Rheology and adhesive properties of filled PIB-based pressure-sensitive adhesives. II. Probe tack and 90° peel testing

Two nanosized fillers (fumed silica Rosil-175 and halloysite nanotubes) were used to eliminate the problem of the cold flow and to increase the adhesion strength for polyisobutylene-based formulations. Well-dispersed silica, having high specific area, allowed to obtain up to 2 orders of magnitude increase in PIB’s shear resistance at 20 wt% Rosil content. PIB–20 wt% Rosil formulations mostly demonstrated slightly increased tack characteristics – up to 20–50%. Adhesive peel of the PIB-Rosil systems was observed with the peel strength of the systems staying at the level of the pristine PIB matrices or slightly changing (depending on the film thickness and peeling rate). Transition to the mixed failure mode was observed for thin PIB-20 wt% Rosil films tested under increased peeling rate accompanied by up to 300% peel strength increase. Formation of the three-dimensional filler networks in PIB-halloysite formulations allowed notably lower increase in the shear resistance of the systems – only 4–5 times in the case of much higher filler content (40 wt%), which was connected with the low strength of the network. Incorporation of 40 wt% halloysite into the PIB matrix did not lead to notable changes in tack properties, except for the tack of 150-μm films – in this case, 30–60% decrease in the tack characteristics was obtained. Peel strength of PIB-halloysite systems stays at the level of the pristine PIB matrices or increases up to 300% when the failure mode shifts from adhesive for the thin films to cohesive for the thick films.