Preparation Of Doped And Surface Functionalized Titania Nanotubes And Study On Thermal Stability And Flame Petardant Properties Of Polymer Composites

During the last few decades, a new class of nanometer sizes range meterials has been extensively investigated and the properties of special morphology of nano-meterials have been gradually more and more research. Now the research mainly focuses on carbon nantubes, layered corbon meterials and inorganic materials, less on other special morphology nano-materials. The researches about special morphology nano-materials in flame retardant polymer nanocomposotes were even rarely reported. In this paper, TIO2nanotubes (TNTs) were synthesized in a hydrothermal process, and modified to improve the catalytic properties or compatibility for polymers. Combined with current flame retardant research, the potential of TNTs to improve the flame retardancy of polymers were studied, and the roles played by them in the flame retardant mechanism were explored. The main reseatch works are as follows:1. Titania dioxide nanotubes, synthesized via hydrothermal treatment, were incorporated in polystyrene by in situ bulk radical polymerization. In the presence of TNTs, the thermal stabilities of the nanocomposites were increased, and the combustion characteristics of the polymer were improved effectively. DP-MS and TG-FTIR analysis of the gas phase degradation products of PS/TNTs nanocomposites confirmed an increase in the yield of inter-chain reaction product; it is felt that the radical recombination reactions cause the retention of the degradation products for a longer period of time thus spreading out the degradation in time and reducing the peak value. In order to improve the dispersion, TiO2nanotubes were surface modified with phenl dichlorophosphate (PDCP). The formation of the TNTs-PDCP (TP) was confirmed by FTIR, TGA and XPS. PS/TP nanocomposies were prepared by in situ bulk radial polymerization. The TP were dispersed homogeneously throughout the composites even load to7wt.%. The adsorption of PS segments onto the TP leaded to restriction of mobility of the PS chains causing the increase of Tg for nanocomposites. Due to the presence of TP, polystyrene gave a very reduction for the peak heat release rate and addition for the Tmax. The presence of TP increased the thermal stability, probably because of inhibiting effects of the TP on some degradation stages of the thermal degradation of PS. The evolved products of polystyrene and polystyrene nanocomposites were studied using TGA-FTIR and DP-MS. Since the TP in the nanocomposites act as a barrier and adsorption to heat and mass transfer, the degradation pathway of polystyrene had been changed. In the presence of TP, additional products were evolved through radical recombination reactions.2. The highly efficient intumescent flame retardant systems (APP and PER) were prepared by the addition of TNTs or OMT. Their applications in EVA were studied. It was found that the addition of TNTs or OMT could effectively inhibit the dripping, thereby enhancing UL-94rating of the material. The results of cone calorimeter test of EVA/IFR (APP:PER=2:1) system indicated that addition of TNTs and OMT could extend the burning time and reduced the value in the first heat release peak. TG showed that the existence of TNTs or OMT cound slowly the mass loss rate of the third phase weight loss of the EVA/IFR system. The results of cone calorimeter test of EVA/IFR (APP:PER=4:1) system showed that the addition of TNTs or OMT, would extend the burning time of the system. The presence of TNTs could effectively reduced PHRR and gentled heat release trends. Effects of OMT in the system were similar. But OMT has no effect in THR. The results for thermal stability analysis indicated that weight loss rete of material in its main weight loss stage was slowly by the addition of synergistic agent, and the residual char in high temperature comditions was increased. The effect of TNTs in the char layer was obvious. It could promote to form dense char on the surface layer, change the char morphology. Raman structure also comfirmed the regularity of char layer increased after TNTs added.3. TiO2nanotubes were surface modified by PDCP and dispersed homogeneously throughout the epoxy resin system. Resin properties had been influenced with percent of the nanotubes. Nanotubes infusion changes the morphology of the resin systems that increased the Tg of the bulk matrix, the mechanical and thermal properties of the nanocomposites. MCC data showed that the peak heat release rate and total heat release of the epoxy/TNTs nanocomposites were significantly reduced compared with pure EP. Moreover, TG-FTIR and DP-MS had proved that the TNTs were capable of ameliorating the thermal stability and combustion behavior of the polymer matrix because the TNTs retarded the release of inflammable gas and changed the degradation pathway.4. Ce-TNTs were synthesized by the hydrothermal method. TEM and XPS confirmed that the Ce ion was doped in TNTs wall successfully. The thermal stability and burning behaviors of PS/IFR were improved by introducing Ce-TNTs. It was noted from the TG data that the Tmax of PS/IFR sample under air atmosphere, with0.1 wt.%of Ce-TNTs, was about20℃higher than the pure PS/IFR and PS/IFR/TNTs. The LOI value of the PS/IFR with0.1wt.%of Ce-TNTs could be increased to28.5and its residual char was more compact and stronger than that of the PS/IFR and PS/IFR/TNTs. Meanwhile, the UL-94rating of PS/IFR system was improved from no rating to V0. The results of the real time FTIR indicated that the addition of Ce-TNTs changed the decomposition process to make residual char more compact. All results indicated that Ce-TNTs had a significant synergistic effect on the flame retardancy of PS/IFR.5. The phosphorus, oxychloride reacted with the surface hydroxyl groups to introduce of phosphorus. And then made the unreacted phosphorus chlorine bond with the HEA to introduce of double bonds to improve the TNTs dispersion in the matrix to improve the flame retardant efficiency. FTIR, TG and XPS data proved the success of the reaction. It was found that the modified TNTs can effectively reduce the pyrolysis rate of the UV-curing. The combustion performance of the nanocomposites was improved as modified TNTs addition.0.1wt.%of the modified TNTs addition made the material PHRR reduced about35%. DMA research shown that a small amount of modified TNTs (0.1wt.%) added in could effectively improve the elastic modulus of the materials. All in all, modified TNTs could effectively improve the combustion and thermal stability of the UV-curried. These data provided an experimental basis and theoretical bass for the TNTs application in UV curing system.