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.

Thermal Degradation Kinetics of Intumescent Halogen-free Flame-retarding HIPS and Its Retarding Mechanism

The thermal degradation kinetics and flame-retarding mechanism of a new intumescent halogen-free flame-retarding high impact polystyrene (HIPS) were studied by the conventional dynamic thermogravimetric analysis (TGA). The parameters of the thermal degradation kinetics were ratified by comparing the Kissinger mold with the Coat-Redern mold. Therein, according to the ordinary reaction limit of Ea/RTmax, the reaction nth-order was ascertained by the relationship between αmax and n at the maximum reaction rate. By means of TGA-FTIR and Py-GC/MS, the flame-retarding mechanism was analyzed. The experiment results indicated that the parameters of the thermal degradation kinetics were similar by the two molds, and it turned out to be that the activation energy of the flame-retarding HIPS was less than that of pure HIPS, in other words, the flame retardant has already been decomposed before HIPS decomposition, releasing a great deal of non-flaming gas (such as ammonia and its ramification, water vapour and so on), then retarding flaming in air. At the same time, adding the flame retardant resulted in promoting the reaction to chain-transfer, then decreasing non-monomer in flame and forming the char crosslink, which could stop flaming in air and isolate heat transfer in condensed phase.