Physical corona treatment

Electric discharge (corona, cold plasma) is another method of physical treatment. Corona treatment is one of the most interesting techniques for surface oxidation activation. This process changes the surface energy of the cellulose fibers [28]. In the case of wood surface activation it increases the amount of aldehyde groups [291. 

Some physical techniques can be classified into flame treatments, corona treatments, cold plasma treatments, ultraviolet (UV) treatment, laser treatments, x-ray treatments, electron-beam treatments, ion-beam treatments, and metallization and sputtering, in which corona, plasma, and laser treatments are the most commonly used methods to modify silicone polymers. In the presence of oxygen, high-energy-photon treatment induces the formation of radical sites at surfaces these sites then react with atmospheric oxygen forming oxygenated functions. 

Many pretreatment techniques are used in practice (Table 8.2). The normal physical method used to improve the adhesive strength of the coating to the substrate is to slightly roughen the surface by solvent treatment, abrasion, or blasting. Some plastics (e.g., polyolefins) require special pretreatment methods processes that modify the surface molecular layers of the plastic to increase their polarity have proved suitable (e.g., flaming, immersion in an oxidizing acid, immersion in a benzophenone solution with UV irradiation, corona treatment, plasma treatment). 

In spite of these disadvantages, plasma treatment of polymers is an attractive process to produce the required surface modification. By using different types of gas, various chemical functionalities can be introduced on the surface. In general, more uniform surfaces are produced by plasmas than by flame and corona treatments. The modification is typically confined to the surface without changing the bulk physical and chemical properties of the pol)uner. 

The processing of linen fabrics by CORONA treatment has an effect on some physical and mechanical properties of fabrics, namely in ... 

Atmospheric plasma systems have been developed in response to a number of issues with 3D corona treatment systems that were discussed in Section 5.6.4.1. Even though the same physical phenomenon, electrical breakdown of gases at atmospheric pressure (electrical discharge), is used, the methods of creation and application of this discharge are completely different. 

Lukes, P. Water treatment by pulsed streamer corona discharge. PhD Thesis. Prague Institute of Plasma Physics AS CR 2001. 

Physical methods include plasma treatments, UV irradiation, corona discharge, and flame treatment. Among these, plasma treatment is widely used for the surface modification of synthetic polymers. Plasma can be obtained by exciting gases into an energetic state by radio frequency, microwave, or electrons from a hot filament discharge. Generation of plasma requires a vacuum, which normally poses several... 

It has been pointed out that surface treatment of fibers significantly improves the physical strength of the composite (14). The reinforcing fibers should be surface-treated before use. Examples of the treatment include chemical treatment, such as silane compounds and titanates (20), and (fiysical treatment such as corona and ultraviolet pl na (14). 

Polymer surface modifications are omnipresent in applications where the surface properties of materials with favorable bulk properties are insufficient. By altering the surface characteristics using physical or chemical modification the desired surface properties may be achieved. Such treatments are required e.g. to enhance printability of films, the adhesion of paints, metal or other coatings, biocompatibility, protein resistances/reduced biofouling, etc. The diverse approaches met in practice include, among others, wet chemical and gas phase chemistry, plasma or corona, UV/ozone and flame treatments. In most cases surface chemical modification reactions take place that alter the surface energy in a desired way. For example,... 

A very simple but yet time-consuming treatment to improve amorphous electret materials is physical aging prior to corona charging. For instance, the charge retention ofUltem 1000 films after 24h at 120 °C can be raised from 18% to 95% when the films were physically aged at 200 °C for 4 days. 

Wild, J. Stranathan, J. (1957). Influence of External Treatments on Electret Behavior. The Journal of Chemical Physics, Vol.27, Nq5, pp. 1055-1059 Yovcheva, T. Avramova, L Mekishev, G. Marinova, T. (2007). Corona-charged polypropylene electrets analyzed by XPS. Journal of Electrostatics, Vol.65, pp. 667-671 Zhongfu, X. Yuda, W. Guamao, Y. Ximin S. (1991). Corona Charging at Elevated Temperature and Charge Transport for Mylar PETP Foils. 7th Int Symp. on Electrets... 

Infrared light absorption and reflection of the uncoated and A1 coated surfaces of polymier films were investigated and discussed in this chapter. Two commercial biaxially oriented pol q)ropylene samples coated with A1 by physical vapor deposition technique were examined. The samples called commercial film 1 and commercial film 2 were provided by POLINAS and POLIBAK companies, respectively. They were 16 pm and 19 pm thick and their one surface was coated with A1 after a corona discharge treatment. 

For surface modification applications, thick grafting layers are unnecessary and even undesirable because they may change bulk physical properties of the polymer, such as crystallinity and tensile modulus. A two-step method can be used to minimize the formation of the homopolymer. The polymer is preirradiated in air to produce peroxide groups on the surface. Grafting is subsequently initiated thermally in contact with a monomer. Other methods such as corona discharge, ozone treatment, and plasma treatment have also been used to generate peroxide groups on polymer surfaces. 

Physical methods involve surface fibrillation, electric discharge (corona, cold plasma), etc. Cold plasma is already a very effective method to modify the siuface of natural polymers without changing their bulk properties. This method has been used for increasing adhesion and compatibility between two polymers (lorio et al. 1997 Petash et al. 1995 Tu et al. 1994). Physical treatments change stmctural and surface properties of the fiber and thereby influence the mechanical bonding with the matrix. 

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