Kinetic investigations on TiO_2 nanoparticles as photo initiators for UV-polymerization in acrylic matrix

摘要

TiO_2 nano-particles of anatase, useful as photosensitive initiators to induce free radical polymerization in acrylic monomers have been prepared by chemical synthesis. Appropriate surface modification of TiO_2 has been achieved to compatibilise the particles with the acrylic monomers to obtain an almost homogeneous distribution down to the primary particle size. The surface modification has been additionally fine tuned in such a way, that an efficient transfer of the electrons generated on TiO_2 during UV-exposure towards the monomer mixture could be achieved in order to start the polymerization reaction. In this direction, particles have been synthesized in-situ and ex-situ with the acrylic matrix using different precursors and surface modifiers. Ex-situ produced particles had to be dispersed finally into the acrylate monomer mixture. Residual solvent has been removed by distillation. The formation of the anatase modification could be shown by XRD. Particle sizes were determined by PCS, which showed a distribution between 1-10 nm depending on the used preparation method. Transmission electron microscopy prepared from the UV-polymerized coating layers proved the homogeneous distribution of the anatase nano-particles. Kinetic investigations on the photo-polymerization behavior have been accomplished by photo-DSC and IR. Curing time was determined in dependence on the materials composition.