Formation of boehmite crystals on microblasted aluminum surface to enhance performance of metal–polymer direct joining

Abstract

Abrasive blasting can be used for the surface treatment of injection molded direct joining (IMDJ), which is a process to join a surface treated metal and an injection molded polymer directly. IMDJ using abrasive blasting has a lot of excellent features but has not been extensively applied because its performance, such as joining strength, is not high enough. This study presents a secondary surface treatment to enhance joining strength of IMDJ specimens. The secondary treatment, which is a boehmite process using only pure water without any chemicals, produces nano-needles of boehmite crystals on aluminum that are expected to enhance mechanical interlocking and the resultant joining strength. In this study, the joining specimens have been evaluated by a cross-sectional analysis and a tensile shear test to confirm the elemental composition of the metal–polymer interface and the strength, respectively. The results clearly show that the secondary treatment enhances joining strength, which improves the prospects for further applications of IMDJ technology in future.