Plasma treatment natural fiber

Synthetic fibers do not contain natural impurities although there are added impurities such as sizing materials and oil stains. Therefore, their pretreatment process is simpler than other natural fibers. However, synthetic fibers such as polyester and acrylic have poor wettability, dyeability, and antistatic behavior. After plasma treatment, the fiber surface gets physically altered, and hydrophilic functional groups are introduced to the fiber surface, which improves the wettability of the fiber significantly. In recent years, many researchers have studied ways to modify polyester textile materials, and good results have been obtained (Morent et al., 2008). 

There are many reasons for surface treatment of the fibers. In one process,introduction of functional groups is described. The equipment designed for this process includes a cleaning vessel, a vacuum drier, and a plasma treatment vessel. The fiber is first treated with a solvent, which is subsequently removed in the vacuum drier to remove all residual solvent. The surface is then modified by a plasma treatment. Cleaning removes dirt from the natural fibers and impurities from man-made fibers. Water, hydrocarbons, and halogenated hydrocarbons are used in an enclosed system. Surface etching and cleaning techniques which were used in the past released solvents and other materials to environment, especially because the fibers were not sufficiently dried. 

Thomas S (2002) Cellulose fiber reinforced composites new challenges and opportunities. 4th International Wood and Natural Fibre Composites Symposium, Kassel Germany, April 10-11 Tu X, Young RA, Denes F (1994) Improvement of bonding between cellulose and polypropylene by plasma treatment. Cellulose 1 87-106 Urbanczyk G (1985) Nauka o Wloknie. WNT, Warszawa... 

The aforementioned studies show that plasma treatment can be a potential physical surface modification method to improve the mechanical properties of the natural fiber reinforced composites (NFRCs). However, supplementary research in this area is required to implement more energy-efficient and consistent treatment technologies. 

Essentially, physical methods are employed on natural fiber during processing in order to separate natural fiber bundles into individual filaments and also to modify the surface structure of the fibers so as to improve the use of natural fibers in composites. Physical methods can be divided into two categories viz (1) steam explosion and thermomechanical processes and (2) plasma, dielectric barrier techniques, radiation modification, ultrasonic treatment, and corona discharge. In an effort to impart and improve reactivity, these physical treatments have been used to modify thermoplastic polymeric films like polyethylene and polypropylene and thermosets, such as epoxy. 

Physical methods for treating natural fibers before biocomposite processing involve electrical discharges such as cold plasma and corona, electron beam irradiation, ultraviolet (UV) treatment, and ultrasonic treatment,. Such physical approaches are of great interest because, in general, the processes are dry, clean, labor-friendly, environment-friendly, and fast in comparison with most of the chemical methods, which are wet processes. Under appropriate treatment conditions, they can effectively modify structural and surface characteristics of natural fibers, thereby improving the mechanical and thermal properties of biocomposites as well as enhancing the interfacial adhesion between the natural fibers and the polymer matrix. 

There are a number of papers reporting the surface treatment of cellulose-based natural fibers and the property improvement of biocomposites through the surface modification of natural fibers by means of plasma treatment [96-99]. 

However, an important problem in using natural fiber as reinforcement in plastic is the poor adhesion between natural fibers and polymer matrix. In order to optimize this fiber/matrix interface and to promote adhesion, various chemical treatments can be applied on surface fibers [19-25]. Physical treatment includes heat, plasma, corona and surface fibrillation [26]. 

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