Functionalized inorganic/organic nanocomposites as new basic raw materials for adhesives and sealants

A high content of nano sized silica and alumina filler was embedded in radiation-curable acrylate formulations by acid catalyzed silylation using trialkoxysilanes. By grafting methacryloxy and vinyl functionalized silanes polymerization-active silico-organic nanoparticles were prepared. In radiation (UV,EB)-induced polymerization reactions these modified nanoparticles form covalent crosslinks to acrylate substrates, thus efficiently modifying their viscoelastic properties. To elucidate the structure of the surface-grafted methacryloxypropyl-, vinyl-, and n-propyl-trimethoxysilane 29Si MAS NMR and MALDI-TOF mass spectrometry were employed. In accordance with NMR findings, MALDI-TOF MS showed highly condensed oligomeric siloxanes comprising more than 20 monomeric silane units. A ladder-like structure of bound polysiloxanes is proposed rather than a simplified picture of tridentate silane bonding. Hence, silane coupling agents do not only modify the chemical nature of the filler surface but also strongly effect the rheological properties of the acrylate nanodispersions.