| The development and commercialization of nano particles such as: nano clays (NCs), carbon nano tubes (CNTs) and Polyhedral Oligomeric Silsesquioxanes (POSS), offer new possibilities to tailor adhesives in the nano scale range. Four types of POSS, with reactive mono-functional group of isocyanate, glycidoxyl, amino and nonreactive octaphenyl were incorporated at concentrations of 1, 3 and 5wt. % into polyurethane (PU) based adhesive. Thermo-mechanical bulk properties were studied using Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). Adhesive properties were using lap shear and peel tests. Atomic Force Microscopy (AFM) was carried out in order to study the nano scale morphology.; According to DMA measurements neat PU exhibits a Tg at ≈ 30°C. By increasing the POSS concentration, PU/POSS-glycidoxypropyl increased Tg gradually up to 50°C for 5 wt. %, PU/POSS-octaphenyl increased by 10°C for 5 wt. %, while POSS concentration had no effect on Tg for PU/POSS-isocyanatopropyl. Incorporating POSS-octaphenyl, POSS-isocyanatopropyl and POSS-glycidoxypropyl into PU improved the shear strength by 230%, 178% and 137% respectively. POSS-aminoethyl exhibited lower shear and peel strength while POSS-isocyanatopropyl provide the best balance of both higher shear and peel strength compared to neat PU. The functional group of POSS, its reactivity and the nature of POSS in the PU network whether it acted as a nanofiller or bulky side chain varied the thermo-mechanical, morphological and adhesive properties. Understanding the structure properties relationships of POSS/polyurethane based-adhesives nanocomposites contribute to tailoring adhesives in the nano scale range for any requirements. |
