Strength shear test for adhesive joints between dissimilar materials obtained by multicomponent injection

The multicomponent injection molding process enables the combination of different materials in a single step. However, one of the challenges of this new technology is related to the adhesive strength between dissimilar materials. In this work, specimens were overmolded with dissimilar composite materials made of polypropylene and coconut fibers added with coupling agents. By means of a new patented device specially produced to evaluate the adhesive strength of such different materials under pure shear stress, it was possible to measure the force necessary to promote the detachment of dissimilar surfaces. Electron microscopy and contact angle analyses were used to better understand the adhesion phenomenon between such dissimilar materials. Although a maleic anhydride additive promoted better anchoring between fibers and the polymer matrix, it was observed that the composite without coupling agents exhibited the greatest adhesive strength between dissimilar surfaces.