Papers by Keyword: Hydrophilicity

Abstract: Freshwater is essential in sustaining human life on the planet and the demand for potable water has increased for the past years due to population growth and modernization. However, the natural resources of water have become polluted/contaminated due to industrialization and other human activities. The development of membrane technology, especially with the creation of nanocomposite materials, provides a solution to treat polluted or contaminated water through various separation processes resulting in the production of clean water fit for human consumption. In this study, polysulfone was added with zeolite nanoparticles to fabricate nanocomposite membranes via non-solvent induced phase separation (NIPS) method to enhance the hydrophilicity and mechanical strength of the membrane suitable for water and wastewater applications. The nanozeolite was added in varying concentrations; 1% 5% and 10% and the fabricated membranes were characterized via Contact Angle Goniometer, universal testing machine (UTM) and scanning electron microscopy (SEM) to determine the contact angle, tensile strength, and surface morphology, respectively. Based on the characterization data, the 1% concentration showed the highest tensile strength and the lowest contact angle measurement. The 1% nanozeolite concentration is the optimum membrane formulation due to the enhanced hydrophilicity and mechanical strength of the material.

Abstract: The present study utilized high-impact polystyrene, a polymer with good mechanical, thermal and chemical stability, for its potential as a filter material and matrix for nanozeolite – a well-known adsorbent for wastewater treatment. Different concentrations of nanozeolite (0.25%, 0.5%, and 0.75%) were added to the high-impact polystyrene matrix and were fabricated intocomposite membranes via hand-casting method. The membranes were characterized using Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, and Contact Angle Goniometer to discuss their functionality in the removal of nanocontaminants from wastewater like dyes. Results showed that nanozeolite can control the porosity and pore size of the High-impact polystyrene polymer while also improving its hydrophilicity; these are important considerations in the removal of organic dyes from wastewater.

Abstract: Titanium dioxide (TiO₂) has been exploited extensively as it shows remarkable performance in photocatalytic applications. TiO₂ thin films can be deposited onto window glass which is workable for self-cleaning applications. In this article, we have studied the role of substrate temperature for spray pyrolysis (SP) of TiO₂ thin films for studying self-cleaning applications. For thin film deposition, TiO₂ sol is prepared by the sol-gel synthesis technique. The samples are deposited at room temperature and 250 °C, respectively. The samples are characterized via Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and UV-Vis spectroscopy to determine the morphology, surface roughness, and optical properties of the thin films. SEM and AFM results show that samples deposited at 250 °C (pre-heated samples) have uniform size distribution, and defined grain boundaries, respectively. The results also show that the pre-heated sample is highly transparent in the visible region of the solar spectrum when analyzed by the steady-state UV-Vis spectrophotometer. The wettability of the prepared thin films is measured, and the results show that the pre-heated sample shows a hydrophilic character. The self-cleaning property of prepared thin films is evaluated by the photodegradation of Rhodamine B dye. It is observed that the pre-heated substrates show better photoactivity in presence of UV light irradiation. Hence, due to their hydrophilic nature and better photoactivity, these pre-heated thin films deposited by spray pyrolysis can be employed as efficient coatings for self-cleaning glass applications.

Abstract: Poly (ethylene terephthalate) (PET), also commonly called as polyester, is the most widely used polymer for the production of synthetic fibres over the past fifty years. The frequent use of this PET is due to its high mechanical strength combined with other properties such as the resistance to chemical products, stretching and abrasion. The fibre’s hydrophobicity also impacts the difficulty of cleaning these materials [1, 2]. Previous works shows that treatment with concentrated NaOH solutions can greatly improve hydrophilicity of PET fibre [1, 2, 3, 4]. However a significant decrease of mechanical properties takes place during this process. In this work, chemical strategies to counteract this negative effect and further increase the hydrophilicity of PET fibre’s has been tested. In particular, the effect of polyvinyl alcohol (PVA) and N, N ́-dimethylol-4, 5-dihydroxyethyleneurea (DMDHEU) chemically modified resin in the functionalization of saponified PET was carefully analysed. The treated fabrics were characterized by scanning electron microscopy (SEM), contact angle, ATR-FTIR spectroscopy and differential scanning calorimetry (DSC). When the best process conditions were considered for PVA-DMDHEU application, the modified PET presented a contact angle of 33.9o, stain release grade of 4 and a 45.6% increase in its mechanical properties when compared to saponified PET.

Abstract: Plasma hydrophilization and subsequent hydrophobic recovery in Bambara groundnuts are studied for the first time. Bambara groundnut seeds were treated with cold plasma (CP) for 10 seconds at 10 watts using water as a monomer. The contact angle, as well as physical and chemical changes, were used to determine the kinetics of hydrophobic recovery. The hydrophilic state of Bambara groundnut seeds had decreased after 60 days, but not to original hydrophobicity, and also the recovery rate is slower than those observed on synthetic polymer. However, this slower hydrophobic recovery makes CP treatment as an effective method for long-term seed storage.

Abstract: The purpose of this study was to evaluate the effect of weak magnetic fields on the structure and physical properties of chitosan (Ch) membranes. The membranes were prepared by a casting method using chitosan and a solvent of acetic acid. The magnetic field of 1.5 mT is applied during the membrane-forming reaction with administration times of 2, 4, 8, and 12 hours. The membranes formed were named M-2h, M-4h, M-8h, and M-12h, respectively. The chitosan membrane without magnetic fields is used as a control, namely M-0. The structure and physical properties of the membranes were examined using Fourier Transform Infra-Red (FTIR) spectrophotometer, water uptake test, dynamic mechanical analysis (DMA), and X-ray diffraction (XRD). The result showed that the membranes with magnetic fields are thicker compared to the control membrane. FTIR analysis revealed that some peaks of the membranes with magnetic fields shifted to the higher or lower wavenumber with increased or decreased absorption intensity. The membranes become stronger and more flexible; their degree of crystallinity increases as increasing the time of the magnetic fields' application, and their hydrophilicity improved. The membranes' crystal structure becomes more regular, and their degree of crystallinity increases as increasing the time of the application of the magnetic fields; and their mechanical properties such as ultimate tensile strength, tensile modulus, and elongation at break were improved. Those results explain that the structure and physical properties of chitosan membranes were significantly affected by the membrane-forming reaction's magnetic fields.

Abstract: Polyester fabric has the disadvantage of poor hydrophilicity which reduces its wearing comfort and limits its usage in clothing industry. Chitosan especially that of low molecular weight is effective in hydrophilic finishing for polyester fabric, while using plasma processing can greatly improve the effect. This is a green and environmental protection process. Two sets of orthogonal experiments and analysis are done to research the factors that influence the plasma processing effect and the chitosan finishing effect which points out the variation tendency and the best processing conditions.

Abstract: In this work, polyethersulfone (PES) was blended with bio-based polymers, PLA (hydrophobic polymer) and PEG (hydrophilic polymer), in order to improve the antifouling properties of PES membranes. This was done by way of non-solvent induced phase separation. Membrane properties such as morphology, hydrophilicity/hydrophobicity, adsorption fouling and mechanical properties were characterized. All blended membranes displayed higher hydrophilicity than that of pristine PES. This was confirmed by lower water contact angle and higher water adsorption. It was found that membranes with 5 wt% PLA/PEG gave a water contact angle of 65.1° and water adsorption for 4.94. These were the best values obtained. These modifications yielded low protein adsorption leading to reduce membrane fouling. Adding a greater amount of PLA/PEG reduced the membrane pore size, enhanced hydrophilicity and improved the antifouling capability

Abstract: Polymer films are plasma treated to improve surface properties making them hydrophilic or hydrophobic. Expanded polytetrafluoroethylene (ePTFE) is used in a wide variety of applications but only a few report on plasma treated ePTFE. Within these very few studies on ePTFE, the use of ultra-thin membrane could hardly be found. The purpose of this study is to investigate the effect of plasma treatment (Argon-Oxygen) on the hydrophobicity of ultra-thin ePTFE membrane (4um thickness). This study used nine (9) experimental legs of ePTFE subjected to respective plasma power (150W, 315W and 600W) and exposure time (300s, 450s and 600s) for each leg. Contact angle was measured prior and after subjecting to plasma condition using contact angle meter. Energy pen was also used to verify its hydrophobicity. Scanning electron microscopy (SEM) with 10,000x magnification was used to check for any change in surface after exposing to each condition. The findings showed that the membrane surface changed after exposure to plasma. All legs became hydrophilic. 102◦ contact angle was measured from raw sample, but the samples exposed to plasma had contact angles ranging from max of 68◦ to min of 48◦. The results showed that the degree of surface change could be correlated to the plasma parameters applied. Furthermore, the highest radio frequency (RF) power applied resulted to contact angle in the range of 60◦ while the lowest RF power applied resulted to the lowest contact angle, in the range of 40◦, measured. On the other hand, no particular trend was observed based on exposure time. Based on the gathered results, the ultra-thin ePTFE, in order to maintain its hydrophobicity, must not be applied with argon-oxygen plasma treatment. However, if the ultra-thin ePTFE is to be made hydrophilic, argon-oxygen plasma treatment could be applied while adjusting the plasma parameters to meet the desired hydrophilicity level.

Abstract: The goal of this work is to evaluate a common final sterilization technique with EtO by measuring its effect on the physicochemical properties of PVD deposited TiN/TiO₂ coatings on Ti-5Al-4V alloy. As the effectiveness of EtO sterilization corresponds to the operation parameters (temperature, duration, humidity, etc.), two different exposure cycles (cool (MS) at 37 °C for 220 min gas expose and warm (SS) at 55 °C for 100 min expose) were examined. SEM analysis revealed that the surface morphology of the coatings was not changed after both MS and SS treatments. In contrast to Ti 2p and O 1s peaks determined by XPS analysis, C 1s peak of TiO₂ layer decreased with increasing sterilization temperature while the percentage contribution of Ti-OH in O 1s increased. This affected the surface hydrophilicity and free energy that increased from 47.37 for the control sample to 50.77 mJ m^-2 in the case of SS specimen. Additionally, EtO sterilized samples demonstrated decreased values of corrosion and passivation current densities in simulated body fluid (pH 7.4) at 37 ± 0.05 °C as opposed to the control sample. The results indicate the suitability of both mild and severe EtO sterilization methods for improvement of the desired physicochemical properties of gradient TiN/TiO₂ coatings.