聚丙烯/多面体低聚硅倍半氧烷纳米复合材料在不同气氛下的热降解机理

摘要

采用熔融共混的方法制备了聚丙烯(PP)/多面体低聚硅倍半氧烷(POSS)纳米复合材料,利用TG,FTIR和DSC方法分析了该复合材料在不同气氛下的热降解行为,并探讨了热降解行为差异的机理.实验结果表明,PP/POSS纳米复合材料在N2下的热降解温度高于在空气下的热降解温度.在N2气氛下,随POSS添加量的增多,复合材料的热稳定性劣化越严重, POSS在复合材料熔体中发生升华是导致复合材料热稳定性降低的原因.在空气气氛下,随POSS含量的增大,复合材料的热氧稳定性逐渐提高,当POSS添加量为10%(w)时,热降解终止温度可提高近60 ℃.在空气气氛下,POSS有机取代基团的氧化分解及产物CO2和H2O的稀释空气作用可减缓复合材料的分解速度;热氧化降解形成的SiO2可形成保护层阻隔空气与复合材料反应.两者协同作用提高了复合材料在空气气氛下的热氧稳定性.%Polypropylene/octaisobutyl polyhedral oligomeric silsesquioxane(POSS) composites were prepared by melt physical blending method.Thermal and thermo-oxidative stability of composites were investigated by TG,FTIR and DSC. The mechanism of the thermal degradation behavior was further clarified. The results show that all PP/POSS composites displayed the higher thermal stability in the N2atmosphere than that in air atmosphere. In N2atmosphere,with the increase of POSS content, thermal stability of the PP/POSS composites decreased which was mainly caused by the sublimation of POSS. In air atmosphere,the thermo-oxidative stability of the composite increased with the increase of the POSS content. The terminal thermo-oxidative degradation temperature of composites was raised 60 ℃ when the POSS content was 10%(w). In the air atmosphere,the thermal oxidative degradation of organic substituents in POSS and CO2and H2O generated through diluting air decreased the decomposition rate of composite. The degradation of PP/POSS composites was suppressed by the surface coverage of SiO2particles which formed during the thermal oxidative degradation of POSS. The thermal oxidative stability of composites in air atmosphere was improved due to both the decrease of oxygen concentration and the protection effect of SiO2surface coverage.