Hydrophobic Silica Research Articles

Hydrophobic Silica Thin Film derived from Dimethyldimethoxysilane-Tetraethylorthosilicate for Desalination

Silica thin film preparation was carried out from dimethyldimethoxysilane (DMDMS) and tetraethylorthosilicate (TEOS) precursors using the sol-gel method, and the effect of pH on the character of the resulting silica membrane was also studied. The solution pH was varied into 2.21; 3.92; 4.98; 6.44; and 7.21. The resulting xerogel was analyzed using Fourier-transform infrared spectroscopy, Thermogravimetric Analysis, and Gas Sorption Analysis. While the silica thin layer was measured for its hydrophobic character and surface morphology using Scanning Electron Microscope. The presence of DMDMS-TEOS silica thin film had a considerable influence on the hydrophobic nature of the ceramic plate surface. The membrane prepared under neutral conditions produced desirable properties, such as higher thermal stability, greater pore volume, thermal stability, and higher hydrophobicity. For the desalination process, the obtained silica membrane showed excellent separation performance (>99%), especially at low salt concentrations. When the pH increased, the water flux also increased. The thin films worked well for desalination through a pervaporation mechanism.

Sequential impregnation and sol-gel synthesis of Fe-ZnO over hydrophobic silica aerogel as a floating photocatalyst with highly enhanced photodecomposition of BTX compounds from water

Benzene, Toluene, and Xylene (BTX) are included in the floating contaminants which originated from the explosion of oil wells. Photocatalytic oxidation of the some oil spill components like Benzene, Toluene, and Xylene can be a proper way to solve this challenge due to its economic saving, usage of free energy, and environmentally friendly. For this purpose, we have synthesized a hydrophobic catalyst of Fe-ZnO nanoparticles inoculated with silica aerogel (SA). Various percentage of hydrophobic silica aerogel (10, 20 and 30%) was added, as support of catalyst, to Fe-ZnO nanoparticles using impregnation method. The impregnation of silica aerogel to Fe-ZnO nanoparticles caused the photocatalytic performance of nanocatalyst was improved through its increased surface area, and also floated active phase (Fe-ZnO) on water. In order to investigate the impact of the synthetic method of nanocomposite on the activity of synthesized nanophotocatalyst, optimum samples (Fe-ZnO over 20% SiO2) were synthesized using the sol-gel method. The synthesized nanophotocatalysts were characterized using PXRD, FESEM, EDX, UV–Vis, Contact Angle, FT-IR, and BET-BJH analyses. Photocatalytic activity of synthesized nanophotocatalyst was evaluated in the degradation of the BTX after 120 min, under visible light irradiation. In addition, the influence of various parameters including the addition of hydrophobic silica aerogel, pH, catalyst loading, benzene concentration, and reusability was studied on the photodegradation efficiency of Fe-ZnO/SA (20%). The most photocatalytic activity was observed in the optimum condition involving pH = 5, catalyst loading = 1 g/L, and benzene concentration = 5% V/V.

Effect of Hydrophobic Silica Nanochannel Structure on the Running Speed of a Colloidal Damper

A colloidal damper (CD) can dissipate a significant amount of vibrations and impact energy owing to the interface power that is generated when it is used. It is of great practical significance to study the influence of the nanochannel structure of hydrophobic silica gel in the CD damping medium on the running speed of the CD. The fractal theory was applied to observe the characteristics of the micropore structure of the hydrophobic silica gel by scanning electron microscopy (SEM), the primary particles were selected to carry out fractal analysis, and the two-dimensional fractal dimension of the pore area and the tortuous fractal dimension of the hydrophobic silica gel pore structure were calculated. The fractal percolation model of water in hydrophobic silica nanochannels based on the slip theory could thus be obtained. This model revealed the relationship between the micropore structure parameters of the silica gel and the running speed of the CD. The CD running speed increases with the addition of grafted molecules and the reduction in pore size of the silica gel particles. Continuous loading velocity testing of the CD loaded with hydrophobic silica gels with different pore structures was conducted. By comparing the experimental results with the calculation results of the fractal percolation model, it was determined that the fractal percolation model can better characterize the change trend of the CD running velocity for the first loading, but the fractal dimension was changed from the second loading, caused by the small amount of water retained in the nanochannel, leading to the failure of fractal characterization.

Changes in cell wall metabolism and flavor qualities of mushrooms (Agaricus bernardii) under EMAP treatments during storage

To clarify the dynamic changes of cell wall metabolism and flavor components in Agaricus bernardii packed with the packaging materials during storage. The polyethylene (PE), poly (butylene adipate-co-terephthalate)/ poly (l-lactic acid) (ECFPLA) and PBAT/PLLA/ hydrophobic silica (ECFPLASiO2) with a different gas/water vapor permeability were used as equilibrium modified atmosphere packaging (EMAP) materials, and an appropriate gas concentration [O2 (0.01−0.03 %), CO2 (4.58–6.62 %)] was created inside the ECFPLASiO2 packaging, which led to Agaricus bernardii with higher level of cell wall components and lower level of cell wall degrading enzymes during the storage period. For the first time application of HS-SPME–GC–MS on an extract from fresh Agaricus bernardii. The results showed that volatile compounds of fresh Agaricus bernardii mainly consists of alcohols, ketones and aldehydes, with 3-octanol, 3-octanone, 1-octene-3-alcohol and phenylcarbinol being most abundant compounds. During the storage time, the varieties and content of volatile compounds were changed in all treatments. Alcohols, aldehydes, hydrocarbons and esters contents increased during the storage while ketones declined. Among all treatment groups, ECFPLASiO2 group showed higher most abundant compounds and organic acid content. The results suggest that ECFPLASiO2 film could be used to reduce the changes in cell walls and flavor components after harvest and extend the shelf life of Agaricus bernardii.

Recovery of rare earth elements from uranium leach liquors by adsorption with diglycolamic acid ligands and ionic liquids

A series of extraction chromatographic resins containing various phosphorus-containing and DGA-based extractants and ionic liquids was synthesized and their sorption characteristics for rare earth elements (REE) in sulfate solutions were studied. The effects of the type and content of ionic liquid in the stationary phase as well as solid support type on the sorption capacity of the resins for La, Nd and Dy were evaluated. It was shown that the quantity of the stationary organic phase in the resins was 30–35% independent of the matrix type. In the case of the DODGAA: TODGA: [C4mim][Tf2N] system, the matrix type did not affect the resin capacity for REE in sulfuric acid solutions. Acidity of the aqueous phase was one of the most important factors affecting lanthanides sorption from sulfate solutions. The capacity of the sorbents for lanthanides decreased sharply with the increase of acidity of the solution, this decrease was stronger for light REE. The process of REE separation from uranium leach liquors was studied using real leach liquors after separation of uranium. It was shown that a resin based on hydrophobic silica gel impregnated by DODGAA:TODGA:[C4mim][Tf2N] mixture can be recommended for concentration and primary separation of lanthanides from multicomponent industrial solutions. The advantage of this sorbent is a high selectivity for REE over macro amounts of Al and Fe as compared with strong acid cation exchange resins and phosphorus-containing organic extractants, which are widely used for preconcentration. Using this sorbent for selective recovery of REE from uranium leach liquors provided concentration factors of 10–15 for light REE group and 150–300 for heavy REE group.

THE EFFECT OF ADDITIONAL SALT AND ACID ON THE HYDROPHOBIC LAYER OF NANOCOMPOSITE SILICA/POLYSTYRENE (SiO2/PS) ON THE STABILITY PROPERTIES OF UV

In nature there is a phenomenon. Which this phenomenon can be seen in the lotus leaf and taro leaves. a phenomenon called hydropobic (water repellent) properties. This research is a previous research. On application, the hydrophobic coating will mostly break down quickly when applied outside or in harsh environments. So it is very important to develop a durable hydrophobic layer, especially the stability properties against Ultra Violet (Uv). Therefore, this study aims to see the effect of adding salt and acid to the hydrophobic silica / polystyrene nanocomposite (SiO2 / PS) layer on the stability of the Uv. with a polystyrene composition of 0.5 grams and 0.2 grams of silica powder and 0.4 grams of salt and 0.4 grams of acid. The coating method used is the spin coating method and the Uv stability test on the hydrophobic layer is done by drying the layers for one hour under direct sunlight. The results of this study were the contact angle measurements using imagej software, and the crystal grain size by SEM (Scanning electron microscop). UV stability can be seen by changing the contact angle in each sample where the contact angle that can be before irradiation is acid added salt (120.1490C), salt (100.3630C), acid (128.5910C), without mixture (133.6680C) ) and after irradiation is. Salt (92.970C), unmixed (98.1440C), acid added salt (92.1150C), acid (141.5750C). These results may indicate that acid coating is more likely to use hydrophobic / self-cleaning surfaces in harsh environments such as high Uv irradiation, and outdoor applications.

Analysis of the acid and alkali resistance of superhydrophobic paper mulch

Agricultural paper mulch is an indispensable part of modern agriculture. It had the functions of heat preservation, moisture preservation, insect resistance, disease prevention, and weed growth inhibition. In order to extend the service life of the paper mulch, we use the solution immersion method to modify the surface of the paper mulch. A super-hydrophobic paper mulch is mainly prepared by using hydrophobic silica. The static contact angle of the super-hydrophobic paper mulch with water is 160.6°. The super-hydrophobic paper mulch samples were immersed in acid solution (pH = 4.6 H2SO4) and alkaline solution (pH = 8.5 NaOH). The main instruments are contact angle tester, tensile testing machine and high-speed camera. The hydrophobic properties, mechanical properties and rebound properties of the two kinds of paper mulches were compared. The results showed that the tensile strength and droplet bounce height of the superhydrophobic paper mulch decreased after being soaked in acid or alkaline solution for 48 h. The mass loss rate of paper mulch was more significant in acid solution, but its contact angle was still greater than 145°, and it had good bounce performance. After observing the microscopic morphology of its surface, it was found that silica had a micro-rough structure on the surface of the paper mulch. The method was simple and environmentally friendly, and can alleviate the problem of poor acid and alkali corrosion resistance of the paper mulch, and had extraordinary significance for environmental protection.

Impact of altered hydrophobicity and reduced agglomeration on dissolution of micronized poorly water-soluble drug powders after dry coating

The impact of dry coating with hydrophobic or hydrophilic nano-silica at 25–100% surface area coverage on dissolution of micronized poorly water-soluble drugs was investigated by examining their agglomeration and surface hydrophobicity. Ibuprofen (20 µm and 10 µm) and griseofulvin (10 µm) were selected having differing solubility, hydrophobicity, and surface morphology. Characterization involved particle agglomeration via two dry dispersion methods, drug dissolution using the USP IV method, cohesion reduction through shear testing, and powder wettability via the modified Washburn method. Dry coating dramatically reduced the cohesion hence agglomerate size of both the coated ibuprofen particles, but less for griseofulvin, attributed to its surface morphology. For hydrophobic silica, agglomerate size reduction outweighed the adverse impact of increased surface hydrophobicity for ibuprofen. For griseofulvin, the agglomerate reduction was much lower, not able to overcome the effect of increased drug particle hydrophobicity with hydrophobic silica coating. Hydrophilic silica coating reduced hydrophobicity for all three drug powders, leading to the synergistic improvement in the dissolution along with agglomerate size reduction. Overall, the combined effect of the drug particle surface hydrophobicity and agglomerate size, represented by specific surface area, could explain the dissolution behavior of these poorly water-soluble drugs.

Effect of silver and silica nanoparticles on the larvae of pink stem borer Sesamia cretica Lederer, 1857 (Lepidoptera: Noctuidae) and maize plants Zea mays Linneaus, 1753

This study was aimed to evaluate the toxicological and biological effects of three nanoparticles (silver, hydrophilic and hydrophobic silica) at four concentrations (100, 200, 400 and 800 ppm) against 1st instar larvae of Sesamia cretica Lederer, 1857 and its effects on some maize characters. Each concentration and control was repeated 4 times (10 larvae/replicate). Larvae were fed on treated stem maize and mortality rate was recorded. After treatment with LC50 values, the survival larvae were collected and the larval duration, pupal duration, pupal weight, pupation percentage and adult longevity were recorded. Seedling maize plants were sprayed with three concentrations (50, 100 and 200 ppm) at 4 categories (every 1, 3, 7 and 14 days) to detect the effect of nanoparticles on leaf area, extended height and leaf chlorophyll content. Results showed that hydrophilic silica nanoparticle was the most effective, followed by silver nanoparticle then hydrophobic silica nanoparticle with LC50 121.19, 405.71 and 416.82 ppm, respectively. All nanoparticles led to increase in larval durations, reduction of egg number per female and decrease of eggs hatchability rate. All nanoparticles caused positive effect on leaf area, extended height and chlorophyll content. These nanoparticles may be recommended to control S. cretica with positive effects on plant characters.

Mesoporous Silica-Coated Upconverting Nanorods for Singlet Oxygen Generation: Synthesis and Performance.

Photodynamic therapy (PDT) has been reported as a possible pathway for the treatment of tumors. The exploration for promising PDT systems thus attracts continuous research efforts. This work focused on an ordered core–shell structure encapsulated by mesoporous SiO2 with the upconverting emission property following a surfactant-assisted sol–gel technique. The mesoporous silica shell possessed a high surface area-to-volume ratio and uniform distribution in pore size, favoring photosensitizer (rose bengal) loading. Simultaneously, upconverting nanocrystals were synthesized and used as the core. After modification via hydrophobic silica, the hydrophobic upconverting nanocrystals became hydrophilic ones. Under near-infrared (NIR) light irradiation, the nanomaterials exhibited strong green upconverting luminescence so that rose bengal could be excited to produce singlet oxygen. The photodynamic therapy (PDT) feature was evaluated using a 1O2 fluorescent indicator. It was found that this core–shell structure generates 1O2 efficiently. The novelty of this core–shell structure was the combination of upconverting nanocrystals with a mesoporous SiO2 shell so that photosensitizer rose bengal could be effectively adsorbed in the SiO2 shell and then excited by the upconverting core.

Removal of Oil Pollution in water using hydrophobic silica

Nowadays the contamination in waters by oily substances turns out to be a problem of world-wide scope and although some methods of removal of oils in water exist; these present some limitations; therefore, this project proposes the use of hydrophobic silicas as absorbent materials for oily substances. Modified silicas (R-SiO2) were synthesized using the Stöber method, modifying the surface by co-condensation. Tetraethyl-orthosilicate (TEOS) and two surface modifiers were used as silica former: Methyl-trimethoxysilane (MeTEOS) and n-octyl-triethoxysilane (nOctyl-TEOS). The R-SiO2 were characterized by infrared spectroscopy identifying the modifying groups and their hydrophobicity was qualitatively evaluated according to the change in solubility in water. Finally, the removability of an automotive motor oil was evaluated by determining the amount of oil removed per gram of modified silica.

Synergistic toughening of poly(lactic acid)/poly(ethylene vinyl acetate) (PLA/EVA) by dynamic vulcanization and presence of hydrophobic nanoparticles

AbstractThe presented research reports a successful preparation of a super toughened poly(lactic acid)/poly(ethylene vinyl acetate) (PLA/EVA) blend using simultaneous dicumyl peroxide (DCP)‐induced dynamic vulcanization and addition of hydrophobic spherical silica nanoparticles (NPs). The torque evolution during melt mixing of the samples was assessed to track the dynamic vulcanization process. NPs were localized mainly in the EVA droplets and at the interface where a layer of particles was formed with a small amount dispersed in the PLA matrix. The incorporation of NPs or DCP induced compatibilization, causing a drastic decline in the size of EVA droplets in addition to improving the interfacial adhesion. On the other hand, simultaneous dynamic vulcanization and NPs incorporation synergistically affected the compatibilization of EVA and PLA phases. Differential scanning calorimetry (DSC) was employed to analyze the thermal transition and crystallization behavior of the samples. Simultaneous incorporation of silica nanoparticles and DCP at an optimum content significantly improved the tensile toughness, elongation at break, and impact strength, giving rise to super toughened PLA/EVA blend. The elongation at break and impact strength of the dynamically vulcanized PLA/EVA blend containing 5% nanosilica showed an increase from 7% to 175% and 5.1 to more than 77 kJ/m2, respectively as compared to the neat sample. Based on SEM analysis of the fractured surface of the tensile samples, cavitation in combination with intensive shear yielding of the matrix were dominating toughening mechanisms. Finally, the effect of DCP and NPs on the microstructural properties of the sample was investigated through rheological evaluations.

A comparison between the effects of hydrophobic and hydrophilic silica aerogel fillers on tensile and thermal properties of unsaturated polyester composites

A comparison between the effects of hydrophobic and hydrophilic silica aerogel fillers on tensile and thermal properties of unsaturated polyester composites

Preparation and hydrophobicity modification of poly(vinylidene fluoride‐co‐hexafluoropropylene) membranes for pervaporation separation of volatile organic compound from water

AbstractIn this study, novel nanocomposite membranes were fabricated for the removal of isopropyl benzene, a volatile organic compound (VOC), from water via pervaporation (PV). The membranes were made of poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) copolymer. In order to improve the hydrophobic properties of the membranes, hydrophobic silica nanoparticles that had been surface modified by hexamethyldisilazane were used as the nanofiller in the PV membranes, for the first time. Incorporating hydrophobic silica nanoparticles into PVDF‐HFP and increasing its concentration up to 9 wt% enhanced membrane hydrophobicity. Evaluation of membrane performance in VOC separation from water showed that the membrane containing 9 wt% of silica had the highest VOC separation factor, so that the values of total flux, separation factor, and PV separation index (PSI) were 3.77 g/m2/h; 42,483.81; and 158,788.50 g/m2/h for this membrane, respectively. The separation factor and PSI value of the mentioned membrane were almost 204 and 5 times higher than that of the neat PVDF‐HFP membrane.

Preparation of single-ion conductor solid polymer electrolyte by multi-nozzle electrospinning process for lithium-ion batteries

In this work, a method for preparing solid polymer electrolytes with function of single ion conduction (SICs-SPEs) is developed and reported. A solid state ionic conduction path with three-dimensional interpenetrating network was constructed by multi-nozzle electrospinning technology and a followed hot pressed treatment. Here, two components of SICs-SPEs were chosen where one component is a single ion conducting lithium salt with polyanion structure, and the other component is a solid polymer electrolyte matrix with the function of conducting lithium ions in solid state. This stable three-dimensional interpenetrating network structure is beneficial to inhibit the separation of the two components. At the same time, the introduction of hydrophilic and hydrophobic silica (SiO2) reduces the crystallinity of polyethylene oxide (PEO) and promotes the dissociation of lithium ions, respectively, thereby the ionic conductivity of the prepared single-ion conductor solid polymer electrolyte can be increased to 5.4 × 10−5 S cm−1 at 60 °C, and the lithium-ion transference number (tLi+) can be increased to 0.96. This method can also adjust the performance of the solid state polymer electrolyte through balancing the ration of composition by controlling the number of spinning nozzle. It provides a practical way to develop functional solid polymer electrolyte by electrospinning technology with nozzle design.

Hydrophobic Mesoporous Silica Particles Modified With Nonfluorinated Alkyl Silanes.

This work reports the preparation of hydrophobic mesoporous silica particles (MSPs) modified with nonfluorinated alkyl silanes. Alkyl silanes were grafted onto the surface of the MSPs as a function of the length of nonfluorinated alkyl chains such as propyltriethoxysilane (C3), octyltriethoxysilane (C8), dodecyltriethoxysilane (C12), and octadecyltriethoxysilane (C18). Moreover, the grafting of the different alkyl silanes onto the surface of MSPs to make them hydrophobic was demonstrated using different conditions such as by changing the pH (0, 4, 6, 8, and 13), solvent type (protic and aprotic), concentration of silanes (0, 0.12, 0.24, 0.36, 0.48, and 0.60 M), reaction time (1, 2, 3, and 4 days), and reaction temperature (25 and 40 °C). The contact angles of the alkyl silane-modified MSPs were increased as a function of the alkyl chain lengths in the order of C18 > C12 > C8 > C3, and the contact angle of C18-modified MSPs was 4 times wider than that of unmodified MSPs. The unmodified MSPs had a contact angle of 25.3°, but C18-modified MSPs had a contact angle of 102.1°. Furthermore, the hydrophobicity of the nonfluorinated alkyl silane-modified MSPs was also demonstrated by the adsorption of a hydrophobic lecithin compound, which showed the increase of lecithin adsorption as a function of the alkyl chain lengths. The cross-linking ratios of the modified silanes on the MSPs were confirmed by solid-state 29Si-MAS nuclear magnetic resonance (NMR) measurement. Consequently, the hydrophobic modification on MSPs using nonfluorinated alkyl silanes was best preferred in a protic solvent, with a reaction time of ∼24 h at 25 °C and at a high concentration of silanes.

Bifunctional poly (l-lactic acid)/hydrophobic silica nanocomposite layer coated on magnesium stents for enhancing corrosion resistance and endothelial cell responses

Biodegradable magnesium (Mg)-based vascular stents can overcome the limitations of conventional permanent metallic stents, such as late in-stent restenosis and thrombosis, but still have difficulty retarding degradation while providing adequate mechanical support to the blood vessel. We incorporated silica nanoparticles surface-functionalized with hexadecyltrimethoxysilane (mSiNP) into a poly (l-lactic acid) (PLLA) coating as a physical barrier to disturb the penetration of the corrosive medium as well as a bioactive source that releases silicon ions capable of stimulating endothelial cells. The corrosion resistance and biocompatibility of this bifunctional PLLA/mSiNP nanocomposite coating were investigated using different weight ratios of mSiNP. The nanocomposite coating containing more than 10 wt% of the mSiNP (PLLA/10mSiNP and PLLA/20mSiNP) significantly delayed the corrosion of the Mg substrate and exhibited favorable endothelial cell responses, compared to the pure PLLA coating. Specifically, the calculated corrosion rates of PLLA/10mSiNP and PLLA/20mSiNP decreased by half, indicating the durability of the coating after immersion in simulated body fluid for 12 days. Based on the in vitro cellular response, the incorporation of the mSiNPs into the PLLA coating significantly improved the endothelial cell responses to the Mg substrate, showing better initial cell surface coverage, migration, and proliferation rate than those of pure PLLA. These results indicate that the PLLA/mSiNP nanocomposite coatings have significant potential to improve the corrosion resistance and vascular compatibility of biodegradable Mg-based vascular stents.

Improved CO2 adsorption capacity and fluidization behavior of silica-coated amine-functionalized multi-walled carbon nanotubes

The adsorption capacity and fluidization behavior of silica-coated amine-functionalized multi-walled carbon nanotubes (MWCNTs) were studied in this work. The coupling of both studies is fundamental for the practical application of CO2 sorbents in fluidized beds. Sorbents were prepared by hydrolysis of tetraethylorthosilicate (TEOS) onto acid-treated multi-walled carbon nanotubes followed by impregnation with monoethanolamine (MEA). The effects of different loading amounts of MEA and TEOS on CO2 uptake were investigated using thermogravimetric analysis under a simulated flue gas composed of 15%CO2/85% N2. At the optimal loadings of TEOS (30 ml) and MEA (30 wt%) on MWCNTs, 2.67 wt% of CO2 was captured at 25 °C, while the adsorption capacity of the pristine MWCNTs before any modification was negligible. Adsorption/desorption tests repeated 25 times also showed that the prepared sorbent has excellent stability during the cyclic operation; 9.42% reduction of the uptake was reported. Fluidizability of the most promising sorbent was also assessed when adding hydrophobic silica nanoparticles (NPs). Maximum bed expansion of 3.9 was achieved in the presence of 7.5 wt% silica NPs which was comparable by the amount of 2.24 belonged to raw MWCNTs. Enhancement of fluidity may be attributed to the decreased van der Waals attraction forces between the particles of sorbent. Besides, the CO2 adsorption capacity of the sorbent mixed with 5 wt% silica NPs was surprisingly increased by approximately 8%, reaching ~3 wt% of CO2.

Effects of Hydrophobic Silica on the Performance of Silicone-Based Antifoams

The efficiency of an antifoam consists of polydimethylsiloxane oil, hydrophobe silica particles, and either Sodium Dodecyl Sulfate (SDS) as an anionic surfactant, or Octyl phenyl deca ethylene oxide (Triton X-100) as nonionic surfactant for use in aqueous system is investigated. The performance of different combinations of oil, silica particles, and surfactant in control of foam height was determined using Bickerman Shaking test. The effect of surfactant in reducing the surface tension was determined using Wilhelmy test. The sizes of dispersed oil droplets and silica particles were determined using both optical and electronic microscopy. It was found that increasing the silica content of the antifoam mixture and using sharp-edged particles increase the performance of antifoam and decrease the foam disappearance time. This Observation was the same for both cases of using anionic and nonionic surfactants. It was also found that, as the inert gas purging rate increases, the time of deactivation decreases to less than a minute; a favorable performance for good quality antifoam.

Robust Superhydrophobic Surface on Polypropylene with Thick Hydrophobic Silica Nanoparticle-Coated Films Prepared by Facile Compression Molding

Superhydrophobic surfaces have been extensively studied for their unique interfacial interaction between water and the surface, and they can be used for self-cleaning, drag reduction, anti-icing, and other applications. To make the superhydrophobic surfaces, nano/microscale structures and a low surface energy should be realized. The development of a durable superhydrophobic surface was hindered by the vulnerability of the surface to mechanical contact. To improve the robustness of the superhydrophobic surface toward mechanical damage, the hydrophobic polypropylene (PP) surface was coated with a thick layer of hydrophobic silica nanoparticles (SNPs) using a simple compression molding process. The thick layer consists of SNPs and PP, and the roles of SNPs and PP are nano/microscale structures with a low surface energy and binder for nanoparticles, respectively. This revealed improvement in the superhydrophobic tendency, with an apparent contact angle of about 170° and a sliding angle of less than 5°. The morphology and the corresponding elemental analysis of the PP/SNPs coated films were investigated using field emission scanning electron microscopy and energy-dispersive spectrometry. The mechanical durability of the superhydrophobic surface was evaluated by the scotch tape test and scratch test with sandpaper. The coated films with SNPs showed the superhydrophobic behavior after 25 tape tests. In addition, the coated films with SNPs showed a contact angle greater than 150° and a sliding angle less than 10° after a 100-cm scratch test with 1000 grit sandpaper, under a weight of 500 g, on an area of 40 × 40 mm2. The chemical stability of PP/SNPs coated films was also investigated in acidic, neutral, and alkaline medium solutions. The films showed good stability under the acidic and neutral medium solutions even after 24 h, but an alkaline medium could damage the surface. The obtained results demonstrated the robustness of the superhydrophobic coating with SNPs.