Investigation of the effect of dual-size coatings on the hydrophobicity of cotton surface

A series of silica nanoparticles with two different length scales were introduced onto the cotton substrates to study the correlation between the surface structure and observed hydrophobicity. SiO₂ nanoparticles of 7, 12, 20, and 40 nm in size were individually functionalized using 3-aminopropyl triethoxysilane or 3-glycidoxypropyltrimethoxysilane. Amino functionalized silica nanoparticles were durably attached to the cotton surface that was previously treated with epichlorohydrin. By depositing an additional layer of epoxy modified silica nanoparticles, a dual-size hierarchical coating was obtained. It was found that the order of deposition of particles to develop dual-size coatings determines the surface roughness, hydrophobicity and the amount of silica loaded on the cotton substrate. Deposition of the bigger nanoparticles on top of smaller ones resulted in rougher surfaces, higher hydrophobicity and higher amount of silica loading onto the cotton surface. A strong correlation between the size ratio of deposited nanoparticle combinations and the amount of silica loading was observed. It was found that there is also a direct relationship between the surface roughness and the hydrophobicity of the samples generated. Based upon these correlations, it is now possible to tune surface roughness and subsequent wettability by controlling the sizes of the dual-type nanoparticle layers.     

Counterion exchange to achieve reversibly switchable hydrophobicity and oleophobicity on fabrics

We describe a simple layer-by-layer (LbL) technology and counterion exchange procedure to tune the liquid wettability of commercially available cotton fabrics. A polyelectrolyte multilayer is deposited on the fabric surface by the LbL technology, and counterion exchange is used to control the surface composition and thereby to modulate the solid surface energy. The tunability of the solid surface energy, along with the inherent re-entrant texture of the cotton fabric, results in simultaneously switchable wettability between a nonwetting state and a fully wetted state for water and hexadecane. This switchable hydrophobicity and oleophobicity can be explained within a robustness factor, which is a quantitative criterion for the transition between the two states. The counterion exchange can be confirmed by X-ray photoelectron spectroscopy analysis.     

Formation of a surface covalent organic framework based on polyester condensation

The reaction between 1,3,5-tris(4-hydroxyphenyl)benzene and benzene-1,3,5-tricarbonyl trichloride leads to polyester condensation and formation of a novel COF on an Au(111) surface. The characterization performed in situ by means of variable temperature STM and XPS reveals the formation of an array of hexagonal cavities with ca. 2 nm size.     

Formation of micro-arc coatings on the surface of D16 aluminum alloy

Results of a study of how optically black coatings are formed by micro-arc oxidation on the surface of D16 aluminum alloy are reported. Coatings with high optical properties were obtained on this alloy in the pulsed anodic-cathodic mode of treatment in the electrolyte composition developed in the study.     

Surface modifications of Li-ion battery electrodes with various ultrathin amphoteric oxide coatings for enhanced cycleability

Ultrathin ZnO, ZrO₂, and Al₂O₃ surface coatings are deposited via atomic layer deposition (ALD) with high conformality and atomic scale thickness control to enhance the electrochemical performance of LiMn₂O₄ for applications in lithium ion batteries. Two types of ALD-modified LiMn₂O₄ electrodes are fabricated: one is ALD-coated LiMn₂O₄ composite electrode and the other is electrode composed of ALD-coated LiMn₂O₄ particles and uncoated carbon/polyvinylidenefluoride network. Cycling performance and cyclic voltammetric patterns reveal that ZnO ALD coating is the most effective protective film for improving the electrochemical performance of LiMn₂O₄ at either 25 or 55 °C, followed by ZrO₂ and Al₂O₃. After 100 electrochemical cycles in 1 C at 55 °C, the electrode consisting of LiMn₂O₄ particles coated with six ZnO ALD layers (as thin as ~1 nm) delivers the highest final capacity, more than twice that of the bare electrode. It is also found that amphoteric oxide coating on LiMn₂O₄ particles can enhance the cycleability of LiMn₂O₄ more effectively than coating on the composite electrode. Furthermore, for ALD coating either on the composite electrode or on LiMn₂O₄ particles, the effect of oxide ALD modification for improving capacity retention and increasing specific capacity of LiMn₂O₄ is more phenomenal at elevated temperature than at room temperature.     

Modification of fluorocopolymer coatings by telomers to improve their hydrophobicity

In this work, modification of coatings based on FP-5182 lacquer that is prepared from the copolymer of trifluorochloroethylene and vinylidenefluoride (F-32L) has been performed in order to improve their hydrophobicity. Several approaches to modification have been suggested, among which is the use of telomeric solutions of tetrafluoroethylene that were synthesized in various solvents, variation of the roughness of the coating surface by the aerosil powder, and a combination of these two approaches. The wetting properties of coatings have been studied, and improvement of the hydrophobic characteristics during their modification has been demonstrated.     

Poly(bis-2,2,2-trifluoroethoxymethyl oxetane): enhanced surface hydrophobicity by crystallization and spontaneous asperity formation

We report a spontaneous increase in the contact angle (104 degrees --> 136 degrees +/- 4 degrees ) for a semicrystalline polyoxetane with symmetrical CF3CH2OCH2 side chains. Poly(bis-trifluoroethoxymethyl)oxetane, P(B-3FOx), Mn = 21 kDa, was prepared by a modification of conventional cationic ring opening polymerization. At ambient temperature, the polymer is between Tg (-39 degrees C) and Tm (approximately 70 degrees C). Tapping mode atomic force microscopy (TM-AFM) revealed an interesting process-dependent topology. Coatings that were melted and slow-cooled displayed increasing roughness over the course of 4-6 weeks at 25 degrees C. The result was a topology characterized by sharp micrometer-scale ridges and asperities. The heat of fusion increases from an initial value of 21.9 J/g after slow cooling (non-isothermal melt crystallization) to 28 J/g after 6 weeks (non-isothermal melt crystallization plus isothermal melt crystallization). The coating appearance changes from transparent with a slight haze to translucent. The changing topology was accompanied by a 30 degrees increase in the water contact angle, up to 140 degrees , attributed to an asperity-rich surface yielding a discontinuous three-phase contact line and to a change in the proportions of crystalline and amorphous area fractions accompanying crystallization.     

Hybrid silica coatings on polycarbonate: enhanced properties

Hybrid silica coatings based on 3- glycidoxypropyltriethoxysilane (GPTES), tetraethylorthosilicate (TEOS) and colloidal silica were deposited on polycarbonate (PC) by the sol–gel method, in order to obtain a material with enhanced properties with respect to raw PC (mainly scratch resistance, hydrophobicity and density), and consequently reach increased durability. The necessity of performing a N₂-plasma treatment on PC (before coating deposition) was highlighted in order to obtain a good adherence between the coating and the substrate: XPS measurements showed that after treatment, nitrogenous radicals had formed on the PC surface and were able to link covalently with the sol during its deposition. Adherence was also higher when young sols (<8-day-old) were used. Different alkoxysilanes/colloidal silica ratios were tested to optimize the coating resistance: crack resistance of the coatings was found to be greater when the ratio was high. Scratch resistance of raw PC was enhanced as soon as PC was coated, irrespective of the alkoxysilanes/colloidal silica ratio or the sol ageing time. The density of the coatings was assessed by environmental ellipsometric porosimetry and found to be very high. Water contact angle measurements showed that the hydrophobicity of the coatings was inferior to raw PC. The addition in the sol of a small wt% of octyltriethoxysilane (OTES), 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FTES) and silicone surface additive (BYK-306) allowed a significant increase in hydrophobicity of the samples.     

Thermal analysis of the polyester profiled fiber

This paper deals with the structure and properties of fibrous materials based on special types of profiled synthetic fibers. Fibrous materials were prepared in the form of integrated knitted fabric where on its flash side were different profiles of polyester fibers and on its right side were a combination of polyester and cotton fibers. The mechanical and physiological properties of knitted fabrics were evaluated. These types of integrated knitted fabrics were used for the sports garments where the measured properties considerably influence clothing comfort.     

钛材表面疏水图案化对成骨细胞生长的影响

本文通过共沉淀法合成纳米羟基磷灰石,然后采用电泳沉积法在钛材表面沉积羟基磷灰石涂层,并通过氟硅烷浸泡法构建疏水化图案,对制得的样品采用透射电镜、扫描电镜、X射线衍射、红外光谱仪、接触角测量仪进行表征,并与成骨细胞共培养,采用MTT、ALP法检测疏水图案对成骨细胞生长的影响。结果表明,本实验成功在钛材表面构建了疏水图案,且这种图案对成骨细胞生长有一定的抑制作用,通过构建不同的疏水图案,可以达到调控成骨细胞生长方向的作用。     

基于Box-Behnken Design对聚酯纤维的表面改性

借助Box-Behnken Design,选取PTFE乳液对聚酯纤维LD550进行表面改性,考察浓度、温度和时间对改性效果的影响.结果表明:改性适宜条件为PTFE浓度15%、温度99.5℃以及涂覆时间18h.适宜条件改性样的断裂强力保持率提高了约9.89%.     

Importance of dynamic surface tension to the residual water content of fabrics

At the end of the final spin cycle of the laundry process, the residual moisture content (RMC) of fabric is directly related to the dynamic surface tension of the residual water in the fabric. The LaPlace equation for capillary rise predicts that the capillary rise of solutions in a capillary is proportional to the surface tension at the air-liquid interface. If fabric can be considered to be a large ensemble of capillaries due to interfiber spacing, then the RMC of fabrics will be directly related to the surface tension of residual solution in the fabric. The use of a tailored rinse additive has the potential to decrease the surface tension of solution significantly, thus leading to a decrease in the residual water content of the fabric. It is expected that as the surfactant concentration increases the surface tension decreases. Hence, the RMC of fabrics must decrease with increasing surfactant concentration. However, a peak is observed in the RMC of fabrics before the critical micelle concentration (CMC) is reached. Prior to the CMC, it is proposed that a sudden adsorption of surfactant is occurring on the fabric surface leading to a decrease in bulk monomer concentration. The decrease in free monomer concentration should result in an increase in the equilibrium surface tension of the residual solution leading to a concomitant increase in RMC. Because the dynamic surface tension is measured on a short time scale (on the order of milliseconds), there will be less adsorption of monomer onto the newly created air-liquid interface of the bubbles during the measurement process. This decrease in adsorption should lead to a pronounced increase in the dynamic surface tension. This indeed was observed. The RMC correlates very well with the dynamic surface tension of the residual solution.     

Influence of antimicrobial finishes on the biodeterioration of cotton and cotton/polyester fabrics: Leaching versus bio-barrier formation

The influence of antimicrobial activity of two contemporary finishes, specifically a dispersion of colloidal silver (Ag) and 3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride (Si-QAC), on the degree of biodeterioration of 100% cotton (CO) fabric and fabric composed of a mixture of cotton and polyester (CO/PET) was studied. Ag was chosen for the leaching agent, while Si-QAC was used as the bio-barrier-forming agent. The biodeterioration of samples finished with different concentrations of Ag and Si-QAC was analysed from a standard soil burial test after 3, 6 and 12 days of exposure to soil microflora. SEM micrographs revealed intensive biodeterioration of the unfinished cellulose fibres, while the highly biologically resistant polyester fibres remained undamaged. A controlled release of Ag successfully inhibited biodeterioration of the cellulose fibres in the CO and CO/PET fabrics when its concentration reached a lethal, biocidal concentration. Contrary to the effects of Ag, the bio-barrier formation of Si-QAC on CO and CO/PET fabrics was insufficient to protect the cellulose fibres during longer periods of soil burial, irrespective of its concentration. Intensive chemical changes to the cellulose were clearly seen from the FT-IR spectra of all of the samples. The resistance of the polyester component to biodeterioration did not provide any significant protection for the cotton component in CO/PET fabric.     

Parametrization strategy for the MolFESD concept: quantitative surface representation of local hydrophobicity

We derive a new model for the established concept of the molecular free energy surface density (MolFESD) yielding a more rigorous representation of local surface contributions to the overall hydrophobicity of a molecule. The model parametrization makes efficient use of both local and global information about solvation thermodynamics, as formulated earlier for the problem of predicting free energies of hydration. The free energy of transfer is separated into an interaction contribution and a term related to the cavity formation. Interaction and cavity components are obtained from the statistical three-dimensional (3D) free energy density and a linear combination of surface and volume terms, respectively. An appropriate molecular interaction field generated by the program Grid is used as an approximate representation of the interaction part of the 3D free energy density. We further compress the 3D density by means of a linear combination of localized surface functions allowing for the derivation of local hydrophobic contributions in the form of a free energy surface density. For a set of 400 compounds our model yields significant correlation (R(2) = 0.95, sigma = 0.57) between experimental and calculated log P values. The final model is applied to establish a correlation between partial free energies of transfer for a series of sucrose derivatives and their relative sweetness, as studied earlier in the group of the authors. We find considerable improvement regarding the rms error of the regression thus validating the presented approach.     

Atomic layer deposition of conformal inorganic nanoscale coatings on three-dimensional natural fiber systems: effect of surface topology on film growth characteristics

Atomic-scale material deposition is utilized to achieve uniform coverage and modification of the surface properties of natural fiber and woven fabric materials, where irregular nanoscale features are embedded in a macroscale interpenetrating fiber network. The complex surface topology of the woven fabric results in significantly different film-growth thickness per ALD cycle as compared to planar surfaces coated using the same process conditions, likely due to reactant adsorption within the fiber starting material, as well as impeded reactant transport out of the fabric system during the purge cycle. Cotton textiles modified with conformal nanoscale Al2O3 are found to show extreme hydrophobic effects, distinctly different from planar surfaces that receive the same coatings. The results highlight key concerns for achieving controlled conformal coatings on complex surfaces and open the possibility for new textile finishing approaches to create novel fabric-based materials with specialized function and performance.     

Adhesion of Cryptosporidium parvum and Giardia lamblia to solid surfaces: the role of surface charge and hydrophobicity

Adhesion of Cryptosporidium parvum and Giardia lamblia to four materials of different surface charge and hydrophobicity was investigated. Glass beads were used with and without three polymer coatings: aminosilines (A0750), fluorosilines (T2494), an amino cationic polymer. Surface charge density and hydrophobicity of the beads were characterized by measuring the zeta potential (ZP) and the contact angle, respectively. Adhesion was derived from batch experiments where negatively charged (oo)cysts were mixed with the beads and recovery was determined by counting (oo)cysts remaining in suspension using a flow cytometer. Experimental results clearly show that adhesion to solid surfaces of C. parvum is different from G. lamblia. Adhesion of C. parvum to positively charged, hydrophilic beads (82% recovery relative to control) indicated that surface charge was the more important factor for C. parvum, dominating any hydrophobic effects. Adhesion of G. lamblia cysts to negatively charged, hydrophobic beads (0% recovery relative to control) indicated that although hydrophobicity and surface charge both played a role in the adhesion of G. lamblia to solid surfaces, hydrophobicity was more important than surface charge.     

Effect of AgNP distribution on the cotton fiber on the durability of antibacterial cotton fabrics

Cellulose - Silver nanoparticles (AgNPs) loaded on the cotton fiber can endow the fiber with good antibacterial activity, but the AgNPs on the surface of cotton fiber will leach out with the...     

Effect of growth on surface charge and hydrophobicity of Staphylococcus aureus

Modifications in the surface charge and hydrophobicity of Staphylococcus aureus Oxford during growth were studied by analysing electrophoretic mobility and adherence to hydrocarbons (hexadecane), respectively. Bacterial concentration had no effect upon the measurements. Both surface charge and hydrophobicity varied during the exponential phase of growth (1 to 4 h): surface charge decreased significantly (p < 0.001), while hydrophobicity increased (p < 0.001). In the stationary phase (4 to 9 h), the surface charge increased significantly (p < 0.001), whereas hydrophobicity showed no change. Cationized ferritin decreased the surface charge and had no effect on hydrophobicity. These results suggest that in S. aureus, different structures could be responsible for their surface charge and hydrophobic properties.     

Effect of the feeding mode of cross-linker and microcapsule on the corrosion resistance and hydrophobicity of composite coatings

The interface combination of anti-corrosive materials and polymer matrix has a significant effect on the overall performance of the composite coating. However, past research has focused on blending anti-corrosive materials to improve the performance of the polymer matrix. Herein, we proposed a layer-by-layer spray-coating process to further enhance the reinforcing effect of anti-corrosive materials on the polymer matrix by changing their feeding modes. In this paper, taking waterborne polyacrylate (WPA) as an example, two kinds of reinforcement materials commonly used to improve the corrosion resistance of polymer matrix were introduced into the coating system and then applied to the tinplate: cross-linker and microcapsule. Firstly, five types of WPA composite coating systems were designed according to the feeding mode of aziridine cross-linker and the position of benzotriazole@zinc oxide microcapsules (BTA@ZnO MCs). Electrochemical impedance spectroscopy (EIS) and electrical equivalent circuits were used to evaluate the corrosion resistance of these composite coating systems and analyze their electrochemical processes. By spraying the mixture of WPA and aziridine crosslinker as the bottom layer and BTA@ZnO MCs as the top layer, the resulting composite coating exhibited higher corrosion resistance and hydrophobic properties. Scanning electron microscope (SEM) and contact angle tests indicated that the feeding mode of aziridine cross-linker and the position of BTA@ZnO MCs played important roles in the compactness and hydrophobicity of the composite coating. Subsequently, the effects of the amount of aziridine cross-linker and BTA@ZnO MCs on the corrosion resistance and physical properties of the composite coating were further analyzed by EIS, water absorption test, contact angle test and atomic force microscopy (AFM). The significant improvement in the corrosion resistance of this composite coating was mainly attributed to the synergistic effect of highly cross-linked network structure and superhydrophobic surface.     

Interpretation of colloidal dyeing of polyester fabrics pretreated with ethyl xanthogenate in terms of zeta potential and surface free energy balance

Data are presented on the adsorption of the colloidal dye Disperse Blue 3 onto polyester fabric (Dacron 54, Stile 777), the fabric being pretreated with different amounts of the surfactant potassium ethyl xanthogenate (PEX). This study has been made by means of both the evolution of the zeta potential of the fiber/dye interface and the behaviour of the surface free energy components of the above systems. The kinetics of adsorption of the process of dyeing, using 10(-4) M of PEX in the pretreatment of the fabric, shows that increasing temperature of adsorption decrease the amount of colloidal dye adsorbed onto the fabric. This fact shows that the principal mechanism involved in this adsorption process is physical in nature. The adsorption isotherms of the colloidal dye onto polyester pretreated with different amounts of PEX, shows that the adsorption of the dye is favored with the increase in the concentration of the surfactant used in the pretreatment. This fact shows that the pretreatment with PEX is a very interesting aspect of interest in textile industry. The zeta potential of the system fabric/surfactant shows that this parameter is negative (about -25 mV) for the untreated fiber and decreases in absolute value for increasing concentration of the surfactant on the fiber, the value of the zeta potential of the system being -5 mV for 10(-2) M of PEX. This behavior can be explained for the chemical reaction nucleophilic attack between the carboxyl groups of polyester, ionized at pH 8, and the thiocarbonyl group of the xanthogenate ion. On the other hand, the zeta potential of the system polyester pretreated with PEX/Disperse Blue 3 at increasing concentrations of the surfactant and the dye shows that this parameter increases its negative value strongly with increasing concentration of the surfactant used in the treatment. This can be explained for the hydrogen bonds between the hydroxy groups of the dye and the S- ions of the thiocarbonyl group of the surfactant preadsorbed onto the fiber.