Christoph Schmüser

Fraunhofer Institute for Manufacturing Technology and Advanced Materials

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Ralph Wilken

Fraunhofer Institute for Manufacturing Technology and Advanced Materials

Christopher Dölle

Fraunhofer Institute for Manufacturing Technology and Advanced Materials

Heba Abdallah

National Research Centre

Ahmed M. Shaban

National Research Centre

Marwa Shalaby

National Research Centre

Jürgen Meichsner

Universität Greifswald

ВГ

В. Г. Данилов

National Research University Higher School of Economics

Matthias Ott

Fraunhofer Institute for Manufacturing Technology and Advanced Materials

Andreas Hartwig

Fraunhofer Institute for Manufacturing Technology and Advanced Materials

Evgeni Jolondz

University of Bremen

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Fraunhofer Institute for Manufacturing Technology and Advanced Materials

University of Bremen

National Research Centre

Universität Greifswald

National Water Research Center

Chemnitz University of Technology

Fraunhofer Society

Helios Dr. Horst Schmidt Kliniken Wiesbaden

Institut für Technische und Angewandte Physik (Germany)

Institute of Physical Chemistry

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Chemical surface modification for RO membranes based on GO‐mixed polymers for water desalination and biofouling study

Polymer Engineering and Science (2023)

Marwa Shalaby Heba Abdallah Ralph Wilken Christoph Schmüser Ahmed M. Shaban

Abstract The modification of conventional polyamide reverse osmosis (RO) membranes with grafted methacrylic acid in the presence of nanomaterial is disclosed. To decrease fouling, this study shows the effectiveness of grafting a hydrophilic methacrylic acid (PMAA) and graphene oxide (GO) nanosheet. The change in membrane surface after coating method with different layers was obvious. The results of the ATR‐FTIR, SEM, AFM, contact angle investigations from side and enhanced rejection and permeability from other side proved that the grafting and modification processes had been successful. In comparison between different modifications based on grafting for thin film and blend RO membranes (RO T, RO P, and RO PG), it was found that the modified membrane nominated RO TG membranes showed less biofouling. The modified membrane with 1.25 weight percent PMAA concentration and 0.4 weight percent distributed GO had the lowest contact angle, the least fouling, the highest chlorine resistance, and improved desalination performance. Highlights Biofouling study for modified RO membranes Chlorine resistance membranes for water desalination Enhanced surface hydrophilicity through grafting of polyamide membranes

Biofouling

Surface Modification

Poly(N-isopropylacrylamide)

Thin-film composite membrane

10.1002/pen.26591

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Citations (1)

Near-Surfaces and Bulk Modification of Silicone Rubber under UV- and Vacuum UV-Irradiation Using Excimer and Hg Lamps

ACS Omega (2024)

Christopher Dölle Christoph Schmüser Igor Quiring Ralph Wilken

The surface properties of silicone rubber can be modified by irradiation with light from the vacuum ultraviolet (VUV) spectral range of less than 200 nm. After VUV-irradiation at 185 nm with a low-pressure mercury (Hg) lamp, a reduction in residual-dust-coverage (PA fibers) of up to 80% was found. At the same time, the long wavelength UV-radiation at 254 nm of the Hg lamp causes a reduction in the optical transmission properties of the silicone bulk. The near-surface and bulk modification of optically highly transparent silicone rubber was analyzed using XPS, ATR, transmission measurements, and investigations into the reduction of the residual-dust-coverage. A comparison was made between a Hg lamp and an excimer lamp at 172 nm. The results provide valuable information for selecting the appropriate irradiation source, depending on the desired spectral range for a given application. The results indicate that excimer lamps should be preferred for optical applications in the UV-spectral range, while Hg lamps are equally suitable for applications in the visible spectral range despite low transmission losses of less than 0.5%. The irradiation dose data were obtained using a ray tracing simulation as part of these investigations to overcome limitations of UV-sensors, such as their accelerated aging and angular dependence.

Excimer

Silicone rubber

Silicone Elastomers

10.1021/acsomega.4c04823

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Effect graphene oxide nanostructure/tannic acid on mixed polymeric substrate‐surface modified RO membranes

Journal of Applied Polymer Science (2022)

Marwa Shalaby Heba Abdallah Ralph Wilken Christoph Schmüser Ahmed M. Shaban

Abstract In this work, polyamide (PA) layer of (TFC) thin‐film composite in reverse osmosis (RO) membranes are compared to facile cost‐effective lower rejection RO‐ blend membranes using graphene oxide. Polyvinyl alcohol (PVA) is cross‐linked with glutaraldehyde hydrogel and thereby showing the effect of a fixed concentration of graphene oxide (GO) at different surface modification stages. Surface grafting using methacrylic acid is performed to govern the role of the protective layer on the efficiency of the covered TFC layer as membranes performance regarding salt rejection and permeability. GO concentration of 0.25 wt% in PVA solution shows a maximum % rejection reaching 70 for 3PG and the highest permeate flux for 1PG is 45.52 LMH. While the TFC membranes T and TG have shown higher rejection percentages to reach 88.31% for 3TG of and the highest permeate flux is 30.7 LMH for 1TG and decreases to reach 24.56 LMH for 3TG. Different membrane characterizations are fulfilled through surface morphology, wettability, BET area, and adsorptive fouling. Optimized ratios for tannic acid, ZnO‐nanostructure, and graphene oxide with the mixed polymeric substrate are reached. The effect of graphene oxide in the surface grafting layer over blend and TFC membranes are presented.

Glutaraldehyde

Nanofiltration

Tannic acid

10.1002/app.53195

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Modification of Polydimethylsiloxane Coatings by H₂ RF Plasma, Xe₂* Excimer VUV Radiation, and Low‐Energy Electron Beams

Macromolecular Materials and Engineering (2012)

Petra Swiderek Evgeni Jolondz Jan Hendrik Bredehöft T. Borrmann Christopher Dölle

Abstract The crosslinking of thin liquid PDMS layers by three different technically relevant processes, H 2 radio‐frequency plasma treatment, Xe 2 * excimer VUV irradiation, and low‐energy electron beam processing is investigated. The modifications to the layers due to the processing are monitored by means of RAIRS. Plasma processing of liquid PDMS leads to a direct conversion to a SiO x ‐like material of the topmost layers, whereas a gradual transition from PDMS to the same product is observed upon VUV irradiation. Electron exposure does not induce oxidation. The initiating steps of the conversion induced by the interaction with VUV photons, low‐energy electrons, or their combined effect with ions and H atoms in the plasma are discussed. The latter creates a high density of damage sites. magnified image

Excimer

Polydimethylsiloxane

Plasma Processing

10.1002/mame.201100353

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Citations (6)

Surface Treatment by Physical Irradiation for Antifouling, Chlorine-Resistant RO Membranes

Membranes (2023)

Marwa Shalaby Heba Abdallah Ralph Wilken Christoph Schmüser Ahmed M. Shaban

Reverse osmosis (RO) membranes represent a strategic tool for the development of desalination and water treatment processes. Today's global needs for clean water supplies show stressing circumstances to secure this supply, relying upon desalination and wastewater treatment and reuse, especially in Egypt and the Middle East. However, chlorine attack and fouling of polyamide layers, the active (selective) layers of RO membranes, are representing a great obstacle to seriously spreading the use of this technology. One promising way of fouling control and chlorine resistance is surface modification using grafting by plasma or vacuum ultraviolet (VUV) irradiation as a layer-by-layer assembly on polyamide membranes. Several studies have shown the effect of grafting by plasma using methacrylic acid (atmospheric pressure plasma) and showed that grafted coatings can improve PA membranes toward permeation compared with commercial ones with fouling behavior but not chlorine resistance. In this work, the techniques of layer-by-layer (LBL) assembly for previously prepared PA RO membranes (3T) using a mixed-base polymer of polysulfone and polyacrylonitrile in the presence of nanographene oxide (GO) without chemical grafting and with chemically grafted poly-methacrylic acid (3TG) were used. Membranes 3T, 3TG, a blank one (a base polymer membrane only was surface modified using VUV activation (AKT), and one with a grafted layer with polyethylene glycol (VUV-PEG) were prepared. These were then compared with polydimethylsiloxane (VUV-PDMS) and another surface modification with low-pressure plasma using acrylic acid (acryl) and hexadimethyl siloxane (GrowPLAS). The tested membranes were evaluated by short-term permeation and salt rejection experiments together with fouling behavior and chlorine resistance. A clear improvement of chlorine resistance and antifouling was observed for 3T membranes under plasma treatment, especially with the grafting with polyacrylic acid. Better antifouling and antichlorine behaviors were achieved with the vacuum UV treatment.

Biofouling

10.3390/membranes13020227

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Surface Pretreatment of Fiber-Reinforced Plastics via VUV Radiation

Key engineering materials (2017)

Christoph Schmüser Kira Rosanova Christopher Dölle

Fiber-reinforced plastics (FRP) are of great importance for the transport sector, the aerospace industry, for wind power plants, in the building sector and in the field of sports and leisure applications. Optimization of the adhesive bonding process for FRP structures, especially the surface preparation prior to bonding, will be of a central importance in forthcoming expansion of FRP use. In this connection the key problem depends on the FRP polymer matrix. In the case of duroplastic matrix the main problem is the presence of release agent on the surface of joining components. For the thermoplastic matrix such as polypropylene (PP), the main problems are the low surface energy and the inertness of its surface. Conventional pretreatment methods, such as manual grinding, shall be replaced by energetic radiation technics like VUV lamps (vacuum ultraviolet spectral range: 100 – 200 nm). This approach is a non-contact method, characterized by high treatment homogeneity and material-saving properties, combined with no further fibers to be released. The surface of the thermoplastics is activated by the incorporation of oxygen, release agent contamination on the thermoset is cleaned or modified [1 - 8]. The results of the VUV surface activation of PP and CFRP with regard to the incorporation of functional groups, increase of surface energy, matrix degradation and the adhesion increase of adhesive bonds are presented. In addition, studies on the release agent coating and the release agent modification by VUV radiation are presented. The work is completed by considerations concerning possibilities to accelerate the process (in particular, wavelength dependence, influence of an inert gas or the moisture content). Finally, an evaluation of the VUV pretreatment is carried out on the basis of two specific applications.

Polypropylene

Thermosetting polymer

Surface Modification

10.4028/www.scientific.net/kem.742.70

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Photocatalytic thin Films Prepared by Plasma Curing of Non‐Reactive Siloxane Dispersions Containing TiO₂ Particles

Contributions to Plasma Physics (2012)

Matthias Ott Christopher Dölle В. Г. Данилов Andreas Hartwig Jürgen Meichsner

Abstract Photocatalytic TiO 2 layers prepared by PVD or CVD processes are already produced industrially. The deposited TiO 2 needs a sufficiently high concentration of the photocatalytically active anatase phase which is produced at higher substrate temperature. As a consequence, the PVD/CVD techniques are limited to heat‐resistant substrates. A novel approach for plasma hybrid coating technology is presented here using the advantages of a cold low‐pressure plasma process in combination with non‐reactive siloxane (polydimethylsiloxane – PDMS) dispersions containing sub‐micron TiO 2 particles for surface functionalisation. As the result, a mechanically stable composite film containing TiO 2 particles with a diameter of up to several times the average coating thickness is generated. The film consists of a top SiO2‐like surface layer and, depending on the initial film thickness, an underlying gradually demethylated and crosslinked siloxane. Although the TiO 2 particles are partially covered by a thin matrix layer of several nanometres, the thin coating shows photocatalytic activity as demonstrated by UV‐degradation of methylene blue. The photocatalytic activity depends on the TiO 2 particle concentration in the film and can be further enhanced by exposing the TiO 2 surface by CF4 plasma etching of the composite film (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Siloxane

Polydimethylsiloxane

10.1002/ctpp.201210055

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Citations (1)