Corona Treatment

(sometimes referred to as air plasma) is a surface modification technique that uses a low temperature corona discharge plasma to impart changes in the properties of a surface.

The corona plasma is generated by the application of high voltage to sharp electrode tips which forms plasma at the ends of the sharp tips. A linear array of electrodes is often used to create a curtain of corona plasma. Materials such as plastics, cloth, or paper may be passed through the corona plasma curtain in order to change the surface energy of the material. All materials have an inherent surface energy (dyne level). Surface treatment systems are available for virtually any surface format including dimensional objects, sheets and roll goods that are handled in a web format. Corona treatment is a widely used surface treatment method in the plastic film, extrusion, and converting industries.

Corona treatment

Corona discharge

Corona discharge equipment consists of a high-frequency power generator, a high-voltage transformer, a stationary electrode, and a treater ground roll. Standard utility electrical power is converted into higher frequency power which is then supplied to the treater station. The treater station applies this power through ceramic or metal electrodes over an air gap onto the material’s surface.

Two basic corona treater stations are used in extrusion coating applications. Bare Roll and Covered Roll. On a Bare Roll treater station the dielectric encapsulates the electrode. One a Covered Roll station it encapsulates the treater base roll. The treater consists of an electrode and a base roll in both stations. In theory a Covered Roll treater is generally used to treat non-conductive webs, and a Bare Roll treater is used to treat conductive webs. However, manufacturers who treat a variety of substrates on the same production line may choose to use a Bare Roll treater.

Source: http://en.wikipedia.org

El tratamiento corona

Tanto los films como los objetos de plástico poseen superficies impermeables (no porosas) y químicamente inertes cuyas tensiones son bajas, lo que las hace no receptivas para adherirse a los substratos, tintas para imprimir, adhesivos y lazas o recubrimientos.
El tratamiento corona aumenta la energía de la superficie de los films plásticos, foils, papel y polímeros a fin de incrementar la permeabilidad de los mismos para favorecer a la adhesión de las tintas, cubiertas y adhesivos.
El tratamiento da mejores resultados cuando un substrato es tratado en el momento de la extrusión y en la línea de producción antes de su conversión (converting).
El tratamiento corona incrementa la calidad y la productividad ya que, luego de haber realizado dicho tratamiento, se obtendrá no sólo mayor calidad y rapidez en la impresión, sino que también existe una cantidad menor de desperdicios.

El efecto corona