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 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.

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.

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.

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.

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.

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.

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.

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.

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.

SURFACE MODIFICATION OF POLYPROPYLENE MICROPOROUS MEMBRANE BY TETHERING POLYPEPTIDES

Two kinds of polypeptides were tethered onto the surface of polypropylene microporous membrane （PPMM） through a ring opening polymerization of L-glutamate N-carboxyanhydride initiated by amino groups which were introduced by ammonia plasma and y-aminopropyl triethanoxysilane treatments. X-ray photoelectron spectroscopy （XPS）, attenuated total reflectance Fourier transform infrared spectroscopy （FT-IR/ATR）, scanning electron microscopy （SEM）, together with water contact angle measurements were used to characterize the modified membranes. XPS analyses and FT-IR/ATR spectra demonstrated that polypeptides are actually grafted onto the membrane surface. The wettability of the membrane surface increases at first and then decreases with the increase in grafting degrees of polypeptide. Platelet adhesion and murine macrophage attachment experiments reveal an enhanced hemocompatibility for the polypeptide modified PPMMs. All these results give evidence that polypeptide grafting can simultaneously improve the hemocompatibility as well as reserve the hydrophobicity for the membrane, which will provide a potential approach to improve the performance of polypropylene hollow fiber microporous membrane used in artificial oxygenator.

CHEMICAL MODIFICATION OF THE SURFACE OF CALCIUM ALGINATE GEL BEADS

The chemical modification of the surface of calcium alginate gel beads (CAGB) via grafting copolymerization with vinyl acetate (VAc) was studied. The optimum reaction conditions with activation and graft copolymerization two steps were explored. First, 5 grams CAGB with 2.5 mm initial diameter was initiated with 0.0493 mol/L K2S2O8 at 51 °C for 30 min in 15 mL 1 % PVA/H2O. Then 4.34 moi/L VAc was added dropwise and the reaction was allowed to proce at 48 °C for 3 h. The grafting efficiency could come up to 30%. It was found the stability of modified CAGB in the air and in electrolyte solutions was greatly improved.

Study on the Surface Modification of Hydrophobic Polyacrylate Intraocular Lens

In this study, the polyacrylate intraocularr lens is irradiated by argon ion which can produce free radicals. In order to obtain better hydrophilic and lower platelets adhesion, monomer vinyl pyrrolidone (NVP) is grafted onto the hydrophobic polyacrylate intraocular lens surface in a certain reaction conditions. Specific changes in intraocular lens are detected by static contact angle (CA), scanning electron microscope (SEM) and light transmittance. The results show that this surface modification can greatly improve its hydrophilic character and surface formation.

Myringoplasty Modification Adopted to Overcome Some Long and Short Term Surgical Issues

Objective/Hypothesis: We have tried to present some of our concerns regarding the usually adopted surgical techniques of Myringoplasty with their possible solutions. Also we have tried to present digital recordings of pre and post-operative findings in reference cases, which have been provided rarely in available literature. Pre- and post-operative pictures and videos of two representative cases are attached. Study design: This prospective study was carried out in MMABM hospital. Forty six (46) ears, 37 patients underwent tympanoplasty by the modified dual grafting technique and the results were analysed. Results: Objectives of tympanic membrane repair, dry ear, closure of AB gap, and stoppage of tinnitus if any, were achieved in all cases. Small residual perforations which healed over time were seen in two cases in cartilage deficient areas. Conclusion: Dual graft modified techniques served as an effective alternative myringoplasty technique.

Surface Modification of Barium Sulfate Particles

In this study, surface modification of barium sulfate was investigated using several model molecules for chemical treatment: ethanesulfonic acid, butyric acid, trimethoxy(propyl) silane and phosphoric acid 2-hydroxyethyl methacrylate. Samples were characterized by FT-IR and TGA to check the capability of these model molecules to interact with BaSO4 surface. The results pointed out the presence of an organic layer around the surface after the chemical treatment even after several washings to remove all species in excess. Model molecules were grafted onto BaSO4 surface and grafted density was determined. It reveals that phosphoric acid and carboxylic acid are the best candidates for the modification of BaSO4 surface. Both can be used as anchoring groups to modify the hydrophilic balance of barium sulfate surface in order to avoid the formation of aggregates and to improve the compatibility of this filler within hydrophobic polymer matrix.

电力设备用皱纹纸理化特性分析及模拟改性研究

绝缘皱纹纸是变压器和互感器及高压电缆等电力设备必须的绝缘材料,目前超(特)高压电力设备用高性能皱纹纸全部依赖进口,为实现高端电力设备用皱纹纸国产化以及提升皱纹纸长期可靠性,亟需开展皱纹纸理化特性及性能提升技术研究。本文开展了不同厂家皱纹纸理化性能测试与对比分析,提炼出影响皱纹纸性能的关键理化参数。通过接枝改性技术向皱纹纸纤维素体系中引入3种官能团,利用Materials Studio软件对改性前后纤维素体系的电、热、力学性能进行分析,探究了不同官能团对纤维素体系各项性能的影响。结果表明:苯环对纤维素体系热性能的提升最为明显,亚甲基长链能提高纤维素体系的绝缘性能,苯环能够提高纤维素体系的力学性能。

天然植物纤维ATRP改性的研究进展

天然植物纤维是一种绿色可再生资源,具有来源丰富、价格低廉、可生物降解、物化性能丰富可调等特点,已成为化学、材料等领域研究的热点。然而,由于天然植物纤维具有易吸湿、易受霉菌微生物侵害、与非极性聚合物界面相容性差等缺点,限制了天然植物纤维材料的高效和高附加值应用,有必要对其进行改性处理。原子转移自由基聚合(ATRP)是一种有别于传统意义上的自由基聚合法,因其活性可控、分子设计能力强,被广泛用于天然植物纤维材料功能化改性。本文结合作者课题组及国内外的研究情况,介绍了天然植物纤维ATRP改性的反应机理,归纳总结了近年来ATRP在竹木纤维、棉纤维、麻纤维以及其他植物纤维改性方面的研究进展,阐述了电子转移活化再生催化剂原子转移自由基聚合(ARGET ATRP)在植物纤维功能化改性中优势及发展应用,其能够提高接枝聚合物复合材料的疏水性、疏水耐久性,提高复合材料的生物相容性、抗菌性和吸附性等生物性能,并且还能提升复合材料的力学性能。最后对天然植物纤维ATRP改性面临的问题进行了总结并展望了其发展前景。

β-环糊精修饰哌嗪基聚酰胺制备耐氯复合纳滤膜

为提高聚酰胺纳滤膜的耐氯性能,本研究以哌嗪基聚酰胺分离层作为基础层,利用膜表面残余的酰氯基团,再次进行界面反应,将β-环糊精(β-CD)修饰到膜表面制备改性复合纳滤膜,对改性复合膜的表面形貌、化学组成和特性进行了表征,阐述了复合膜结构和性能之间的关系。通过对比实验得出β-CD最佳反应质量分数为0.2%,反应时间为2 min,经优化的改性膜纯水通量达到126.40 L/(m^(2)·h·MPa),对硫酸钠(Na2SO_(4))、硫酸镁(MgSO_(4))、无水氯化镁(MgCl_(2))、氯化钠(NaCl)的截留率分别为95.90%、91.76%、36.43%和31.76%。改性膜在不同pH值的次氯酸钠溶液中浸泡后,表现出稳定的高通量和盐截留性能,具备优异的耐氯特性,在72 h的长期运行实验中,改性膜性能未发生较大变化,具备长期运行的要求。本研究结合了β-环糊精的纳米空腔结构与酯基的耐氯特性,为高渗透选择性耐氯纳滤膜的制备提供了一种新策略。