【作者】 李洪彦；

【导师】 郑俊萍；

【作者基本信息】 天津大学 ， 材料学， 2013， 博士

【摘要】 硅橡胶与其他橡胶相比最为显著的特征在于其优异的热稳定性，被广泛用作高温环境下的弹性材料。硅橡胶作为高性能合成橡胶中的重要一员，在现代高新技术、航空航天等高科技领域有着不可替代的地位。为了使硅橡胶适应更为苛刻的高温环境，提高硅橡胶热稳定性的研究被广泛开展。提高硅橡胶的热稳定性有许多方法，其中添加耐热添加剂是最为简便有效的方法之一。层状硅酸盐、聚合物、金属和金属氧化物等均可以作为硅橡胶的耐热添加剂。氧化铁作为众多耐热添加剂中最常使用的一种也被科学家们广泛研究。碳纳米管(CNTs)以其特殊的结构和优异的性能，在诸多领域都有潜在应用。因此对于CNTs的研究也非常广泛。近年来，将CNTs与高分子基体复合来提高复合材料力学、电导和热稳定性的研究也有很多报道。本论文将CNTs，α-Fe2O3，γ-Fe2O3，γ-Fe2O3与CNTs的混合物(γ-Fe2O3+CNTs)以及γ-Fe2O3修饰的CNTs (γ-Fe2O3-CNTs)与高温硫化硅橡胶体系复合。研究了氧化铁晶型以及氧化铁和CNTs间的协同作用对硅橡胶复合材料热氧稳定的影响。结果表明：CNTs的存在会改变氧化铁粒子的晶型，使其由α晶型转变为γ晶型，同时可以增加γ-Fe2O3的比表面积。与其他对照组相比，γ-Fe2O3-CNTs/硅橡胶试样具有较高的热氧稳定性。为了探究硅橡胶复合材料的热氧降解机理，从热老化过程中耐热添加剂的变化以及硅橡胶热降解产物的变化两个角度出发进行研究。结果表明：γ-Fe2O3/硅橡胶比α-Fe2O3/硅橡胶具有更高的热氧稳定性是源于γ-Fe2O3/硅橡胶热氧老化过程中的γ-Fe2O3的晶型变化。γ-Fe2O3与CNTs的协同作用，使得γ-Fe2O3在热氧老化过程中有更多的Fe元素发生了价态变化。由于CNTs具有的导热性，以及γ-Fe2O3与CNTs的协同作用，使得γ-Fe2O3-CNTs/硅橡胶试样在热氧降解过程中的侧甲基氧化的气体产物量大幅降低，从而提升复合材料的热氧稳定性。以γ-Fe2O3-CNTs作为无机粒子修饰CNTs的代表，以氨基单封端的聚二甲基硅氧烷(APDMS)修饰的CNTs(CNTs-APDMS)作为化学修饰CNTs的代表，利用Raman等手段表征复合材料在不同应变下的界面和相互作用。结果表明：CNTs-APDMS/硅橡胶会在相对较高的应变(250%)下才发生明显的界面破坏现象，且这种破坏会直接影响复合材料的热氧稳定性。而γ-Fe2O3-CNTs/硅橡胶虽在相对较低的应变(100%)下就发生界面的破坏，但这种破坏未影响其热氧稳定性。更多还原

【Abstract】 Silicone rubber is one of the most important types of high performance rubberand known to exhibit excellent thermal stability over conventional carbon backbonerubber. With the rapid development of science and technology, a demand for highperformance silicone elastomer, especially for thermal resistant silicone rubber, hasincreased greatly. A lot of researches focus on the improvement of thermal stability ofsilicone rubber. There are many methods for improving the thermal oxidative stabilityof silicone rubber. Adding thermal resistant additives into silicone rubber matrix is acommon one. Layered silicate, polymer, metal, metal oxide, etc. can be used asthermal resistant additives of silicone elastomer. As one of the most convenient andeffective thermal resistant additives, metal oxides or hydroxides have been widelyinvestigated.Attentions have been paid to carbon nanotubes (CNTs), which consists ofrolled-up graphene sheet built from sp2carbon units, because of its potentialapplications due to extraordinary physical, chemical and mechanical properties.Recently, great interests have been shown on CNTs as an additive of polymer due toits advantages of small size, high aspect ratio, particularly excellent mechanicalproperties, high electrical conductivity, and high thermal conductivity.The effects of crystalline forms of iron (III) oxide and the synergy betweenγ-Fe2O3and CNTs on the thermal oxidative stability of silicone rubber were studied.A series of silicone rubber based composites filled with CNTs, α-Fe2O3, γ-Fe2O3, amixture of γ-Fe2O3and CNTs (γ-Fe2O3+CNTs), and γ-Fe2O3modified CNTs(γ-Fe2O3-CNTs) were prepared, respectively. The results indicated that the presence ofCNTs affected the crystalline form of attaching Fe2O3which was changed from α to γ.γ-Fe2O3also got an enlarged special surface area in the γ-Fe2O3-CNTs. γ-Fe2O3-CNTswas a more effective thermal resistant additive than the others.In addition, the changes of the thermal resistant additives and the gas products ofthe silicone rubber composites during the thermal oxidative aging were alsoinvestigated. The results showed that the γ-Fe2O3was a more effective thermalresistant additive than α-Fe2O3due to the changes of crystalline form during thethermal aging. A synergy was found in the γ-Fe2O3-CNTs and much more changes ofvalence made γ-Fe2O3-CNTs as a more effective thermal resistant additive. The improvement of the thermal oxidative stability of γ-Fe2O3-CNTs/silicone rubber wasdue to the thermal conductivity of CNTs and the enhanced γ-Fe2O3by the CNTs. Theenhanced γ-Fe2O3sharply reduced the amount of the gases obtained from theoxidation of the side methyl groups of silicone rubber.To investigate the effect of the interfacial interaction on the thermal oxidativestability of chemical modified CNTs/silicone rubber composite and nanoparticleattached CNTs/silicone rubber composite, poly (dimethylsiloxane) grafted CNTs(CNTs-APDMS) and γ-Fe2O3-CNTs were prepared and embedded into silicone rubbermatrix respectively. The interfacial interaction between the CNTs and the matrix atvarying strains were investigated through the use of Raman spectroscopy, and theeffect of the variation of the interfacial interaction on the thermal oxidative stability ofthe SR was also studied. It was found that the interfacial interaction ofCNTs-APDMS/silicone rubber composite and γ-Fe2O3-CNTs/silicone rubber weredamaged at250%strain and100%strain, respectivily. After the thermal oxidativeaging, the mechanical properties of the CNTs-APDMS/SR composite decreasedsharply due to the damaged interface and the thermal stability was also reduced, butsuch damage did not affect the γ-Fe2O3-CNTs/silicone rubber composite on itsthermal stability.更多还原