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Materials used in this study: bleached hardwood Kraft pulp treated with enzymes under controlled conditions, with progressive increase in enzymatic digestion time by 30 min steps for each subsequent sample
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We find that nitrogen plasma treatment of micro/nanofibrillated cellulose films increases wettability of the surface by both liquid polar water and nonpolar hexadecane. The increased wetting effect is more pronounced in the case of polar liquid, favouring the use of plasma treated micro/nanofibrillated cellulose films as substrates for a range of i...
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... amount of 3 mg of enzyme per gram of pulp fibre was added to a 2.5 w/w% suspension and the temperature was increased to 57 °C at pH 5.5 during hydrolysis, whilst keeping under constant agitation. The period of digestion was increased for each subsequent sample in 30 min steps, Table 1. The enzymatic activity was terminated by adjusting the pH to 9-10 by sodium carbonate and increasing the temperature to 90 °C. ...
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... enzymatic pretreatment of pulp as a route for producing low-charged MNFC resulted in the produc- tion of short fibrils, which, in the case studied here, have much lower aspect ratio than MFC and NFC produced via chemical oxidative pretreatment or mechanical refining alone, as illustrated in Fig. 1 comparing MNFC/300/and MNFC/0/suspensions (Table 1), revealing much shorter fibrils obtained upon 300 min of enzymatic hydrolysis. ...
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... device was operated at 6 kV DC and 300 electric field pulses per second (Hz) for the prescribed durations of time, for all the films, as a higher voltage resulted in burning of the thin MNFC films, especially for those made from pulp exposed to long enzymatic pretreatment time. (Table 1). Transparency and uniformity of films increases with hydrolysis time ...
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... as the roughness is also seen to increase as a function of plasma treatment for the lower crystalline samples (less exposure to enzymatic breakdown), one would expect from the Wenzel model that the wettability would increase. That we see a recorded increase in n-hexadecane CA, and thus decrease in dispersive FSE, we can conclude that the action of the plasma Fig. 6 Surface modification obtained through XPS data showing a increase in N atoms at constant carbon content, and b change in ratio of C-O/O- C=O groups Fig. 7 Surface free energy (SFE) of MNFC films as a function of the treatment time (Table 1) discharge on the amorphous part is initially to reduce the dispersive energy component, and so likely act, at least partially, to breakdown first the amorphous content resulting in debonding and hence roughening ( Hansson et al. 2011). This effective etching of amorphous parts of fibrils is then replaced by the action of nitrogen attachment, such that the higher average FSE values regained in the more crystalline samples after plasma treatment are significantly higher than the theoretical FSE 59.4 mJ m -2 of cellulose, and this is achieved via the major contribution of the plasma-induced increase in polar component. ...
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Citations
... Optical sintering with laser [18], infrared (IR) [58], plasma [59], or flash light [60] at room temperature have emerged as attractive alternatives to overall thermal treatment due to its high speed and compatibility with soft and porous substrates. Balliu et al studied the effect of laser sintering on inkjet-printed AgNP layers (850 ± 150 nm thick) on seven different types of papers with a galvanometric scanning mirror system at 250 kW cm −2 [61]. ...
Soft electronic devices enable new types of products for an ergonomic interaction of humans with a digital environment. The inkjet (droplet on demand) printing of electrically conductive ink on soft substrates such as paper, textile, and polymers is a promising route for the prototyping and small-scale production of soft electronics that is efficient, cost-saving, and provides a rapid turnaround due to its fully digital workflow. The choice of materials and processing parameters is challenging, however, due to the combined complexity of metal-containing inks, their dynamics during droplet ejection, the active role of the porous substrate, and possible post-deposition steps. This review focuses on recent developments in inkjet printing of metal inks onto soft, porous substrates and their applications. The first section discusses the general principles in the inkjet printing of metal inks, including drop formation and jetting, wetting, and post treatment processes. The second section deals with the effect that the porosity of substrates has on the drying, diffusion, and adhesion of inks. Finally, current challenges and achievements of inkjet-printed, metal-containing inks are discussed.
... This characteristic favors greater amounts of hydrogen bonds with water molecules. For this reason, adhesion forces overcome the cohesion forces, increasing the scattering of liquid on the film surface (Dimic-Misic et al. 2019). The thickness ranged between 20 µm and 36 µm ( Figure 5A). ...
The characteristics of cellulose micro/nanofibrils (MFC/CNF) can be improved with pre-treatments of the original fibers. The present work is proposed to study pre-treatment with sodium silicate (Na2SiO3) on bleached fibers of Eucalyptus sp. (EUC) and Pinus sp. (PIN) and its effects on the quality index of MFC/CNF. Particle homogeneity, turbidity, and microstructure of the suspensions were evaluated. Similarly, the physical-mechanical, and barrier properties of the films were studied. With the results obtained for suspensions and films, the quality index (QI) was MFC/CNF calculated. The smallest particle dimension was observed for MFC/CNF of Pinus sp. with 10 % of Na2SiO3, as well as the lowest turbidity (∼350 NTU) was obtained for MFC/CNF of Pinus sp. with 5 % of Na2SiO3.The pre-treatments reduced the transparency of the films by ∼25 % for EUC and ∼20 % for PIN. The films presented a suitable barrier to UVC radiation, water vapor, and oil.The tensile strength of EUC and PIN films was increased by 20 % using 10 % of Na2SiO3. The same concentration of Na2SiO3 provided QI 70 for EUC MFC/CNF. The Na2SiO3 was efficient to obtain the MFC/CNF with interesting properties and suitable to generate films with parameters required for packaging
... 21 Katarina Dimic-Misic and co-workers modied enzyme pretreated bre-derived MNFC lm surfaces using nitrogen plasma to enhance their amphiphilic surface affinity to polar and non-polar IP PV inks. 22 Nevertheless, there are few literature concerning the inuence of surface sizing treatment on ink adhesion properties of paper bers. For paper products, the common technologies are tiny droplets printing, pressureless printing, electrostatic printing and ink-jet printing. ...
The surface sizing system of specialty paper with an interpenetrating polyvinyl alcohol-blocked polyurethane polymer network was applied to fabricate paper of high ink adhesion and mechanical properties.
... Reprinted with permission from Refs.[81,83], Elsevier, 2022. Reprinted from Refs.[88,91]. ...
Biopolymers, like polysaccharides and proteins, are sustainable and green materials with excellent film-forming potential. Bio-based films have gained a lot of attention and are believed to be an alternative to plastics in next-generation food packaging. Compared to conventional plastics, biopolymers inherently have certain limitations like hydrophilicity, poor thermo-mechanical, and barrier properties. Therefore, the modification of biopolymers or their films provide an opportunity to develop packaging materials with desired characteristics. Among different modification approaches, the application of cold plasma has been a very efficient technology to enhance the functionality and interfacial characteristics of biopolymers. Cold plasma is biocompatible, shows uniformity in treatment, and is suitable for heat-sensitive components. This review provides information on different plasma generating equipment used for the modification of films and critically analyses the impact of cold plasma on packaging properties of films prepared from protein, polysaccharides, and their combinations. Most studies to date have shown that plasma treatment effectively enhances surface characteristics, mechanical, and thermal properties, while its impact on the improvement of barrier properties is limited. Plasma treatment increases surface roughness that enables surface adhesion, ink printability, and reduces the contact angle. Plasma-treated films loaded with antimicrobial compounds demonstrate strong antimicrobial efficacy, mainly due to the increase in their diffusion rate and the non-thermal nature of cold plasma that protects the functionality of bioactive compounds. This review also elaborates on the existing challenges and future needs. Overall, it can be concluded that the application of cold plasma is an effective strategy to modify the inherent limitations of biopolymer-based packaging materials for food packaging applications.
... 50 Accordingly, various new plasma-based approaches to decrease the surface free energy of fibers have been investigated in recent years. 7,40,48,[51][52][53][54][55][56][57] Hydrophobic 58,59 and superhydrophobic surfaces 60,61 have attracted considerable attention in both scientific and industrial sectors over recent decades, owing to their potential applications in self-cleaning, 14,62 antisticking anticontamination, 31,63 drag reduction, 64,65 icephobicity, [66][67][68] and corrosion resistance. 60,69 Despite the comprehensive reviews on superhydrophobic surfaces, [70][71][72][73][74][75][76][77] plasma-based treatments of textiles, 14,34,51,78 and hydrophobic/superhydrophobic textiles, [79][80][81][82][83][84] there are no review articles specifically describing plasma processing methods for fabricating the superhydrophobic textiles. ...
In this review, we present a comprehensive survey of techniques used to fabricate superhydrophobic—extreme nonwetting—textiles by plasma systems. First, we provide a brief introduction to superhydrophobic surfaces, plasma sources, and plasma surface processing. We then assess the plasma-based techniques capable of producing the required rough surface micronanotextures of superhydrophobic surfaces. The implications of tailoring the specific surface chemistry and texture will be discussed, and finally, we summarize future challenges and issues to be addressed for ensuring a better understanding and use of superhydrophobic fabrics.
... While the plasma exposure mainly induces increased surface roughness by etching on the scale of micrometre dimensions, chemical reactions caused by plasma exposure are known also to produce even finer scale changes in surface roughness [56,57]. It has been documented that the combination of micro and macro roughness gives the best results to control wettability as they act either to decrease the depth of air pockets, whilst simultaneously lowering the contact angle to enhance super-wettability, or, on the contrary, create surface patterning, which leads to liquid meniscus discontinuity and hence super-hydrophobicity [58][59][60]. Cold DBD plasma exposure of MNFC-based composites can, therefore, be an alternative to conventional treatments that utilise fossil-based chemicals that increase roughness and compatibility with other molecules and particles, such as dyes, conductive fillers and inks [55]. Larger contact area, when coupled with chemical moieties from different gas types can lead to the enhanced application of ultrafine coatings [37]. ...
The surface of cellulose films, obtained from micro nanofibrillated cellulose produced with different enzymatic pretreatment digestion times of refined pulp, was exposed to gas plasma, resulting in a range of surface chemical and morphological changes affecting the mechanical and surface interactional properties. The action of separate and dual exposure to oxygen and nitrogen cold dielectric barrier discharge plasma was studied with respect to the generation of roughness (confocal laser and atomic force microscopy), nanostructural and chemical changes on the cellulose film surface, and their combined effect on wettability. Elemental analysis showed that with longer enzymatic pretreatment time the wetting response was sensitive to the chemical and morphological changes induced by both plasma gases, but distinctly oxygen plasma was seen to induce much greater morphological change while nitrogen plasma contributed more to chemical modification of the film surface. In this novel study, it is shown that exposure to oxygen plasma, subsequently followed by exposure to nitrogen plasma, leads first to an increase in wetting, and second to more hydrophobic behaviour, thus improving, for example, suitability for printing using polar functional inks or providing film barrier properties, respectively.
... For instance, modifying the gas environment enables controlling the reactive species in the plasma to induce several functional groups on the polymer surface. This provides a way of changing the wettability properties to improve hydrophilicity (Dimic-Misic et al. 2019;Dumitrascu et al. 2005;Pejić et al. 2020) or hydrophobicity (Chan et al. 2020). Another advantage of AP-DBDs is the possibility of treating polymers in the form of powders (Arpagaus et al. 2018;Pichal et al. 2009) which makes this technology suitable for its implementation up to industrial scales. ...
Despite promising characteristics such as the biodegradability and the environmentally benign nature of cellulose nanocrystal (CNC) based composites, their poor dispersion and agglomeration in thermoplastic matrix during the melting process is a “bottleneck” in the development of these composites. In this work, a cylindrical atmospheric pressure dielectric barrier discharge was employed to functionalize CNCs to reduce their surface hydrophilicity and improve their dispersion in polar organic solvents. Three different gas mixtures were used for plasma treatment, argon/methane, argon/silane and an argon/methane followed by argon/silane. In all cases, the plasma treatment was conducted below 90 °C as determined from optical emission spectroscopy analysis. The X-ray diffraction analysis of both raw and plasma-treated CNC powder confirmed that the CNC crystallographic properties remained unchanged after plasma treatment. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis revealed the presence of hydrophobic C–Hx moieties on the CNC granular surface after argon/methane plasma treatment whereas SiHx, Si–O–Si, SiC bonds were formed after argon/silane plasma treatment. Under these experimental conditions, water wettability tests revealed some significant water repellency for the treated cellulosic material. Moreover, the SiHx moieties formed in silane-treated CNCs clearly enhanced the hydrophobicity of the CNC powder. Contrariwise, the sole CHx moieties synthesized by argon/methane plasma did not yield such enhancement of the CNC wettability. High-resolution scanning electron microscopy images showed the presence of agglomerated granules with 5–10 µm diameters in size. The surface functionalities of CNC powder enhanced its dispersibility in polar solvents. Overall, this study emphasizes that atmospheric pressure dielectric barrier discharge is suitable to process thermo-sensitive CNCs.
Graphic abstract
... Furthermore, the convective cooling of the jet flow makes a DBDjet useful for processing materials at low temperature. The reactive species of DBD plasma can modify the wettability of the cellulose surface, which is beneficial for electronic ink trapping (Dimic-Misic et al. 2019). ...
This study demonstrates a method for patterning paper-based microfluidic devices. An octadecyltrichlorosilane (OTS) solution is used to coat a chromatography paper to make it hydrophobic. A low-temperature (~ 32.9 °C) atmospheric-pressure dielectric-barrier-discharge jet with a shadow mask is then used to pattern hydrophilic stripes on the OTS-coated hydrophobic paper. In this manner, 1-mm-wide hydrophilic stripes are patterned successfully. Liquids are demonstrated to be transported and mixed in the hydrophilic stripes. Water contact angle measurement, X-ray photoelectron spectroscopy, surface profiler, optical emission spectroscopy, and scanning electron microscopy are used to characterize effect of pattering.
Surface modification of cellulose acetate filter rods with low temperature plasma was performed to explore the retention and adsorption effect of modified filter rods on typical components (CO, H2O, benzene, and formaldehyde) in cigarette smoke. The surface structure and composition of the cellulose acetate filter rods were modified by changing the plasma treatment time. The modified filter rods were characterized by N2 physical adsorption (BET), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), contact angle of H2O, Fourier transform infrared spectroscopy (FTIR) and in situ DRIFTS. Various functional groups were found on the surface of filter rods with the introduction of plasma modification, which exhibited strong retention performance for water vapor in cigarette smoke at room temperature and significantly enhanced adsorption for harmful substances (CO, benzene, and formaldehyde) in cigarette smoke.
