| 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. |
PDF Full Text Request