Marian Valentin

Photo-actuating materials based on elastomers and modified carbon nanotubes

Abstract. The photo-actuating behavior of new polymeric nanocomposite materials based on a commercial elastomer, an ethylene-vinylacetate copolymer (EVA), filled with multiwalled carbon nanotubes (MWCNT) was investigated. A good dispersion of the MWCNT within the elastomeric matrix was ensured by using a novel, specific compatibilizer consisting of pyrenyl and cholesteryl groups. A uniaxial orientation of the MWCNT within the matrix was induced with shear forces by employing a special custom-made punch/die system. Good dispergation and alignment of the MWCNT within the matrix were demonstrated by scanning electron microscopy. Transmission electron microscopy showed a good dispersion of the MWCNT within the composite. Photo-actuation was qualitatively characterized by atomic force microscopy and quantitatively characterized by nanoindentation. The samples prepared in the form of Braille element showed expansion upon illumination by light diodes. The maximal height deformation changes about 15% was detected when a blue diode was used.

Surface Behavior of Polyamide 6 Modified by Barrier Plasma in Oxygen and Nitrogen

Polyamide (PA) 6 was modified by diffuse coplanar surface barrier discharge (DCSBD) plasma in an atmosphere of nitrogen and oxygen. The surface roughness decrease of PA 6 was detected by AFM and nano-indentation after modification in DCSBD plasma. A significant increase in O/C and N/C ratios of plasma-modified PA 6 using XPS analysis was found. The results show the importance of introducing oxygenic polar functional groups on the polymeric surface in order to increase its surface energy during a short time of plasma activation. The modification of PA 6 by DCSBD oxygen plasma was more efficient than by nitrogen plasma.

Superhydrophobic Polyester/Cotton Fabrics Modified by Barrier Discharge Plasma and Organosilanes

ABSTRACT In this paper, diffuse coplanar surface barrier discharge plasma at atmospheric pressure has been used for surface modification of polyester/cotton (PESc) fabric, which was subsequently modified by sol–gel process using suitable organofunctional silanes to enhance its hydrophobicity. Modified PESc fabric surfaces were conditioned during the gelling process to obtain the permanent hydrophobicity. The contact angle of water before washing of plasma and sol–gel pretreated PESc fabric was found to be 154° and 151° after standardized washings. It was also demonstrated that the process is applicable at the industrial scale. GRAPHICAL ABSTRACT