Preparation and performance of braid‐reinforced poly(vinyl chloride) hollow fiber membranes

A novel braid‐reinforced (BR) poly(vinyl chloride) (PVC) hollow fiber membrane was fabricated via dry‐wet spinning process. The mixtures of PVC polymer solutions were uniformly coated on the tubular braid which contained polyester (PET) and polyacrylonitrile (PAN) fibers. The influences of braid composition on structure and performance of BR PVC hollow fiber membranes were investigated. The results showed that the prepared BR PVC hollow fiber membranes were composed of two layers which contained separation layer and tubular braid supported layer when the PET and PET/PAN hybrid tubular braids were used as the reinforcement. But the sandwich structure appeared when the PAN tubular braid was used as the reinforcement, which revealed outer separation layer, tubular braid supported layer and the inner polymer layer. The BR PVC hollow fiber membranes that prepared by PET/PAN hybrid tubular braid had favorable interfacial bonding state compared with the membrane prepared by pure PET or PAN tubular braid. The pure water flux of the BR PVC hollow fiber membranes that prepared by the PET/PAN hybrid tubular braid were lower than that prepared by pure PET or PAN tubular braid, but the rejection of Bovine serum albumin was opposite. The tensile strength of prepared BR PVC hollow fiber membrane was higher than 50 MPa. Both of the tensile strength and elongation at break decreased with the increase of the PAN filaments in the PET/PAN hybrid tubular braid. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45068.     

Fabrication and characterization of novel foaming polyurethane hollow fiber membrane

Foam-like materials had attracted great interest as promising absorbent. In this study, thermoplastic polyurethane(TPU) block sponge was synthesized. Polyester(PET) braid tubular reinforced polyurethane(PU) spongy hollow fiber membrane was prepared by a concentric circular spinning method. The method was woven from an outer coated water-blown PU separation layer and inner PET braid tubular. We have developed a simple and useful preparation technique for the PU spongy hollow fiber membrane. For the first time, the PU spongy hollow fiber membrane was prepared using a coating and controlled foaming technique. The influence of toluene isocyanate index on the physical properties, morphology, and structure of flexible PU sponge was discussed in terms of water contact angle(CA), pure water flux(PWF), Fourier Transform Infrared Analysis(FTIR),pressure-responsive property, and pull-out strength. The morphologies of the membranes were investigated by scanning electron microscopy. We have characterized the foams from an intuitive point of view and demonstrated that the dimensional morphology of the membrane was closely related to isocyanate index. The result showed that the surface cell size of the PU sponge hollow fiber membrane gradually decreased with an increase of the isocyanate index. Due to the elasticity of PU at room temperature, the pressure responsive characteristic of the membrane was prepared. When isocyanate index was 1.05, the interface bonding strength of PU spongy hollow fiber membranes reached as high as 0.37 MPa, porosity and PWF were 71.5% and 415.5 L·m~(-2)·h~(-1),respectively.     

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.     

Hydrophilic modification of high‐strength polyvinylidene fluoride hollow fiber membrane

The polyvinylidene fluoride (PVDF)/polyvinyl alcohol (PVA) polymer solutions were coated on the outer surface of PVDF matrix hollow fiber membrane. On the principle of the homogeneous‐reinforced (HR) membrane technology, the reinforced PVDF/PVA (RFA) hollow fiber membranes prepared through the dry‐wet spinning method. The performance of the RFA membranes varies with the PVA concentration in the polymer solution and is characterized in terms of pure water flux (PWF), porosity, a mechanical strength test, and morphology observations by a scanning electron microscopy (SEM). The results of this study indicate that PVA can apparently improve the hydrophilicity of the PVDF hollow fiber membranes. The growing enrichment of the hydrophilic components PVA on the membrane surface is determined by X‐ray photoelectron spectroscopy. The RFA membranes have a favorable interfacial bonding between the coating layer (PVDF/PVA) and the matrix membrane (PVDF hollow fiber membrane), as shown by SEM. The elongation at break of the RFA membranes increases much more than that of the matrix membrane that is endowed with the better flexibility of the membrane performance. PWF decreases much more compared with that of the matrix membrane. The RFA membranes have a lower flux decline degree during the process of protein solution and ink solution filtration compared with that of the matrix membrane. POLYM. ENG. SCI., 54:276–287, 2014. © 2013 Society of Plastics Engineers     

Pervaporation of water/alcohol mixtures through chitosan/cellulose acetate composite hollow‐fiber membranes

For the purpose of separating aqueous alcohol by the use of pervaporation technique, a composite membrane of chitosan (CT) dip‐coated cellulose acetate (CA) hollow‐fiber membranes, CT‐d‐CA, was investigated. The effects of air‐gap distance in the spinning of CA hollow‐fiber membranes, chitosan concentration, and sorts of aqueous alcohol solutions on the pervaporation performances were studied. Compared with unmodified CA hollow‐fiber membrane, the CT‐d‐CA composite hollow‐fiber membrane effectively increases the permselectivity of water. The thickness of coating layer increases with an increase in chitosan concentration. As the concentration of chitosan solution increased, the permeation rate decreased and the concentration of water in the permeate increased. In addition, the effects of feed composition and feed solution temperature on the pervaporation performances were also investigated. The permeation rate and water content in permeate at 25°C for a 90 wt % aqueous isopropanol solution through the CT‐d‐CA composite hollow‐fiber membrane with a 5‐cm air‐gap distance spun, 2 wt % chitosan dip‐coated system were 169.5 g/m² h and 98.9 wt %, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1562–1568, 2004     

Polyvinyl alcohol/polysulfone (PVA/PSF) hollow fiber composite membranes for pervaporation separation of ethanol/water solution

Polysulfone (PSF) hollow fiber membranes were spun by phase‐inversion method from 29 wt % solids of 29 : 65 : 6 PSF/NMP/glycerol and 29 : 64 : 7 PSF/DMAc/glycol using 93.5 : 6.5 NMP/water and 94.5 : 5.5 DMAc/water as bore fluids, respectively, while the external coagulant was water. Polyvinyl alcohol/polysulfone (PVA/PSF) hollow fiber composite membranes were prepared after PSF hollow fiber membranes were coated using different PVA aqueous solutions, which were composed of PVA, fatty alcohol polyoxyethylene ether (AEO₉), maleic acid (MAC), and water. Two coating methods (dip coating and vacuum coating) and different heat treatments were discussed. The effects of hollow fiber membrane treatment methods, membrane structures, ethanol solution temperatures, and MAC/PVA ratios on the pervaporation performance of 95 wt % ethanol/water solution were studied. Using the vacuum‐coating method, the suitable MAC/PVA ratio was 0.3 for the preparation of PVA/PSF hollow fiber composite membrane with the sponge‐like membrane structure. Its pervaporation performance was as follows: separation factor (α) was 185 while permeation flux (J) was 30g/m²·h at 50°C. Based on the experimental results, it was found that separation factor (α) of PVA/PSF composite membrane with single finger‐void membrane structure was higher than that with the sponge‐like membrane structure. Therefore, single finger‐void membrane structure as the supported membrane was more suitable than sponge‐like membrane structure for the preparation of PVA/PSF hollow fiber composite membrane. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 247–254, 2005     

Preparation of PET threads reinforced PVDF hollow fiber membrane

PET threads were incorporated in the support layer of hollow fiber membrane in axial direction as a special reinforcement material for the purpose of improving the mechanical properties of PVDF hollow fiber membranes. It was found that the reinforcement threads had a limited effect on the separation-related properties of the membrane, such as porosity and pore size, but the tensile strength of the reinforced membrane was improved several folds. Also, the criterion of choosing reinforced fiber materials was suggested.     

Preparation of PFSA‐PVA/PSf hollow fiber membrane for IPA/H2O pervaporation process

Using Na⁺ form of perfluorosulfonic acid (PFSA) and poly(vinyl alcohol) (PVA) as coating materials, polysulfone (PSf) hollow fiber ultrafiltration membrane as a substrate membrane, PFSA‐PVA/PSf hollow fiber composite membrane was fabricated by dip‐coating method. The membranes were post‐treated by two methods of heat treatment and by both heat treatment and chemical crosslinking. Maleic anhydride (MAC) aqueous solution was used as chemical crosslinking agent using 0.5 wt % H₂SO₄ as a catalyst. PFSA‐PVA/PSf hollow fiber composite membranes were used for the pervaporation (PV) separation of isopropanol (IPA)/H₂O mixture. Based on the experimental results, PFSA‐PVA/PSf hollow fiber composite membrane is suitable for the PV dehydration of IPA/H₂O solution. With the increment of heat treatment temperature, the separation factor increased and the total permeation flux decreased. The addition of PVA in PFSA‐PVA coating solution was favorable for the improvement of the separation factor of the composite membranes post‐treated by heat treatment. Compared with the membranes by heat treatment, the separation factors of the composite membranes post‐treated by both heat treatment and chemical crosslinking were evidently improved and reached to be about 520 for 95/5 IPA/water. The membranes post‐treated by heat had some cracks which disappeared after chemical crosslinking for a proper time. Effects of feed temperature on PV performance had some differences for the membranes with different composition of coating layer. The composite membranes with the higher mass fraction of PVA in PFSA‐PVA coating solution were more sensitive to temperature. It was concluded that the proper preparation conditions for the composite membranes were as follows: firstly, heated at 160°C for 1 h, then chemical crosslinking at 40°C for 3 h in 4% MAC aqueous solution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Perfluorosulfonic acid—Tetraethoxysilane/polyacrylonitrile (PFSA‐TEOS/PAN) hollow fiber composite membranes prepared for pervaporation dehydration of ethyl acetate–water solutions

Preparation of organic‐inorganic composite membranes and their pervaporation (PV) permeation and separation characteristics for the aqueous solution of ethyl acetate were described. Polyacrylonitrile (PAN) hollow fiber ultrafiltration membrane as support membrane, the mixtures of perfluorosulfonic acid (PFSA) and tetraethoxysilane (TEOS) by the sol‐gel reaction as the coating solution, the PFSA‐TEOS/PAN hollow fiber composite membranes by the different annealing conditions were prepared. The swelling of PFSA in ethyl acetate aqueous solutions was inhibited with addition of TEOS. The PFSA‐TEOS/PAN composite membranes containing up to 30 wt % TEOS in coating solution exhibited high selectivity towards water, then the selectivity decreased and permeation flux increased with increasing the TEOS concentration more than 30 wt %. When the PFSA‐TEOS/PAN composite membranes were annealed, the separation factor increased with increasing annealing temperature and time. Higher annealing temperature and longer annealing time promoted the crosslinking reaction between PFSA and TEOS in PFSA‐TEOS/PAN composite membranes, leading to the enhanced selectivity towards water. For the PFSA/PAN and PFSA‐TEOS/PAN composite membrane with 5 and 30 wt % TEOS annealed at 90°C for 12 h, their PV performance of aqueous solution 98 wt % ethyl acetate were as follows: the separation factors were 30.8, 254 and 496, while their permeation flux were 1430, 513 and 205 g/m² h at 40°C, respectively. In addition, the PV performance of PFSA‐TEOS/PAN composite membranes was investigated at different feed solution temperature and concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Positively charged hollow‐fiber composite nanofiltration membrane prepared by quaternization crosslinking

Poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA) can be crosslinked by interfacial polymerization to develop a positively charged dense network structure. According to this mechanism, a positively charged hollow‐fiber composite nanofiltration (NF) membrane was prepared by quaternization to achieve a crosslinked PDMAEMA gel layer on the outer surface of polysulfone hollow‐fiber ultrafiltration (UF) membranes with a PDMAEMA aqueous solution as a coating solution and p‐xylylene dichloride as an agent. The preparation conditions, including the PDMAEMA concentration, content of additive in the coating solution, catalyzer, alkali, crosslinking temperature, and hollow‐fiber substrate membrane, were studied. Fourier transform infrared spectroscopy and scanning electron microscopy were used to characterize the structure of the membranes. This membrane had a rejection to inorganic salts in aqueous solution. The rejection of MgSO₄ (2 g/L aqueous solution at 0.7 MPa and 25°C) was above 98%, and the flux was about 19.5 L m^?2 h^?1. Moreover, the composite NF membranes showed good stability in the water‐phase filtration process. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation of dual‐layer acetylated methyl cellulose hollow fiber membranes via co‐extrusion using thermally induced phase separation and non‐solvent induced phase separation methods

Dual‐layer acetylated methyl cellulose (AMC) hollow fiber membranes were prepared by coupling the thermally induced phase separation (TIPS) and non‐solvent induced phase separation (NIPS) methods through a co‐extrusion process. The TIPS layer was optimized by investigating the effects of coagulant composition on morphology and tensile strength. The solvent in the aqueous coagulation bath caused both delayed liquid–liquid demixing and decreased polymer concentration at the membrane surface, leading to porous structure. The addition of an additive (triethylene glycol, (TEG)) to the NIPS solution resolved the adhesion instability problem of the TIPS and NIPS layers, which occurred due to the different phase separation rates. The dual‐layer AMC membrane showed good mechanical strength and performance. Comparison of the fouling resistance of the AMC membranes with dual‐layer polyvinylidene fluoride (PVDF) hollow fiber membranes fabricated with the same method revealed less fouling of the AMC than the PVDF hollow fiber membrane. This study demonstrated that a dual‐layer AMC membrane with good mechanical strength, performance, and fouling resistance can be successfully fabricated by a one‐step process of TIPS and NIPS. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42715.     

Analysis of physical properties of PET/CD‐PET polyblend hollow fiber and its kinetics of alkaline hydrolysis

Cationic dyeable poly(ethylene terephthalate) (CD‐PET) was formed by copolymerizing dimethylterephthalate (DMT),5‐sodium sulfonate dimethyl isophthalate (SIPM) with a molar ratio of 2% and ethylene glycol (EG). Blends of regular poly(ethylene terephthalate) (PET) and CD‐PET were spun into hollow fibers. The fibers were then treated with aqueous NaOH. This study investigated the physical properties of PET/CD‐PET polyblend hollow fibers and their kinetic behavior of alkaline hydrolysis using differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), the density gradient method, a gel permeation chromatograph (GPC), a rheometer, and regression analysis of the statistical method. For the alkaline hydrolysis kinetics equation of PET, CD‐PET, and PET/CD‐PET polyblend materials: ? dW/dt = KC^αA^β, β values of chip and POY/ FOY hollow fibers are equal to 1. Moreover, R² of the kinetics equation of chip/POY/FOY for a from 1.09–1.35/1.08–1.32/1.06–1.29 were better than those of a = 1. Experimental results indicate that the rate constant of alkaline hydrolysis was CD‐PET hollow fiber > PET/CD‐PET polyblend hollow fibers > PET hollow fiber and FOY > POY > > Chip. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3601–3610, 2002     

Engineering design of outer‐selective tribore hollow fiber membranes for forward osmosis and oil‐water separation

Outer‐selective thin‐film composite (TFC) hollow fiber membranes offer advantages like less fiber blockage in the feed stream and high packing density for industrial applications. However, outer‐selective TFC hollow fiber membranes are rarely commercially available due to the lack of effective ways to remove residual reactants from fiber's outer surface during interfacial polymerization and form a defect‐free polyamide film. A new simplified method to fabricate outer‐selective TFC membranes on tribore hollow fiber substrates is reported. Mechanically robust tribore hollow fiber substrates containing three circular‐sector channels were first prepared by spinning a P84/ethylene glycol mixed dope solution with delayed demixing at the fiber lumen. The thin wall tribore hollow fibers have a large pure water permeability up to 300 L m^?2 h^?1 bar^?1. Outer‐selective TFC tribore hollow fiber membranes were then fabricated by interfacial polymerization with the aid of vacuum sucking to ensure the TFC layer well‐attached to the substrate. Under forward osmosis studies, the TFC tribore hollow fiber membrane exhibits a good water flux and a small flux difference between active‐to‐draw (i.e., the active layer facing the draw solution) and active‐to‐feed (i.e., the active layer facing the feed solution) modes due to the small internal concentration polarization. A hyperbranched polyglycerol was further grafted on top of the newly developed TFC tribore hollow fiber membranes for oily wastewater treatment. The membrane displays low fouling propensity and can fully recover its water flux after a simple 20‐min water wash at 0.5 bar from its lumen side, which makes the membrane preferentially suitable for oil‐water separation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4491–4501, 2015     

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.     

Toughening of recycled poly(ethylene terephthalate)/glass fiber blends with ethylene–butyl acrylate–glycidyl methacrylate copolymer and maleic anhydride grafted polyethylene–octene rubber

The aim of this study was to improve the toughness of recycled poly(ethylene terephthalate) (PET)/glass fiber (GF) blends through the addition of ethylene–butyl acrylate–glycidyl methacrylate copolymer (EBAGMA) and maleic anhydride grafted polyethylene–octene (POE‐g‐MAH) individually. The morphology and mechanical properties of the ternary blend were also examined in this study. EBAGMA was more effective in toughening recycled PET/GF blends than POE‐g‐MAH; this resulted from its better compatibility with PET and stronger fiber/matrix bonding, as indicated by scanning electron microscopy images. The PET/GF/EBAGMA ternary blend had improved impact strength and well‐balanced mechanical properties at a loading of 8 wt % EBAGMA. The addition of POE‐g‐MAH weakened the fiber/matrix bonding due to more POE‐g‐MAH coated on the GF, which led to weakened impact strength, tensile strength, and flexural modulus. According to dynamic rheometer testing, the use of both EBAGMA and POE‐g‐MAH remarkably increased the melt storage modulus and dynamic viscosity. Differential scanning calorimetry analysis showed that the addition of EBAGMA lowered the crystallization rate of the PET/GF blend, whereas POE‐g‐MAH increased it. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

影响渗透汽化中空纤维复合膜分离性能的制备工艺研究

采用聚乙烯醇（ＰＶＡ）为分离层的模材料,以浸涂工艺把ＰＶＡ复合到聚砜（ＰＳ）或聚丙烯腈（ＰＡＮ）的中空纤维支撑层上,在长度为０．４ｍ的不锈钢管中组装若干根中空纤维复合膜测定对乙醇水溶液的渗透汽化（ＰＶ）分离性能。结果表明,ＰＶＡ／ＰＡＮ中空纤维复合膜的性能优于ＰＶＡ／ＰＳ,内径较大（１．３ｍｍ）的优于内径上（０．４ｍｍ）者,ＰＶＡ水溶液在中空纤维支撑层上的涂复次数对复合膜ＰＶ分离性能、以及ＰＶＡ／     

Polydimethylsiloxane/postmodified MIL‐53 composite layer coated on asymmetric hollow fiber membrane for improving gas separation performance

Composite layer containing postmodified MIL‐53 (P‐MIL‐53) was exploited to be coated on as‐fabricated asymmetric hollow fiber membrane for improving gas separation performance. The morphology and pore size distribution of P‐MIL‐53 particles were characterized by SEM and N₂ adsorption isotherm. The EDX mapping and FTIR spectra were performed to confirm the presence of P‐MIL‐53 deposited on the outer surface of hollow fiber membranes. The results of pure gas permeation measurement indicated that incorporation of P‐MIL‐53 particles in coating layer could improve permeation properties of hollow fiber membranes. By varying coating times and P‐MIL‐53 content, the membrane coated with PDMS/15%P‐MIL‐53 composite by three times achieved best performance. Compared to pure PDMS coated membrane, CO₂ permeance was enhanced from 29.96 GPU to 40.24 GPU and ideal selectivity of CO₂/N₂ and CO₂/CH₄ also increased from 23.28 and 26.95 to 28.08 and 32.03, respectively. The gas transport through composite membrane was governed by solution‐diffusion mechanism and CO₂ preferential adsorption of P‐MIL‐53 contributed to considerable increase of CO₂ solubility resulting in accelerated permeation rate. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44999.     

Effect of polyethylene glycol molecular weights and concentrations on polyethersulfone hollow fiber ultrafiltration membranes

Polyethersulfone (PES) hollow‐fiber membranes were fabricated using poly(ethyleneglycol) (PEG) with different molecular weights (MW = PEG200, PEG600, PEG2000, PEG6000, and PEG10000) and poly(vinyl pyrrolidone) PVP40000 as additives and N‐methyl‐2‐pyrrolidone (NMP) as a solvent. Asymmetric hollow‐fiber membranes were spun by a wet phase‐inversion method from 25 wt % solids of 20 : 5 : 75 (weight ratio) PES/PEG/NMP or 18 : 7 : 75 of PES/(PEG600 + PVP40000)/NMP solutions, whereas both the bore fluid and the external coagulant were water. Effects of PEG molecular weights and PEG600 concentrations in the dope solution on separation properties, morphology, and mechanical properties of PES hollow‐fiber membranes were investigated. The membrane structures of PES hollow‐fiber membranes including cross section, external surface, and internal surface were characterized by scanning electron microscopy and the mechanical properties of PES hollow‐fiber membranes were discussed. Bovine serum albumin (BSA, MW 67,000), chicken egg albumin (CEA, MW 45,000), and lysozyme (MW 14,400) were used for the measurement of rejection. It was found that with an increase of PEG molecular weights from 200 to 10,000 in the dope solution, membrane structures were changed from double‐layer fingerlike structure to voids in the shape of spheres or ellipsoids; moreover, there were crack phenomena on the internal surfaces and external surfaces of PES hollow‐fiber membranes, pure water permeation fluxes increased from 22.0 to 64.0 L m^?2 h^?1 bar^?1, rejections of three protein for PES/PEG hollow‐fiber membranes were not significant, and changes in mechanical properties were decreased. Besides, with a decrease of PEG600 concentrations in the dope solution, permeation flux and elongation at break decreased, whereas the addition of PVP40000 in the dope solution resulted in more smooth surfaces (internal or external) of PES/(PEG600 + PVP40000) hollow‐fiber membranes than those of PES/PEG hollow‐fiber membranes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3398–3407, 2004     

The preparation and performance of short carbon fiber reinforced adhesive for bonding carbon/carbon composites

A short carbon fiber reinforced adhesive for bonding carbon/carbon composites was developed. We found that when the thickness of the bonding layer was 80 μm, the concentration of short carbon fiber was 0.2 wt.%, and the heat-treatment temperature was 1000 °C, the adhesive could operate below 1700 °C and endure 20 times of thermal shock circles at 1500 °C. Finite element and micrograph analysis indicated that the bonding strength was larger than the interlaminar shear strength of carbon/carbon substrate, so that the fracture did not occur in the bonding layer but the carbon/carbon substrate. Weibull distribution analysis results showed that the Weibull modulus was 21.56 and the bonding strength was 11.43 MPa. We investigated that short carbon fiber could advance the tensile strength and thermal shock resistance of the adhesive, release residual stress and inhibit extension of micro-crack in the bonding layer.     

Hydrophilic modification of poly(vinylidene fluoride) membrane with poly(vinyl pyrrolidone) via a cross‐linking reaction

A highly hydrophilic hollow fiber poly(vinylidene fluoride) (PVDF) membrane [PVDF‐cl‐poly(vinyl pyrrolidone) (PVP) membrane] was prepared by a cross‐linking reaction with the hydrophilic PVP, which was immobilized firmly on the outer surface and cross‐section of the PVDF hollow fiber membrane via a simple immersion process. The cross‐linking between PVDF and PVP was firstly verified via nuclear magnetic resonance measurement on PVP solution after cross‐linking. The hydrophilic stability of the modified PVDF membrane was evaluated by measuring the pure water flux after different times of immersion and drying. The anti‐fouling properties were estimated by cyclic filtration of protein solution. When the cross‐linking time was as long as 6 hr and the PVP content reached 5 wt %, the pure water flux (J_v) was constant as ～ 600 L m^?2 hr^?1. The hydrophilicity of the PVDF‐cl‐PVP membrane was significantly enhanced and exhibited a good stability. The PVDF‐cl‐PVP membrane showed an excellent anti‐protein‐fouling performance during the cyclic filtration of bovine serum albumin solution. Therefore, a highly hydrophilic and anti‐protein‐fouling PVDF hollow fiber membrane with a long‐term stability can be prepared by a simple and economical cross‐linking process with PVP. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013