Study On The Preparation And Property Of Nano-TiO₂/Polypropylene Composites

Polypropylene is a kind of thermoplastic resin with excellent comprehensive properties, andit possesses extensive application in various fields and so far exhibits a promising developmentprospects. It is a kind of materials of the four major synthetic fibers. The polypropylene fibershave many advantages including light weight, high strength and corrosion resistance etc. Usingblending modification method, people have been developing the anti-bacterial, anti-static, farinfrared and other modified PP fibers in succession. However, with PP as the matrix, nano-TiO2for photocatalytic modifier, it is still in study to develop the preparation technology andapplication of the PP photocatalytic fiber. For the PP fibers, the non-selective degradation fororganic matters over TiO2nanoparticles cause a main technical problem that the nano-TiO2maydegradate the fibers matrix. Besides, it is necessary to solve the other series of problems, such asthe particle’s reunion and the spinnability of the blends.Through coated with SiO2inorganic porous membrane, it can avoid directly contactbetween organic matrix and nano-TiO2, meanwhile, made the matrix to obtain the effectiveprotection. Thus, the nano-TiO2remains the photocatalytic activity, also improved itsdispersibility. In this paper, polypropylene was used as matrix, the SiO2-coated TiO2nanoparticles prepared by liquid phase deposition were used as modifier, and theSiO2@TiO2/polypropylene composites were prepared by melt blending method. Themicromorphologies and structures of the modified SiO2@TiO2nanoparticles were characterizedby transmission electron microscopy (TEM), X-ray energy dispersive spectrometer (EDS),fourier transform infrared (FT-IR). The rheological properties, crystallinity and thermalproperties of the SiO2@TiO2/polypropylene composites were analyzed by capillary rheometer,thermal platform polarizing microscope, differential scanning calorimetry (DSC) and XRD, etc.The obtained results as following:1. Based on the TEM result, the nano-TiO2particles could be entrapped by uniform thickness of SiO2coatings via liquid phase deposition method. According to the results of EDSand FT-IR, SiO2were existed on the surface of nano-TiO2particles, and the combinationbetween SiO2and TiO2was based on chemical bond. After dispersion and coupling, the blendsof nano-SiO2@TiO2particles with PP possessed better compatibility and fluidity. And thedispersion of nano-TiO2particles were improved after the coating treatment.2. The melt of SiO2@TiO2/PP belonged to non-Newtonian fluid. The addition ofSiO2@TiO2modifier would not change the flow type, but it enhanced the non-Newtonianbehavior of PP melt and also increased its flowing resistance. The viscosity flow activationenergy of the melt increased with the increasing of SiO2@TiO2. Moreover, the rheologicalproperty of all the SiO2@TiO2/PP samples appeared extensional thinning behavior, withtemperature rising, both the extensional stress and extensional viscosity decreased. Theextensional flow activation energy of SiO2@TiO2/PP blend melt reduced with increasingextensional strain rate, apparent extensional viscosity of the melt became larger with the increaseof SiO2@TiO2content. The experiment of degradation indicated that SiO2-coated TiO2weakenedthe effect of thermal oxidation on PP matrix, which made TiO2/PP composites performance moresteady and easier to process.3. Adding SiO2@TiO2nanoparticles as modifier, the structure of PP wouldn’t besignificantly changed. However, it would have an impact on regularity of SiO2@TiO2/PPcomposites. with the increment of the SiO2@TiO2, the grain size of PP would decrease andcrystallinity of PP would be improved, which was helpful to form compact structure. With fastercooling rate, The semi-crystallization time (t1/2) of the SiO2@TiO2/PP composites woulddecrease, and the crystallization peak temperature (Tp) decreased. Through a contrastive analysisbetween Jeziorny and Mo methods, it could be found that, the Mo method was more suitable forstudying the non-isothermal crystallization kinetics of the SiO2@TiO2/PP composites.