膨胀型无卤阻燃HIPS热分解动力学及阻燃机理研究

利用动态热失重法(TGA)研究了一种新型的膨胀型无卤阻燃高抗冲聚苯乙烯(HIPS)热降解反应动力学及阻燃机理, 通过对Kissinger模型和Coat-Redern (C-R)模型求解的热降解反应的动力学参数对比, 最终确定反应的动力学参数. 其中, 反应级数n的确定是通过一般反应对Ea/RTmax取值范围的限定, 利用最大热降解速率所对应的失重率αmax与n的关系, 确定其取值. 并采用TGA-FTIR及Py-GC/MS对材料气相产物及热裂解产物进行了阻燃机理的研究. 研究表明, 两种反应的热降解反应动力学参数基本一致, 其中阻燃HIPS的平均表观活化能小于纯HIPS, 说明在HIPS分解之前, 无卤阻燃剂已经开始分解, 释放的难燃气体(氨气及其衍生物、水蒸气等)在气相中起到阻燃的作用. 同时阻燃剂的添加, 促使反应向链转移反应飘移, 使燃烧产物中非单体化合物增加, 而在凝聚相中形成的致密的炭层结构也起到阻燃的效果.     

阻燃高抗冲聚苯乙烯热降解研究

利用热失重-红外联用仪(TGA-IR)分析了高抗冲聚苯乙烯(HIPS)的热降解过程,结合热裂解气相色谱-质谱联用仪(Py-GC/MS)分析了HIPS的热裂解产物,利用化学方程式阐述了HIPS自由基降解反应.对十溴二苯乙烷、三氧化二锑复配阻燃体系的热降解过程进行了研究,讨论了阻燃HIPS的凝聚相阻燃、气相阻燃机理.实验表明,HIPS燃烧时主要发生β-断裂,大量烟雾主要由苯乙烯、甲苯、α-甲基苯乙烯、苯乙烷、丁二烯等组成,其中凝聚相主要是1,3,5-三苯基苯乙烯及其他部分低聚物.在不同的温度下,阻燃HIPS的热裂解产物不同,在较高的温度下,小分子化合物明显增多.     

Fabrication and performance optimization of Mn-Zn ferrite/EP composites as microwave absorbing materials

Magnesium-substituted Mn0.8Zn0.2Fe2O4 ferrite is synthesized by the sol–gel combustion method using citrate acid as the complex agent. The electromagnetic absorbing behaviors of ferrite/polymer coatings fabricated by dispersing Mn–Zn ferrite into epoxy resin （EP） are studied. The microstructure and morphology are characterized by X-ray diffraction and scanning electron microscope. Complex permittivity, complex permeability, and reflection loss of ferrite/EP composite coating are investigated in a low frequency range. It is found that the prepared ferrite particles are traditional cubic spinel ferrite particles with an average size of 200 nm. The results reveal that the electromagnetic microwave absorbing properties are significantly influenced by the weight ratio of ferrite to polymer. The composites with a weight ratio of ferrite/polymer being 3：20 have a maximum reflection loss of –16 dB and wide absorbing band. Thus, the Mn–Zn ferrite is the potential candidate in electromagnetic absorbing application in the low frequency range （10 MHz–1 GHz）.