Replacement of Wet Primers by Atmospheric Plasma Treatment for Increased Surface Energy and Adhesion

Replacement of Wet Primers by Atmospheric Plasma Treatment for Increased Surface Energy and Adhesion

Nicolas Vandencasteele
Coating Plasma Innovation

Most polymers have a low surface energy and therefore require the use of a primer to improve wettability and allow further coating or gluing. Classically, wet primers are used. Those require a drying step that can limit treatment speed or dramatically increases the size of the coating line. Wet primers, especially solvent based ones, are posing environmental impact issues and sometimes are targeted by new legislations. Atmospheric plasma treatment allows to selectively modify the surface composition of almost every polymer by grafting functionals species that can mimic the reactive groups found in wet primers. Contrary to wet primer, plasma treatment is only taking place in gas phase and does not use any solvent. This allow to have extremely compact installation; a typical plasma treatment unit is around 1m wide (machine direction) and high treatment speed of 100s of meters per minute. Plasma uses mainly nitrogen gas (non-toxic, non-flammable, readily available), the chemistry of the plasma is controlled by adding ppm level of reactive gases (dopants). Multi electrodes system allows complexes treatments in a single pass by using a different dopant in each electrode. The treatment has no visual or mechanical impact on the treated materials and is especially suited to high performances polymers (fluorinated, PEEK…). We’ll present results of wettability and adhesion improvement on such high performances polymers comparing different plasma chemistries and a range of adhesives.