Study On PET/TiO₂ Nanocomposite Property And Spinning Simulation

Nano Titanium Oxide (TiO₂) has been widely used as light, electric, magnetic, catalytic and antimicrobatic materials due to its excellent properties. Nano TiO₂ is also the important inorganic material for the functional polymeric composites and fibers. However, the difficulty of the nano particles dispersing in the high-viscosity polymer melts has limited the development of high-quality composite products. The in-situ polymerization is not fit for preparing high-content of nano TiO₂ and large molecular weight PET because of the catalytic activity of nano TiO₂, although it has been employed to produce the nano composites based on poly(methl methacrylate), polycaprolactam, and polyimide, where the nano particles dispersing uniformly. So blending is still a common method to prepare PET nano composite. Therefore, it is necessary to investigate the dispersing of nano TiO₂ in PET by surface grafting.The radical grafting polymerization of MMA initiated by azo groups onto the nano particles surface was investigated in details. 3-Glycidoxypropyltrimethoxysiliasne (GPS), a kind of coupling agent, was introduced onto the surface of the particles. Then the introduction of azo groups onto the particles surface was achieved by the esterification reaction to initiate the radical polymerization of MMA. The structure of the grafted nano particles was characterized by IR. It is proved that the MMA did begrafted onto the particles surface. From measurements, it is clear that the monomer conversion and grafting percentage, grafting efficiency were related the surface character of nano particles. From TEM photos and UV, it indicates that the grafted particles dispersed well in acetone because of which surface stress decreased.The polymeric nanocomposites based on PET were prepared through blending. The crystallization behavior of the PET nano composites were studied by DSC. It is found that the nano TiO₂ particle increased the melting temperature and crystallization temperature of PET, while the PMMA grafted TiO₂ had little effect. The crystallinity of PET decreased at different extent according to the different nano particles. The non-isothermal crystallization kinetics was analyzed by Jeziorny equation and Mo equation. It indicates that the crystallization rate of PET decreased and the crystallization activity energy increased because of the surface interaction between the nano particles and PET macromolecular. The rheology behavior of the PET nano composites were measured using RS300 rotation rheometer. It is found that the shear viscosity of composites decreased and the flow activity energy increased when the nano particle were added. The major reason is the degradable effect of nano TiC^on PET, which made the molecular weight of PET decrease. However, when the nano TiO2 were grafted with PMMA, the degradable effect was weakened.Based on the above research, the basic equations of the melt spinning of polymeric nano composites have been developed according to the fundament of spinning and characteristic of nano-composite formation. On the basis of the established equations, dynamics model of the melt spinning of polymeric nano-composites have been established and the varieties of velocity, velocity gradient, temperature, orientation and tension stress have been simulated at different spinning speed in the different system of PETnano composite. It shown that the tension stress, the maximum of velocity gradient and the rate of radius change increase with the increase of content of nano particles, while the temperature show no difference at the different content.