Graft modification of ZnO nanoparticles with silane coupling agent KH570 in mixed solvent

The reaction of ZnO nanoparticles grafted with KH570 silane coupling agent was carried out in water-alcohol mixed solvent. Several characterization methods were applied to analyzing the results of surface modification such as Soxhlet extraction, Fourier transform infrared spectroscopy （FT-IR）, transmission electron microscopy （TEM）, thermogravimetry （TG）, differential scanning calorimetry （DSC） and zeta potential （ζ）. The results of FT-IR and TG-DSC show that the desired reaction chains have been covalently bonded on the surface of ZnO nanoparticles. Zetasizer results reveal that the maximal absolute value of ζ of the modified ZnO particles in acetone medium was 67.0 mV, which was much higher than that of the unmodified ZnO particles. So the surface of nanosized ZnO changed from hydrophilicity to hydrophobicity and the dispersity of ZnO nanoparticles were improved simultaneously. Finally, the mechanism of graft modification was discussed.

Surface Modification of Fire-retardant Asphalt with Silane Coupling Agent

The theory and approach of the surface modified of asphalt fire-retardant with silane coupling agent were introduced. The optimum silane dosage was determined, and the structure and properties of the asphalt fire-retardant before and after the surface modification were characterized by infrared spectrum and thermo gravimetric analysis. The dispersion effect of asphalt flre-retardant was studied. The influence of the surface modification on the hydrophilicity and lipophilicity of the asphalt fire-retardant was analyzed. The experimental results showed that there were physical and chemical interactions between the silane coupling agent and the asphalt fire-retardant, which reduced the surface polarity of the asphalt fire retardant. The optimum silane coupling agent dosage was 0.95% of the asphalt fire retardant. The surface modification improved the thermal stability, dispersibility and lipophilicity of the asphalt fire retardant, which enhanced the compatibility between asphalt fire retardant and asphalt.

Polymer grafting modification of the surface of nano silicon dioxide

Based on the composite modification technology of the surface of nano Silicondioxide by non-soap emulsion polymerization, it is verified that there are polymer grafted on thesurface of nano silicon dioxide. The modification mechanism and the bonding status on the surface ofnano silicon dioxide after modification were suggested via the results of the infrared spectrum,transmission electronic microscope photograph and X-ray photoelectron spectrum. The hydroxyl formedby hydrolyzing of silane coupling agent reacts with hydroxyl on the surface of nano silicon dioxideto form Si-O-Si bonds by losing water molecules and hence the double bonds are introduced onto thesurface of nano silicon dioxide. The surface of nano silicon dioxide is grafted with polymer throughfree radical polymerization between the double bonds on the surface of nano silicon dioxide andstyrene under the action of initiating agent. The dispersibility of nano silicon dioxide and thecontrollability of surface modification of nano silicon dioxide can be greatly improved by themodification process.

Oxidative coupling of methane:MO_x-modified (M=Ti,Mg,Ga,Zr) Mn_2O_3-Na_2WO_4/SiO_2 catalysts and effect of MO_x modification

Mn_2O_3-Na_2WO_4/SiO_2 is considered as the most promising catalyst for the oxidative coupling of methane（OCM） process; however, it only has a better catalytic performance over 800 °C. To improve its low-temperature performance, an attempt has been made to modify the Mn_2O_3-Na_2WO_4/SiO_2 catalyst using TiO_2, MgO, Ga_2O_3, and ZrO_2. Among the synthesized catalysts, the TiO_2-modified Mn_2O_3-Na_2WO_4/SiO_2 catalyst shows markedly improved low-temperature OCM performance,achieving a high CH_4 conversion of ~23% and a good C_2-C_3 selectivity of ~73% at 700 °C（the catalyst bed temperature）, along with promising stability for at least 300 h without signs of deactivation.In comparison with the unmodified Mn_2O_3-Na_2WO_4/SiO_2 catalyst, the TiO_2 modification results in significant improvement in the low-temperature activity/selectivity, whereas the MgO modification has almost no impact and the Ga_2O_3 and ZrO_2 modifications have a negative effect. The X-ray diffraction（XRD） and Raman results reveal that the formation of a MnTiO_3 phase and a MnTiO_3-dominated catalyst surface is crucial for the improvement of the low-temperature activity/selectivity in the OCM process.

Surface organic modification of Fe_3O_4 nanoparticles by silane-coupling agents

Fe3O4 nanoparticles were prepared by chemistry co-precipitation and the mean crystal size was 17.9 nm measured by XRD. After it had been treated by silane-coupling agents KH570, magnetic micro-spheres dispersed in organic medium glycol were gained and the mean size of Fe3O4 nanopowders was 33.7 nm. So it can be concluded that magnetic micro-sphere is made of a few Fe3O4 crystals. Many factors of modification were researched, such as the time of ball milling, the content of Fe3O4 and the content of KH570. The modification of Fe3O4 is relative to the time of ball milling, but the dominant function is affected by the content of Fe3O4 and KH570. When the content of Fe3O4 is known, there is a suitable content of KH570. Different content of Fe3O4 will make the different suitable content of KH570, but the range of latter is less than former, which is relative to the distribution of KH570 on Fe3O4 surface or in the solution.

Chemical Modification of Scraped Tires through Grafting with 2-Acrylamido-2-methylpropansulfonic Acid

Scrap vulcanized rubber is amongst a bigger waste polymers. It does not decompose easily owing to its cross linked structure. Modification of scrap tires powder by the grafting with 2-acrylamido-2-methylpropanesulfonic acid (AMPS) is described. The grafting is achieved through free radical initiation. The effects of different amount of monomer and initiator were examined. Also the influence of reaction time and temperature were investigated. The grafted waste rubber was characterized by FT/IR, SEM and DSC measurements. The proposed mechanism of the grafting reaction is discussed. From DSC and SEM studies of WR-g-AMPS compared with PAMPS and WR, the results show that the particle size and crystallinity were enhanced for the grafted copolymers. The obtained modified scraped tires will used as an ion exchanger for the future applications.

MODIFICATION OF MULTI-WALLED CARBON NANOTUBES WITH POLY(NITRILOETHYLENENITRILOVINYLENE)“GRAFTING TO”THE SURFACE

A mild and facile way was used to prepare poly(nitriloethylenenitrilovinylene)-grafted multi-walled carbon nanotubes(MWCNTs-g-PNENV)nanocomposites via the"grafting to"method.The MWCNTs-g-PNENV nanocomposites are well dispersible in polar solvents such as water,tetrahydrofuran and ethanol.Chemical structure of the resulting product was characterized by Fourier transform infrared(FTIR)spectroscopy,transmission electron microscopy(TEM)and thermal gravimetric analysis(TGA).FTIR showed that the"grafting to"process belonged to covalent attachment mechanisms.TEM observations indicated that the MWCNTs were coated with a uniform PNENV layer,and the MWCNTs existed as a hard backbone.TGA data also showed that the PNENV shell was successfully grafted to the side wall of MWCNTs.

Grafting modification on the surface of titanium dioxide by polystyrene

Based on the technology of titanium dioxide grafting modification withpolystyrene (PS), the modification mechanisms are studied and the polystyrene-grafting states on thesurface of titanium dioxide have been set up. Under the synergistic actions of mechanical force,chemistry and heat, macromolecular free radicals of PS are created, at the same time, the O-O bondsof titanium dioxide are broken and the oxide free radicals produced, and the numbers of oxygen atomare increased and crystal lattice defects rich electrons are formed on the surface of titaniumdioxide. The radical polymerization is the main reaction between PS and titanium dioxide and C-Obonds form in the process of modification. Multi-sites chemical adsorption also exists besidesgrafting between PS and titanium dioxide.

Coupling Agent Grafting Assisted Synthesis of C3N4-ZrO_(2) Heterojunction Composites with Enhanced Photocatalytic Performance

Heterojunction composites were prepared by silane coupling agent grafting from synthesized graphitic carbon nitride(g-C_(3)N_(4))and commercially available zirconia(ZrO_(2)).The samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),Fourier transform infrared(FT-IR)spectroscopy,UV-vis diffuse reflectance spectroscopy(DRS),photoluminescence(PL)spectroscopy,and electrochemical impedance spectroscopy(EIS).The photocatalytic activity of the composites was evaluated by the degradation of methylene blue(MB)under visible light irradiation.The results showed that heterojunction composites of g-C_(3)N_(4) and ZrO_(2) could be successfully prepared by coupling agent grafting.The optimal mass ratio of g-C_(3)N_(4) and ZrO_(2) was 2:1,with an activity that was 3.8 times higher than g-C_(3)N_(4) and 15.3 times higher than ZrO_(2).This was ascribed to the stronger light absorption,faster interfacial charge transfer,and lower photogenerated carrier recombination of the heterojunction composites.

Study on Surface Modification of Glass Bead by a Block Copolymer Coupling Agent

A tri-block copolymer coupling agent polystyreneblock-poly （n-butyl-acrylate）-block-poly （y-methacryloxypro pylt rimethoxysilane）（PS-b-PnBA-b-PMPS） was synthesized by atom transfer radical polymerization （ATRP）, and its molecular structure was characterized by fourier-transform infrared spectra, hydrogen nuclear magnetic resonance and gel permeation chromatography. The glass bead was treated with the block copolymer coupling agent, and then studied by transmission electron microscopy. The result showed that strong interaction was formed between the block copolymer coupling agent and the surface of glass bead, and then the block of poly（n-butylacrylate） formed a layer of film on the surface.

Synthesis and Characterization of Lignin Grafting Modification-based Aliphatic Superplasticizer

Lignin as the main component of black liquor is generally employed to modify aliphatic superplasticizer（AFS）. However, the modification effect is hard to evaluate correctly due to the uncertain molecular structure of lignin and the disturbance from the complexity of black liquor compositions. In this paper, the purified lignin via acid precipitation from straw black liquor is used to modify AFS. The modified AFS named as LAFS for short presents lower molecular mass than AFS. It is assumed that it is due to the single active site of guaiacol segments in lignin by which lignin graft modifies AFS in virtue of methylolation reaction. In order to verify this assumption, guaiacol and dihydro eugenol as the typical segments of lignin macromolecule were selected, respectively, as the simplified model compounds of lignin to modify AFS, and corresponding products are abbreviated in GAFS and DAFS. Both GAFS and DAFS show the lower molecular mass than unmodified AFS. FTIR and TG-DTG analyses prove that lignin is successfully grafted onto AFS. The graft modification of lignin results in a decrease in electrostatic epulsion, but an enhanced steric hindrance. Therefore, although the replacement rate of lignin in LAFS was about 23.3%, the dispersion performance was only slightly affected.

SURFACE MODIFICATION OF MICROPOROUS POLYPROPYLENE MEMBRANES BY GRAFT POLYMERIZATION OF N,N-DIMETHYLAMINOETHYL METHACRYLATE

Surface modification of microporous polypropylene hollow fiber membranes was performed by radical-induced graft polymerization of N,N-dimethylaminoethyl methacrylate (DMAEMA). The influences of temperature, monomer concentration and pre-adsorbed amount of benzoyl peroxide on grafting degree were studied respectively. It was found that the appropriate graft temperature was 75 'C, at which the grafting degree was the highest and the hydrolytic decomposition of DMAEMA the lowest. Scanning electron photomicrography and the average pore diameters of the modified membranes demonstrated that part of the micropores on the membrane surface was plugged by the grafted polyDMAEMA chains, especially at high grafting degree. Contact angle and water swelling experiments showed that a moderate grafting degree could improve the hydrophilicity of the membranes. In the range of 11.3%-12.0% grafting degree, the water swelling percentage reached its maximum (51.1%) and the contact angle reached its minimum (74 degrees). The bovine serum albumin (BSA) adsorption experiment indicated that the grafted polyDMAEMA had a dual effect on protein adsorption. At the first stage, the BSA adsorption decreased with increasing of DMAEMA grafting degree. As the interaction between BSA and polyDMAEMA on membrane surface increased, the BSA adsorption increased with increasing of DMAEMA grafting degree.

Surface Modification of Nanometre Silicon Carbide Powder with Polystyrene by Inductively Coupled Plasma

An investigation was made into polystyrene （PS） grafted onto nanometre silicon carbide （SIC） particles. In our experiment, the grafting polymerization reaction was induced by a radio frequency （RF） inductively coupled plasma （ICP） treatment of the nanometre powder. FTIR （Fourier transform infrared spectrum） and XPS （X-ray photoelectron spectroscopy） results reveal that PS is grafted onto the surface of silicon carbide powder. An analysis is presented on the effectiveness of this approach as a function of plasma operating variables including the plasma treating power, treating time, and grafting reaction temperature and time.

MODIFICATION OF SILK FIBER via EMULSION GRAFT COPOLYMERIZATION WITH FLUOROACRYLATE

2,2,3,3,4,4,5,5-Octafluoropentyl acrylate was grafted onto silk fiber in a two-step heterogeneous system through the vinyl bonds of acryloyloxyethyl isocyanate modified on the silk.The grafted copolylner was analyzed by FTIR and WAXD,and the results revealed that the fluoroacrylate was successfully grafted onto silk fiber and the crystalline structure of silk fibroin withβ-sheet structure was not changed after graft copolymerization.The FT-IR corrected method was used to simulate the grafting yield onto sil...

Graft Modification of N,N'-methylene- bisacrylamide onto Silk in the Presence of Air

The graft modification of N, N'-methylene-bisacrylamide (NNMBAA) onto silk using eerie ammonium sulfate, potassium persulfate, ammonium persulfate and 2, 2-azobis (isobutyronitrile) as the initiators has been studied in the presence of air. To establish reaction conditions for the graft modification of NNMBAA onto silk, the effect of different variables such as the initiator concentration, monomer concentration, acetic acid concentration, time of polymerization, reaction temperature and liquor ratio (fabric: liq.) have been studied. The optimum grafting conditions were found. As evidence of grafting, analyses of amino acid composition and alkali solubility have been carried out. Grafting caused changes in amino acid composition and alkali solubility of silk. The observation has been explained in relation to structural changes in the grafted silk.

Surface modification of silicone rubber by CF4 radio frequency capacitively coupled plasma for improvement of flashover

The flashover performance of insulating materials plays an important role in the development of high-voltage insulation systems.In this paper,silicone rubber(SIR)is modified by CF4 radio frequency capacitively coupled plasma(CCP)for the improvement of surface insulation performance.The discharge mode and active particles of CCP are diagnosed by the digital single-lens reflex and the spectrometer.Scanning electron microscopy and x-ray photoelectron spectroscopy are used for the surface physicochemical properties of samples,while the surface charge dissipation,charge accumulation measurement,and flashover test are applied for the surface electrical characteristics.Experimental results show that the fluorocarbon groups can be grafted and the surface roughness increases after plasma treatment.Besides,the surface charge dissipation is decelerated and the positive charge accumulation is inhibited obviously for the treated samples.Furthermore,the surface flashover voltage can be increased by 26.67%after 10 min of treatment.It is considered that strong electron affinity of C–F and increased surface roughness can contribute to deepening surface traps,which not only inhibits the development of secondary electron emission avalanche but also alleviates the surface charge accumulation and finally improves the surface flashover voltage of SIR.

Current Strategies of Surface Modifications to Polyurethane Biomaterials for Vascular Grafts

As the number of patients suffering from cardiovascular diseases and peripheral vascular diseases rises,the constraints of autologous transplantation remain unavoidable.As a result,artificial vascular grafts must be developed.Adhesion of proteins,platelets and bacteria on implants can result in stenosis,thrombus formation,and postoperative infection,which can be fatal for an implantation.Polyurethane,as a commonly used biomaterial,has been modified in various ways to deal with the adhesions of proteins,platelets,and bacteria and to stimulate endothelium adhesion.In this review,we briefly summarize the mechanisms behind adhesions,overview the current strategies of surface modifications of polyurethane biomaterials used in vascular grafts,and highlight the challenges that need to be addressed in future studies,aiming to gain a more profound understanding of how to develop artificial polyurethane vascular grafts with an enhanced implantation success rate and reduced side effect.

Significantly improved high-temperature energy storage performance of commercial BOPP films by utilizing ultraviolet grafting modification

Commercial biaxially oriented polypropylene(BOPP)film capacitors have been widely applied in the fields of electrical and electronic engineering.However,due to the sharp increase in electrical conduction loss as the temperature rises,the energy storage performance of BOPP films seriously degrades at elevated temperatures.In this study,the grafting modification method is facile and suitable for large-scale industrial manufacturing and has been proposed to increase the high-temperature energy storage performance of com-mercial BOPP films for the first time.Specifically,acrylic acid(AA)as a polar organic molecular is used to graft onto the surface of commercial BOPP films by using ultraviolet irradiation(abbreviated as BOPP-AA).The results demonstrate that the AA grafting modification not only slightly increases the dielectric constant,but also significantly reduces the leakage current density at high-temperature,greatly improving the high-temperature energy storage performance.The modified BOPP-AA films display a discharged energy density of 1.32 J/cm3 with an efficiency of>90%at 370 kV/mm and 125℃℃,which is 474%higher than that of the pristine BOPP films.This work manifests that utilizing ultraviolet grafting modification is a very efficient way to improve the high-temperature energy storage performance of commercial BOPP films as well as provides a hitherto unexplored opportunity for large-scalable production applications.

Plasma Surface Modification of Kevlar Fibers

Cold plasma techniques were used to treat the surface of Kevlar-49 fibers. The dynamic parameters of wetting, contact-angles and surface energy of the fiber before and alter the treatment were compared to see the changes in the wetting property. ESCA and electron spin resonance were utilized to examine the chemical composition and the attached free radicals of the fiber surface. The results, together with changes in the magnitude of the contact-angle and the number of free radicals with time after the plasma treatment do not show any ageing effect. Single filament test revealed that the tensile strength was not impaired but even improved somewhat after the plasma treatment. The experiment shows that the interlaminar shear strength of Kevlar fiber reinforced epoxy resin compo- site is increased for more than 60％% after the treatment.

Plasma Induced Grafting of PMMA onto Titanium Dioxide Powder

Grafting of polymer of methyl methacrylate （PMMA） onto titanium dioxide powder is investigated in this paper. The graft polymerization reaction is induced by dielectric-barrier- discharge produced N2 plasma treatment of titanium dioxide surfaces. IR, XPS and TGA results show that PMMA is grafted onto the surfaces of titanium dioxide powder. And crystal structure of the titanium dioxide powder observed with XRD spectra is unchanged after plasma graft polymerization.