Synthesis and properties of solid structural adhesives modified in-situ using 1D and 2D-type microfillers

Synthesis and properties of UV-crosslinkable structural adhesives tapes (SATs) based on butyl acrylate, glycidyl methacrylate, 2-hydroxypropyl acrylate and 4-acryloyloxy benzophenone copolymer as well as epoxy resin modified with glass flakes (representing the 1D-type fillers) and a needle-shaped wollastonites (as a 2D-type fillers), were described. An influence of fillers introduction into SAT during poly(meth)acrylate binder preparation, on self-adhesive features, curing behavior (using DSC and FTIR analysis) and overlap shear strength of aluminum/SAT/aluminum joint system has been investigated. Although cohesion values of UV-crosslinked SAT have not varied in case of filler incorporation into tape composition, improved tack as well as higher adhesion to steel for SATs composition containing silane-treated wollastonite have been noted. Structural adhesives tapes with either 1D or 2D-type fillers exhibited lower enthalpy of curing process (in comparison with unfilled sample) while SATs containing glass flakes reached higher temperature of exothermic peak as well. Additionally, epoxy groups conversion of UV-precured PSAs (analyzed during thermal curing at 140 °C) was significantly lower for samples containing both types of tested microfillers than for sample of reference tape. In case of short-time thermal curing process (i.e. 15 min at 140 °C), the highest overlap shear strength for unfilled structural adhesives tape was noted while SAT modified with silane-untreated wollastonite exhibited better mechanical properties than other samples cured 30 min at 140 °C.