Grafting PIP Onto Surfaces Of Silica Nanoparticles And Its Application

Due to its small particle size and large specific surface area,silica?SiO₂?nanoparticles possess strong surface adsorption,thermal resistance,electric resistance and other aspects.It has unique characteristics in many disciplines and fields and has irreplaceable effects.However,the poor compatibility of SiO₂nanoparticles with the polymer matrix affects the filling effect and limits its application.Therefore,it needs to be modified.In this paper,SiO₂nanoparticles were prepared by the St?ber method,and then polymer chains were grafted from the surfaces of SiO₂nanoparticles via reversible addition-fragmentation chain transfer?RAFT?polymerization to improve its compatibility with the polymer matrix,which were used to modify polypropylene?PP?,high density polyethylene?HDPE?and polystyrene?PS?.The main research results are as follows:?1?The RAFT agent was synthesized and polyisoprene?PIP?rubber was grafted from the surfaces of SiO₂nanoparticles via RAFT polymerization,and SiO₂-g-PIP composite nanoparticles were obtained,which were used to modify PP.The measurement results of dynamic light scattering?DLS?,field-emission transmission electron microscopy?TEM?,Fourier transform infrared spectroscopy?FT-IR?,thermogravimetric analysis?TGA?,X-ray photoelectron spectroscopy?XPS?measurements prove that the flexible PIP macromolecular chains have been successfully bonded to the surfaces of SiO₂nanoparticles.Mechanical property,scanning electron microscope?SEM?,TGA,differential scanning calorimetry?DSC?,and rheological property measurements indicate that the mechanical properties and thermal stability of PP/SiO₂-g-PIP composites are superior to those of pure PP and PP/SiO₂composites.When the amount of SiO₂-g-PIP composite nanoparticles added is 2 wt.%,the tensile strength of PP/SiO₂-g-PIP composites reach 32.44 MPa,and the notched impact strength amounts to 9.11 k J/m²,which is 28%and 109%higher than that of pure PP,respectively.The addition of nanoparticles plays the role of heterogeneous nucleation and improves the crystallinity of PP.?2?The HDPE/SiO₂ and HDPE/SiO₂-g-PIP composites were prepared via melt blending,and their structure and properties were characterized.The measurements of mechanical properties,TGA,DSC,SEM and rheological property suggest that the mechanical properties of HDPE/SiO₂-g-PIP composites are superior to those of pure HDPE and HDPE/SiO₂composites.SiO₂-g-PIP composite nanoparticles increase the maximum thermal decomposition temperature of the composites by 24.7?in comparison with pure HDPE,and increase the crystallization temperature and crystallinity of HDPE.?3?PS was modified by SiO₂ nanoparticles and SiO₂-g-PIP composite nanoparticles via melt blending method.The measurements of mechanical properties,TGA,SEM and rheological property demonstrate that compared with SiO₂nanoparticles,SiO₂-g-PIP composite nanoparticles give rise to more significant increase in the mechanical properties and thermal stability of PS.Moreover,the impact strength of PS/SiO₂-g-PIP?98/2?composites is improved by 185%in comparison with that of PS.