Journal of Adhesion Science and Technology, Vol.17, No.15, 2023-2045, 2003
Liquid crystalline adhesives for polypropylene joints
This study was devoted to the investigation of the adhesion of epoxy resins to polypropylene adherends. In particular, the study was carried out as follows: synthesis of both a liquid crystalline (LC) and a bisphenol-A-based resin, their characterization and their further evaluation as adhesives for polypropylene adherends. This was done in order to evaluate the difference between an LC epoxy resin and an isotropic one in adhesive applications. The adherends chosen were neat polypropylene (PP) and polypropylene reinforced with 20 and 40 wt% talc (PP20 and PP40, respectively). The effect of two different pre-treatments (simple degreasing and acid etching) on the polypropylene adherends was also evaluated. It was shown that the adhesion strength of the liquid crystalline adhesive was higher compared to that of the isotropic one. The higher adhesion was related to the extra ductility demonstrated by the LC epoxy resin, which was due to its particular microstructure. Moreover, the acid etching pre-treatment performed on polypropylene adherends prior to bonding improved the adhesion at the interface with the resin. The increased stiffness of the adherends due to the presence of talc turned out to be beneficial to obtain more resistant joints.
Keywords:structural adhesives;liquid crystalline thermosets;epoxy resins;plastic/plastic adhesion;fracture resistance