Preparation and characterization of a composite nanofiltration membrane interfacially polymerized from cis,cis‐1,3,5‐triaminocyclohexane and trimesoyl chloride

cis,cis‐1,3,5‐Triaminocyclohexane (TAC) was synthesized and used to prepare composite nanofiltration (NF) membranes by interfacial polymerization with trimesoyl chloride (TMC). The surface elemental composition, morphology, and hydrophilicity of the prepared NF membranes were characterized. The separation performances were examined with various salts and polyethylene glycol (PEG400, PEG600) solutions. The effects of preparation conditions were also systematically studied. The NF membrane was negatively charged and exhibited a salt rejection in the order Na₂SO₄ (98.2%) > MgSO₄ (90.8%) > MgCl₂ (84.5%) > NaCl (54.6%). The water permeability was 1.56 L m^?2 h^?1 bar^?1, and the molecular weight cutoff was 600 Da. The TAC/TMC membrane exhibited some characteristics that were different from the ones made from common diamines such as m‐phenylenediamine: (1) the surface was smoother, without a ridge‐and‐valley structure; (2) there were two kinds of crosslinking points in the polyamide chains; (3) the active layer was formed faster (only 5 seconds was required to reach a Na₂SO₄ rejection of 98%). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43511.     

3,5-二氧基苯甲酰哌嗪和均苯三甲酰氯界面聚合法制备复合纳滤膜

A new aromatic diamine,3,5-diaminobenzoylpiperazine (3,5-DABP),was synthesized from 3,5-diaminobenzoic acid and 1-formyl piperazine.The structure of 3,5-DABP was identified by FT-IR spectra and 1H NMR spectra.With 3,5-DABP as aqueous monomer and trimesoyl chloride (TMC) as organic monomer,thin film composite (TFC) nanofiltration membranes were prepared by interfacial polymerization technology.The salt rejection order of these TFC membranes is Na2SO4>MgSO4>MgCl2>NaCl.This sequence indicates that the membranes are negatively charged.     

Preparation and characterization of carboxylated multiwalled carbon nanotube/polyamide composite nanofiltration membranes with improved performance

Polyamide thin‐film composite nanofiltration (NF) membranes were prepared via the interfacial polymerization (IP) process of piperazine and 1,3,5‐trimesoyl chloride on the polysulfone/nonwoven fabric ultrafiltration membrane surface. Carboxylated multiwalled carbon nanotubes (cMWNTs) were incorporated into the aqueous phase during the IP process to improve the membrane performance. The composition and morphology of the membrane surface were examined by means of attenuated total reflectance–Fourier transform infrared spectroscopy, scanning electron microscopy–energy dispersive spectrometry, and atomic force microscopy. The effects of the cMWNTs content on the membrane hydrophilicity, separation performance, and antifouling properties were characterized through water contact angle and crossflow filtration measurements. The experimental results show that membrane surface hydrophilicity, water permeability, salt rejection (R ), and antifouling properties all improved. In particular, when the cMWNTs content was 50 ppm, the magnesium sulfate R of the composite NF membrane reached a maximum value of 98.5%; meanwhile, the membrane obtained an obviously enhanced water flux (62.1 L m^?2 h^?1 at 0.7 MPa), which was two times larger than that of the original NF membrane. The modified NF membranes showed enhanced antifouling properties; this was mainly attributed to changes in the microstructures and surface features of the polyamide layer after the addition of the cMWNTs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45268.     

Codeposition of catechol–polyethyleneimine followed by interfacial polymerization for nanofiltration membranes with enhanced stability

Thin‐film composite (TFC) nanofiltration (NF) membranes were fabricated via the codeposition of catechol (CCh) and polyethyleneimine (PEI) followed by subsequent interfacial polymerization with trimesoyl chloride (TMC) on the surface of polysulfone ultrafiltration substrates. The detailed structures and surface properties were characterized by X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, ζ potential analysis, and water contact angle measurement. The surface properties, including the roughness, hydrophilicity, surface potential, and NF performances, were facilely tuned through variation of the codeposition time of CCh–PEI for the prepared TFC membranes. The optimized membrane achieved a high rejection (ca. 93%) of MgCl₂ with a flux of around 31 L m^?2 h^?1 under 0.7 MPa. The results also reveal that the codeposition process endowed the final membranes with much better structural stability in alcohol and improved chlorine resistance compared to commonly interfacial polymerized ones with PEI and TMC. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45422.     

Preparation and characterization of braided tube reinforced polyacrylonitrile hollow fiber membranes

Polyacrylonitrile (PAN) and polyester (PET) braided hollow tube that used as a special reinforcement are braided from their filaments via two‐dimensional weaving techniques. PAN braided tube reinforced homogeneous PAN hollow fiber membranes and PET braided tube reinforced heterogeneous PAN hollow fiber membranes are prepared by concentric circles squeezed‐coated spinning method. As for PAN hollow fiber membrane, the effects of PAN concentration on the performance of the prepared hollow fiber membranes are investigated in terms of pure water flux, protein rejection, mechanical strength, and morphology observations by a scanning electron microscope (SEM). The interfacial bonding state of the braided tube reinforced PAN hollow fiber membranes is studied by constant speed stretching method. Results show that the breaking strength of two‐dimensional braided tube reinforced PAN hollow fiber membranes is higher than 80 MPa. The structure of separation surface is similar to the structure of an asymmetric membrane. With the increase of polymer concentration, the membrane flux decreases while the retention rate of BSA increase. The membrane porosity and maximum pore size have the same decreasing tendency as the increase of PAN concentration. The results also show that the interfacial bonding state of the PAN two‐dimensional braided tube reinforced homogeneous PAN hollow fiber membranes is better than that of the PET two‐dimensional braided tube reinforced heterogeneous PAN hollow fiber membranes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41795.     

Preparation and characterization of high‐selectivity hollow fiber composite nanofiltration membrane by two‐way coating technique

A novel coating technique, named as two‐way coating (TWC), was explored to prepare hollow fiber composite (HFC) nanofiltration (NF) membrane through interfacial polymerization from piperazine (PIP) and trimesoyl chloride (TMC) on the lumen side of hollow fiber polysulfone ultrafiltration membrane with an effective membrane area of 0.4 m². The optimum preparation conditions were systematically investigated and obtained as follows: PIP 0.023 mol/L, TMC 0.0057 mol/L, air blowing rate 2.7 m/s for 30 min after aqueous coating, aqueous coating pressure 0.1 MPa, organic solution flowing rate 0.32 m/s, and heat treating time 3 min. The resultant HFC membrane showed a high selectivity of divalent ion and monovalent ion. Salt rejections of MgSO₄ and NaCl were 98.13 and 18.6% with the permeate flux of 32.6 and 40.2 L m^?2 h^?1 at 0.7 MPa, respectively. Field emission scanning electron microscopy images indicated that composite membrane prepared by TWC technique had a uniform active layer from the upper end to the bottom of the hollow fiber. And the salt rejection and permeate flux showed almost no difference between different membrane sections. Stability results suggested that good reproducibility could be obtained by TWC technique for the preparation of high‐performance HFC NF membrane. The resultant NF membrane showed a high removal rate of chemical oxygen demand and chroma of landfill leachate which were approximately 100%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41187.     

A thin film composite membrane supported by a hydrophilic poly(vinyl alcohol‐co‐ethylene) nanofiber membrane: Preparation,characterization, and application in nanofiltration

In this study, a fabricated hydrophilic poly(vinyl alcohol‐co‐ethylene) (PVA‐co‐PE) nanofiber membrane was used as the middle support layer to prepare thin film composite (TFC) membranes for nanofiltration. The effects of the supporting nonwoven layer, grams per square meter (GSM) of nanofiber, reaction time, heat treatment, monomer concentration, operating pressure, and pH value on the separation performance of the TFC membranes were analyzed. These results show that the TFC membranes prepared with the PVA‐co‐PE nanofiber membrane can be used to filtrate different metal ions. For NaCl, Na₂SO₄, CaCl₂, CuCl₂, CuSO₄, and methyl orange solutions, the rejection rates of the TFC membrane with nonwoven polyester as the supporting layer and a nanofiber GSM of 12.8 g/m² are 87.9%, 93.4%, 92.0%, 93.1%, 95.8%, and 100%, respectively. This indicates the potential application of the PVA‐co‐PE nanofiber membrane in the preparation of nanofiltration and reverse‐osmosis TFC membranes. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46261.     

Preparation and characterization of novel polyamide paraffin MEPCM by interfacial polymerization technique

A novel polyamide‐paraffin microencapsulated phase change material (MEPCM) was prepared by interfacial polymerization technique using 1,3,5‐benzenetricarbonyl chloride (TMC) and ethylenediamine as monomers and 30# paraffin as core material. Morphology, chemical composition, thermal properties of the MEPCM were studied by scanning electron micrograph, FT‐IR spectrum, differential scanning calorimeter analysis and thermogravimetric analysis. The solvent resistances of the MEPCM were also studied by observing the morphology changes of the MEPCM under optical microscope. Results indicate that the MEPCMs prepared under optimal conditions have spherical shape with average diameter of 6.4 µm, and the polyamide shell has successfully packaged the paraffin core. The MEPCM has a high efficiency in storing and releasing heat. The latent heat is 121.7 J/g and the microencapsulation ratio is 87%, 5% weight loss temperature is 260°C. The MEPCM is stable in H₂SO₄ solution (ω = 0.98), NaOH solution (ω = 0.40), ethanol, acetone, ether, dimethylformamide while can be destroyed by ZnCl₂ solution (ω = 0.60). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci, 2013     

Preparation and characterization of ceramic nanofiltration membrane prepared from hazardous industrial waste

Kiln rollers, which are widely used in ceramic tiles production, are usually subjected to surface grinding to remove the contaminations. The resulted fine powder is considered useless waste and a hazardous source of environmental pollution particularly as it contains health-threatening fine free silica. In the present paper, the grind waste from kiln rollers was reused as raw material in the fabrication of nanofiltration ceramic membrane. The samples of produced ceramic membranes were formed into disks by adding 15% (by weight) organic binder solution with 2% concentration, then pressed at 35 MPa, dried and fired at temperatures range from 1100°C to 1300°C for 1 hour soaking time. It was found that the best firing temperature to produce nanofiltration ceramic membrane is 1250°C, where the ceramic membrane provides high removal of turbidity and high monovalent, divalent, and trivalent salts separation percentage.     

界面聚合法PI/PP耐溶剂复合纳滤膜的制备与表征

以丙烯酰胺接枝的聚丙烯(PP)超滤膜为支撑层,间苯二胺(MPD)、均苯四甲酰氯(BTAC)分别为水相及有机相功能单体,通过界面聚合及其后续的酰亚胺化制备了聚酰亚胺(PI)/PP耐溶剂复合纳滤膜。讨论了水相浓度、有机相浓度及酰亚胺化溶液配方等条件对复合膜结构及其分离性能的影响。分别采用傅里叶红外光谱仪(FTIR)、扫描电子显微镜(SEM)表征分离层的化学组成及复合膜的形态结构,得到膜的分离、透过及其耐溶剂性能。结果表明,有机相浓度的影响最为显著,支撑膜表面形成了均匀致密的PI分离层,复合膜呈负电性,并具备优秀的耐溶剂性能。实验范围内,MPD、BTAC的浓度分别为8、2 g·L-1,酰亚胺化溶液乙酸酐∶三乙胺∶苯体积比为1∶1∶10时,所制备膜的分离性能较佳,对Na2SO4、酸性艳蓝6B的截留率分别达93.8%和96.9%。     

Design and characterization of polypropylene matrix/glass fibers composite materials

In this article, polymer composites based on polypropylene (PP) matrix reinforced with short glass fibers type E (GF‐type E) were obtained. However, to ensure good interfacial adhesion and stress transfer across the interface, the influence of the chemical functionalization of the phases was analyzed. The better interfacial adhesion is assured by the use of maleic anhydride grafted PP and amino‐functionalized GF. The obtained composite materials were tested from the point of view of composition, morphology, and mechanical properties. It can conclude that the chemical functionalization of the two phases is beneficial from the point of view of compatibility of the phases and consequently higher mechanical properties are obtained. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42163.     

Preparation and characterization of asymmetric polyethersulfone nanofiltration membranes: The effects of polyvinylpyrrolidone molecular weights and concentrations

In this study, asymmetric flat‐sheet polyethersulfone (PES) nanofiltration (NF) membranes were prepared via immersion precipitation phase inversion with the addition of polyvinylpyrrolidone (PVP). The effects of PVP with the molecular weights (MW) from 17 to 1400 kDa and the concentration from 0 to 3.0 wt % on the morphologies and performances of PES membranes were systematically studied. The prepared membranes were characterized by SEM, AFM, ATR‐FTIR, contact angle, membrane porosity, the water flux, and the rejection measurement. The results indicated that the porosity and the hydrophilicity of PES NF membrane increased with increasing PVP concentration, and the hydrophilicity of PES NF membrane also improved with increasing PVP MW. The enhancements of the porosity and hydrophilicity resulted in the higher water flux of PES NF membrane. The rejection of Bordeaux S (MW 604.48 Da) for the prepared PES membrane was increased to above 90% with the low PVP concentration, but it turned to decrease remarkably when the PVP concentration reached to a critical value which related to PVP MW. It was concluded that the addition of a small amount of PVP could significantly increase the permeability of PES NF membrane and maintain its rejection of Bordeaux S above 90%. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43769.     

Experimental study of the effect of zeolite 4A treated with magnesium hydroxide on the characteristics and gas‐permeation properties of polysulfone‐based mixed‐matrix membranes

Nowadays, new methods for gas‐separation processes are being quickly developed. The separation of CH₄/CO₂ and CH₄/H₂ is usually the subject of most related research studies, especially in the membrane gas‐separation process, because of their important role in industry. In this study, we attempted to improve the separation properties of a polysulfone/zeolite 4A mixed‐matrix membrane by modifying the zeolite particle surface. The method included a simple ion‐exchange reaction of magnesium chloride with ammonium hydroxide that yielded the formation and precipitation of magnesium hydroxide whiskers on the surface of the zeolites. The whiskers could omit most of the nonselective voids by interlocking the polymer chains through them and, consequently, improve the permeability, selectivity, and elastic modulus of the membranes. X‐ray diffraction, energy‐dispersive X‐ray spectroscopy, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and dynamic mechanical analysis proved all the changes recorded after the particle and membrane treatments. SEM images showed the petal‐like morphology of the whiskers that formed on the surface of the particles after the reaction against the smooth surface of the untreated zeolite. At a 30 wt % loading of particles in the polymeric matrix, the selectivities for H₂/CH₄ and CO₂/CH₄ increased by 69 and 56%, respectively; in contrast, the H₂ and CO₂ permeabilities decreased by 2.5 and 10%, respectively. The modulus of elasticity for the treated membrane also increased by 14 and 30% compared to those of the pure and untreated membranes, respectively. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44329.     

Development of antifouling poly(vinyl chloride) blend membranes by atom transfer radical polymerization

In this study, antifouling poly(vinyl chloride) (PVC) blend membranes were prepared by blending the PVC based amphiphilic copolymer PVC‐g‐poly(hydroxyethyl methacrylate) (PVC‐g‐PHEMA), synthesized by atom transfer radical polymerization (ATRP), into the hydrophobic PVC matrix via the nonsolvent‐induced phase separation method. The in situ ATRP reaction solutions were also used as the blend additives to improve membrane performance. Attenuated total reflectance–Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy indicated that the blend membranes based on the two blend routes exhibited similar surface chemical compositions. The membrane morphology and surface wettability were determined by scanning electronic microscopy and water contact angle measurement, respectively. The blend membranes showed improved water permeability, comparable rejections and enhanced antifouling properties compared with the pure PVC membrane. The PVC blend membranes also had excellent long‐term stability in terms of chemical compositions and fouling resistance. The results demonstrated that ATRP was a promising technique to synthesize amphiphilic copolymer and prepare stable blend antifouling membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45832.     

Preparation of highly selective nanofiltration composite membranes based on a novel soluble rigidly contorted monomer

Nanofiltration composite membranes with high selectivity are one of the most critical cores in water treatment, and regulating the surface charge and pore structure of active separation layers in thin film composite membranes is one of the most effective means to improve the selectivity of composite membranes. This article synthesized a novel monomer with positive charge and a rigid twisted Tröger's base structure (named TBDA-SO₃), which was manipulated to improve the microporous structure and surface charge of the composite membrane. By interfacial polymerization, TBDA-SO₃, and piperazine were co-reacted with trimesoyl chloride to successfully prepare positively charged, highly selective, and strongly microporous polyamide composite nanofiltration membranes. The best-performing composite nanofiltration membrane in this article has a permeability similar to that of the control group's poly(piperazine amide) (PPA) membrane (pure water flux, 7.8 L m⁻² h⁻¹ bar⁻¹), but has excellent divalent cation selectivity (52.57), which is 4.4 times that of the control group's PPA membrane.     

Photo‐induced grafting of poly(ethylene glycol) onto polyamide thin film composite membranes

In this study, the surface grafting of poly(ethylene glycol) (PEG) onto commercial polyamide thin film composite (TFC‐PA) membranes was carried out, using ultraviolet photo‐induced graft polymerization method. The attenuated total reflection Fourier transform infrared spectra verify a successful grafting of PEG onto the TFC‐PA membrane surface. The scanning electron microscope and atomic force microscope analyses demonstrate the changes of the membrane surface morphology due to the formation of the PEG‐grafted layer on the top. The contact angle measurements illustrate the increased hydrophilicity of the TFC‐PA‐g‐PEG membrane surfaces, with a significantly reduced water contact angles compared to the unmodified one. Consequently, the separation performance of the PEG‐grafted membranes is highly improved, with a significant enhancement of flux at a great retention for removal of the different objects in aqueous feed solutions. In addition, the antifouling property of the modified membranes is also clearly improved, with the higher maintained flux ratios and the lower irreversible fouling factors compared to the unmodified membrane. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45454.     

Morphological and nanomechanical characterization of anisotropic interfacial characteristic regions in CF/PA6 composites at different cooling rates

Macroscopic tensile tests on neat PA6 and CF/PA6 prepregs showed that the cooling rate significantly affects the mechanical properties of CF/PA6 composites because of their different crystallization behaviors both at the fiber surface and in the matrix. Polarizing optical microscopy, static nanoindentation (SNI), and dynamic mechanical imaging (DMI) tests were used to characterize the anisotropic morphologies and nanomechanical performances of the interfacial characteristic regions in CF/PA6 composites at five different cooling rates. As a result, the seven interfacial characteristic regions inside the CF/PA6 composites were clearly distinguished. The interphase thickness of the CF/PA6 composites decreased with a decrease in the cooling rate. On the contrary, the interphase modulus and transcrystallinity thickness and modulus showed significant increases with a decrease in the cooling rate. The DMI and SNI test results were in agreement with each other and with the macromechanical test results. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44106.     

Zwitterionic‐polymer‐functionalized poly(vinyl alcohol‐co‐ethylene) nanofiber membrane for resistance to the adsorption of bacteria and protein

A zwitterionic poly(vinyl alcohol‐co‐ethylene) (PVA‐co‐PE) nanofiber membrane for resistance to bacteria and protein adsorption was fabricated by the atom transfer radical polymerization of sulfobetaine methacrylate (SBMA). The PVA‐co‐PE nanofiber membrane was first surface‐activated by α‐bromoisobutyryl bromide, and then, zwitterionic SBMA was initiated to polymerize onto the surface of nanofiber membrane. The chemical structures of the functionalized PVA‐co‐PE nanofiber membranes were confirmed by attenuated total reflectance–Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. The morphologies of the PVA‐co‐PE nanofiber membranes were characterized by scanning electron microscopy. The results show that the poly(sulfobetaine methacrylate) (PSBMA) was successfully grafted onto the PVA‐co‐PE nanofiber membrane, and the surface of the nanofiber membrane was more hydrophilic than that of the pristine membrane. Furthermore, the antibacterial adsorption properties and resistance to protein adsorption of the surface were investigated. This indicated that the PSBMA‐functionalized surface possessed good antibacterial adsorption activity and resistance to nonspecific protein adsorption. Therefore, this study afforded a convenient and promising method for preparing a new kind of soft and nonwoven dressing material with antibacterial adsorption and antifouling properties that has potential use in the medical field. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44169.     

Preparation of hybrid composite microspheres containing nanosilicon via microsuspension polymerization

Hybrid composite microspheres with nano‐Si as the core and poly(styrene‐co‐acrylonitrile) as a shell are successfully prepared by a two‐step polymerization technique, which includes dispersion polymerization of styrene and 3‐methacryloxypropyl trimethoxysilane in ethanol for surface modification of nano‐Si followed by microsuspension polymerization of styrene and acrylonitrile in an aqueous phase for encapsulating nano‐Si into an SAN copolymer matrix. The structure and surface properties of modified nano‐Si are investigated by Fourier transform infrared spectroscopy (FTIR) and contact angle. The hybrid composite microspheres are systematically characterized by energy dispersive spectroscopy, thermogravimetric analysis, and transmission electron microscopy (TEM). According to the FTIR spectra and the contact angle experiments, it was determined that a hydrophobic polymer layer was formed on the surface of nano‐Si. TEM showed that nano‐Si was homogeneously dispersed in SAN particles when the loading capacity of nano‐Si in the hybrid composite microspheres was less than 20 wt %. Moreover, scanning electron microscopy and X‐ray photoelectron spectroscopy revealed that there were large amounts of nano‐Si absorbed on the surface of the hybrid composite microspheres, and the mean particle size became much larger when the loading amounts of nano‐Si reached 25 wt %. From this, it can be inferred that nano‐Si overflows from the inner core to the outside surface in the emulsification process and acts as an inorganic dispersant. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43101.     

Preparation and modification of thin film composite membrane using a bulky dianhydride monomer

One of the most effective methods to modify thin film composite (TFC) membranes is changing the chemistry of top selective layer by different monomers and different monomer concentrations. Herein, we report the preparation of modified TFC membranes using a pyromellitic dianhydride (PMDA) mixed with organic phase (trimesoyl chloride) and meta phenylene diamine (MPD). By manipulating the PMDA amount in organic phase, the structures and chemical compositions of polyamide selective layer could be modified. It was realized that the presence of PMDA could result in a modified membrane with higher surface roughness, less dense selective layer, more surface charge density, and better hydrophilic properties and consequently less fouling. The optimum PMDA concentration was found 0.05 wt%, such that the obtained membrane had 35.6 L m⁻² h⁻¹ pure water flux, about 1.6-fold higher than the reference membrane with similar salt rejection. Fouling intensity for the reference membrane was 38.1%, while for the modified membranes it decreased to 16.7%.