Investigating Interfacial Bonds in Multi-Component Molding: Polymer-Polymer and Polymer-Metal Adhesion

Multi-Component Molding (MCM) enables the combination of different materials and components in a single manufacturing process, allowing the creation of complex and functional products. Still, inherent challenges related with distinct physical and mechanical properties of the materials tend to arise, namely the adhesion of the involved materials. The development of strategies to improve polymer-polymer and polymer-metal adhesion is of great importance to ensure the integrity of final parts. In this work, an experimental campaign covering different operational conditions of that moulding process was conducted in order to infer on the adhesion quality of the injected parts. The Influence of a coupling agent, maleic anhydride-modified high-density polyethylene (MAMHDPE), on the adhesion quality between PA6 reinforced with 30% (weight) glass fibers (PA6-GF30) and HDPE has been investigated on overmoulded parts. Furthermore, different thermal (mould pre-heating temperature) and surface conditions (simplified flame treatment and mechanical abrasive sanding) were applied to improve the adhesion between a silver-plated bronze insert and HDPE (insert molding). Adhesion tests on the polymer-polymer show an increase of materials’ adhesion when using the coupling agent. Moreover, scanning electron microscopy (SEM) imaging reveals a lower tendency towards defects occurrence at the polymer-metal interface for higher processing temperature in the insert moulding process.