Study On Preparation, Characterization And Properties Of Nano-TiO₂, SiO₂ Doped Polystyrene Materials

Polystyrene is the most promising target capsules materials for inertialconfinement fusion (ICF) experiment. Polystyrene doped with high Z (atom number)materials may allow the modification of target properties and provide diagnosticsignals of the targets during the different stages of the implosion. It is one of themost important studies to directly incorporate dopants in nano-scale into polystyrenematrix.Nano-SiO₂ and TiO₂ doped polystyrene materials were prepared by means ofin-situ polymerization and melt blending in this dissertation. The effect of couplingagents and ultrasonic action on the surface state and dispersibility of nanoparticleswere characterized using SEM, TEM, EDS, XRD, XPS and FTIR. The mechanicalproperties, thermal properties and the dispersibility of nanoparticles in polystyrenematrix were also characterized and discussed. The results show as follows.After surface modification, the content of C element increased and P elementappeared, and the density of the –C=O and -O-H groups decreased on the surface ofnano-TiO₂. It indicated that coupling agents had reacted with the hydroxyl groups onthe surface of TiO₂. The polarity and the aggregation of nano-TiO₂ reduced, but thedispersibility and thermal weight-loss percentage of nano-TiO₂ increased comparedwith bare nano-TiO₂. The crystal structure of nano-TiO₂ is anatase;the grain sizeswere decreased and the amorphous boundaries of TiO₂ were thickened bymodification.Nano-TiO₂ doped polystyrene materials were prepared using in-situpolymerization technology, and the molecular weight and the tensile properties ofpolystyrene were increased by incorporated nano-TiO₂ in the polymerization system.The mean size of nano-TiO₂ was less than 100nm, and nano-TiO₂ showed ahomogeneous dispersion in polystyrene matrix. The polystyrene doping materialsrevealed higher thermal stability and glass transformation temperature than that ofvirgin polystyrene for the interaction between nano-TiO₂ and matrix.The nano-SiO₂ and TiO₂ doped polystyrene materials were also prepared bymelt blending, and the mechanical properties of polystyrene were enhanced thoughdoping nanoparticles at lower loading. Nanoparticles could reinforce and toughenpolystyrene matrix, but the different coupling agents showed different effect on themodification of nanoparticles and the properties of doping materials. Modifiednano-SiO₂ and TiO₂ could be well dispersed in polystyrene matrix, respectively.The thermal decomposition curves of nano-SiO₂ and TiO₂ doped polystyrenematerials prepared by melt blending revealed that the temperatures of thermaldecomposition were shifted towards high temperature. The glass transmissiontemperatures increased for doping nanoparticals in polystyrene. The studies ofthermal decomposition kinetics indicated that the speed of thermal decompositiondecreased and activation energy of thermal decomposition increased compare withvirgin polystyrene.