Water-ethanol separation by pervaporation through plasma graft polymerized membranes

Water-ethanol permselective membranes were prepared through plasma graft polymerization of acrylic acid, methacrylic acid, and acrylamide onto porous polypropylene film. In these membranes, the functions of permseparation and mechanical properties are shared respectively to the graft polymer layer and the substrate film. Higher permselectivity of water is achieved with the ionization of the acrylic acid and the methacrylic acid-grafted membranes. Permselectivity is dependent on the degree of grafting, and it is necessary to fill the pores of substrate film with graft polymers. Permseparation of water was investigated with respect to the feed ethanol concentration and also to the temperature dependence.     

Grafting of acrylamide to nylon-6 by electron beam preirradiation. IV. Sorption of water in nylon grafted acrylamide membranes

Membranes prepared by extensive grafting of acrylamide onto nylon-6 films exhibit high water sorption capacity. Swelling of the membranes increases after treatment with aqueous solutions of formic acid. Sorption of water into these annealed membranes reaches values of ca. 25 moles of water per mole of grafted acrylamide. The sorption characteristics of the swollen membrane-gels crosslinked with bis-acrylamide were explored. Membranes grafted with acrylamide, crosslinked with bis-acrylamide and annealed with formic acid reach the maximum swelling capacity at low graft yields.     

HTPB‐based polyurethaneurea membranes for recovery of aroma compounds from aqueous solution by pervaporation

Hydroxyterminated polybutadiene (HTPB)‐based polyurethaneurea (PU), HTPB‐PU, was synthesized by two‐step polymerization and was firstly used as membrane materials to recover aroma, ethyl acetate (EA), from aqueous solution by pervaporation (PV). The effects of the number–average molecular weight (M_n) of HTPB, EA in feed, operating temperature, and membrane thickness on the PV performance of HTPB‐PU membranes were investigated. The membranes demonstrated high EA permselectivity as well as high EA flux. The DSC result showed two transition temperatures in the HTPB‐PU membrane and contact angle measurements revealed the difference of hydrophobicity of the membrane at both sides, which were induced by glass plate and air, respectively, due to movement of the soft hydrophobic polybutadiene (PB) segments in HTPB‐PU chains. Furthermore, the PV performance of the HTPB‐PU membrane with the hydrophobic surface facing the feed was much better than that with the hydrophilic surface. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 552–559, 2007     

Plasma-grafting of fluoroalkyl methacrylate onto PDMS membranes and their VOC separation properties for pervaporation

A polydimethylsiloxane (PDMS) membrane was improved by graft polymerization of 1H,1H,9H-hexadecafluorononyl methacrylate (HDFNMA) by plasma, which had the effect of increasing the selectivity for volatile organic compounds (VOCs). The use of an easy quantitative analysis for the pervaporation through plasma-grafted PDMS membranes was investigated. The degrees of grafting on the inside and reverse side of the grafted PDMS membranes were lower than on the surface. Only part of the HDFNMA sorbed into the PDMS membrane was grafted onto the PDMS membrane. The relationship between the feed concentration and the permeate concentration was observed to be linear. The pervaporation through the grafted PDMS membrane could be used for easy quantitative analysis. The solubility of VOCs for the grafted PDMS membrane was high when compared with the solubility for the PDMS membrane. The grafted PDMS membrane that had high VOC concentrations of the sorbed solution showed an excellent separation performance. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1835–1844, 1999     

Plasma surface graft of acrylic acid onto a porous poly(vinylidene fluoride) membrane and its riboflavin permeation

Acrylic acid was grafted onto the surface of commercial poly(vinylidene fluoride) (PVDF) membrane using plasma polymerization techniques. Graft reaction was confirmed by X-ray photoelectron spectroscopy (XPS) spectra and attenuated total reflectance Fourier transform infrared spectra. Grafting rate was dependent on plasma exposure time. For argon plasma at 30 W, grafting rate decreased after maximum rate was observed at 30 s exposure. PVDF membrane with 30 s plasma exposure and subsequently grafted with acrylic acid (AA-3) showed the greatest O_1s/F_1s area ratio in XPS spectra. Thus its graft density and degree of polymerization were the largest among the graft membranes. Permeation of riboflavin through all poly(acrylic acid)-g-PVDF membranes showed a decrease in permeability of riboflavin in pH 4–5. © 1996 John Wiley & Sons, Inc.     

Synthesis and characterization of hydrophobically modified poly(vinyl alcohol) hydrogel membrane

Hydrophobically modified poly(vinyl alcohol), [PVA] was synthesized by graft copolymerization of N-tertiary butyl acrylamide [NTBA] onto PVA by free radical polymerization. The incorporation of NTBA onto PVA chains was confirmed by elemental analysis, FT-IR and NMR spectroscopy. A series of graft copolymers with different contents of NTBA were prepared and membranes were casted from these copolymer solutions in dimethyl sulfoxide. The increase in hydrophobicity with an increase in NTBA content was investigated by contact angle measurements. The swelling behaviour of membranes as a function of temperature, hydrophobic content, annealing temperature and period was studied. Permeability of solutes through these membranes was investigated as a function of solute size, membrane hydrophobicity and temperature. The swelling behaviour of the copolymer membranes showed that the lower content of NTBA gives discontinuous volume transition with respect to temperature whereas, the presence of higher amounts of NTBA showed decreased swelling ratios with very little influence of temperature on the swelling. The permeabilities of solutes through these membranes were strongly dependent on the size of the solute, solution temperature and hydrophobicity of the membrane. The copolymer membranes were further characterized using DSC, DMA and XRD. The peak becomes broader as the NTBA content increases.     

Low protein fouling polypropylene membrane prepared by photoinduced reversible addition‐fragmentation chain transfer polymerization

In this study, 2‐hydroxyethyl methacrylate and N‐isopropyl acrylamide was block grafted onto the polypropylene macroporous membrane surface by photo‐induced reversible addition‐fragmentation chain transfer (RAFT) radical polymerization with benzyl dithiobenzoate as the RAFT agent. The degree of grafting of poly(2‐hydroxyethyl methacrylate) on the membrane surface increased with UV irradiation time and decreased with the chain transfer agent concentration increasing. The poly(2‐hydroxyethyl methacrylate)‐ grafted membranes were used as macro chain transfer agent for the further block graft copolymerization of N‐isopropyl acrylamide in the presence of free radical initiator. The degree of grafting of poly(N‐isopropyl acrylamide) increased with reaction time. Furthermore, the poly(2‐hydroxyethyl methacrylate)‐ grafted membrane with a degree of grafting of 0.48% (wt) showed the highest relative pure water flux and the best antifouling characteristics of protein dispersion. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Fouling control in a submerged membrane‐bioreactor by the membrane surface modification

To improve the antifouling characteristics, polypropylene microporous membranes (PPHFMMs) were surface‐modified by the sequential photoinduced graft polymerization of acrylic acid and acrylamide. The grafting density and the grafting chain length, which played important roles in the antifouling characteristics, were controlled in the first and the second step, respectively. The ATR/FTIR results clearly indicated the successful modification on the membrane surface. The static water contact angle of the modified membrane reduced obviously with the increase of the grafting chain length. The contact angle of the acrylic acid modified membranes was lower than that of the acrylamide modified membrane with similar grafting chain length. The grafting chain length increased with the increase of UV irradiation time and monomer concentration. The grafting chain length of poly(acrylic acid) (PAAc) was lower than that of the polyacrylamide (PAAm) under the same polymerization conditions. Pure water flux for the modified membranes increased with the increase of grafting chain length, and had maximums. The antifouling characteristics of the modified membranes in a submerged membrane‐bioreactor (SMBR) were evaluated. The modified membranes showed better filtration performances in the SMBR than the unmodified membrane, and the acrylic acid grafted membrane presented better antifouling characteristics than acrylamide modified membranes. The results demonstrated that the surface carboxyl‐containing membranes were better than the surface amido‐containing membranes. The results of Pearson correlations demonstrated that the PAAc modified membranes with longer grafting chain length had higher flux recoveries, while the PAAm modified membranes with longer grafting chain length had lower flux recoveries. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Divinyl benzene cross‐linked HTPB‐based polyurethaneurea membranes for separation of p‐/o‐xylene mixtures by pervaporation

Cross‐linked hydroxy terminated polybutadiene (HTPB)‐based polyurethaneurea (PU), HTPB‐divinyl benzene (DVB)‐PU, was synthesized by a three‐step polymerization process. It was first used as membrane material to separate p‐/o‐xylene mixtures by pervaporation (PV). The effects of the content of cross‐linker DVB, feed concentration, and operating temperature on the PV performance of HTPB‐DVB‐PU membranes were investigated. The membranes demonstrated p‐xylene permselectivity as well as high total flux. The introduction of DVB significantly enhanced the temperature resistance ability of the HTPB‐DVB‐PU membranes. With increasing DVB content, the separation factor increased while the total flux decreased a little. The highest separation factor reaches 2.01 and the total flux is 33 g/m²h with feed concentration of 10 wt % p‐xylene at 30°C. These PV performances with increasing DVB content were explained in terms of the view point of chemical compositions and physical structures of the HTPB‐DVB‐PU membranes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

有机硅烷交联PDMS/陶瓷复合膜的制备及渗透汽化汽油脱硫性能

采用有机硅烷γ-氨丙基三甲氧基硅氧烷（APTMS）,对聚二甲基硅氧烷（PDMS）进行交联改性,以ZrO₂/Al₂O₃陶瓷复合膜为支撑体,制备了一系列有机硅烷交联的PDMS/陶瓷复合膜。通过扫描电镜（SEM）、傅里叶红外光谱（FTIR）、热重分析（TGA）对改性效果和膜结构进行了表征。将所制备的PDMS/陶瓷复合膜应用于渗透汽化脱除模拟汽油中的有机硫化物（噻吩）,考察了交联剂APTMS含量、操作温度、料液含硫量等因素对复合膜渗透汽化脱硫性能的影响。实验结果表明,有机硅烷交联的PDMS膜相比于传统正硅酸乙酯（TEOS）交联的PDMS膜,通量和硫富集因子均有所提高。随着进料温度和原料液中硫含量的升高,膜的渗透通量均增大,而硫富集因子均减小。当APTMS质量分数为15%、进料温度为25℃、噻吩质量浓度为100mg/kg时,渗透通量为0.46 kg/（m²·h）,硫富集因子达到3.5。     

淀粉丙烯酰胺表面控制反应机理及接枝产物结构表征

以木薯淀粉和丙烯酰胺为主要原料,采用反相乳液聚合方法合成淀粉丙烯酰胺接枝共聚物,并通过红外光谱、电镜扫描、X射线衍射、热分析等手段对接枝共聚产物进行结构分析和聚合机理探讨。实验结果显示,淀粉与丙烯酰胺的反应主要发生在淀粉团粒表面,符合表面控制反应机理;接枝共聚物中含有淀粉和丙烯酰胺成分;共聚反应改变了原淀粉的聚集形态,接枝产物基本上为无定形的聚集态结构;但对淀粉的热稳定性影响不显著。     

Surface modification of polyamide TFC membranes via redox‐initiated graft polymerization of acrylic acid

In this work, the redox‐initiated graft polymerization of acrylic acid (AA) onto the surface of polyamide thin film composite membranes has been carried out to enhance membrane separation and antifouling properties. The membrane surface characteristics were determined through the attenuated total reflection Fourier transform infrared spectra, scanning electron microscopy, atomic force microscopy, and water contact angles. The membrane separation performance was evaluated through membrane flux and rejection of some organic compounds such as reactive red dye (RR261), humic acid, and bovine serum albumin in aqueous feed solutions. The experimental results indicated that the membrane surfaces became more hydrophilic and smoother after grafting of AA. The modified membranes have a better separation performance with a significant enhancement of flux at a great retention. The fouling resistance of the modified membranes is also clearly improved with the higher maintained flux ratio and the lower irreversible fouling factor compared to the unmodified one. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45110.     

Surface photografting of hydrophilic vinyl monomers onto diethyldithiocarbamated polydimethylsiloxane

Photografting of vinyl monomers has been studied to make hydrophilic polydimethylsiloxane (PDMS) surfaces. A chlorine-containing polydimethylsiloxane (C-PDMS) prepared by polymerization of chloromethylheptamethylcyclotetrasiloxane was photocured on a glass plate. The crosslinked C-PDMA was subjected to a reaction with sodium diethyldithiocarbamate. The diethyldithiocarbamated PDMS was then photoirradiated in the presence of hydrophilic vinyl monomers such as 2-hydroxyethylmethacrylate and acrylamide to afford surface-grafted PDMS. Several vinyl monomers were found to graft onto the PDMS surface, as revealed by their attenuated total reflectance infrared and ESCA spectra. Hydrophilicity of the grafted PDMS surfaces was confirmed by the decrease in their water contact angle.     

多孔膜基材对等离子体接枝膜微观结构的影响

采用等离子体诱导接枝聚合法,在有机聚偏氟乙烯(PVDF)膜、尼龙(N6)膜和无机多孔阳极氧化铝(PAA)膜上接枝甲基丙烯酸(MAA),系统地研究了多孔膜基材及接枝工艺条件对接枝开关膜微观结构的影响。结果发现,对于PVDF基材膜,单体溶液脱气次数越多接枝率越大。对于不同类别的多孔膜基材,采用相同工艺条件接枝时,N6膜的接枝率高于PVDF膜,PAA膜接枝率最低。在接枝率相近的时候,接枝层在PVDF膜整个断面孔内和表面均存在,而N6膜则主要集中在表层。在PAA膜上接枝时发现,等离子体照射功率的强弱对基材膜的影响很大,当功率超过50W时,PAA膜表层就会被刻蚀而导致膜的质量减轻。     

Cationic Graft Polymerization of 2-Oxazolines on Poly(vinyl alcohol) Derivatives

The graft polymerization of various monomers onto PVA has been studied by radical polymerization mechanism. Successful grafting of acrylonitrile (AN), acrylamide (AAm), acrylic acid, methyl methacrylate, and vinyl acetate was reported by using chemical (Minoet al., 1959; Ide, 1961; Maskimov et al., 1965) and radiation (Misra et al., 1987) methods. On the other hand, less attention has been paid to ionic graft polymerization. Sasson and Zilkha reported on grafting formaldehyde onto potassium-metallated PVA (Sasson and Zilkha, 1969). Galin studied grafting of AN and propane sulfone onto sodium-metallated PVA (Galin, 1971). We used the same anionic system for the polymerization of AAm (Ikeda and Suzuki, 1980).     

Preparation of ion‐exchange membranes by hydrolysis of radiation‐grafted polyethylene‐g‐polyacrylamide membranes

Polyethylene‐g‐polyacrylamide membranes were prepared by graft polymerization of acrylamide onto polyethylene films using a preirradiation method. The ion‐exchange membranes were obtained by the hydrolysis of grafted films so as to transform amide groups into carboxyl groups. The fraction of amide groups transformed into carboxyl groups was limited to ～0.5. The characterization and thermal behavior of membranes with different degrees of grafting were evaluated by FTIR, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) measurements. The heat of fusion and the crystallinity of polyethylene decreased considerably in the hydrolyzed membranes depending on the degree of grafting. It was found that the grafting of acrylamide led to the reduction in crystallinity due to disruption of the crystallites (crystal defects) and dilution of the inherent crystallinity (dilution effect). The contribution of the hydrolysis step to the crystallinity decrease was negligible. The thermal stability of the membranes as obtained from TGA showed considerable enhancement after hydrolysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 149–154, 2003     

Plasma‐induced solid‐state polymerization modified poly(tetrafluoroethylene) membrane for pervaporation separation of aqueous alcohol mixtures

Acrylamide (AAm) solid state polymerization was induced using argon plasma to improve the pervaporation performance of poly(tetrafluoroethylene) (PTFE) membranes (PTFE‐g‐PAAm) in aqueous alcohol mixtures. The surface morphology, chemical composition, and hydrophilicity changes in the PTFE and PTFE‐g‐PAAm membranes were investigated using ATR‐FTIR, SEM, AFM, X‐ray photoelectron spectroscopy, and water contact angle measurements. The surface hydrophilicity rapidly increased with increasing Ar exposure time, but decreased after longer Ar exposure time because of the degradation in the PTFE‐g‐PAAm membrane grafted layer. Compared with the hydrophilicity of the pristine PTFE membrane (water contact angle = 120°), the argon plasma induced acrylamide (AAm) solid‐state polymerization onto the PTFE surface (water contact angle = 43.3°) and effectively improved the hydrophilicity of the PTFE membrane. This value increases slowly with increasing aging time and then reaches a plateau value of about 50° after 10 days of storage under air. The pervaporation separation performances of the PTFE‐g‐PAAm membranes were higher than that of the pristine PTFE membrane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:909–919, 2006     

Functionalizing of polyurethane surfaces by photografting with hydrophilic monomers

Poly(ester urethane) (PU) with functional groups (amide, hydroxyl, carboxyl) on surfaces were prepared by grafting monomers such as acrylamide (AAm), hydroxyethyl acrylate (HEA), and methacrylic acid (MAA) onto the PU membranes. Grafting copolymerization was carried out by the combined use of photooxidization and UV irradiation grafting. The PU membrane was photooxidized in hydrogen peroxide solution under UV light to yield hydroperoxide groups on the surface and then irradiation grafting with monomer in water. The ATR‐FTIR spectrum, X‐ray photoelectron spectroscopy characterized the grafted copolymers and verified the occurrence of grafting copolymerization. The results showed that the content of hydroperoxide groups yielded was dependent on the photooxidization time and reached maximum at about 8 h. Grafting copolymerization was enhanced when irradiating by UV light. The degree of grafting was increased with the increase of content of hydroperoxide groups, irradiation time, and monomer concentration. The grafting copolymerization was enhanced when an appropriate amount of ferrous ions was added. After grafting, the wettability of PU and the water absorption percentage increased with the degree of grafting. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2505–2512, 2000     

利用低温等离子体进行聚砜膜的表面改性

利用低温等离子体引发接枝反应,在表面带负电的聚砜膜上引入带正电的单体聚合物,从而减少膜表面净电荷.通过测定膜的电渗流量来确定其表面电荷以作为膜表面改性效果的定量评价标准.考察了照射时间、照射功率和接枝反应时间对膜改性效果的影响,并对比了原膜与改性膜的膜污染特性.结果表明,改性后的膜表面净电荷减少,抗污染特性提高.     

The effect of polymer surface modification via interfacial polymerization on polymer–protein interaction

Membrane separation is an important processing technology used for separating food ingredients and fractionating value‐added components from food processing byproducts. Long‐term performance of polymeric membranes in food protein processing is impeded by the formation of fouled layers on the membrane surface as a result of protein adsorption onto the membrane surface. Surface modification of synthetic membranes, i.e., changing surface characteristics to reduce protein adsorption permanently, is one of the innovative ways of reducing the fouling of membrane surfaces. In this study, surface modification of flat‐sheet ultrafiltration membrane, polyethersulfone (PES), was investigated in improving the hydrophilicity of PES surfaces, thereby reducing adsorption of the protein caused by hydrophobic–hydrophobic interaction between the protein and the membrane. Hydrophilic polymer grafting through thin‐film composite using interfacial polymerization was employed to improve the hydrophilicity of the commercial PES membranes. Poly(vinyl alcohol), poly(ethylene glycol), and chitosan were chosen as hydrophilic polymers to graft on PES membrane because of their excellent hydrophilic property. Modified PES membranes were characterized by contact angle, FTIR, XPS, and AFM. Contact angles of modified PES membranes were reduced by 25 to 40% of that of the virgin PES membrane. XPS spectrum supported that the PES membranes were successfully modified by interfacial polymerization. Tapping‐mode AFM was used to examine the changes in surface topography of modified PES membranes. The PES membranes modified by interfacial polymerization showed lower roughness (from 1.2 to 2.0 nm) than that of virgin PES membrane (2.1 nm). The results of these instrumental analyses indicated that the PES membranes were successfully enhanced hydrophilically through interfacial polymerization. The protein adsorption on the modified membranes was reduced by 30 to 35% as a result of surface modification of the PES membranes using interfacial polymerization technique. Published 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009