Mechanical characterization and separation tests of a thermoplastic reinforced adhesive used for automotive applications

In the last decades, the use of structural and no structural adhesive has been increasing a lot in the automotive sector due to the advantages they can offer compared to traditional fasteners. Although they present many advantages, the impossibility to dismantle easily adhesive joints in order to substitute, recycle, reuse vehicle components or avoid waste for bonding errors is a factor that can limit their use. Furthermore, in Europe, the need to separate vehicle components for reuse and recycling is constrained by two Directives, 2000/53/EC and 2000/64/EC. These Directives set the objectives of reuse and recyclability for automotive vehicles, which are 95% and 85% respectively by an average weight per vehicle. For these reasons, it is very important to find a feasible solution to these problems. A promising technology for the separation of plastic joints, bonded with thermoplastic adhesives, uses nanomodified thermoplastic adhesives that are sensitive to electromagnetic fields. In this work, the mechanical behavior of adhesive joints made with a polyolefin adhesive, used in the automotive industry for bonding plastic components, have been studied. In particular, the adhesive has been modified with three different weight concentrations (3%, 5% and 10%) of iron oxide nanoparticles in order to make it sensitive to electromagnetic fields. These nanoparticles heat when are under the effect of an electromagnetic field and consequently they can melt the thermoplastic adhesive allowing for the joint separation. The mechanical properties of the joints prepared with the pristine and nanomodified particles have been studied by means of SLJ specimen with different overlap length and thicknesses. The adhesive joints prepared with the modified adhesives present a slightly higher load and a larger ductility compared to the ones prepared with the pristine one. Furthermore, separation tests have been performed in order to assess the times to disassemble these adhesive joints. Scanning electron microscope analysis has been used to assess the dispersion of the particles.