018-05-01
影响因子：
4.3
通讯作者：
Li, Bin
中科院分区：
文献类型：
--
作者：
Xu, Miao-Jun;Xia, Si-Yu;Li, Bin
采用无水哌嗪与磷酸发生成盐反应，在氮气气氛下加热脱水聚合，合成了多磷酸哌嗪磷氮系阻燃剂，简称PPAP。其化学结构通过傅里叶变换红外（FTIR）光谱、13C和31P固态核磁共振测量得到了很好的表征。将合成的PPAP和固化剂间苯二胺共混到环氧树脂(EP)中制备阻燃EP热固性材料。通过极限氧指数（LOI）、垂直燃烧（UL-94）、热重分析/红外光谱（TG-IR）和锥形量热仪测试研究了PPAP对固化EP/PPAP复合材料阻燃性和热降解行为的影响。分别通过扫描电子显微镜（SEM）和X射线光电子能谱（XPS）研究了固化环氧树脂的炭残留物的形貌和化学成分。结果表明，在EP热固性材料中掺入5wt% PPAP时，阻燃EP热固性材料成功通过了UL-94 V-0可燃性等级，LOI值高达30.8%。 TGA结果表明，合成的PPAP阻燃添加剂具有较高的热稳定性和优异的炭化能力。同时，PPAP的加入，由于其催化分解作用，促使环氧树脂基体提前分解和炭化，从而在高温下获得更高的成炭率。 EP热固性材料残炭的形貌结构和XPS分析结果表明，PPAP的引入有利于材料表面在燃烧过程中形成足够、更致密、均匀的含磷氮阻燃元素的残炭层。形成的优质炭层有效阻止了热量的传递和扩散，限制了可燃气体的产生，抑制了烟雾的排放，从而减少了热量和烟雾的释放。
A phosphorus-nitrogen containing flame retardant additive of polyphosphoric acid piperazine, defined as PPAP, was synthesized by the salt-forming reaction between anhydrous piperazine and phosphoric acid, and the dehydration polymerization under heating in nitrogen atmosphere. Its chemical structure was well characterized by Fourier transform infrared (FTIR) spectroscopy, 13C and 31P solid-state nuclear magnetic resonance measurements. The synthesized PPAP and curing agent m-phenylenediamine were blended into epoxy resin (EP) to prepare flame retardant EP thermosets. The effects of PPAP on the fire retardancy and thermal degradation behavior of cured EP/PPAP composites were investigated by limiting oxygen index (LOI), vertical burning (UL-94), thermogravimetric analysis/infrared spectrometry (TG-IR) and cone calorimeter tests. The morphologies and chemical compositions of char residues for cured epoxy resin were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The results demonstrated that the flame retardant EP thermosets successfully passed UL-94 V-0 flammability rating and the LOI value was as high as 30.8% when incorporating 5wt% PPAP into the EP thermosets. The TGA results indicated that the synthesized PPAP flame retardant additive possessed high thermal stability and excellent charring capability. Meanwhile, the incorporation of PPAP stimulated the epoxy resin matrix to decompose and charring ahead of time due to its catalytic decomposition effect, which led to a higher char yield at high temperature. The morphological structures and the analysis results of XPS for char residues of EP thermosets revealed that the introduction of PPAP benefited the formation of a sufficient, more compact and homogeneous char layer containing phosphorus-nitrogen flame retardant elements on the material surface during combustion. The formed char layer with high quality effectively prevented the heat transmission and diffusion, limited the production of combustible gases, and inhibited the emission of smoke, leading to the reduction of heat and smoke release.