Chemical modification corona treatment

The surface modification of polymers for improvement of adhesive bonding, and altering surface properties in general without concomitant modification of bulk properties is an active area of research in both industrial and academic laboratories and has been accomplished by a variety of means ranging from Corona discharge treatment, direct chemical modification and by interaction with plasmas excited in inert gases either capacitively or inductively27. ... 

There are many different methods for modifying polymer surfaces to improve their adhesion and wetting properties. They include chemical etching and oxidation, ion bombardment, plasma treatments, flame treatment, mechanical abrasion and corona-discharge treatments (1.2). Especially flame and corona treatments are widely used for the modification of polyolefin surfaces to enhance, for instance, their printabilify. Despite the widespread use of such processes in industry, the understanding of the fundamental processes which occur at the polymer surface is very limited. This is undoubtedly due to the shallow depth to which the polymer is modified, typically 5 nm or less. 

In this paper some applications of static SIMS to a variety of modified polymer surfaces are described. They include plasma treatments in reactive and inert gases, corona treatment in air, as well as thermal and ion beam modifications of polymer-metal interfaces. The examples presented and discussed here primarily serve to illustrate the capabilities of static SIMS for the study of such surfaces and interfaces. More detailed discussions of the actual chemical processes that proceed in several of the systems cited will be published elsewhere. 

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,... 

The modification of polymer surfaces both in terms of structure and functionality is a subject that has been evidenced to be of theoretical and practical interest [ 1,2]. In this sense, a large amount of literature has been published describing a wide variety of surface chemical modification approaches such as flame or corona treatments, chemical reactions (in solution), plasma or UV treatments or the application of polymer coatings among others [3-11],... 

Chemical modification of wood. Corona and plasma treatment. Wood estaification. Wood etherification. Reactions between wood and isocyanates. Reactions of wood with siloxanes. Reactions of wood with furfuryl alcohol. Wood-based composites... 

Several fiber treatments are reported in literature [9], namely (a) physical treatments, such as solvent extraction (b) physico-chemical treatments, like the use of corona and plasma discharges or laser, y-ray and UV bombardment and (c) chemical modifications, both by the direct condensation of the coupling agents onto the cellulose surface and by various grafting strategies calling upon polycondensations and free-radical or ionic polymerizations. 

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. 

Surface Treatment. Most film surfaces require surface treatment for use in subsequent steps of coating, printing, lamination, or metallization. This treatment results in the chemical modification of the polymer at the surface. The most widely employed surface modification is oxidation of the polymer to create a polar smface (43). Processes that are widely employed are corona and flame treatment. Wet chemical oxidative treatments are seldom used and are restricted to low speed operations. A new surface oxidation technique has been recently developed which uses an atmospheric plasma generated in a hollow cathode with helium or helium gas blends (44). 

It can be seen that to achieve a given level of chemical modification, flame, corona and plasma require much shorter treatment times than ozone or UV or a combination of UV plus ozone. 

Surface modification refers to the modification that occurs only on the surface of a polymer material without further internal modification. Surface modifications of polymeric materials include surface chemical oxidation, corona surface treatment, surface flame treatment, surface heat treatment, surface plasma treatment, surface metallization processing, ion implantation, and surface grafting polymerization. Because surface modification occurs only on the surface of materials, the performance does not change uniformly. 

The ability to create an effective heat seal may be limited by surface contamination. During packaging operations, contents in the form of liquids or powders may adulterate the sealing surfaces, preventing interdiffiision of the polymer. Other factors that may detrimentally affect sealing inelude blooming of additives to the surfaee and chemical surface modification such as corona treatment. 

Several environment-friendly surface preparation for the treatment of mbber soles with radiations have been recently studied. These treatments are clean (no chemicals or reactions by-products are produced) and fast, and furthermore online bonding at shoe factory can be produced, so the future trend in surface modification of substrates in shoe industry will be likely directed to the industrial application of those treatments. Corona discharge, low-pressure RF gas plasma, and ultraviolet (UV) treatments have been successfully used at laboratory scale to improve the adhesion of several sole materials in shoe industry. Recently, surface modification of SBR and TR by UV radiation has been industrially demonstrated in shoe industry... 

The modification of the chemical composition of polymer surfaces, and thus their wettability with chemical substances, can be realized in different ways electric discharges more commonly called Corona effect, oxidation by a flame, plasma treatment, UV irradiation and also UV irradiation under ozone atmosphere. Numerous studies have been devoted to the effects of these different treatments. More recently, Strobel et al. [204] compared the effects of these treatments on polypropylene and polyethylene terephthalate using analytical methods such as E.S.C.A., F.T.I.R., and contact angle measurements. They demonstrated that a flame oxidizes polymers only superficially (2-3 nm) whereas treatment realized by plasma effect or Corona effect permits one to work deeply in the polymer (10 nm). The combination of UV irradiation with ozone flux modifies the chemical composition of the polymers to a depth much greater than 10 nm, introducing oxygenated functions into the core of the polymer. 

Surface modification of a polymer prior to metallization is widely used to improve adhesion. The most common surface modifications employed are electric discharge (corona and plasma) and, more recently, ion-beam treatments QJ- Several mechanisms have been proposed for the improved adhesion after such surface modifications (2). These include mechanical interlocking, the elimination of weak boundary layers, electrostatic attractions, and chemical bonding. All of these can play a role in adhesion depending on the surface modification used, metal/polymer system, type of metal deposition, and the extent of polymer preparation employed. However, for low power, short exposure modifications, the formation of new chemical species which can provide nucleation and chemical bonding sites for subsequent overlayers is considered to be of prime importance (3-51. 

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