Surface Modification Of Polypropylene Membrane Research Articles

Surface modification of polypropylene membrane by helium plasma treatment for membrane distillation

Helium plasma was used to modify the surface of commercial polypropylene capillary membranes applied for membrane distillation. The membranes were manufactured for microfiltration and had a thin skin layer with low porosity. The plasma reactions such as etching and re-deposition resulted in a substantial modification of the skin layer. The surface porosity and pore diameters increased due to plasma treatment and resulted in 25% enhancement of the permeate flux during membrane distillation (MD). Although the plasma treatment caused hydrophilization of the membrane surface, the resistance of membranes to wetting did not deteriorate and the permeate conductivity at a level of 5 μS/cm was retained for 200 h of the MD process with NaCl solution. The model calculations confirmed that wetting only of the surface pores did not cause a significant decrease in MD efficiency, while the calculated efficiency decreased by 30% when the wetted layer reached half the thickness of the membrane wall. The modified membranes demonstrated good stability and the permeate purity was similar during the 300 h desalination of Baltic Sea Water after three years of their storage. The separation of water contaminated by oil (50 ppm) revealed that hydrophilic compounds on the membrane surface formed in helium plasma treatment significantly reduced oil fouling.

Surface modification of polypropylene membrane for the removal of iodine using polydopamine chemistry

The development of stable and effective iodine removal systems would be highly desirable in addressing environmental issues relevant to water contamination. In the present research, a novel iodine adsorbent was synthesized by self-polymerization of dopamine (PDA) onto inert polypropylene (PP) membrane. This PP/PDA membrane was thoroughly characterized and its susrface propeties was analyzed by various analytical techniques indcluding field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH), contact angle, and surface free energy measurement. The PP/PDA membranes were subsequently used for batchwise removal of iodine at different temperatures (25–70 °C), pH (2–7), and surface areas (1–10 cm2) to understand the underlying adsorption phenomena and to estimate the membrane capacity for iodine uptake. The increase in temperature and pH both led to higher adsorption of iodine. The present approach showed a removal efficiency of over 75% for iodine using 10 cm2 PP/PDA membrane (18.87 m2 g−1) within 2 h at moderate temperatures (∼50 °C) and pH > 4, about 15 fold compared to the PP control membrane. The adsorption kinetics and isotherms were well fitted to the pseudo-second-order kinetic and Langmuir isotherm models (R2 > 0.99). This adsorbent can be recycled and reused at least six times with stable iodine adsorption. These findings were attributed to the homogenous monolayer adsorption of the iodide on the surface due to the presence of catechol and amine groups in the PP/PDA membrane. This study proposes an efficient adsorbent for iodine removal.

Surface Modification of Polypropylene Membrane Using Biopolymers with Potential Applications for Metal Ion Removal

This work aims to present the modification of polypropylene (PP) membranes using three different biopolymers, chitosan (CHI), potato starch (PS), and cellulose (CEL), in order to obtain three new materials. The modified membranes may be degraded easier than polypropylene ones and could be used as selective membranes for metal ions removal, among other applications. For this purpose, the UV energy induced graft copolymerization reaction among polypropylene membrane, acrylic acid, benzophenone (as photoinitiator), and the biopolymer (CHI, PS, or CEL) was conducted. The results of FT-IR-ATR, XRD, TGA, DSC, SEM, BET, and AFM analyses and mechanical properties clearly indicate the successful modification of the membrane surface. The change of surface wettability was monitored by contact angle. The grafting reaction depends on natural polymer, reaction time, and concentration. In order to prove the potential application of the modified membranes, a preliminary study of sorption of metal ion was carried out. For this purpose, the PP-CHI membrane was chosen because of the high hydrophilicity, proportionate to -OH and NH2; these groups could act as ligands of metal ions, provoking the interaction between PP-CHI and M+ (PP-CHI-M+) and therefore the metal ion removal from water.

Surface modification of polypropylene membrane by polyethylene glycol graft polymerization

Polypropylene hollow fiber microporous membranes have been used in a wide range of applications, including blood oxygenator. The hydrophobic feature of the polypropylene surface causes membrane fouling. To minimize fouling, a modification consisting of three steps: surface activation in H2 and O2 plasma, membrane immersion in polyethylene glycol (PEG) and plasma graft polymerization was performed. The membranes were characterized by contact angle measurement, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), tensile test, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Oxygen transfer of modified membranes was also tested. The stability of grafted PEG was measured in water and in phosphate buffer saline (PBS) at 37°C. Blood compatibility of modified surfaces was evaluated by the platelet adhesion method. Water contact angel reduction from 110° to 72° demonstrates the enhanced hydrophilicity, and XPS results verify the presence of oxygenated functional groups due to the peak existence in 286eV as a result of PEG grafting. The results clearly indicate that plasma graft-polymerization of PEG is an effective way for antifouling improvement of polypropylene membranes. Also, the results show that oxygen transfer changes in PEG grafted membranes are not significant.

Surface modification of polypropylene membrane by acrylate epoxidized soybean oil to be used in water treatment

AbstractSurface modification of a microporous polypropylene (PP) membrane was performed by graft polymerization of acrylated epoxidized soybean oil (AESO) using UV radiation. This is a simple, environmentally friendly, and low cost method. The factors affecting the grafting degree such as monomer concentration and reaction time were studied. The morphological and microstructure changes of the membrane were characterized by scanning electron microscopy (SEM) and information regarding elemental composition was obtained by energy dispersive X‐ray spectroscopy (EDS). Surface functionalization was studied by X‐ray photoelectron spectroscopy (XPS). Thermal properties were analyzed by differential scanning calorimetry (DSC). The hydrophilicity increment was confirmed by pure water contact angle and swelling measurements. The filtration capability of the modified membrane was analyzed by determining color, turbidity, and chemical oxygen demand (COD) removal from a residual raw water. The results indicated that the contact angle of pure water on the grafted membrane decreased from 90° to 57°. The modified membrane shows filtration capability by removing color in 52% and reducing 95% of turbidity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Surface Modification of Polypropylene Membrane by RF Methane/Oxygen Mixture Plasma Treatment

The hydrophilic surface modification of micro-porous polypropylene (PP) membranes is achieved by low-pressure 13.56 MHz RF methane (CH4)/oxygen (O2) gas mixture plasma treatment. The changes in surface wettability and surface free energy were examined by static contact angle analysis. The static water contact angle of the plasma modified membrane notably decreased with increases in treatment time and plasma power. The obvious increase in the surface energy of polypropylene membranes due to CH4/O2 mixture gas plasma treatments was also observed. Optical emission spectroscopy (OES) was used to analyze the chemical species of CH4/O2 mixture gas plasma treatment. The variations in the surface morphology and chemical structure of the micro-porous PP membranes were confirmed by confocal laser scanning microscopy (CLSM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) measurements. XPS analysis showed significantly higher surface concentrations of oxygen functional groups for CH4/O2 mixture gas plasma-modified polypropylene membrane surfaces than for the originally unmodified polypropylene membrane surface. The experimental results show the important role of chemical species in the interaction between a CH4/O2 mixture gas plasma and a membrane surface, which can be controlled by surface modification to tailor the hydrophilicity of the membrane to the requirements of various applications.

Surface Modification of Polypropylene Membrane by RF Methane/Oxygen Mixture Plasma Treatment

Surface Modification of Polypropylene Membrane by RF Methane/Oxygen Mixture Plasma Treatment

Induced super hydrophilicity due to surface modification of polypropylene membrane treated by O 2 plasma

Radio frequency (RF) plasma offers a unique route for the surface modification of polymer. The influence of the plasma treatment on the basic properties of the porous membranes such as effective void volume and the flow rate were investigated. It was shown that the polymer ablation significantly alters the hydrophilicity leading to the enhancement of the water flux. Here, the polypropylene membrane was tested by O 2 plasma to emphasize that the contact angle nonlinearly decreases with the treatment time. The XPS surface sensitive technique was applied to confirm the drastic skin change of the oxygen content showing that membrane becomes super hydrophilic due to the significant O 2 implant.

The effects of (macro)molecular structure on hydrophilic surface modification of polypropylene membranes via entrapment

Entrapment of a variety of ethyleneoxide-containing substances from nonpolar solutions into polypropylene (PP) microfiltration membrane surface for hydrophilic modification was studied. The results from gravimetric weight gain, surface characterization by contact angle measurements and ATR-IR spectroscopy, water flux measurements and protein adsorption revealed that poly(ethylene glycol)s (PEGs) were ineffective, while many nonionic amphiphilic substances, especially some tri-block copolymers of poly(ethyleneoxide) (PEO) and poly(propylene oxide) (PPO) were very effective for PP surface modification. The relationship between modifier structure and architecture and entrapment behavior was investigated by studying the micellization of the amphiphilic modifiers in nonpolar solutions via pyrene-probe fluorescence and 1H NMR spectroscopy. We observed that the balanced structure of nonionic tri-block (macro)molecules tended to promote the formation of reverse micelles. For the most efficient polymeric modifiers, the lowest reverse critical micelle concentration (RCMC) had been observed. We conclude that a block copolymer structure and architecture promoting the self-association in the nonpolar solvent is the basis for a high modification efficiency, and that reverse micelles are involved in the entrapment modification performed at concentrations above RCMC. A different mechanism has been deduced for amphiphilic modifiers with low molar mass. This work provides more comprehensive insights in surface entrapment as a easy to perform physical surface modification method for polymeric materials.

Surface modification of polypropylene membrane to improve antifouling characteristics in a submerged membrane-bioreactor: Ar plasma treatment

To improve the antifouling characteristics of polypropylene hollow fiber microporous membranes in a submerged membrane-bioreactor for wastewater treatment, the surface-modification was conducted by Ar plasma treatment. Surface hydrophilicity was assessed by water contact angle measurements. The advancing and receding water contact angles reduced after the surface modification, and hysteresis between the advancing and receding water contact angles was enlarged after Ar plasma treatment due to the increased surface roughness after surface plasma treatment. After continuous operation in a submerged membrane-bioreactor for about 55 h, the flux recovery after water cleaning and the flux ratio after fouling were improved by 20.0 and 143.0%, while the reduction of flux was reduced by 28.6% for the surface modified membrane after 1 min Ar plasma treatment, compared to those of the unmodified membrane. Morphological observations showed that the mean membrane pore size after Ar plasma treatment reduced as a result of the deposition of the etched species; after it was used in the submerged membrane-bioreactor, the further decline of the mean membrane pore size was caused by the deposition of foulants. X-ray photoelectron spectroscopy and infrared spectroscopy confirmed that proteins and polysaccharide-like substances were the main foulants in the precipitate.

A Comparative Study of Hydrophilic Modification of Polypropylene Membranes by Remote and Direct Ar Plasma

Surface modification of polypropylene membrane by argon (Ar) plasma-induced graft polymerization with hydrophilic monomer [acrylic acid (AA) in this work] was investigated. It was found that both the distance of the membrane from the Ar plasma center and the plasma power had a strong influence on the surface modification, hydrophilicity and graft yield (GY) of the treated membrane. Results suggest that remote plasma treatment with a proper sample position, plasma power and graft polymerization leads to a membrane surface with not only less damage, but also more permanent hydrophilicity, than direct plasma treatment does. By analyzing the morphology and the chemical composition of the membrane surface by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), as well as Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) respectively, a possible mechanism was tentatively revealed.

Surface modification of polypropylene membranes by γ-ray induced graft copolymerization and their solute permeation characteristics

Porous hydrophobic polypropylene (PP) membranes were subjected to the surface modification by the γ-ray induced graft copolymerization with hydrophilic 2-hydroxyethyl methacrylate (HEMA). The structural changes and surface morphologies of the modified PP membranes were characterized by a Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA) and field emission scanning electron microscopy (FE-SEM). Peroxides produced from γ-ray irradiation were determined by a 1,1-diphenyl-2-picryl hydrazyl (DPPH) method and the surface hydrophilicities of membranes were measured by a static contact angle measurement. The contact angle of the modified membranes reduced with the degree of grafting (DG) of HEMA onto the membrane surface, and it decreased up to about half of that before modification. The permeation behaviors of all membranes were investigated by a bovine serum albumin (BSA) filtration experiment. As a result, the DG of the modified membrane increased with the reaction time. However, in the case of irradiation dosage it showed the maximum value at 20 kGy. Also, the modified membrane showed a higher solution flux, lower BSA adsorption, and the better flux recovery after cleaning than that of the unmodified membrane. Particularly, 40.6% grafted membrane showed a two-fold increase in a BSA solution flux, 62% reduction in total fouling and three-fold increase in flux recovery after chemical cleaning.

Surface modification of polypropylene membrane by low‐temperature plasma treatment

AbstractMicroporous polypropylene membranes were low temperature plasma treated with acrylic acid and allylamine. Parameters of plasma treatment were examined and optimized for the enhancement of membrane performance properties. Excess power damaged the membrane surface and excess monomer flow rate increased the reactor pressure to interfere with the glow discharge. Longer plasma treatment time resulted in even more plasma coating and micropore blocking. The contact angle with water decreased and wettabilities increased with the increase of plasma treatment time. Deposition of the plasma polymer on the membrane surface was confirmed by FTIR/ATR spectra of the treated surface. In determining the flux, the hydrophilicity of the surface played a role as important as that of the micropore size. Adequate plasma treatment could enhance both water flux and solute removal efficiency. Results from the BSA (bovine serum albumin) solution test confirmed that fouling was greatly reduced after the plasma treatment. The BSA solution flux through the plasma‐treated membranes depended on pH, whereas pH variation had no serious effects on the untreated membrane. Modification of the surface charge by the plasma treatment should exert a substantial influence on the adsorption and removal of BSA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1555–1566, 2001