![]() ![]() Therefore, new properties may be generated by SLP to the liquid dispersions of cellulose. Furthermore, the reactive species which appear at the liquid/plasma/particles interface 17, 18 may initiate specific reactions and may contribute to bonds breakage on the cellulose surface. Various liquid media or a wide variety of reactive gases may be used in the discharge. This procedure is environmentally friendly and has additional benefits related to the use of low temperatures during treatment, relatively simple installations (without vacuum components) and low operating cost. Submerged liquid plasma (SLP) is a recent research topic and a promising route to modify powder materials and nanomaterials. Such phenomena are avoided when the powders are dispersed in liquids. All reported treatments were applied to cellulose in the form of films, sheets or membranes 12, 13, 14, 15, 16 as the plasma treatment of cellulose powders or fibers in vacuum or open atmosphere is a difficult task, affected by adverse phenomena such as suction, spreading, or limited contact. Similarly, bacterial cellulose membranes modified by nitrogen-containing plasma showed enhanced cell adhesion and viability 13. In particular, the oxidative plasma treatment and grafting of L-lactide onto cellulose films led to an increased interfacial compatibility in polymer-cellulose composites 16. Moreover, plasma treatment is intensively studied to improve the surface properties of cellulose films or sheets 12, 13, 14, 15, 16. Earlier works have reported on the effect of high power ultrasonication in the release of cellulose nanofibers from microcrystalline cellulose 9 or from microalgae 10. It is worth to mention that the energy provided by cavitation is within the hydrogen bond energy levels and may induce both defibrillation and reorganization in the amorphous phase of cellulose 11. Both physical (shear forces, surface erosion, cavitation) and chemical (oxidizing radicals) mechanisms are involved in this process. Ultrasound technology is considered a green approach with high potential in the defibrillation of cellulose 9, 10. Intensive research is devoted to design new, eco-friendly and industrially applicable methods for the preparation of cellulose nanofibers and their functionalization. Generally, the procedures to prepare cellulose nanofibers from a cellulosic source are laborious and expensive and they may obscure the extraordinary benefits of cellulose by using or disposing dangerous chemicals. Enzymatic or acid hydrolysis and mechanical refining are often used as pretreatments to activate cellulose and to induce a more rapid disintegration 8. The release of the cellulose crystals is determined by the penetration of the acid through the amorphous and defect zones of cellulose which leads to the split of cellulose particles. ![]() Acid hydrolysis using sulfuric, phosphoric or hydrochloric acid is one of the most used methods to obtain cellulose nanocrystals. Cellulose can be extracted from a multitude of sources (wood, plants, algae) or from cellulosic wastes by using combined mechanical, chemical or biological methods 2. Special attention is given to cellulose nanofibers as reinforcements in polymers to improve their properties 2, 3, 4, 5, 6, 7. cellulose, may be used in a large range of applications, from food to medical devices 1, 2, 3, 4, 5, 6. The most widespread polymer on the earth, i.e. This submerged liquid plasma processing method offers a unique approach for the activation of cellulose for defibrillation and functionalization, aiming towards an improved reinforcing ability of biopolymers. Depending on the plasma treatment applied, poly (3-hydroxybutyrate) composites fabricated with the plasma modified cellulose fibers showed better thermal stability and mechanical properties than pristine PHB. Furthermore, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy have been applied to investigate the surface functionalization of MCC with oxygen or nitrogen moieties. An enhanced defibrillation of MCC has been observed following the application of SLP. ![]() The plasma generated either in an inert (argon) or reactive (argon: oxygen or argon:nitrogen) gas was used in MCC dispersions in water or acetonitrile:water mixtures. In this work we demonstrate the modification of microcrystalline cellulose (MCC) by applying the SLP combined with ultrasonication treatments. Up to now, this technique has been mostly applied to carbonaceous materials, however, SLP shows great potential as a low-cost and environmental-friendly method to modify cellulose. Submerged liquid plasma (SLP) is a new and promising method to modify powder materials. ![]()
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