Plasma functionalization of polypropylene with acrylic acid

Tailor-made surfaces of polymer materials are required, e.g. for the improvement of their printability or adhesion and for many applications concerning medical equipment or life science products. Polypropylene (PP) is one of the few common polymers widely used in technical applications. But often the surface chemistry has to be modified by introducing special chemical functionalities like carboxylic groups or by coating the PP with thin films, e.g. with poly(acrylic acid). The radio frequency plasma technique was used for functionalization and coating of PP by using acrylic acid as monomer gas. After optimization of the plasma parameters, high concentration of carboxylic groups as well as solvent-stable thin films with good adhesion to the PP substrates could be obtained. Characterization of the plasma-modified PP substrates was performed by using the captive bubble method, ESCA (Electron Spectroscopy for Chemical Analysis) and fluorescence spectroscopy in combination with derivatization techniques and FTIR (Fourier Transformation Infrared Spectroscopy). The thickness of the polymer films was analyzed by AFM (Atomic Force Microscopy).