Surface Modification And Dispersion Of Nano Oxide Particles And Its Application To Polymer Friction Materials

Nano-friction has been actively studied since nineties in fundamental tribology research field. It is an advanced two-disciplinary subject of material science and tribology. Whether nano-particles can play a positive role in nano-composites greatly depends on the interface effect and the dispersion behavior. Graft modification on nano-particle surfaces was performed in the dissertation. Polymer coatings formed on the surfaces of nano-particles. Thus dispersion stability of the nano-particles in polymer matrices was improved due to the steric hindrance effect. Nano-composites with high dipersibility and low filling content were thus obtained.Nano-particles were modified with polyol via direct grafting, coupling agent grafting, and TDI activation method. Modification was performed by grafting PBT prepolymer via condensation polymerization on nano-particle surfaces. Results demonstrated that the grafting molecule chains were combined with the functional groups on nano-particle surfaces via chemical bonds. The grafting polymers were mainly distributed on the surfaces instead of bulk. SEM images showed that the diameters of nano-particles were enlarged obviously. The color was dark in the center while it is light around. The grafted particles presented a definite core-shell structure. The original nano-particles agglomerated whereas the modified version had an excellent dipersibility in organic media. The grafted particles dispersed singly and there was no agglomeration or adhesion between them.Investigation on nano-particle filled POM and PBT nano-composites indicated the grafted version dispersed homogeneously in the polymer matrices and no agglomeration occurred. Most of the particles were covered with polymers and the interfaces between nano-particles and matrices were blurred. It demonstrated the modified particles have good compatibility with the matrices and there were strong interface effects between the two phases. Strength and especially toughness of the nano-composites were improved since the grafting chains cross-linked and twisted with the polymer chains, and flexible...