Papers by Keyword: Hydrophobic

Abstract: The surface wettability of metallic biomaterials significantly influences the biological response of biomedical implants. However, the optimal degree of wettability depends on the specific coating or surface treatment applied to the biomaterial. Researchers have widely utilised hydroxyapatite coatings to modify implant surfaces to enhance bioactivity, biocompatibility, and osseointegration. This review article discussed the impact of hydroxyapatite-doped coatings on the surface wettability of metallic biomaterials. A systematic search of Scopus and Web of Science databases was conducted to review recent studies investigating the wettability and biological response of hydroxyapatite-doped coatings applied through standard implant surface deposition techniques. Results reveal that hydroxyapatite-doped coatings are typically hydrophilic and have higher surface energy than uncoated hydrophobic metallic surfaces. The hydrophilic nature promotes better interaction with biological fluids, resulting in cell adhesion and proliferation. The rough and porous surface increases wettability as fluid can easily penetrate the craters. Further research may elucidate the complex connectivity of deposition method process parameters with surface wettability and biological outcomes. This review briefly overviews current research on hydroxyapatite-doped coatings and their effects on surface wettability and biointegration.

Abstract: The core structure of the emulsion was hydrolyzed and condensed by vinyltriethoxysilane and phenyltriethoxysilane, and the shell structure was synthesized by radical polymerization of butyl acrylate, methyl methacrylate, and vinyltriethoxysilane. The Zeta potential of the prepared silicone emulsion was maintained at-40 mV. The emulsion has good stability. Transmission electron microscopy can be used to study the core-shell structure of latex particles. The water contact angle of silicone-modified acrylate coating can reach 94°, and its mechanical durability, alkali resistance, and salt corrosion resistance are better than that of pure acrylate coating.

Abstract: Cassava starch bioplastics have been known well as an alternative plastic replacing conventional petrochemical plastics, which have difficulty degrading rapidly in the environment. Cassava peels as waste is a potential eco-friendly starch source for biodegradable plastic. This study investigated the effect of graphene as a nanofiller on the hydrophobic properties of cassava peel starch film. Bioplastic was synthesized using the melt blending method by adding graphene in various amounts, which were 3 wt%, 5 wt%, and 7 wt%. Graphene was found to be able to increase the contact angle of the films up to 93° with the addition of 5 wt%. Graphene also affects water absorption properties. These results indicate that the hydrophobic properties of cassava peel starch films could be modified by adding graphene nanofiller.

Abstract: In this study, fluoroacrylate palm oil polyurethane (FPOPU) was synthesized with different synthesis methods. FPOPU was synthesized stepwise starting with the synthesis of acrylated epoxidized palm oil (AEPO) by a reaction of acrylic acid (AA) and triethylamine (TEA) as the catalyst. Then, palm oil polyurethane (POPU) was formed by the reaction of AEPO with isophorone diisocyanate (IPDI) and hydroxyethyl acrylate (HEA) as an end cap agent. POPU was further added with 1,6 hexanediol diacrylate (HDDA), trimethyloltripropane triacrylate (TMPTA), and heptafluorodecyl methyl-metacrylate (HDFDMA) monomers to form FPOPU. FPOPU synthesis methods were studied by manipulating the sequence of chemicals added, temperature, and mixing time of POPU. The FPOPU mixture was finally cast onto a silicone mold with 1 mm thickness and cured under UV radiation at 120 seconds. Based on the analysis, pre-mixed IPDI with HEA at 60°C for 15 min followed by the addition of AEPO at 60°C and further mixed for 3 hours (Method 2) shows the complete formation of the urethane chain. It is proven by the existence of NH peak at 3500 cm^-1 and the disappearance of NCO peak at the range of 2200-2500 cm^-1 indicating the NCO functional group has completely reacted with OH group in AEPO. The addition of fluorination also can be proved by the existence of CF stretching at 1012 cm^-1. This study provides information regarding comparison between the synthesis method of FPOPU.

Abstract: The study of water condensation phenomena is important in order to evaluate the performance of materials and coatings employed in the fabrication of waste heat recovery units including heat exchangers, heat pipes, condensing economizers and related functional surfaces. Fast evaluation of lab-scale samples is important during research and development of coatings for wetting phenomena under controlled, reproducible, and stable humidity and temperature conditions of both sample and environment. To study these effects, we report on the construction of a lab-scale condensation chamber, along with its evaluation and benchmarking with superhydrophobic coatings on stainless steel using perfluorooctyl silane (PFOTS). A working unit has been successfully fabricated and applied in a highly responsive device capable of recording the condensation performance of flat specimens under controlled conditions. Sample temperature was maintained with 0.10 °C deviation. The humidity response time of the chamber is 17.2 s per degree of RH% while the maximum relative humidity variation is +/- 3.2%RH. The unit successfully delivered valuable data over hydrophillic, hydrophobic and superhydrophobic surfaces. Data useful for studying open research issues such the relationship of contact angle and condensation phenomena.

Abstract: In this research, a hydrophobic surface has been successfully created using a mixture of silica sand and methyltrimethoxysilane (MTMS) precursor. This research aims to determine the effect of varying the volume of MTMS on the hydrophobic surface. The MTMS as silica precursor was synthesized with Stöber method. The variation used is the volume of the MTMS precursor, while the silica from silica sand is made constant. The volume variation of the MTMS precursor is 9.5 ml, 19 ml, 28.5 ml and 38 ml. The MTMS/SiO2 composite which has been synthesized then get mixed with steel ship paint and coated on the steel plate surface as a topcoat. The MTMS/SiO2 composite was further characterized by X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), Water Contact Angle (WCA), and Atomic Force Microscope (AFM) which were employed to investigate crystal structure, morphology of particle, hydrophobicity on a surface, and topography of the three-dimensional surface layer respectively. The type of liquid used in the WCA characterization is seawater. XRD characterization results show that silica sand has a quartz phase, MTMS has an amorphous phase and MTMS/SiO2 composite tends to have an amorphous phase. SEM characterization show that the particle size of silica sand that has been mixed with MTMS is around 8 – 20 μm. WCA characterization show that the addition of silica powder on the topcoat increase surface roughness and WCA, so that the steel plate surface has good hydrophobic properties. The highest water contact angle obtained in this research was 109o by seawater.

Abstract: The existing methods of confering hydrophobic properties to various building materials are considered. Obtaining special, including hydrophobic, properties of water-emulsion paints is a very relevant task. Previously, a method was developed for producing an emulsion of a polysiloxane stabilized with polyvinyl alcohol. The paper describes the possibility of using a hydrophobisating emulsion of polyhydrosiloxane as a functional additive for an acrylic water-dispersion paint. This emulsion is capable of forming coatings on dense and porous surfaces with an adjustable contact angle up to 105 °. The use of this emulsion, with its sufficient coalescence for volumetric hydrophobization of coatings, makes it possible to obtain a high contact angle on the surface. In the paper, it was assumed that the partial introduction of small amounts (up to 10 %) of a hydrophobizing emulsion into water-dispersion paints would allow achieving the contact angle of wetting for similar coatings consisting exclusively of emulsion. It is shown that the introduction of small amounts of a hydrophobizing emulsion with an auxiliary coalescing action of ethylene glycol makes it possible to impart hydrophobic properties to the surface of the resulting coating. When the optimum concentration of ethylene glycol in the coating is reached, dissolution and transport (yield) of polysiloxane to the surface is ensured. The research carried out made it possible to develop a paint composition with a hydrophobizing emulsion with a contact wetting angle of about 100 °, which ensured the hydrophobicity of the previously hydrophilic coating of a water-dispersion acrylic paint.

Abstract: Cerium oxide (CeO₂) is one of potential candidates of hydrophobic coatings servicing in harsh environments. In this letter, abraded CeO₂ surface was prepared using sandblasting treatment to investigate the wetting mechanism under the condition of impact abrasive wear. The water contact angle (WCA) of the abraded surface increased from 62.8° to 93.7° after aging in ambient air for about 700 h. The hydrophobic self-optimisation mechanism of the abraded CeO₂ surface is due to the hierarchical structure formed during impact abrasive wear and the surface adsorption of airborne hydrocarbon, resulting the wetting state changed from “Wenzel state” to “Cassie-Baxter State”.

Abstract: Water scarcity is growing and in particularly in regions where population is high. It is estimated by world wild life organization that two thirds of human population may face water shortage by 2025. However, the amount of water available on earth covers approximately two thirds of the total surface area, but most of the water is seawater. Seawater cannot be used for any human use due to the high salinity levels. Desalination processes have been implemented on various scales whereby reverse osmosis is the most successful. However, such system is too complex and expensive. An alternative system utilizing humidification-dehumidification process for desalination is proposed in this paper. The process involves the use of a novel hydrophobic membrane allowing the humidification. Two configurations have been tested in a closed loop cycle, namely: static and moving membrane. The results from the experiments have shown that the efficiency of the moving membrane configuration is higher than the static by 46%. And based on 1 Litre brine feed, 50% of the volume has been successfully desalinated.

Abstract: Nanofibers membrane are potential material for water filtration, and surface properties of the membrane are an important factor to avoid fouling on the membrane surface. The combination of filter material is known to influence the membrane surface properties. We investigated the mixture of polyacrylonitrile (PAN) and cellulose acetate (CA) on the nanofiber membrane by electrospinning. This blend was dissolved in dimethylformamide as feed polymer in electrospinning technique. We prepared the ratio of PAN to CA were 0:10, 4:6, 5:5, 6:4, and 10:0 in 8 wt%. All the membranes formed fiber, except 0:10 which only created a thin layer from the sprays. Contact angle measurements related to membrane surface properties were measured and resulted in 128^o, 126^o, and 125^o for 4:6, 5:5 dan 6:4 membranes, respectively. This results indicated that all PAN/CA membranes had hydrophobic properties. The hydrophobic property was also observed by Fourier transform infrared (FTIR) spectroscopy, a sharp peak of-CH₃ appeared. It is interesting while mixing two hydrophilic polymers we obtain a hydrophobic membrane.