Bonding corona discharge 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. ... 

While not changing the chemical composition of the fiber extensively, physical treatments cause variations in structural and surface properties of the fiber and consequently affect the mechanical bonding to the polymer matrix. Thermal treatment, corona and plasma treatments can be given as examples to physical treatments applied on plant fibers [3]. Ragoubi et al. [33] reported an increase in mechanical and thermal properties of reed fiber-reinforced PLA and PP composites upon corona discharge treatment of fibers. 

Adhesives manufacturers are continually trying to develop adhesives to meet the needs of industry. One group of plastics that have been difficult to bond are polyolefins and related low-energy substrates (see Surface energy). They could not be bonded without elaborate surface preparation such as Flame treatment or Plasma pre-treatment, Corona discharge treatment or oxidative chemical methods. 

Another process that promotes chemical adhesion is the pre-treatment of low energy surface materials. This can be considered as a dry priming process, as no wet chemicals are used. Corona discharge treatment, dielectric barrier discharge, flame and Plasma treatment are widely used techniques in Pre-treatments of polyolefins. This reactive surface allows chemical bonding with the applied adhesive. 

Plasma treatments. Yet to become a mainstream treatment for rubber to plastics bonding. Corona discharge. 

Plasma Arc Treatment - In adhesive and solvent bonding, a method for treating the surfaces of parts prior to solvent and adhesive bonding, in which an electrical current between two electrodes in a gas at low pressure exeites the gas particles, producing free radicals. Contaminants are stripped from the surface of the part, and wettability is increased by reduction of the contact angle. Also ealled plasma discharge, plasma treatment. See also Corona Discharge Treatment... 

Labels used for blow molding are typically constructed of paper or polymer film and require a heat-activated adhesive for adhesion purposes. The adhesive can be applied either during co-extrusion when the film is being produced, or at final conversion of the label. During the latter, the adhesive is applied to the reverse side of the label facestock and activated by heat while the label is in the mold. The use of corona discharge treatment on polymer film labels is advised and usually sufficient at a minimum level of 38-40 dynes/cm. Bonding takes place when the adhesive is activated by heat and expansion within the mold. 

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... 

Atmospheric corona discharge has been used to increase the surface energy of wood surfaces by oxidative activation (Back and Danielsson, 1987). Improved bonding of a water-based acrylate lacquer was found following corona treatment of the wood surface, with no improvement found when a solvent-based alkyd system was used. 

Parts molded from polyetherimide can be assembled with all common thermoplastic assembly methods. Adhesives that are recommended include epoxy, urethane, and cyanoacrylate. However, service temperature must be taken into consideration in choosing an adhesive because PEI parts are generally used for high-temperature applications. Good adhesion can be effected by simple solvent wipe, but surface treatment by corona discharge, flame treatment, or chromic acid etch will provide the highest bond strengths. 

Several reports on the activation of lignocellulosic surface by corona discharge, microwave plasma, and ozone treatments have been published (120-22). Strong bonds were produced between thermoplastics and wood by corona treatment of wood surfaces and particularly by treatment of polyethylene and polystyrene surfaces. With 5-min treatment wood—polymer—wood bonds of over 569 psi... 

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