Preparation And Properties Of Halloysite Nanotubes/Silicone Composites

To integrate two or more different types of materials through hybrid or assembly at nanoscale level is an important way for preparing new kinds of nanocomposites or hybrid materials with unique structure and properties. Halloysite nanotubes(HNTs),which are natural silicate nanotubes with excellent characteristics such as low cost, high strength, heat resistance and so on, have attacted extensive interesting in fabricating HNTs/polymer nanocomposites with special structure and promising performance.In the present work, the new kind of material hydrophobic etched-HNTs/silicone composites were prepared by solution blending.The comprehensive properties of the composites including mechanical properties, dielectric properties, flame retardancy properties and interfacial compatibility were investigated in detail.Sulfuric acid treatment provided an efficient method for controllable enlargement of HNTs lumen diameter. The etching time and temperature played important roles in the process that alumina removal from the nanotubes After treated by 2mol/L sulfuric acid(80℃ treated for 96h), the alumina was almost removed from the nanotube and the etched-HNTs still kept perfect nanotube strcture.The etched-HNTs was successfully modified by hexamethyldisilazane(HMDS) and the etched-HNTs surface was grafted by Si(CH3)3 groups, which expressed hydrophobic and the contact angle was higher than 120°.In addition, the study for grafting process concluded that grafted amounts would have reached the biggest when HMDS amounts was 2%, meanwhile reaction temperature was 120℃ and reaction time was 5 h.Hydrophobic etched-HNTs/silicone nanocomposite was successfully prepared through solution blending.When nanotubes amounts was 2%, SEM showed that the interface between the resin and nanotubes was rough, which cofirned they are compatible. And the tensile strength is increased by 31% than that of silicone resin, the elongation at break increased by 23.4%.Flame retardant properties of hydrophobic etched-HNTs/silicone nanocomposite was obviously improved as nanotubes amounts was increasing. While the nanotues amounts was 10%, the limiting oxygen index reached 41.2% and the flame retardancy level was V-0 as silicone resin was 35.1% and V-1, which confirmed that the prepared hydrophobic etched-HNTs were effective flame retardants for silicone resin.