Plasma treatment is a reliable technology for activating plastic surfaces. Modifications of the surface are evaluated trough measurements of the surface tension, based on which the adhesion adhesion potential can be derived.
Sufficient adhesion is a requisite for manufacturing hybrid structures. In a new approach hybrid structures, consisting out of a semi-porous polypropylene-based particle foam core and a polyurethane surface layer. The adhesion between these two materials is insufficient the surface of the particle foam has to be improved by plasma treatment. Since both the treatment with plasma and the evaluation by means of contact angle measurement reach their limits, the particle foam surfaces require adapted plasma treatment parameters in order not to impair the physical integrity and optical appearance of the surface.
The standard DIN EN 828, for the measurement of wettability by determining the contact angle, requires flat surfaces which only occur to a limited extent in particle foams. Guidelines on how experience with plasma treatment and contact angle measurement of closed and homogeneous plastic surfaces that can be transferred to semi-porous surfaces of particle foams are currently not known.
In this work, a novel approach for an adapted plasma treatment that was determined for thin-walled semi-porous particle foam surfaces is presented. By investigating closed and semi-porous plastic surfaces of the same material type, correlations and influencing factors were determined.
The degree of surface tension modification by plasma was quantified by means of contact angle measurements. For this purpose, guidelines in correlation to DIN EN 828 in appliance for semi-porous surfaces were worked out. In the final step, the relationship between surface activation, contact angle measurement and adhesion was demonstrated using the floating roller method.