Hydrophobic Recovery Research Articles

Modification of malachite surfaces with lead ions and its contribution to the sulfidization flotation

Malachite is a common copper-oxide resource, and it is usually enriched by sulfidization flotation. Its floatability and recovery are greatly determined by the surface sulfidization results. In this paper, Pb(NO3)2 is used to pretreat malachite, and the sulfidization mechanism of malachite was studied through microflotation experiments, zeta-potential determination, adsorption tests, XPS and ToF-SIMS. The flotation and adsorption results show that the malachite floatability after pretreatment with Pb ions improved significantly. Compared with Na2S treatment, the maximum recovery increased by 42.6% after treatment with lead ions and Na2S. The zeta potential results showed that lead ions (such as Pb(OH)+) could adsorb on the malachite surface, and the surface active sites of malachite were increased. XPS results indicate that lead ions adsorbed onto the mineral surface through the interaction between Pb species, S species and O species. The formation for new species (such as Pb-S) enhanced the malachite sulfidization. ToF-SIMS was used to visualize the three-dimensional distribution of lead- and sulfur-species adsorbed on the malachite surface. It demonstrated that the sulfidization layer increased after pretreatment with Pb(NO3)2, facilitating the surface hydrophobicity and flotation recovery of malachite.

Low-frequency plasma activation of nylon 6

In the study reported in this paper, a series of reproducible conditions were employed to uniformly functionalize nylon 6 surfaces using a commercially available, low-frequency (40 kHz), low-pressure plasma system, utilizing oxygen plasma as a reactive gas. Initially, the plasma-treated samples were investigated using static contact angle measurements, showing a progressive increase in wettability with increasing plasma activation time between 10 and 40 s. Such an increase in wettability (and therefore increase in adhesive capabilities of the surfaces) was attributed to the creation of surface C-OH, C=O, and COOH groups. These surface-chemical modifications were characterized using x-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometry (SSIMS). Surface radical densities were also shown to increase following plasma activation, having been quantified using a radical scavenging method based on the molecule 2,2-diphenyl-1-picrylhydrazyl (DPPH). The samples were imaged and analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM), to confirm that there had been no detectable alteration to the surface roughness or morphology. Additionally, the “hydrophobic recovery” or “ageing” of the activated polymer samples, post-plasma treatment, was also investigated in terms of wettability and surface-chemistry, with the wettability of the sample surfaces decreasing over time due to a reduction in surface-oxygen concentration.

Investigation of the Impact of Cold Plasma Treatment on the Chemical Composition and Wettability of Medical Grade Polyvinylchloride

The impact of the Corona, dielectric barrier discharge, and low pressure radiofrequency air plasmas on the chemical composition and wettability of medical grade polyvinylchloride was investigated. Corona plasma treatment exerted the most pronounced increase in the hydrophilization of polyvinylchloride. The specific energy of adhesion of the pristine and plasma-treated Polyvinylchloride (PVC) tubing is reported. Plasma treatment increased markedly the specific free surface energy of PVC. The kinetics of hydrophobic recovery following plasma treatment was explored. The time evolution of the apparent contact angle under the hydrophobic recovery is satisfactorily described by the exponential fitting. Energy-dispersive X-ray spectroscopy of the chemical composition of the near-surface layers of the plasma-treated catheters revealed their oxidation. The effect of the hydrophobic recovery hardly correlated with oxidation of the polymer surface, which is irreversible and it is reasonably attributed to the bulk mobility of polymer chains.

Effect of wettability of substrate on metal halide perovskite growth

In the last decade, inorganic–organic hybrid perovskites have demonstrated a dramatic increase in photoconversion efficiency by engineering the perovskite composition, as well as adjusting the properties of the charge transporting materials. The nucleation and growth of the perovskite layer are governed by the surface properties of the substrate and depend on its wetting properties defined by the roughness and the species adsorbed. Fixing all fabrication conditions of a PSC but only changing the wettability of the substrate is practically difficult because varying the surface hydrophilicity can contribute side effects such as chemical identity change or adsorption of new species on the surface. Herein, we studied a double-layered TiO2/SnO2 ETL for perovskite deposition and we changed the hydrophilicity of the samples using hydrophobic recovery after UV exposure. Thus, the effect of wettability of the substrate on nucleation and growth of the perovskite layer was elucidated under minimized interference. It was found that the influence of the wetting properties of the substrate on the growth of perovskite can be exaggerated in the literature since the increase in the grain size of the perovskite layer is just 14% bigger if the water contact angle of the substrate increases from 3° to 72°.

Robust, healable and hydrophobically recoverable polydimethylsiloxane based supramolecular material with dual-activate hard segment

In this paper, a novel dual-activate hard segment strategy is proposed for the fabrication of polydimethylsiloxane (PDMS) based supramolecular polymer (PDMS-PDITC-IPDI). The unique design endows the PDMS-PDITC-IPDI with high toughness (43.1–24.5 MJ/m3), tensile strength (11.3–6.6 MPa) and elongation at break (730%–615%), and the mechanical properties and dynamic property can be regulated by varying degrees of hard segment activation. Moreover, the PDMS-PDITC-IPDI polymers exhibit excellent self-recovery property during successive loading-unloading processes. Additionally, both wettability damage caused by O2 plasma treatment and mechanical damage can be healed by simple heating, showing good hydrophobic recovery and self-healability. Taking advantages of merits of the PDMS-PDITC-IPDI, the applications of the material as recyclable adhesive and 3D printing material are also investigated.

Polymer Infused Porous Surfaces for Robust, Thermally Conductive, Self-Healing Coatings for Dropwise Condensation.

Hydrophobic coatings with low thermal resistance promise a significant enhancement in condensation heat transfer performance by promoting dropwise condensation in applications including power generation, water treatment, and thermal management of high-performance electronics. However, after nearly a century of research, coatings with adequate robustness remain elusive due to the extreme environments within many condensers and strict design requirements needed to achieve enhancement. In this work, we enable long-lasting condensation heat transfer enhancement via dropwise condensation by infusing a hydrophobic polymer, Teflon AF, into a porous nanostructured surface. This polymer infused porous surface (PIPS) uses the large surface area of the nanostructures to enhance polymer adhesion, while the nanostructures form a percolated network of high thermal conductivity material throughout the polymer and drastically reduce the thermal resistance of the composite. We demonstrate over 700% enhancement in the condensation of steam compared to an uncoated surface. This performance enhancement was sustained for more than 200 days without significant degradation. Furthermore, we show that the surfaces are self-repairing upon raising the temperature past the melting point of the polymer, allowing recovery of hydrophobicity and offering a level of durability more appropriate for industrial applications.

Recent Advances in Surface Activation of Polytetrafluoroethylene (PTFE) by Gaseous Plasma Treatments.

Fluorinated polymers are renowned for their chemical inertness and thus poor wettability and adhesion of various coatings. Apart from chemical methods employing somewhat toxic primers, gaseous plasma treatment is a popular method for the modification of surface properties. Different authors have used different plasmas, and the resultant surface finish spans between super-hydrophobic and super-hydrophilic character. Some authors also reported the hydrophobic recovery. The review of recent papers is presented and discussed. Correlations between plasma and/or discharge parameters and the surface finish are drawn and the most important conclusions are summarized. The concentration of oxygen in the surface film as probed by X-ray photoelectron spectroscopy is inversely dependent on the concentration of oxygen in gaseous plasma. The predominant mechanism leading to hydrophilic surface finish is bond scission by deep ultraviolet radiation rather than functionalization with reactive oxygen species.

Hydrophobic recovery of cross-linked polydimethylsiloxane films and its consequence in soft nano patterning

Cross-linked polydimethylsiloxane (PDMS) films and surfaces obtained by thermal cross-linking of commercially available Sylgard 184 are widely utilized in many areas of science, due to superior thermal stability, low dielectric constant, transparency and biocompatibility. Cross-linked PDMS surfaces are weakly hydrophobic and several experiments, particularly the ones that utilize capillary-driven microscale flow require the modulation of the surface wettability. A well-known strategy to achieve the same is by exposing the Sylgard 184 surface to UV/ozone (UVO) treatment at room temperature. Depending on the duration of exposure, the wettability drops from hydrophobic to a near-complete wetting (water contact angle ~10°), due to the formation of a surface oxide layer. However, under normal atmospheric conditions, these surfaces recover their hydrophobicity over a period of time due to diffusive migration of the uncrosslinked oligomers to the surface, and formation of a hydrophobic dimethyl silicone layer. We explore the hydrophobic recovery process as a function of cross-linker concentration and UVO exposure time and show how a partially or fully recovered PDMS stamp may influence subsequent nanopatterning, including the possible creation of features with different morphology using a single stamp.

Non-thermal plasma activation of BPDA-PPD polyimide for improved cell-material interaction

Biocompatible BPA-PPD polyimide is widely used in the packaging of implantable devices. Plasma activation can improve its interaction with the surrounding tissue upon implantation. The influence of He, air, N2 and Ar plasma activation on polyimide's surface hydrophilicity, roughness, topography, composition and cell-surface interaction was evaluated, along with the influence of hydrophobic recovery on such properties. All plasma activations increased the surface hydrophilicity but neither the roughness nor topography changed. The increase was attributed to the incorporated O- and N-functionalities. 24 h after the activations the surface hydrophilicity decreased while maintaining the functionalities, due to the functionalities’ reorientation/migration towards the bulk of polyimide. Air and N2 activations improved the cell-surface interactions with fibroblasts. These were equally influenced by the surface hydrophilicity and the surface functionalities availability. The hydrophobic recovery lowered the initial cell adhesion but not the cell proliferation, as the hydrophobic recovery was progressively reversed in the culture media.

Improvement of acrylic-urethane paint adhesion to PP-EPDM surface by mediated electrochemical oxidation

Adhesion improvement of an acrylic-urethane paint on a bumper surface made from polypropylene/ethylene-propylene-diene monomer was investigated at long term after electrochemical treatment by 2N nitric acid and 0.6M Silver (II)-nitrate /2N nitric acid. The stability of the electrochemically treated samples was examined at different aging times by ATR and SEM. The results were also compared to those of the untreated and flame-treated samples. Accelerated UV weathering analysis along with morphology study by SEM approved the effectiveness of the Ag (II) treatment technique in long term particularly at curvature area of the bumper. For the Ag (II) treated samples, the increase in adhesion strength was sustained even after 650 hours exposure to UV irradiation in wet condition prior to bonding. In addition, the stability of the Ag (II)-treated surface was maintained for at least three months. In case of the flame-treated surface, hydrophobic recovery during aging in environment was found to reduce the polarity of the PP-EPDM surface. The pull-off test showed Ag (II) treatment can enhance adhesion strength of the acrylic-urethane coating on to PP-EPDM in comparison with the flaming method by 20.7%. Moreover the results of zeta potential analysis for Ag (II) treated blend showed a typical acidic surface.

Suppression of Hydrophobic Recovery in Photo-Initiated Chemical Vapor Deposition

Photo-initiated chemical vapor deposition (PICVD) functionalizes carbon nanotube (CNT)-enhanced porous substrates with a highly polar polymeric nanometric film, rendering them super-hydrophilic. Despite its ability to generate fully wettable surfaces at low temperatures and atmospheric pressure, PICVD coatings normally undergo hydrophobic recovery. This is a process by which a percentage of oxygenated functional group diffuse/re-arrange from the top layer of the deposited film towards the bulk of the substrate, taking the induced hydrophilic property of the material with them. Thus, hydrophilicity decreases over time. To address this, a vertical chemical gradient (VCG) can be deposited onto the CNT-substrate. The VCG consists of a first, thicker highly cross-linked layer followed by a second, thinner highly functionalized layer. In this article, we show, through water contact angle and XPS measurements, that the increased cross-linking density of the first layer can reduce the mobility of polar functional groups, forcing them to remain at the topmost layer of the PICVD coating and to suppress hydrophobic recovery. We show that employing a bi-layer VCG suppresses hydrophobic recovery for five days and reduces its effect afterwards (contact angle stabilizes to 42 ± 1° instead of 125 ± 3°).

Effect of surface characteristics and environmental aging on wetting of Cr-coated Zircaloy-4 accident tolerant fuel cladding material

With the goal of increasing the performance and safety of existing nuclear power plants, the research and development of Accident Tolerant Fuels (ATFs) are of high priority within the nuclear community. Two widely studied ATF concepts are the replacement of currently used zirconium alloy for other cladding materials that provide resistance to hydrogen production during accident conditions or the deposition of protective functional coatings on the Zircaloy cladding that mitigate the risk. While different protective coating options are being considered, Cr-coating is predominant. In this study, Cr-coating on Zircaloy-4 substrates were produced by Plasma Assisted Physical Vapor Deposition (PAVD), aiming at investigating their surface characteristics that may have an impact on the efficiency of heat transfer. The thickness, structure, and mechanical properties of the coatings were examined by scanning electron microscopy, focused ion beam, X-ray diffraction, and microindentation. Furthermore, surface topography, surface energy conditions, and surface chemistry were assessed using contact profilometry, atomic force microscopy, contact angle goniometry, and X-ray photoelectron spectroscopy. The static contact angle reduced from 75° for as-received substrates to almost 20° after coating. This significant increase in wettability observed after chromium deposition on Zircaloy changed with aging. For instance, over time, a hydrophobic recovery on the plasma-treated surfaces was detected. Correlations between surface chemistry and surface energy studies helped to explain the variation in contact angle with aging time. Results demonstrated that the formation of chromium oxides and hydroxides, and other carbonaceous species affected the surface coating affinity with water upon ambient exposure.

Surface modifications to polydimethylsiloxane substrate for stabilizing prolonged bone marrow stromal cell culture

Polydimethylsiloxane (PDMS) has been extensively used as a supporting material for studies of cell mechanobiology, cell micropatterning and microscale-cell analysis in microfluidic chips due to its numerous advantages, such as low cytotoxicity, ease of modification, inexpensive costs and biocompatibility. However, the innate hydrophobicity of PDMS often poses a problem for stable cell adhesion, seriously limiting its applicability for prolonged cell culture. UV exposure and protein coating are suboptimal solutions, while chemical surface functionalization is often associated with laborious procedures and producing environmental toxics. Plasma treatment can render a hydrophilic substrate by altering the surface chemistry, but such effect is often short-lived due to its tendency to hydrophobic recovery. Variation of physical properties of the substratum are known to influence cell behaviour. Nevertheless, the combination of varying PDMS substratum properties via base:curing agent ratio and plasma treatment to stabilize the long-term culture of bone marrow derived stromal cells (BMSCs) still remain poorly understood. In this study, we developed a protocol to maintain the hydrophilicity of the plasma-treated PDMS over a range of substratum properties. This study demonstrated that varying the substratum properties of PDMS can enhance the stability of BMSC culture for at least three weeks, while plasma treatment with or without additional collagen coating further enhanced such effect. The changes in the physical properties of PDMS have rendered difference in BMSCs adhesion, proliferation and in-vitro plasticity, thereby offering a simple and effective strategy for PDMS surface modification to enable long term cell analysis in PDMS-based culture platform.

Hydrophilicity and optic property of polyethylene glycol coating on polydimethylsiloxane for fast prototyping and its application to backlight microfluidic chip

The polydimethylsiloxane (PDMS) is widely applied to prototyping of various categories by coating or molding due to bio-compatibility, transparency, and flexibility. However, the native hydrophobicity and short-time recovery after O2 plasma treatment for the microfluidic chip are the defects in self-driven capillary pumping and long-term stability. Good optical transparency is necessary for backlight experiment observation. In addition, the self-bond in dual-tone PDMS-to-PDMS casting leads to a separation problem during demolding, which prevents rapid prototyping application. In this article, the coating of polyethylene glycol (PEG) with molecular weights (MW) of 6000 and 1000 denoted as PEG6000 and PEG1000 on PDMS is investigated as an anti-stiction layer for rapid prototyping as well as for the surface modification on the hydrophilicity and backlight optic property of PDMS for the microfluidic chip application. The contact angles of both PEG6000 and PEG1000 coated PDMS after 21 days are 42.6° and 41.7°, respectively, for good hydrophilicity; however, the pure O2-PDMS without PEG coating after 1.5 h has hydrophobic recovery to 78.7°. After PDMS-to-PDMS demolding, the PEG6000 coated PDMS has some broken area on the surface, while the PEG1000-PDMS keeps a whole smooth surface. Regarding transparency, the PEG1000-PDMS has a higher transmittance of about 55–70% near to the PDMS of 65–78% in visible wavelength, but the PEG6000-PDMS one is vague about 15%. It is attributed to PEG1000 of much smaller molecules with a lower light scattering and absorbance compared to PEG6000. The PEG1000-PDMS of good hydrophilicity, transparency, and anti-stiction properties makes it a good candidate for the capillary-driven microfluidic chip application.

Role of Micro and Nano Filler Combination in Hydrophobic Recovery of Glass Fiber Reinforced Epoxy Composites under Various Contaminants

Use as outdoor insulators in high voltage power transmission is a potential application of epoxy composites. Vulnerability of these insulators to various stresses when exposed to external environment, limit their potential. Better pollution performance in hostile environments can be achieved in these composites by using nano and micro combination of fillers. This paper discusses the merits of using combination of micro and nano fillers consisting of silica, alumina, ATH, CaCO3 and MgO in glass epoxy to demonstrate that they serve a better alternative to the conventional glass epoxy composite insulation systems. Extensive investigations have been carried out on hydrophobic recovery of these composites for understanding their pollution performance under various contaminants such as NaCl, seawater, acid and cement. The addition of filler combinations to glass epoxy enhanced the hydrophobic properties of the composites compared to the glass epoxy without fillers. The results revealed that the composite with MgO filler showed 37% increase in contact angle in as-cast form compared to contact angle of epoxy without fillers.

Recovery and cleaning of fine hydrophobic particles using the Reflux™ Flotation Cell

The Reflux Flotation Cell (RFC) consists of a vertical vessel located above a series of parallel inclined channels. This novel system, which is the inverse of an existing gravity separation system known as the Reflux Classifier, provides a powerful mechanism for enhancing bubble-liquid segregation. The usual link between the imposed gas flux and water recovery in the froth product is decoupled through this mechanism, resulting in the establishment of a concentrated bubbly zone throughout the upper section of the cell, and no froth zone. A downwards fluidization arrangement promotes strong washing of the flotation product, to remove the hydrophilic slimes from the hydrophobic concentrate. The mechanism also provides for strong control of the bias flux, allowing a significant positive bias flux to be established. A feed suspension of fine coal tailings containing hydrophobic coal and hydrophilic mineral matter was subjected to the novel flotation, providing an ideal basis for studying the interplay between the hydrophobic particle recovery, inferred by the combustible recovery, and the product grade, inferred by the mineral matter content of the product, expressed by the ash %. The feed ash % was about 43 wt%. The product cleaning was compared to firstly, the results from the tree flotation method, and secondly, a newer method known as Coal Grain Analysis (CGA). The RFC results were found to lie to the left of the tree curve, converging to the limit described by the CGA analysis. This work suggests the RFC and CGA provide a form of mutual validation on the limits of cleaning, though more work will be needed to confirm this finding. The RFC was operated with a volumetric feed flux of the order 1 cm/s, a rate comparable to that of conventional flotation systems, with the bias flux ranging from 0.0 cm/s to 1.9 cm/s. For a fixed gas flux of 1.1 cm/s, increases in the liquid bias flux from 0.0 cm/s to 1.0 cm/s resulted in a decrease in product ash from 18.2% to 7.8%, and a reduction in combustible recovery from the order 87% to 75.6%. Operating at the lowest gas flux of 0.6 cm/s, and the strongest bias flux of 1.9 cm/s yielded a low product ash of 6.7% at the reduced combustible recovery of 64%.

Thickness estimation of the silica-like thin layers via swelling-driven wrinkling instability

In the present study, we report a simple, yet facile route to thickness characterization of the UV/ozone (UVO) treated polydimethylsiloxane (PDMS) thin layer via osmotically-driven wrinkling instability. Through the UVO oxidation process of PDMS, a bi-layered film with local moduli-mismatch regions (i.e., the top UVO exposed region of a thin stiff (less-elastomeric) SiOx layer and the bottom region of an unmodified, elastomeric PDMS foundation) was generated. When ethanol directly dropped on top of a bi-layered film and swelled preferentially a lower elastomeric PDMS foundation, the wrinkles were produced in the confined area within the three-phase contact trace of the ethanol droplet, and then vanished completely as the ethanol evaporated irreversibly. The wrinkle wavelength was observed to be magnified as the mixing ratio of base monomer and curing agent increased from 7:1 to 8:1 to 9:1 to 10:1. The increasing wavelength as a function of increasing UVO treatment time (tUVO) reflected increasing thickness of the silica-like layer. For a given ratio, the SiOx thickness was found to increase similarly to the wrinkling wavelength as the tUVO increased. The thickness varied from 22.3 ~ 43.4 nm to 51.1 ~ 99.3 nm as the tUVO varied from 12 min to 60 min. A hydrophobic recovery of a hydrophilic thin SiOx film created by UVO treatment was observed by examining the wrinkle wavelength as a function of elapsed time. As time passed by, a decrease in the wrinkle wavelength confirmed the hydrophobic-to-hydrophilic transition.

Effect of crystallinity on the recovery rate of superhydrophobicity in plasma-nanostructured polymers.

This study explored the optimum conditions to achieve superhydrophobicity in polyethylene terephthalate (PET) in terms of crystallinity and microstructure. Surface superhydrophobicity was achieved by nanostructures induced by oxygen plasma etching and the recovery process of low surface energy through thermal aging of various PETs; semi-crystalline biaxial PET (B-PET) film, amorphous PET (A-PET) film, and semi-crystalline PET (F-PET) fabric. Under the anisotropic plasma etching, the nanostructures on the B-PET film were the longest, followed by the F-PET fabric, which developed a hierarchical micro/nanostructure, then the A-PET film. During thermal aging at 80 °C near Tg, the plasma-treated A-PET film recovered its superhydrophobicity within 3 h, while the plasma-treated B-PET film did not exhibit superhydrophobicity. At 130 °C, higher than Tg, the plasma-treated B-PET film recovered its superhydrophobicity within 1 h, but the plasma-treated A-PET film became opaque as its nanostructures deformed, decreasing its superhydrophobicity. The plasma-treated F-PET fabric exhibited faster recovery and greater superhydrophobicity than the plasma-treated B-PET film, due to its hierarchical micro/nanostructure. In addition, hydrophobic recovery during thermal aging was proved with a decrease in surface polar groups, lowering the surface energy using XPS analysis. Therefore, by designing the ratio of crystal to amorphous regions and surface micro/nanostructures, one can rapidly fabricate superhydrophobic PETs without additional surface finishing.

Investigation on the electrical, thermal and mechanical properties of silicone rubber nanocomposites

Addition of alumina nano particles to silicone rubber (SR) has shown a significant improvement in electrical, mechanical and thermal properties of the SR nanocomposites. Static contact angle and water droplet-initiated corona inception voltage exhibited a marginal change on inclusion of nano alumina into SR matrix. Alumina filler improved the corona ageing resistance of the composites; however, a marginal reduction in the rate of hydrophobicity recovery is observed. Laser induced breakdown spectroscopy proved as an effective tool to rank the performance of the SR nano composites. Variation of crater depth with energy of laser pulse and number of laser pulses follows the exponential relation. Plasma temperature calculated by optical emission spectroscopy is in line with the amount of damage caused to the surface of the specimen by water droplet-initiated discharge. Dielectric response spectroscopic studies indicate that inclusion of nano fillers has resulted in lower interfacial polarization and lower imaginary permittivity. It is observed through dynamic mechanical analysis that the composites have higher storage modulus and the activation energy compared to base SR.

Direct plasma treatment approach based on non-thermal gliding arc for surface modification of biaxially-oriented polypropylene with post-exposure hydrophilicity improvement and minus aging effects

Aging phenomenon or hydrophobic recovery of plasma-treated surfaces is a major concern in various fields of application. Post-plasma decay of treatment level can lead to problems such as delamination and incompatibility. Considerable work has been done to understand the fundamental mechanisms of aging, from which several approaches have been developed to tackle it. Most of the released solutions require additional and further steps after or before the plasma exposure to stabilize the treatment level and prevent its downfall. This per se causes process difficulties and increases production costs. Herein, a single-step gliding arc plasma-based method is investigated for modification of biaxially-oriented polypropylene (BOPP). Findings approved post-treatment progressive hydrophilicity improvement in this method. Surface characteristics’ alterations were assessed instantly after the treatment and with intervals during five weeks via ATR-FTIR, XPS, AFM, FESEM, GIXRD, and contact angle measurement (static and dynamic) in order to explain the plasma effects and aging findings. Results indicated that this treatment approach could make a significant contribution to the field of plasma surface treatment via introducing a feasible and fast method that can be carried out in a single step and at the atmospheric pressure with minus aging effects and without the unfavorable hydrophobic recovery phenomenon.