In this study,to efficiently remove Pb(Ⅱ) from aqueous environments,a novel L-serine-modified polyethylene/polypropylene nonwoven fabric sorbent(NWF-serine)was fabricated through the radiation grafting of glycidyl me...In this study,to efficiently remove Pb(Ⅱ) from aqueous environments,a novel L-serine-modified polyethylene/polypropylene nonwoven fabric sorbent(NWF-serine)was fabricated through the radiation grafting of glycidyl methacrylate and subsequent L-serine modification.The effect of the absorbed dose was investigated in the range of 5–50 kGy.NWF-serine was characterized by Fourier transform infrared spectroscopy,thermogravimetric analysis,and scanning electron microscopy.Batch adsorption tests were conducted to investigate the influences of pH,adsorption time,temperature,initial concentration,and sorbent dosage on the Pb(Ⅱ) adsorption performance of NWF-serine.The results indicated that Pb(Ⅱ) adsorption onto NWF-serine was an endothermic process,following the pseudo-second-order kinetic model and Langmuir isotherm model.The saturated adsorption capacity was 198.1 mg/g.NWF-serine exhibited Pb(Ⅱ) removal rates of 99.8% for aqueous solutions with initial concentrations of 100 mg/L and 82.1% for landfill leachate containing competitive metal ions such as Cd,Cu,Ni,Mn,and Zn.Furthermore,NWF-serine maintained 86% of its Pb(Ⅱ) uptake after five use cycles.The coordination of the carboxyl and amino groups with Pb(Ⅱ) was confirmed using X-ray photoelectron spectroscopy and extended X-ray absorption fine structure analysis.展开更多
The hydrophilicity, dyeing and antistatic ability of polypropylene microfibre (PPMF) were improved by plasma-induced vapor grafting with acrylic acid. The effects of plasma discharge time, power, liquid phase acrylic ...The hydrophilicity, dyeing and antistatic ability of polypropylene microfibre (PPMF) were improved by plasma-induced vapor grafting with acrylic acid. The effects of plasma discharge time, power, liquid phase acrylic acid temperature and environmental temperature on grafting yield were investigated. The existence of grafted polyacrylic acid (PAA) was verified by ESCA and ATR FT-IR. The morphology of grafted PAA was directly observed by SEM. The wicking test shows that the hydrophilicity of modified PPMF is greatly enhanced. The dyeability test of modified PPMF was carried out using Dispersion Yellow. It was found that the dye uptake ratio is linear to the weight percent of grafting. The antistatic ability was indicated by specific resistance. The specific resistance of modified PPMF was reduced to 10(6) similar to 10(7) Ohm . cm, thus the antistatic ability was considerably improved.展开更多
Grafting copolymerization of styrene and acrylic acid onto polypropylene fabric had been studied by using a pre-irradiation technique. The polypropylene fabric Samples were irradiated by Y-ray and electron beam under ...Grafting copolymerization of styrene and acrylic acid onto polypropylene fabric had been studied by using a pre-irradiation technique. The polypropylene fabric Samples were irradiated by Y-ray and electron beam under the conditions of air and nitrogen gas, respectively. The effect of absorbed dose, monomer concentration in solvent, reaction temperature and reaction time on the degree of grafting were determined. The effects of metallic salts and sulphuric acid on the grafting yield of acrylic acid were also examined. The samples irradiated by electron beam give a much higher degree of grafting than those by Y -ray when styrene was grafted to polypropylene fabric. However, the grafting yield of acrylic acid on polypropylene fabric in the presence of metallic salts and sultric acid showed the opposite results from the case of styrene. This effect is reasonably interpreted by assuming that the grafting is dominated by trapped radicals and peroxides in pre-irradiated polypropylene.展开更多
BACKGROUND Chronic large to massive rotator cuff tears are difficult to treat and re-tears are common even after surgical repair.We propose using a synthetic polypropylene mesh to increase the tensile strength of rota...BACKGROUND Chronic large to massive rotator cuff tears are difficult to treat and re-tears are common even after surgical repair.We propose using a synthetic polypropylene mesh to increase the tensile strength of rotator cuff repairs.We hypothesize that using a polypropylene mesh to bridge the repair of large rotator cuff tears will increase the ultimate failure load of the repair.AIM To investigate the mechanical properties of rotator cuff tears repaired with a polypropylene interposition graft in an ovine ex-vivo model.METHODS A 20 mm length of infraspinatus tendon was resected from fifteen fresh sheep shoulders to simulate a large tear.We used a polypropylene mesh as an interposition graft between the ends of the tendon for repair.In seven specimens,the mesh was secured to remnant tendon by continuous stitching while mattress stitches were used for eight specimens.Five specimens with an intact tendon were tested.The specimens underwent cyclic loading to determine the ultimate failure load and gap formation.RESULTS The mean gap formation after 3000 cycles was 1.67 mm in the continuous group,and 4.16 mm in the mattress group(P=0.001).The mean ultimate failure load was significantly higher at 549.2 N in the continuous group,426.4 N in the mattress group and 370 N in the intact group(P=0.003).CONCLUSION The use of a polypropylene mesh is biomechanically suitable as an interposition graft for large irreparable rotator cuff tears.展开更多
Membrane surfaces modified with poly(N-vinyl-2-pyrrolidone) (PNVP) can be endowed with hydrophilicity, biocompatibility and functionality. In this work, atmospheric pressure dielectric barrier discharge plasma gra...Membrane surfaces modified with poly(N-vinyl-2-pyrrolidone) (PNVP) can be endowed with hydrophilicity, biocompatibility and functionality. In this work, atmospheric pressure dielectric barrier discharge plasma graft polymerization of N-vinyl-2-pyrrolidone (NVP) onto polypropylene (PP) microporous membrane surface was studied. The experimental results reveal that plasma treatment conditions, such as discharge power, treatment time and adsorbed NVP amount, have remarkable effects on the grafting degree of NVP. Structural and morphological changes on the membrane surfaces were characterized by attenuated total reflection-Fourier transform infrared spectroscopy (FT-IR/ATR), X-ray photoelectron spectroscope (XPS) and field emission scanning electron microscopy (FE-SEM). Water contact angles of the membrane surfaces were also measured by the sessile drop method. Water contact angles on the membrane surfaces decrease with the increase of NVP grafting degree, which indicates an enhanced hydrophilicity for the modified membranes. The effects of grafting degrees on pure water fluxes were also measured. It is shown that pure water fluxes increase with grafting degree firstly and then decrease adversely. Finally, filtration of bovine serum albumin (BSA) solution and platelets adhesion of the PNVP modified membranes show good protein resistance and potential biocompatibility due to the enhancement of surface hydrophilicity.展开更多
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 co...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.展开更多
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 intr...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.展开更多
By dynamic method under UV irradiation, commercial melt-blown polypropylene (PPMB) filter element was modified with acrylamide (AAm) using benzophenone (BP) as initiator. Attenuated total reflection-Fourier tran...By dynamic method under UV irradiation, commercial melt-blown polypropylene (PPMB) filter element was modified with acrylamide (AAm) using benzophenone (BP) as initiator. Attenuated total reflection-Fourier transform infrared spectroscopy and scanning electron microscope verified that polyacrylamide chain was grafted on the fiber surface of PPMB filter element. Elemental content analysis with energy dispersive X-ray of fibers revealed that the polymerization content in the inner part of filter element was relatively higher than that in the outer. Degree of grafting changed with initiator concentration, monomer concentration, reaction temperature and reached 2.6% at the reaction condition: CBp=0.06 mol/L, CAAm=2.0 mol/L, irradiation time: 80 min, temperature: 60℃. Relative water flux altered with the hydrophilicity and pore size of filter element. In the antifouling test, the modified filter gave greater flux recovery (approximately 70%) after filtration of the water extract of Liuweidihuang, suggesting that the fouling layer was more easily reversible due to the hydrophilic nature of the modified filter.展开更多
To study the effect of some parameters, such as, length and fraction of glass fiber (GF), and the fraction of maleic anhydride grafted polypropylene (PP-g-MAH), on the mechanical properties of glass fiber reinforced p...To study the effect of some parameters, such as, length and fraction of glass fiber (GF), and the fraction of maleic anhydride grafted polypropylene (PP-g-MAH), on the mechanical properties of glass fiber reinforced polypropylene (GF/PP) composites, tensile tests, bending tests and impact tests were conducted. Scanning electron microscope (SEM) was used to characterize the fracture mechanisms of the composites. The results show that, compared with 3 mm GF, 9 mm GF can significantly improve the strength of the composite better. Addition of PP-g-MAH, a kind of grafting agent, into the PP-30% LGF composite can result in a better mechanical properties because of the strengthening of the bonding interface between the matrix and the fiber. When the mass fraction of GF is 30% and the PP-g-MAH fraction is 6%, the mechanical properties of the composite are the best.展开更多
Previously, Polyvinyl Alcohol (PVA) and phenolic resin were used for resin impregnated bamboo fiber reinforced PP composites which was manufactures for resin impregnated bamboo fiber with polypropylene (PP). Resin imp...Previously, Polyvinyl Alcohol (PVA) and phenolic resin were used for resin impregnated bamboo fiber reinforced PP composites which was manufactures for resin impregnated bamboo fiber with polypropylene (PP). Resin impregnation method can show improvement on tensile strength of fiber. However, to reduce the contact surface area and low inter-facial shear strength (IFSS) between impregnated resin and matrix, using 40% weight fraction of bamboo fiber in PP matrix, PVA impregnated composites with mean flexural and tensile strength 10% higher than untreated composites were produced butphenolic resin impregnated fiber reinforced composition’s mechanical properties were decreased. In this study maleic anhydride grafted polypropylene (MAPP) was used to increase interfacial shear strength between resin impregnated fiber and PP. With 10% MAPP, IFSS between resin impregnated fiber and PP increased more than 100% and reinforced composites. MAPP with untreated, phenolic resin and PVA impregnated cases showed similar mechanical properties. Yet in water absorption test, the PVA treatment with bamboo/PP composites increased water absorption ratio. But with 10% MAPP, matrix PP water absorption ratio decreased like phenolic resin impregnated fiber reinforced composites. 10% MAPP with resin impregnated bamboo fiber reinforced PP composites can improve IFSS, mechanical properties of composite and can decrease water absorption PVA resin impregnated bamboo fiber reinforced composites.展开更多
The solid phase graft copolymerization of polypropylene (PP) andmethacrylic acid (MAA) was investigated. benzoyl peroxide(BPO) wasused as initia- tor. The influence of the reactive time,concentration of initiator and ...The solid phase graft copolymerization of polypropylene (PP) andmethacrylic acid (MAA) was investigated. benzoyl peroxide(BPO) wasused as initia- tor. The influence of the reactive time,concentration of initiator and monomer on degree of graft and meltflow index of graft copolymer(PP-MAA) was discussed. The effect ofgraft copolymer on mechanical properties of The glass fibre (GF)reinforced PP composites was also Studied. It is proved that graftcopolymer could obviously Increase the interfacial adhesive strengthbetween PP and GF.展开更多
Polypropylene(PP)is considered to be a rather promising material for HVDC cable insulation.Grafting modification has proved to be an effective method on the electrical property improvements of PP.This paper reports on...Polypropylene(PP)is considered to be a rather promising material for HVDC cable insulation.Grafting modification has proved to be an effective method on the electrical property improvements of PP.This paper reports on the highlyenhanced electrical properties of styrene-grafted polypropylene(PP-g-St)and their related mechanism.The influence of grafting styrene on crystallization structures,thermal properties and electrical properties of PP-g-St are characterized and analyzed.These results show that PP-g-St exhibits remarkably enhanced DC volume resistivity,suppressed space charge accumulation and improved DC breakdown strengths as compared to PP.Crystallization observation shows PP-g-St has small,imperfect spherulites with indistinct boundaries,which is strongly correlated to enhanced electrical properties.This study provides an effective grafting strategy to design high-performance HVDC cable insulation materials for bulk power transmission systems.展开更多
The surface of polypropylene (iPP) is modified with glow discharge plasma of Ar, so that the modified surfaces of iPP films are obtained. The studies of scanning electron microscopy (SEM) show the surface etching ...The surface of polypropylene (iPP) is modified with glow discharge plasma of Ar, so that the modified surfaces of iPP films are obtained. The studies of scanning electron microscopy (SEM) show the surface etching pattern of iPP films. The chemical structures of iPP films are confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The wetting properties of modified surfaces of iPP films are characterized by contact angle, and the free energy of surfaces is calculated. The free radical of modification surfaces of iPP is measured by chemical method. The surfaces of iPP are achieved with Ar plasma treatment followed by grafting copolymerization with styrene (St) in St. The grafting polymer of St onto iPP is characterized by FTIR. The grafting rate is dependent on plasma exposure time and discharge voltage. The studies show that homopolymerization of St is undergone at the sane time during the graftingcopolymerization of St onto/PP.展开更多
Branch length and density have critical effects on membrane performances; however, it is regarded to be traditionally difficult to investigate the relationship due to the uncontrolled membrane modification methods. In...Branch length and density have critical effects on membrane performances; however, it is regarded to be traditionally difficult to investigate the relationship due to the uncontrolled membrane modification methods. In this study, zwitterionic polymer with controlled grafting branch chain length(degree of polymerization) and grafting density(grafting chains per membrane area) was tethered to the microporous polypropylene membrane surface based on the combination of reversible addition-fragmentation chain transfer(RAFT) polymerization technique with click reaction. The modified membranes were tested by filtrating protein dispersion to highlight the correlations of branch chain length and grafting density with the membrane permeation performances. The pure water flux, the flux recovery ratio are positively and significantly, and the irreversible fouling negatively and significantly correlated with grafting density. These results demonstrate that the larger the coverage of the membrane with poly{[2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl) ammonium hydroxide}(PMEDSAH), the higher the pure water flux and the higher the flux recover ratio, and the lower the irreversible fouling, which shows that high grafting density is favorable to fouling reducing.展开更多
Effects of branches on the crystallization kinetics of polypropylene-g-polystyrene (PP-g-PS) and polypropylene-g- poly(n-butyl acrylate) (PP-g-PnBA) graft copolymers with well-defined molecular structures were s...Effects of branches on the crystallization kinetics of polypropylene-g-polystyrene (PP-g-PS) and polypropylene-g- poly(n-butyl acrylate) (PP-g-PnBA) graft copolymers with well-defined molecular structures were systematically investigated by DSC. The Avrami equation was used to analyze the isothermal crystallization process, while the analysis of nonisothermal crystallization process was based on the Jeziorny-modified Avrami model and Mo model. The kinetics results of isothermal and nonisothermal crystallization verified the peculiar effects of branches on the crystallization process of PP backbones in PP-g-PS and PP-g-PnBA graft copolymers: on one hand, the interaction between branches (n-n interaction between PS branches, or dipole-dipole interaction between PnBA branches) restrained the mobility and reptation ability of the PP backbones, which hindered the crystallization process; on the other hand, the heterogeneous nucleation effect resulting from the branched structure and fluctuation-assisted nucleation mechanism (caused by microphase separation between the PS or PnBA rich phase and the PP rich phase) became more pronounced with increasing branch length, which facilitated the crystallization process.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11605275 and 11675247)。
文摘In this study,to efficiently remove Pb(Ⅱ) from aqueous environments,a novel L-serine-modified polyethylene/polypropylene nonwoven fabric sorbent(NWF-serine)was fabricated through the radiation grafting of glycidyl methacrylate and subsequent L-serine modification.The effect of the absorbed dose was investigated in the range of 5–50 kGy.NWF-serine was characterized by Fourier transform infrared spectroscopy,thermogravimetric analysis,and scanning electron microscopy.Batch adsorption tests were conducted to investigate the influences of pH,adsorption time,temperature,initial concentration,and sorbent dosage on the Pb(Ⅱ) adsorption performance of NWF-serine.The results indicated that Pb(Ⅱ) adsorption onto NWF-serine was an endothermic process,following the pseudo-second-order kinetic model and Langmuir isotherm model.The saturated adsorption capacity was 198.1 mg/g.NWF-serine exhibited Pb(Ⅱ) removal rates of 99.8% for aqueous solutions with initial concentrations of 100 mg/L and 82.1% for landfill leachate containing competitive metal ions such as Cd,Cu,Ni,Mn,and Zn.Furthermore,NWF-serine maintained 86% of its Pb(Ⅱ) uptake after five use cycles.The coordination of the carboxyl and amino groups with Pb(Ⅱ) was confirmed using X-ray photoelectron spectroscopy and extended X-ray absorption fine structure analysis.
文摘The hydrophilicity, dyeing and antistatic ability of polypropylene microfibre (PPMF) were improved by plasma-induced vapor grafting with acrylic acid. The effects of plasma discharge time, power, liquid phase acrylic acid temperature and environmental temperature on grafting yield were investigated. The existence of grafted polyacrylic acid (PAA) was verified by ESCA and ATR FT-IR. The morphology of grafted PAA was directly observed by SEM. The wicking test shows that the hydrophilicity of modified PPMF is greatly enhanced. The dyeability test of modified PPMF was carried out using Dispersion Yellow. It was found that the dye uptake ratio is linear to the weight percent of grafting. The antistatic ability was indicated by specific resistance. The specific resistance of modified PPMF was reduced to 10(6) similar to 10(7) Ohm . cm, thus the antistatic ability was considerably improved.
基金the National Natural Science Foundation of China (29404031 ) and the Korea Science and Technology Foundation
文摘Grafting copolymerization of styrene and acrylic acid onto polypropylene fabric had been studied by using a pre-irradiation technique. The polypropylene fabric Samples were irradiated by Y-ray and electron beam under the conditions of air and nitrogen gas, respectively. The effect of absorbed dose, monomer concentration in solvent, reaction temperature and reaction time on the degree of grafting were determined. The effects of metallic salts and sulphuric acid on the grafting yield of acrylic acid were also examined. The samples irradiated by electron beam give a much higher degree of grafting than those by Y -ray when styrene was grafted to polypropylene fabric. However, the grafting yield of acrylic acid on polypropylene fabric in the presence of metallic salts and sultric acid showed the opposite results from the case of styrene. This effect is reasonably interpreted by assuming that the grafting is dominated by trapped radicals and peroxides in pre-irradiated polypropylene.
文摘BACKGROUND Chronic large to massive rotator cuff tears are difficult to treat and re-tears are common even after surgical repair.We propose using a synthetic polypropylene mesh to increase the tensile strength of rotator cuff repairs.We hypothesize that using a polypropylene mesh to bridge the repair of large rotator cuff tears will increase the ultimate failure load of the repair.AIM To investigate the mechanical properties of rotator cuff tears repaired with a polypropylene interposition graft in an ovine ex-vivo model.METHODS A 20 mm length of infraspinatus tendon was resected from fifteen fresh sheep shoulders to simulate a large tear.We used a polypropylene mesh as an interposition graft between the ends of the tendon for repair.In seven specimens,the mesh was secured to remnant tendon by continuous stitching while mattress stitches were used for eight specimens.Five specimens with an intact tendon were tested.The specimens underwent cyclic loading to determine the ultimate failure load and gap formation.RESULTS The mean gap formation after 3000 cycles was 1.67 mm in the continuous group,and 4.16 mm in the mattress group(P=0.001).The mean ultimate failure load was significantly higher at 549.2 N in the continuous group,426.4 N in the mattress group and 370 N in the intact group(P=0.003).CONCLUSION The use of a polypropylene mesh is biomechanically suitable as an interposition graft for large irreparable rotator cuff tears.
基金Funded by the Foundation for University Young Key Teacher by Zhejiang Province
文摘Membrane surfaces modified with poly(N-vinyl-2-pyrrolidone) (PNVP) can be endowed with hydrophilicity, biocompatibility and functionality. In this work, atmospheric pressure dielectric barrier discharge plasma graft polymerization of N-vinyl-2-pyrrolidone (NVP) onto polypropylene (PP) microporous membrane surface was studied. The experimental results reveal that plasma treatment conditions, such as discharge power, treatment time and adsorbed NVP amount, have remarkable effects on the grafting degree of NVP. Structural and morphological changes on the membrane surfaces were characterized by attenuated total reflection-Fourier transform infrared spectroscopy (FT-IR/ATR), X-ray photoelectron spectroscope (XPS) and field emission scanning electron microscopy (FE-SEM). Water contact angles of the membrane surfaces were also measured by the sessile drop method. Water contact angles on the membrane surfaces decrease with the increase of NVP grafting degree, which indicates an enhanced hydrophilicity for the modified membranes. The effects of grafting degrees on pure water fluxes were also measured. It is shown that pure water fluxes increase with grafting degree firstly and then decrease adversely. Finally, filtration of bovine serum albumin (BSA) solution and platelets adhesion of the PNVP modified membranes show good protein resistance and potential biocompatibility due to the enhancement of surface hydrophilicity.
基金The work was supported by the National Natural Science Foundation of China (Grant No. 20074033) and the High-TechResearch and Development Program of China (Grant no. 2002AA601230).
文摘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.
基金This project was supported by the National Natural Science Foundation of China (No. 20074033)the National Basic Research Program of China (No. 2003CB15705).
文摘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.
基金Project supported by the Natural Science Foundation of Beijing(No.2051002)Science and Technology Programme of Beijing(No.D0205004040421)
文摘By dynamic method under UV irradiation, commercial melt-blown polypropylene (PPMB) filter element was modified with acrylamide (AAm) using benzophenone (BP) as initiator. Attenuated total reflection-Fourier transform infrared spectroscopy and scanning electron microscope verified that polyacrylamide chain was grafted on the fiber surface of PPMB filter element. Elemental content analysis with energy dispersive X-ray of fibers revealed that the polymerization content in the inner part of filter element was relatively higher than that in the outer. Degree of grafting changed with initiator concentration, monomer concentration, reaction temperature and reached 2.6% at the reaction condition: CBp=0.06 mol/L, CAAm=2.0 mol/L, irradiation time: 80 min, temperature: 60℃. Relative water flux altered with the hydrophilicity and pore size of filter element. In the antifouling test, the modified filter gave greater flux recovery (approximately 70%) after filtration of the water extract of Liuweidihuang, suggesting that the fouling layer was more easily reversible due to the hydrophilic nature of the modified filter.
基金Funded by National Natural Science Foundation of China(Nos.51705295,51778351)the Science and Technology Project for the Universities of Shandong Province (No.J16LA58)Shandong University of Science and Technology Research Fund (No.2018 TDJH101)
文摘To study the effect of some parameters, such as, length and fraction of glass fiber (GF), and the fraction of maleic anhydride grafted polypropylene (PP-g-MAH), on the mechanical properties of glass fiber reinforced polypropylene (GF/PP) composites, tensile tests, bending tests and impact tests were conducted. Scanning electron microscope (SEM) was used to characterize the fracture mechanisms of the composites. The results show that, compared with 3 mm GF, 9 mm GF can significantly improve the strength of the composite better. Addition of PP-g-MAH, a kind of grafting agent, into the PP-30% LGF composite can result in a better mechanical properties because of the strengthening of the bonding interface between the matrix and the fiber. When the mass fraction of GF is 30% and the PP-g-MAH fraction is 6%, the mechanical properties of the composite are the best.
文摘Previously, Polyvinyl Alcohol (PVA) and phenolic resin were used for resin impregnated bamboo fiber reinforced PP composites which was manufactures for resin impregnated bamboo fiber with polypropylene (PP). Resin impregnation method can show improvement on tensile strength of fiber. However, to reduce the contact surface area and low inter-facial shear strength (IFSS) between impregnated resin and matrix, using 40% weight fraction of bamboo fiber in PP matrix, PVA impregnated composites with mean flexural and tensile strength 10% higher than untreated composites were produced butphenolic resin impregnated fiber reinforced composition’s mechanical properties were decreased. In this study maleic anhydride grafted polypropylene (MAPP) was used to increase interfacial shear strength between resin impregnated fiber and PP. With 10% MAPP, IFSS between resin impregnated fiber and PP increased more than 100% and reinforced composites. MAPP with untreated, phenolic resin and PVA impregnated cases showed similar mechanical properties. Yet in water absorption test, the PVA treatment with bamboo/PP composites increased water absorption ratio. But with 10% MAPP, matrix PP water absorption ratio decreased like phenolic resin impregnated fiber reinforced composites. 10% MAPP with resin impregnated bamboo fiber reinforced PP composites can improve IFSS, mechanical properties of composite and can decrease water absorption PVA resin impregnated bamboo fiber reinforced composites.
文摘The solid phase graft copolymerization of polypropylene (PP) andmethacrylic acid (MAA) was investigated. benzoyl peroxide(BPO) wasused as initia- tor. The influence of the reactive time,concentration of initiator and monomer on degree of graft and meltflow index of graft copolymer(PP-MAA) was discussed. The effect ofgraft copolymer on mechanical properties of The glass fibre (GF)reinforced PP composites was also Studied. It is proved that graftcopolymer could obviously Increase the interfacial adhesive strengthbetween PP and GF.
基金supported by the Programs Foundation of SINOPEC(No.XLY19005)the Innovative Research Group Project of National Natural Science Foundation of China(No.51921005)。
文摘Polypropylene(PP)is considered to be a rather promising material for HVDC cable insulation.Grafting modification has proved to be an effective method on the electrical property improvements of PP.This paper reports on the highlyenhanced electrical properties of styrene-grafted polypropylene(PP-g-St)and their related mechanism.The influence of grafting styrene on crystallization structures,thermal properties and electrical properties of PP-g-St are characterized and analyzed.These results show that PP-g-St exhibits remarkably enhanced DC volume resistivity,suppressed space charge accumulation and improved DC breakdown strengths as compared to PP.Crystallization observation shows PP-g-St has small,imperfect spherulites with indistinct boundaries,which is strongly correlated to enhanced electrical properties.This study provides an effective grafting strategy to design high-performance HVDC cable insulation materials for bulk power transmission systems.
基金financially supported by the National Natural Science Foundation of China(No.50673073)the Doctoral Foundation of Ministry of Education of China(No.20060056043)
文摘The surface of polypropylene (iPP) is modified with glow discharge plasma of Ar, so that the modified surfaces of iPP films are obtained. The studies of scanning electron microscopy (SEM) show the surface etching pattern of iPP films. The chemical structures of iPP films are confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The wetting properties of modified surfaces of iPP films are characterized by contact angle, and the free energy of surfaces is calculated. The free radical of modification surfaces of iPP is measured by chemical method. The surfaces of iPP are achieved with Ar plasma treatment followed by grafting copolymerization with styrene (St) in St. The grafting polymer of St onto iPP is characterized by FTIR. The grafting rate is dependent on plasma exposure time and discharge voltage. The studies show that homopolymerization of St is undergone at the sane time during the graftingcopolymerization of St onto/PP.
基金financially supported by the National Natural Science Foundation of China (No. 21371008)
文摘Branch length and density have critical effects on membrane performances; however, it is regarded to be traditionally difficult to investigate the relationship due to the uncontrolled membrane modification methods. In this study, zwitterionic polymer with controlled grafting branch chain length(degree of polymerization) and grafting density(grafting chains per membrane area) was tethered to the microporous polypropylene membrane surface based on the combination of reversible addition-fragmentation chain transfer(RAFT) polymerization technique with click reaction. The modified membranes were tested by filtrating protein dispersion to highlight the correlations of branch chain length and grafting density with the membrane permeation performances. The pure water flux, the flux recovery ratio are positively and significantly, and the irreversible fouling negatively and significantly correlated with grafting density. These results demonstrate that the larger the coverage of the membrane with poly{[2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl) ammonium hydroxide}(PMEDSAH), the higher the pure water flux and the higher the flux recover ratio, and the lower the irreversible fouling, which shows that high grafting density is favorable to fouling reducing.
基金financially supported by the National Natural Science Foundation of China for the projects(Nos.51233005 and 51073149)
文摘Effects of branches on the crystallization kinetics of polypropylene-g-polystyrene (PP-g-PS) and polypropylene-g- poly(n-butyl acrylate) (PP-g-PnBA) graft copolymers with well-defined molecular structures were systematically investigated by DSC. The Avrami equation was used to analyze the isothermal crystallization process, while the analysis of nonisothermal crystallization process was based on the Jeziorny-modified Avrami model and Mo model. The kinetics results of isothermal and nonisothermal crystallization verified the peculiar effects of branches on the crystallization process of PP backbones in PP-g-PS and PP-g-PnBA graft copolymers: on one hand, the interaction between branches (n-n interaction between PS branches, or dipole-dipole interaction between PnBA branches) restrained the mobility and reptation ability of the PP backbones, which hindered the crystallization process; on the other hand, the heterogeneous nucleation effect resulting from the branched structure and fluctuation-assisted nucleation mechanism (caused by microphase separation between the PS or PnBA rich phase and the PP rich phase) became more pronounced with increasing branch length, which facilitated the crystallization process.