Sulfonated Kraft Lignin Research Articles

An Innovative Surface Modification Technique for Antifouling Polyamide Nanofiltration Membranes.

In this study, we developed a novel surface coating technique to modify the surface chemistry of thin film composite (TFC) nanofiltration (NF) membranes, aiming to mitigate organic fouling while maintaining the membrane's permselectivity. We formed a spot-like polyester (PE) coating on top of a polyamide (PA) TFC membrane using mist-based interfacial polymerization. This process involved exposing the membrane surface to tiny droplets carrying different concentrations of sulfonated kraft lignin (SKL, 3, 5, and 7 wt %) and trimesoyl chloride (TMC, 0.2 wt %). The main advantages of this surface coating technique are minimal solvent consumption (less than 0.05 mL/cm2) and precise control over interfacial polymerization. Zeta potential measurements of the coated membranes exhibited enhancements in negative charge compared to the control membrane. This enhancement is attributed to the unreacted carboxyl functional groups of the SKL and TMC monomers, as well as the presence of sulfonate groups (SO3) in the structure of SKL. AFM results showed a notable decrease in membrane surface roughness after polyester coating due to the slower diffusion of SKL to the interface and a milder reaction with TMC. In terms of fouling resistance, the membrane coated with a polyester composed of 7 wt % SKL showed a 90% flux recovery ratio (FRR) during Bovine Serum Albumin (BSA) filtration, showing a 15% improvement compared to the control membrane (PA). PE-coated membranes provided stable separation performance over 40 h of filtration. The sodium chloride rejection and water flux displayed minimal variations, indicating the robustness of the coating layer. The final section of the presented study focuses on assessing the feasibility of scaling up and the cost-effectiveness of the proposed technique. The demonstrated ease of scalability and a notable reduction in chemical consumption establish this method as a viable, environmentally friendly, and sustainable solution for surface modification.

Green polycaprolactone/sulfonated kraft lignin phase inversion membrane for dye/salt separation

Exploring environmentally friendly, renewable, and cost-effective raw materials is essential in sustainable membrane fabrication. This study presents a facile and scalable method for fabricating a green and biodegradable tight ultrafiltration membrane for dye/salt separation. This involves simply blending biodegradable polycaprolactone (PCL) with the low-cost biobased sulfonated kraft lignin (SKL) additive. Additionally, we employed acetic acid as a green alternative solvent to enhance the sustainability of the membrane fabrication process. The incorporation of hydrophilic SKL into the PCL matrix resulted in increased hydrophilicity (water contact angle changed from 72° to 56°), surface roughness (increased from 29 nm to 43.5 nm), and enhanced negative electrostatic charge of the membrane (−40 mV to −45 mV). The optimized PCL/SKL membrane (M3) exhibited excellent water flux (∼45 LMH) under 40 psi hydraulic pressure coupled with ∼98 % and ∼10 % rejection rates for reactive red (RR) dye and NaCl, respectively. Moreover, the M3 membrane maintained its exceptional dye/salt fractionation performance while separating the mixtures at low salt concentrations. However, with increasing salt concentration (1–50 g/L), the membrane's RR dye rejection declined from ∼90 % to ∼50 %, with a significant reduction in NaCl and Na2SO4 salts rejection (from ∼14 % to ∼1 % and ∼22 % to –∼1 %, respectively). The M3 membrane exhibited remarkable antifouling properties during dye and humic acid filtration with a high flux recovery ratio (>98 %) and low flux decline rate (<7 %). The PCL/SKL membrane also showed excellent stability and maintained consistent separation performance over a long period. Overall, the novel biodegradable PCL/SKL membrane prepared in this study presents a promising avenue toward sustainable membrane fabrication for wastewater treatment applications.

Valorization of Sulfonated Kraft Lignin as a Natural Dye for the Sustainable Dyeing of Wool Fabrics: Effect of Peroxide Oxidation

Valorization of Sulfonated Kraft Lignin as a Natural Dye for the Sustainable Dyeing of Wool Fabrics: Effect of Peroxide Oxidation

Novel lignosulfonated polyester membranes with remarkable permeability and antifouling characteristics

Polyamide thin film composite (TFC) membranes are the most common nanofiltration and reverse osmosis membranes for wastewater treatment and desalination. Even though polyamide membranes excel in these applications, they can be fouled easily. In this work, we used an alternative approach for these applications: polyester membranes made via interfacial polymerization of terephthaloyl chloride (TPC) and sulfonated kraft lignin (SKL). The novel polyester TFC membranes had much higher negative surface charges than a reference polyamide TFC membrane, helping them reject negatively-charged solutes such as reactive red, reactive black, methyl orange, and most foulants like proteins. The polyester TFC membrane prepared with 7 wt% SKL and 0.2 wt% TPC reached a water flux greater than 50 LMH (liter per square meter per hour) and over 90% dye rejection, which is more than 3 times the water flux of a polyamide TFC membrane at almost the same dye rejection. We propose that compared with more reactive monomers, such as piperazine (PIP) and trimesoyl chloride (TMC), the slower polymerization rate between SKL and TPC increased the free volume in the polyester membrane, which, in turn, increased the membrane permeability while keeping the dye rejection constant. Our findings indicate a promising pathway for developing non-polyamide membranes with competitive separation performance and antifouling properties that could rival current commercial nanofiltration membranes.

"Biomass to Membrane": Sulfonated Kraft Lignin/PCL Superhydrophilic Electrospun Membrane for Gravity-Driven Oil-in-Water Emulsion Separation.

Biobased membranes made with green solvents have numerous advantages in the water purification industry; however, their long-term use is impeded by severe membrane fouling and low structural stability. Herein, we proposed a facile and green approach to fabricate an eco-friendly and biodegradable electrospun membrane by simply blending polycaprolactone (PCL) with sulfonated kraft lignin (SKL) in a green solvent (i.e., acetic acid) without needing any additional post-treatment. We investigated the influence of SKL content on the surface morphology, chemical composition, and mechanical properties of the electrospun membrane. The SKL-modified membranes (L-5 and L-10) showed superhydrophilicity and underwater superoleophobicity with a water contact angle (WCA) of 0° (<3 s) and an underwater-oil contact angle (UWOCA) over 150° due to the combined effect of surface roughness and hydrophilic chemical functionality. Furthermore, the as-prepared membranes demonstrated excellent pure water flux of 800-900 LMH and an emulsion flux of 170-480 LMH during the gravity-driven filtration of three surfactant-stabilized oil-in-water emulsions, namely, mineral oil/water, gasoline/water, and n-hexadecane/water emulsions. In addition, these membranes exhibited superior antioil-fouling performance with excellent separation efficiency (97-99%) and a high flux recovery ratio (>98%). The 10 wt % SKL-incorporated membrane (L-10) also showed consistent separation performance after 10 cyclic tests, indicating its excellent reusability and recyclability. Furthermore, the stability of the membrane under harsh pH conditions was also evaluated and proved to be robust enough to maintain its wettability in a wide pH range (pH 1-10).

Development of Superpermeable Wood-Based Forward Osmosis Membranes

Novel lignin-based membranes with excellent water permeability and salt rejection characteristics were developed for forward osmosis (FO) processes. The fabricated membranes are composed of three layers: (i) a bottom layer of nanofibrous electrospun sulfonated kraft lignin (SKL) (70 wt %) and poly(vinyl alcohol) (PVA) (30 wt %), (ii) an intermediate layer of PVA-glutaraldehyde (GA) hydrogel, and (iii) a top thin film of a selective polyamide (PA) layer. We coated the SKL-PVA support surface with four different PVA hydrogel concentrations (0.25, 0.5, 1, and 2 wt %). Increasing the concentration of the PVA hydrogel, the thickness of the deposited layer was increased accordingly. After forming the PA layer on top of the PVA hydrogel layer by the interfacial polymerization reaction, lignin-based thin film composite (LTFC-X) membranes were obtained, in which X denotes the PVA hydrogel concentration. According to the cross-sectional TEM images, the thickness of the deposited PA layer dropped from 450 nm on the LTFC-0.25 membrane to less than 60 nm in the LTFC-1 membrane. However, a further increase in the PVA hydrogel concentration enhanced the PA layer thickness to over 250 nm. Among all synthesized membranes, the LTFC-0.5 membrane demonstrated the lowest structural parameter (S) of 191.67 ± 5.88 μm, resulting in a minimal internal concentration polarization in this membrane. The FO performances of membranes were evaluated in two different configurations: the active PA layer facing the feed solution (ALFS) and the PA layer facing the draw solution (ALDS). The LTFC-0.5 membrane provided maximum water flux (Jw) in both ALDS (61.33 ± 2.85 LMH) and ALFS (56.60 ± 2.99 LMH) modes. The LTFC-0.5 membrane also showed the lowest specific salt flux (Js/Jw) of 0.087 ± 0.004 g/L among all fabricated membranes in the ALDS mode. However, the LTFC-1 membrane provided the best performance in the ALFS mode with a minimum Js/Jw value of 0.090 ± 0.011 g/L.

Understanding sulfonated kraft lignin re-polymerization by ultrafast reactions in supercritical water

Re-polymerization reactions are a commonly reported issue on the way to the higher recovery of monomers from lignin. The reactivity of monomers obtained from lignin depolymerization and their contribution to the re-polymerization in supercritical water (SCW) was investigated. Sulfonated Kraft lignin (SKL) was used along with four monomers: vanillin, vanillic acid, vanillyl alcohol and acetovanillone. Indulin Kraft lignin was also employed as the reference to understand the re-polymerization of SKL in SCW. The formation of diarylmethane structures was detected in HSQC spectra of solid residue after the SCW process. Lignin released fragments with free phenolic β-O-4 structures, as well as the monomeric product vanillyl alcohol are involved with the formation of o-o´ and o-p ´ diarylmethane structures. Chemical structure of Kraft lignin and its polymeric product after the SCW process was remarkably similar, as shown by HSQC, indicating that re-polymerization reactions occur through cross-linking polymerization, mainly in their fractions of low molecular weight products.

Degradation and flammability of bioplastics based on PLA and lignin

This article presents the preparation of polylactide (PLA)-derived bioplastics, where kraft lignin (L), sulfonated kraft lignin (L-SO3H) or sulfonated kraft lignin in combination with silica (L-SO3H+SiO2) were used as natural additives. The functional groups present in the obtained bioplastics was investigated using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) and their thermal properties were investigated using Differential Scanning Calorimetry (DSC) as well as Thermogravimetric analysis (TG). The impact of different additive combinations as well as the aging process on the properties of bioplastics, including their flammability characteristics, were investigated in detail. Additionally, mechanisms have been proposed to explain the observed network fragmentation during burning.

Technical benefits of using methane as a pyrolysis medium for catalytic pyrolysis of Kraft lignin

Catalytic fast pyrolysis of low sulfonated Kraft lignin was performed under different atmospheric environments such as N2, CH4, and the gas derived from CH4 decomposition (CH4-D). The use of Zn- or Mo-loaded HZSM-5 as catalyst led to a higher pyrolytic oil yield compared to parent HZSM-5 in CH4 and CH4-D atmospheres. The yields of benzene, toluene, and xylenes were increased by the synergistic effects from metal loading, higher H/Ceff ratio, higher acidity, and CH4 activation. The enhanced CH4 activation via metal loading resulted in higher methylation of alkyl moieties and 33% increase in the total yield of benzene, toluene, and xylenes in comparison to parent HZSM-5. A higher H/Ceff ratio of 6 via CH4 decomposition led to the formation of a hydro-pyrolysis environment. Moreover, the CH4-D environment showed H2/CH4 ratio of 0.36 in the product gas which warranted the presence of more H2 under the CH4-D pyrolysis environment.

Dispersion performance of hydroxypropyl sulfonated lignin in aluminum oxide suspension

• Hydroxypropyl sulfonated kraft lignin was compared with lignosulfonate as a dispersant. • The adsorption of the biopolymers on the aluminum oxide surface was studied. • The dispersion, sedimentation, and particle size of the system were studied. • The results confirmed that both biopolymers behaved very similarly in the suspension. • Hydroxypropyl lignin can replace lignosulfonate due to its attractive production process. In this work, the adsorption and dispersion characteristics of hydroxypropyl sulfonated lignin (HSL) were assessed and compared with those of lignosulfonate (LS). HSL was synthesized in an environmentally friendly manner by reacting kraft lignin (KL) with 3-chloro-2-hydroxypropansulfonic acid (CHPS) under alkaline conditions. This reaction produced HSL with a charge density (-2.48 mmol/g) and molecular weight (42,000 g/mol) that were similar to those of LS. The adsorption behavior of HSL and LS on the aluminum oxide surface was fundamentally analyzed using a quartz crystal microbalance with dissipation monitoring (QCM-D). HSL and LS formed films of similar thickness, though the HSL films exhibited looser and more viscous structures. The dynamic and static dispersion behaviors of HSL and LS in an aluminum oxide suspension were investigated via ζ potential, particle size, and sedimentation analyses. HSL and LS decreased the suspended particle size and improved suspension stability via electrostatic repulsion similarly. The similar properties, adsorption behavior, and stabilizing performances of HSL and LS indicate that HSL may be an effective substitute for commercial LS dispersants. Furthermore, its environmentally friendly synthesis and use of widely available KL as a starting material make HSL production a commercially attractive option.

Ionomers From Kraft Lignin for Renewable Energy Applications.

Converting industrial/agricultural lignin-rich wastes to efficient, cost-effective materials for electrochemical devices (e.g., fuel cells) can aid in both bio- and energy economy. A major limitation of fuel cells is the weak ion conductivity within the ~2–30-nm thick, ion-conducting polymer (ionomer)-based catalyst-binder layer over electrodes. Here, we strategically sulfonated kraft lignin (a by-product of pulp and paper industries) to design ionomers with varied ion exchange capacities (IECs) (LS x; x = IEC) that can potentially overcome this interfacial ion conduction limitation. We measured the ion conductivity, water uptake, ionic domain characteristics, density, and predicted the water mobility/stiffness of Nafion, LS 1.6, and LS 3.1 in submicron-thick hydrated films. LS 1.6 showed ion conductivity an order of magnitude higher than Nafion and LS 3.1 in films with similar thickness. The ion conductivity of these films was not correlated to their water uptake and IECs. Within the three-dimensional, less dense, branched architecture of LS 1.6 macromolecules, the –SO3H and –OH groups are in close proximity, which likely facilitated the formation of larger ionic domains having highly mobile water molecules. As compared to LS 1.6, LS 3.1 showed a higher glass transition temperature and film stiffness at dry state, which sustained during humidification. On the contrary, Nafion stiffened significantly upon humidification. The smaller ionic cluster within stiff LS 3.1 and Nafion films thus led to ion conductivity lower than LS 1.6. Since LS x ionomers (unlike commercial lignosulfonate) are not water soluble, they are suitable for low-temperature, water-mediated ion conduction in submicron-thick films.

Generation of sulfonated kraft lignin acrylic acid polymer and its use as a flocculant

ABSTRACT The main purpose of this work was to generate sulfonated lignin-acrylic acid polymer and to study its flocculation performance for aluminum oxide suspension. The sulfonation pretreatment enhanced the charge density and solubility of kraft lignin facilitating its subsequent polymerization with acrylic acid. The maximum anionic charge densities of 3.3 and 2.5 meq/g and maximum molecular weights of 898 and 330 kg/mol were obtained for purified sulfonated lignin – acrylic acid and purified kraft lignin–acrylic acid polymers, respectively. The elimination of polyacrylic acid (i.e., homopolymer) from the lignin derivatives improved the efficiency of lignin products as flocculants for aluminum oxide particles.

Development of antifouling membranes using agro-industrial waste lignin for the treatment of Canada's oil sands produced water

Steam assisted gravity drainage (SAGD) is one of the key technologies that largely contributes to the global oil and gas production. However, the sustainable growth of this technology strongly depends on the judicious management of the mass-produced process-affected water. Membrane separation, considered as an advanced treatment process, fails to efficiently treat the SAGD produced water due to inevitable fouling if the membrane is not modified accordingly. Here, we used an industrial waste derivative of lignin, sulfonated Kraft lignin (SKL), containing highly hydrophilic and negatively charged functional groups, as a bulk modifier for the fabrication of antifouling polyethersulfone (PES) membrane. SKL concentration was varied to tune the internal morphology, permeability, hydrophilicity, and surface charge of the PES membranes. The modified membrane containing the highest amount of SKL additive (3 wt%) exhibited profound enhancement in the flux recovery ratio from 52.2% to 98.2% compared to the pristine PES membrane against the complex mixture of organic pollutants in SAGD produced water. The key parameters that contributed to the enhancement of the antifouling properties of the membranes were the surface hydrophilicity and the negative surface charge. The oil contact angle increased from 132.8°±1.0° for the pristine PES membrane to 146.8°±1.0° for 3 wt% SKL-embedded membrane while its negative surface charge increased by about 3 times under the operational pH (>8) of SAGD produced water. Another distinct feature of the SKL-modified membrane was that the rejection of the organics decreased only slightly from 61.7% for the pristine membrane to 56.1% for the 3 wt% SKL-embedded membrane while the permeability and molecular weight cut-off (MWCO) increased by 43.3 LMH/psi and 144 kDa, respectively. Such a similar removal efficiency of the SKL-modified membrane to the tighter pristine PES membrane was achieved presumably due to the shielding of the hydrophobic negatively-charged foulants by the hydration barrier and the negative charges on the surface of the SKL-modified membrane.

Industrial waste lignin as an antifouling coating for the treatment of oily wastewater: Creating wealth from waste

Treatment of oily wastewater is of paramount importance to prevent unbearable water pollution caused by large discharge volume from industrial and household activities. Membrane technology is an effective oily wastewater treatment technology. However, it suffers from fouling if the membrane element is not modified to possess anti-oil-fouling propensity. Here, we converted an agro-industrial waste into an asset by coating hydrophilic sulfonated kraft lignin on polyethersulfone (PES) membrane using layer-by-layer (LbL) assembly. The polyelectrolytes used in the LbL process were lignin as a polyanion and poly (diallyldimethylammonium chloride) (pDAC) as a polycation. The effects of polyelectrolyte concentration and the number of coating bilayers were examined to fabricate a membrane with an enhanced anti-fouling propensity and minimal loss in permeation performance. The membrane with the highest anti-fouling performance was obtained by coating 3 pDAC/lignin bilayers with 2 wt% concentration of the individual polyelectrolyte solution. This membrane demonstrated a low flux decline of 23.1%, and a high flux recovery ratio of 93.8% when was utilized for the filtration of the n-hexadecane-in-water emulsion as synthetic oily wastewater. The pristine PES membrane showed a flux decline of 44.2%, and the flux recovery ratio of 75.9% under similar test conditions. The improvement in anti-fouling properties of the LbL-assembled membrane was achieved due to its higher underwater oleophobicity (22.6° ± 0.5°) as compared to the pristine PES membrane (71.1° ± 0.7°). The present study opens up a new paradigm to develop anti-fouling membranes by using hydrophilic industrial waste lignin in LbL surface modification of conventional polymeric membranes for oily wastewater treatment.

Sulfonated Kraft lignin addition in urea–formaldehyde resin

Urea–formaldehyde (UF) resins are widely used over the world as an adhesive, principally in the civil construction, but its use leads to formaldehyde emissions when exposed to higher temperatures. In this way, the aim of this study was to evaluate the partial replacement of adhesives made of UF resin by sulfonated Kraft lignin, up to 30 mass%, and study its effects on the mechanism and on the kinetic/thermodynamic parameters of the thermal degradation, as well as on the thermal stability of the UF resin through thermogravimetric analysis and using isoconversional methods. The results showed that the lignin addition to the UF resin was beneficial, as there was synergy between the materials and verification of enhancement of thermal stability. Aside from the changes in the thermal behavior, the probable reduction of the emission of formaldehyde in the second step of degradation of the UF resin was also observed. These results indicate that the lignin can be used as a potential material to partially replace the UF resin.

Improving fire retardancy of cellulosic thermal insulating materials by coating with bio-based fire retardants

Abstract Sustainable thermal insulating materials produced from cellulosic fibers provide a viable alternative to plastic insulation foams. Industrially available, abundant, and inexpensive mechanical pulp fiber and recycled textile fiber provide potential raw materials to produce thermal insulating materials. To improve the fire retardancy of low-density thermal insulating materials produced from recycled cotton denim and mechanical pulp fibers, bio-based fire retardants, such as sulfonated kraft lignin, kraft lignin, and nanoclays, were coated onto sustainable insulating material surfaces to enhance their fire retardancy. Microfibrillated cellulose was used as a bio-based binder in the coating formula to disperse and bond the fire-retardant particles to the underlying thermal insulating materials. The flammability of the coated thermal insulating materials was tested using a single-flame source test and cone calorimetry. The results showed that sulfonated kraft lignin-coated cellulosic thermal insulating materials had a better fire retardancy compared with that for kraft lignin with a coating weight of 0.8 kg/m2. Nanoclay-coated samples had the best fire retardancy and did not ignite under a heat flux of 25 kW/m2, as shown by cone calorimetry and single-flame source tests, respectively. These cost-efficient and bio-based fire retardants have broad applications for improving fire retardancy of sustainable thermal insulating materials.

Hydroxypropyl sulfonated kraft lignin as a coagulant for cationic dye

In this paper, kraft lignin was reacted with 3-chloro-2-hydroxypropansulfonic acid sodium (CHPS) to produce hydroxypropyl sulfonated lignin (SL). The effects of reaction conditions, e.g., the molar ratio of CHPS to lignin, the concentration of NaOH and the reaction temperature and time, on the charge density of resultant SL were investigated. The optimized conditions were found to be 80 °C, 4 h reaction time, 0.05 M NaOH concentration and 5/1 mol/mol of CHPS/lignin, which generated SL with the charge density and molecular weight of −3.33 meq/g and 45,536 g/mol, respectively. The solubility of KL was 9.6 g/L while that of SL was 100 g/L at the neutral pH. The reaction mechanism between kraft lignin and CHPS was fundamentally discussed. The SL was also characterized by elemental analysis and proton nuclear magnetic resonance (1H NMR). The thermal stability and surface activity of the SL were also evaluated and compared with those of commercially produced lignosulfonate (LSS). The efficiency of SL as a coagulant for dye (basic blue 41 and ethyl violet) removal from simulated wastewater was compared with that of LSS. The zeta potential and particle size analyses were conducted to determine the interaction mechanism of dye and lignin derivatives, and the kinetic studies confirmed their fast complexation.

Evolution of sulfur during fast pyrolysis of sulfonated Kraft lignin

Sulfonated Kraft lignin, the most available commercial lignin of today, has high sulfur content due to the extraction and the subsequent sulfonation processes. In this work, the evolution of sulfur during fast pyrolysis of sulfonated Kraft lignin has been studied. Fast Pyrolysis experiments have been done using Py-GC/MS. It is found that main sulfur-containing products in the pyrolytic vapors are present as the following small molecular compounds: H2S, SO2, CH3SH, CH3SCH3, and CH3SSCH3. This indicates that sulfur-containing radicals preferentially combine with the other small radicals such as H and CH3 during fast pyrolysis process. Sulfur is suggested to be mainly present as sulfite (SO−3) and sulfide (S) in the sulfonated Kraft lignin. Sulfite that is incorporated into lignin during the sulfonation process mainly result in the formation of SO2. The nature of the sulfur links created during the Kraft pulping process is difficult to determine, but they are supposed to mainly exist in form of sulfide (S) bonds, which lead to the formation of H2S, CH3SH, CH3SCH3 and CH3SSCH3.

Preparation of sulfomethylated softwood kraft lignin as a dispersant for cement admixture

In this work, the production of sulfonated kraft lignin was assessed on a laboratory scale, and the performance of the product as a dispersant for a cement admixture was assessed.

Rapid functionalisation of cellulose-based materials using a mixture containing laccase activated lauryl gallate and sulfonated lignin

Abstract An innovative method has been developed for the surface hydrophobisation of cellulose-based materials by coating it with a functionalised solution (FS), in which sonicated lauryl gallate (LG, dodecyl 3,4,5,-trihydroxybenzoate), sulfonated kraft lignin, and the enzyme laccase play a pivotal role. The rapid treatment with FS increases the hydrophobicity of cellulose sheets considerably. The FS retention on the paper surface was analysed as a function of refining and application of additives. The properties of the functionalised sheets were assessed by the water-drop test (WDT), and the surface free energy (SFE) was determined via contact angle (CA) measurements in a goniophotometer. WDT resulted in long absorption times of up to 4000 s and CA values were around 130°. Functionalised solution modification of eucalyptus paper sheets decreased SFE essentially from 55 mJ m-2 to 10 mJ m-2. ATR-FTIR suggested that FS was grafted onto the cellulosic sheets. The stability of FS and the control solutions were characterised by Z potential and light scattering measurements. The functionalised solution method is a one-step roll-to-roll process, which is easy to perform also in industrial application without additional investments. It has a potential to substitute the traditional hydrophobing processes.