In order to reduce the agglomeration of nanographene and improve its dispersibility,six silane coupling agents were used to modify the surface of the nanographene particles.Visual inspection,Fourier-transform infrared...In order to reduce the agglomeration of nanographene and improve its dispersibility,six silane coupling agents were used to modify the surface of the nanographene particles.Visual inspection,Fourier-transform infrared spectroscopy,transmission electron microscopy,Raman spectroscopy,and X-ray diffraction were employed to evaluate the dispersion properties of the resulting graphene in an aqueous solution of silane coupling agents.Results show that all six types of silane coupling agents are efficient in promoting the dispersion of graphene in aqueous solutions,and no obvious sedimentation of the graphene dispersion solution is observed after a stationary storage period of 30 d.Taking 3-aminopropyltriethoxysilane(KH-550)as an example,after the graphene is dispersed in the KH-550 aqueous solution,the carboxyl group on the surface of the graphene reacts with the KH-550 amino group to form an amide bond,and KH-550 is successfully grafted onto the graphene surface.Polar functional groups ionize in water,creating an electrostatic repulsion effect,or hydrophilic functional groups form hydrogen bonds with water molecules,which is believed to improve the dispersion stability of graphene.The dispersed graphene is curled and contains many folds.Each fold has about three or four layers,with an interlayer spacing of about 0.65 nm.The dispersed graphene also has a complete lattice and a reduced number of defects.Nanographene disperses well in silane coupling agent aqueous solutions and can,therefore,be used to prepare cement-based composites.展开更多
Surface modification of nanometer titanium dioxide particles and effect of preparing TiO2/P （St-co-DVB） composites by dispersion polymerization are described. To introduce vinyl group onto the surface of titanium di...Surface modification of nanometer titanium dioxide particles and effect of preparing TiO2/P （St-co-DVB） composites by dispersion polymerization are described. To introduce vinyl group onto the surface of titanium dioxide particles, the titanium dioxide particles were surface-modified with a silicane coupling agent, methacryloylpropyltrimethoxysilicane. Polymer encapsulation in the presence of either modified-titanium dioxide particles or unmodified-titanium dioxide particles was carried out by dispersion polymerization of styrene, divinylbenzene in ethanol medium with polyvinylpyrroliclone as stabilizer, and 2, 2＇-azobis（isobutyronitrile） as initiator. The modified-titanium dioxide was analyzed with Fourier-transform infrared spectroscopy（FTIR）, UV-Vis spectrophotometer, thermo-gravimetric analysis and transmission microscope. The polymer encapsulation of modified-titanium dioxide and unmodified-titanium dioxide particles was confirmed with FTIR and transmission electron microscope. Results show that compared with unmodified-titanium dioxide, modified-titanium dioxide is more suitable for preparing inorganic core/orclanic shell composites.展开更多
A new method to chemically modify the surface of nanosized-SiO2 was studied in this paper.Nanosized-SiO2 was grafted with hyperbranched poly(amin ester)through one-spot polycondensation between AB2 monomer and active ...A new method to chemically modify the surface of nanosized-SiO2 was studied in this paper.Nanosized-SiO2 was grafted with hyperbranched poly(amin ester)through one-spot polycondensation between AB2 monomer and active hydroxyl on silica surface in present of catalyst.Compared with the results of FTIR and TEM,it is found hyperbranched poly(amin ester)is successfully grafted on the surface of nanosized-SiO2 and the surface properties have been changed with an expected way.The results indicate that nanosized-SiO2 grafted with hyperbranched poly(amin ester)has better dispersion in the ethanol or chloroform than that unmodified.展开更多
In the present work, 3-methacryloxypropyltrimethoxy-silane silanized silica （SiO2-WD70） and 9,10-dihydro-9-oxa-10-phospha- phenanthrene-10-oxide immobilized silica （SiO2-WD70-DOPO） nanoparticles were prepared. Sil...In the present work, 3-methacryloxypropyltrimethoxy-silane silanized silica （SiO2-WD70） and 9,10-dihydro-9-oxa-10-phospha- phenanthrene-10-oxide immobilized silica （SiO2-WD70-DOPO） nanoparticles were prepared. Silica, SiO2-WD70 and SiO2- WD70-DOPO were incorporated into polypropylene （PP） by melt compounding. Differential scanning calorimetry （DSC）, X-ray diffraction （XRD） and polarized optical microscopy （POM） were employed to investigate the isothermal crystallization behavior of PP and PP/silica composites. The kinetic constant （kn）, and half crystallization time （t1/2） were calculated by Avrami equation, while the surface free energy of folding was calculated by Lauritzen-Hoffman theory. The increased k,, decreased t1/2 and the surface free energy （ere） in the order ofPP, PP/SiO2, PP/SiO2-WD70 and PP/SiO2-WD70-DOPO nanocomposites were attributed to the surface modification of silica. XRD indicated that SiO2-WD70-DOPO addition had no effect on PP crystal structure but accelerated the crystallization rate. POM determined that SiO2-WD70-DOPO addition promoted the nucleation of PP by inducing a higher nucleation density during isothermal conditions. The surface modified nanoparticle SiO2-WD70-DOPO might find possible application as a new type of inorganic nano-sized nucleation agent for PP.展开更多
基金The National Key R&D Program of China(No.2018YFC0406701)the National Natural Science Foundation of China(No.51778133,51739008).
文摘In order to reduce the agglomeration of nanographene and improve its dispersibility,six silane coupling agents were used to modify the surface of the nanographene particles.Visual inspection,Fourier-transform infrared spectroscopy,transmission electron microscopy,Raman spectroscopy,and X-ray diffraction were employed to evaluate the dispersion properties of the resulting graphene in an aqueous solution of silane coupling agents.Results show that all six types of silane coupling agents are efficient in promoting the dispersion of graphene in aqueous solutions,and no obvious sedimentation of the graphene dispersion solution is observed after a stationary storage period of 30 d.Taking 3-aminopropyltriethoxysilane(KH-550)as an example,after the graphene is dispersed in the KH-550 aqueous solution,the carboxyl group on the surface of the graphene reacts with the KH-550 amino group to form an amide bond,and KH-550 is successfully grafted onto the graphene surface.Polar functional groups ionize in water,creating an electrostatic repulsion effect,or hydrophilic functional groups form hydrogen bonds with water molecules,which is believed to improve the dispersion stability of graphene.The dispersed graphene is curled and contains many folds.Each fold has about three or four layers,with an interlayer spacing of about 0.65 nm.The dispersed graphene also has a complete lattice and a reduced number of defects.Nanographene disperses well in silane coupling agent aqueous solutions and can,therefore,be used to prepare cement-based composites.
基金Supported by National High Technology Research and Development Program of China (863 Program) (No. 2004AA302010) and Natural Science Foundation of Tianjin (No. 043186411) .
文摘Surface modification of nanometer titanium dioxide particles and effect of preparing TiO2/P （St-co-DVB） composites by dispersion polymerization are described. To introduce vinyl group onto the surface of titanium dioxide particles, the titanium dioxide particles were surface-modified with a silicane coupling agent, methacryloylpropyltrimethoxysilicane. Polymer encapsulation in the presence of either modified-titanium dioxide particles or unmodified-titanium dioxide particles was carried out by dispersion polymerization of styrene, divinylbenzene in ethanol medium with polyvinylpyrroliclone as stabilizer, and 2, 2＇-azobis（isobutyronitrile） as initiator. The modified-titanium dioxide was analyzed with Fourier-transform infrared spectroscopy（FTIR）, UV-Vis spectrophotometer, thermo-gravimetric analysis and transmission microscope. The polymer encapsulation of modified-titanium dioxide and unmodified-titanium dioxide particles was confirmed with FTIR and transmission electron microscope. Results show that compared with unmodified-titanium dioxide, modified-titanium dioxide is more suitable for preparing inorganic core/orclanic shell composites.
文摘A new method to chemically modify the surface of nanosized-SiO2 was studied in this paper.Nanosized-SiO2 was grafted with hyperbranched poly(amin ester)through one-spot polycondensation between AB2 monomer and active hydroxyl on silica surface in present of catalyst.Compared with the results of FTIR and TEM,it is found hyperbranched poly(amin ester)is successfully grafted on the surface of nanosized-SiO2 and the surface properties have been changed with an expected way.The results indicate that nanosized-SiO2 grafted with hyperbranched poly(amin ester)has better dispersion in the ethanol or chloroform than that unmodified.
基金supported by the National Natural Science Foundation of China(51133009)the National Basic Research Program of China(2012CB720304)the“Strategic Priority Research Program”of the Chinese Academy of Sciences(XDA09030200)
文摘In the present work, 3-methacryloxypropyltrimethoxy-silane silanized silica （SiO2-WD70） and 9,10-dihydro-9-oxa-10-phospha- phenanthrene-10-oxide immobilized silica （SiO2-WD70-DOPO） nanoparticles were prepared. Silica, SiO2-WD70 and SiO2- WD70-DOPO were incorporated into polypropylene （PP） by melt compounding. Differential scanning calorimetry （DSC）, X-ray diffraction （XRD） and polarized optical microscopy （POM） were employed to investigate the isothermal crystallization behavior of PP and PP/silica composites. The kinetic constant （kn）, and half crystallization time （t1/2） were calculated by Avrami equation, while the surface free energy of folding was calculated by Lauritzen-Hoffman theory. The increased k,, decreased t1/2 and the surface free energy （ere） in the order ofPP, PP/SiO2, PP/SiO2-WD70 and PP/SiO2-WD70-DOPO nanocomposites were attributed to the surface modification of silica. XRD indicated that SiO2-WD70-DOPO addition had no effect on PP crystal structure but accelerated the crystallization rate. POM determined that SiO2-WD70-DOPO addition promoted the nucleation of PP by inducing a higher nucleation density during isothermal conditions. The surface modified nanoparticle SiO2-WD70-DOPO might find possible application as a new type of inorganic nano-sized nucleation agent for PP.
