过渡金属氧化物对阻燃剂聚磷酸铵热分解的影响机制

过渡金属氧化物(MO)可以显著影响聚磷酸铵(APP)的热分解过程, 进而改善APP复配膨胀阻燃聚合物材料的阻燃效率。将ZnO、Fe₂O₃、TiO₂掺入到APP中, 采用热失重分析(TGA)、X射线光电子能谱(XPS)和X射线衍射分析(XRD), 考察了3种MO对APP热分解行为的影响, 分析了相互作用过程中金属原子和磷原子化学结合状态的变化以及高温热分解产物的物相结构。TGA和XPS图谱分析结果表明, MO可降低APP的起始热分解温度, 并催化APP释放NH₃和H₂O, 而在热分解后期由于金属磷酸盐的形成可显著增加APP的高温残留量。3种MO催化APP热分解脱NH₃和H₂O的活性由大到小的顺序是:ZnO>Fe₂O₃>TiO₂, 而对APP凝聚相热分解P-O产物的交联能力从大到小的顺序为:Fe₂O₃>ZnO>TiO₂。XRD结果显示, ZnO在高温下与APP反应生成了Zn(PO₃)₂晶体, 而Fe₂O₃和TiO₂与APP反应分别生成了Fe₄(P₂O₇)₃和TiP₂O₇晶体。

Influencing Mechanism of Transition Metal Oxide on Thermal Decomposition of Ammonium Polyphosphate

Transition metal oxide (MO) can obviously influence the thermal decomposition process of ammonium polyphosphate (APP) to improve the flame retardant efficiency of intumescent flame retardant composites based on APP in polymer. ZnO, Fe₂O₃ and TiO₂, in same amount were added into APP to study the influence of MO on thermal decomposition behavior of APP, and to analyze the evolution of chemical state of metallic atoms and phosphorus atom and crystal structure in the interaction processes by thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD) respectively. TGA and XPS spectra showed that MO could catalyze the releasing of NH₃ and H₂O of APP in the earlier period, and increase the high temperature residue in the later period due to the formation of metallic phosphate. The sequence of catalytic activity for the process of releasing of NH₃ and H₂O was as follows: ZnO>Fe₂O₃>TiO₂, and that of cross-linking ability for thermal decomposition product P-O of APP was as follows: Fe₂O₃>ZnO>TiO₂. XRD showed that APP could react with ZnO, Fe₂O₃ and TiO₂ to produce Zn(PO₃)₂, Fe₄(P₂O₇)₃ and TiP₂O₇, respectively, at high temperature.