Effects Of Nano-TiO₂ On Mechanical Property And Thermal Stability Of Polycarbonate Composites

In recent years,polymer nanocomposites have attracted the attention of scholars in the wildword own to their excellent performance and potential application.TiO₂ nanoparticles have unique properties such as non-poisonous,high melting point,large siffness,chemical stability and thermal stability.Adding TiO₂ nanoparticles into polymer matrix can improve their properties such as mechanical,electrical and thermal stability.In this study,polycarbonate?PC?was chosen as the polymer matrix,rutile and anatase nano-TiO₂ particles as filler.The PC/TiO₂ nanocomposites with different ratio?0.5-3 wt%?were prepared through melt blending and injection molding method.The effect of two kinds of nano-TiO₂ particles on the microstructure and mechanical properties of PC/TiO₂ nanocomposites were characterized by fourier transform infrared spectroscopy?FTIR?,scanning electron microscopy?SEM?,universal tensile testing machine and dynamic mechanical property analysis?DMA?.The key results are following:?1?the dispersion of two kinds of nano-Ti O₂ particles was good at low content?1 wt%?,but the size of agglomerate nanoparticles became bigger with the increase of the nano-particle conten.And the agglomeration of anatase TiO₂ nanoparticles was serious than that of rutile.?2?both the two kinds of nano-TiO₂ particles could enhance the toughening effect of PC matrix,and the rutile titanium dioxide nanoparticles had a better effect than that of anatase due to its better combination with PC.?3?the two kinds of nano-TiO₂ particles increased the storage modulus of nanocomposites under the glass transition temperature?Tg?.And the result was proportional to the increase with nanoparticle content.On the basis of the above research,effects of TiO₂ nanoparticles on the bahavior,mechanism and kinetics of thermal degradation of composites were studied.It was studied using some characterization means such as thermogravimetric analysis?TGA?,fourier transform infrared spectroscopy?FTIR?,and thermogravimetric-infrared correlation analysis?TGA-FTIR?,combined with the Kissinger-Akahira-Sunos?KAS?equivalent conversion method.The results and conclusions are following:?1?both the two kinds of nano-TiO₂ particles could improve the thermal stability of PC nanocomposites,and the rutile nano-TiO₂ particles had a better effect than that of anatase nano-TiO₂ particles.?2?the effect of the two kinds of nano-TiO₂ particles on the thermal degradation behavior of the composites included the following three aspects: In the initial stage of thermal degradation reaction,free radicals were produced from the isopropylidene and captured by TiO₂ nanoparticles which delayed the thermal degradation reaction.In the main reaction stage,PC chain underwent complex chemical reactions such as the hydrolysis/alcoholysis reactions and rearrangements of carbonate groups,and the TiO₂ nanoparticles increased the thermal degradation reaction rate of PC nanocomposites because of its catalytic effect.In the last stage of thermal degradation reaction,a barrier network was formed between TiO₂ nanoparticles and the char which hindered the volatilization of the thermal degradation gas products and the release of heat.In this way,the thermal degradation reaction of the internal materials were inhibited.?3?the thermal degradation energy of composites which added the two kinds of nano-TiO₂ particles was higher than that of PC matrix,and the value of activation energy was the largest with the rutile Ti O₂ nanoparticles.