Influence of coupling agents on the adhesion force of dissimilar overmolded polymers: a digital image correlation analysis

Abstract

The increase in the technical and functional requirements of plastic items has led the development of multimaterials. To achieve a good performance in the adhesion of dissimilar materials, in this case, polypropylene and coconut fiber composites, it is fundamental to understand the phenomena related to the specific interface. This work aims to evaluate the adhesion force of different multi-materials, namely between overmolded polymer-coconut composites using the digital image correlation (DIC) technique. First, coconut fiber composites were prepared using three different coupling agents, then they were overmolded with polypropylene. The results show that coupling agents have a positive influence increasing the mechanical properties of such multi-materials under tensile stress. The Lagrange vectors obtained by DIC analysis identified higher stress concentration at the joint edges, where the occurrence of surface cracks led the samples to fail in the region close to the overlap.

Effect of the Process Parameters on the Adhesive Strength of Dissimilar Polymers Obtained by Multicomponent Injection Molding

“…This experimental design was chosen because it could be used to evaluate which injection and overlap parameters have a greater effect on the adhesive strength of dissimilar polymers, that is, the adhesion between PP and the coconut fiber composite (PPFC). More details are presented in [ 20 ], including moment and peeling issues.…”

“…In this work, to evaluate the adhesive strength of dissimilar polymers and composites of coconut fibers, a specific procedure was applied considering a Brazilian patent on a new mechanical device, as described previously by Pisanu et al [ 17 ] (BR 10 20,160 21054). This apparatus measures the adhesive strength between two overmolded materials in an overlapping region and disregards the influence of the forces resulting from the bending moment and/or peeling stress, as described in recent studies performed by Pisanu et al [ 18 , 19 , 20 ]. These experiments evaluated the influence of the injection molding variables over the adhesive forces of overmolded polypropylene (PP) and PP–coir fiber composites, as described in [ 20 ].…”

“…This apparatus measures the adhesive strength between two overmolded materials in an overlapping region and disregards the influence of the forces resulting from the bending moment and/or peeling stress, as described in recent studies performed by Pisanu et al [ 18 , 19 , 20 ]. These experiments evaluated the influence of the injection molding variables over the adhesive forces of overmolded polypropylene (PP) and PP–coir fiber composites, as described in [ 20 ]. It is expected to observe good adhesion because PP polymer chains are the same at interface.…”

Interfacial engineered design of upcycled graphene and hemp fiber reinforced polypropylene compounds as an injection grade for overmoulding process with bio-based prepregs

“…The improvements were calculated according to the results of the OM neat homoPP. After moulding, the homoPP material can be easily removed since it does not adhere to the matrix properly, one of the problematic subjects in the overmoulding composites, according to the literature [48,49]. As shown in Figure S5, the presence of UD bers in fabricated samples did not affect the failure type and also maintained the integrity of the composite during the tests.…”