The functionalization of surfaces is a constant challenge for the industry. Especially when it comes to adhesion, conventional methods quickly reach their limits, particularly when it comes to the pretreatment of very inert or at the same time very sensitive materials. With its innovative and sustainable plasma technology for surface functionalization, the Luxembourg-based company Molecular Plasma Group (MPG) offers customer-specific solutions for precisely these complex applications
MPG's patented MolecularGRIP technology goes far beyond the possibilities of conventional plasma pre-treatment. It can also replace solvent-based adhesion promoters with an environmentally friendly process - often with even better results. Of course, other pretreatment methods can also achieve sufficient adhesion improvement for certain applications, but even there MolecularGRIP technology offers many advantages. Both the use of wet-chemical adhesion promoters with their environmentally harmful and unhealthy properties and the use of plasma technologies for surface activation (e.g. corona treatment) severely restrict the process window for series production. If wet-chemical adhesion promoters have to be dried after application, both methods require rapid further processing, as otherwise the functionalization of the surface loses its effect.
With MPG, on the other hand, organic substances are covalently bonded to any substrates in a one-step, dry process using cold atmospheric plasma, creating a permanent nano-coating that gives the surface a clearly defined function. The immediate and permanent modification of the surface means that the substrates can either be processed immediately or after any period of time (weeks/months). There is therefore no restriction on the processing period after pre-treatment.
Fig. 1: Section through the plasma head (left: PlasmaLine, right: PlasmaSpot )
Another difference to conventional plasma technologies is the energy and temperature level of the process. While high energies are required for pure surface activation through corona treatment, the MPG process is only supplied with just enough energy to generate a very gentle plasma. The plasma now only serves as a vector to radicalize molecules, i.e. to open molecular bonds, so that a covalent bond can then be generated between the molecules of the substrate and the material to be coated. (Figure 1) Last but not least, it is this low energy and thus temperature level that enables the process, in contrast to other technologies, to treat even very sensitive materials (e.g. natural materials such as cellulose) or to immobilize very sensitive substances (e.g. biomolecules such as antibodies, DNA, etc.).
A major advantage of the technology is the wide range of chemicals available for coating the substrates. Apart from the only process-related restriction that the substances must be in liquid form, the entire range of organic chemistry can be used. This allows a wide variety of functions to be created and customer-specific solutions to be developed, whereby the choice of chemistry is always tailored to the system under consideration.
In addition to improving the adhesion of inert materials, the functions range from bio-active surfaces with virucidal, biocidal, anti-biofouling or antimicrobial properties to corrosion protection or targeted filtration through to hydrophobic, hydrophilic and non-stick properties or the deposition of complex biomolecules.
The industrial plasma systems offered by MPG are scalable, fully automated and the process, which takes place under atmospheric conditions, is fully traceable. They can be installed as stand-alone systems or integrated into existing production lines. In addition to the PlasmaSpot system for the functionalization of rather small surfaces, fibres, 3D shapes, powders and particles, the PlasmaLine system is the only atmospheric plasma system on the market that can be used, for example, to treat large surfaces, films, membranes or textiles homogeneously in a continuous process (Figure 2).
Fig. 2: PlasmaLine machine for the continuous coating of rolls - Photo: MPG
While quality control of the pre-treatment in an ongoing series process is only possible to a very limited extent, if at all, when applying wet-chemical adhesion promoters or surface activation, MPG also offers an industrial solution for this. The specially developed vision system ensures at all times that the pre-treatment has taken place to the extent defined in advance. For this purpose, UV tracer molecules are added to the material to be coated and simultaneously deposited homogeneously on the surface. Using the images taken by a UV camera connected in series downstream of the plasma treatment, the intensity of the reflection of the UV light is evaluated by software and used to determine the coating thickness. Integrated into the system's traceability system, this provides 100% control of the process.
To go one step further, MPG has announced an official collaboration with Socomore, one of the world's leading providers of surface preparation in the aerospace sector. With more than 50 years of experience and more than 1000 product approvals from 150 major players in the aerospace and defense sector, Socomore continues to add new products and technologies (Figure 3).
Fig. 3: Coating of aircraft parts - Photo: MPG
The collaboration between Socomore and MPG will combine innovative process technology with reliable chemistry and certification expertise. The solutions developed include the functionalization of composite materials, surface finishing or the replacement of solvent-based primers.
Examples of roll-to-roll applications for composite structures include surface priming of fibers and fabrics (glass fiber, carbon fiber, etc.) for improved adhesion to resins or surface priming for structural adhesion between difficult-to-bond composite tapes (glass, polyolefins, etc.).
Fig. 4: Illustration of the PlasmaPowder system
As an innovative company, MPG is also constantly working on the further development of its plasma systems. The joint venture PartiX, founded in 2021 together with the Belgian company Procept, combines a fluidized bed reactor with MPG's PlasmaSpot system and thus even enables the functionalization of the smallest particles or powders, which represents a technological breakthrough for the industry. While initial applications are currently being developed on a smaller scale, systems ready for series production will soon be available for this purpose (Figure 4).
Literature
- B. Nisol, C. Poleunis, P. Bertrand, F. Reniers, Plasma Process. Polym. 2010, 7, 715.
- B. Nisol, G. Oldenhove, N. Preyat, D. Monteyne, M. Moser,
D. Perez-Morga, F. Reniers, Surface and Coatings Technology 2014, 252, 126.
- B. Nisol, A. Meunier, C. Buess-Herman, F. Reniers,
Plasma Process. Polym. 2015, 12, 991.
- B. Nisol, S. Watson, A. Meunier, D. Juncker, S. Lerouge,
M. R. Wertheimer, Plasma Process. Polym. 2017, 15, e1700132
- B. Nisol, S. Watson, S. Lerouge, M. R. Wertheimer, Plasma Process. Polym. 2016, 13, 965.
- B. Nisol et al. Surface and Coatings Technology 2014, 252, 126.
- Fernando Alba-Elías, Elisa Sainz-García, Ana González-Marcos, Joaquín Ordieres-Meré, Tribological behavior of plasma-
polymerized aminopropyltriethoxysilane films deposited on thermoplastic elastomers substrates, Thin Solid Films, Volume 540, 2013, Pages 125-134, ISSN 0040-6090,
https://doi.org/10.1016/j.tsf.2013.06.028.
- Ignacio Muro-Fraguas, Ana Sainz-García, Paula Fernández Gómez, María López, Rodolfo Múgica-Vidal, Elisa Sainz-García, Paula Toledano, Yolanda Sáenz, Mercedes López, Montserrat González-Raurich, Miguel Prieto, Avelino Alvarez-Ordóñez, Ana González-Marcos, Fernando Alba-Elías, Atmospheric pressure cold plasma anti-biofilm coatings for 3D printed
food tools, Innovative Food Science & Emerging Technologies, Volume 64, 2020, 102404, ISSN 1466-8564,
https://doi.org/10.1016/j.ifset.2020.102404.
- Elisa Sainz-García, María López, Rodolfo Múgica-Vidal, Beatriz Rojo-Bezares, Carmen Lozano, Ana González-Marcos, Paula Toledano, Ignacio Muro-Fraguas, Ana Sainz-García, Yolanda Sáenz, Fernando Alba-Elías, Promotion of biofilm production via atmospheric-pressure plasma-polymerization for biomedical applications, Applied Surface Science
biomedical applications, Applied Surface Science, Volume 581, 2022, 152350, ISSN 0169-4332,
https://doi.org/10.1016/j.apsusc.2021.152350.
- L. Eykens, K. De Sitter, S. Paulussen, M. Dubreuil, C. Dotremont, L. Pinoy, B. Van der Bruggen, Atmospheric plasma coatings for membrane distillation, Journal of Membrane Science, Volume 554, 2018, Pages 175-183, ISSN 0376-7388,
https://doi.org/10.1016/j.memsci.2018.02.067.
- C. R. Piedrahita, K. Baba, R. Quintana, J. Bardon, J. Borek-
Donten, R. Heyberger, P. Choquet, Plasma Processes Polym. 2022; 19:e2200023. https://doi.org/10.1002/ppap.202200023
- J. Borek-Donten, B. Nisol, M. Filimon, M. Lopes, D. Collard,
M. Chassaing, H.-M. Cauchie, R. Heyberger, Plasma Processes Polym. 2022; 19:e2100249.
https://doi.org/10.1002/ppap.202100249
