Three polyethylene (PE) types with different branching structures were subjected to air, water and ethanol aerosol-assisted dielectric barrier discharges (DBD) for surface modification. Using the air DBD the incorporated oxygen concentration was found to be independent on the branching of PE in contrast to the introduction of OH groups, which was PE-2 > PE-1 > PE-3. For water-aerosol DBD the succession of OH concentration was in the order of PE-1 > PE-2 > PE-3. Ethanol aerosol-assisted DBD produced the lowest concentration of OH groups also independent on the branching of PE. The chemical nature of introduced oxygen functional groups was inspected by X-ray photoelectron spectroscopy (XPS) and assigned as C–O, >C=O/CHO/O–C–O and O=C–O.
A convenient way to overcome the chemical inertness of polyolefin surfaces is to expose them to the atmospheric air plasma of a dielectric barrier discharge (DBD). To improve the efficiency in formation of polar groups at the polyolefin surface, different liquids such as water and ethanol were sprayed as aerosol into the plasma zone between the powered electrode and the polyolefin surface. Both sprayed liquids as well as the polyolefin surface were simultaneously activated; thus, the formation of different functional groups at the polyolefin surface was realized. The type of aerosol-sprayed additive, exposure time, power etc. have been found to determine the efficiency with respect to introduction of polar groups.
Different surface treatments of polypropylene (PP) were tested to improve the peel strength of aluminium-PP systems. Plasma exposure followed by chemical grafting of spacers with -SiOH endgroups and thin adhesion promoting layers deposited by aerosol-assisted DBD using aqu. solutions of classic polymers were compared. Both methods were effective, however, –SiOH terminated spacers effected no peeling also after ageing.
Aerosol-based DBD - A simple way to provide polymers with functional groups for adhesion promotion
(2013)
Polypropylene (PP) foils were exposed to the plasma of an atmospheric dielectric barrier discharge (DBD) in presence of different aerosols. Pure liquids such as water, ethanol, and 1/1 mixtures ethanol/water (v/v) or aqueous Solutions of acetic acid, poly(acrylic acid), poly(vinyl alcohol), and ethylene glycolpoly(vinyl alcohol) copolymer were introduced into the DBD. Surface composition, the number of functional groups per 100 C atoms, and water contact angles were correlated with the energy density of DBD plasma exposure.
The wettability of the treated surfaces was investigated for different storage times. Peel strength of the thermally deposited aluminum layer to modified polymer surfaces revealed that the aerosol introduction strongly improves the adhesion between aluminum and polypropylene.