Injection overmolding of polymer‐metal hybrid structures: A review

Abstract

Polymer‐metal hybrid (PMH) structures, also known as metal‐polymer hybrid (MPH) structures, have received considerable attention from industry and academia due to the societal need for developing strong, lightweight, and durable structures for several applications in strategic areas, such as transportation, household appliances, energy, and biomedical devices. Injection overmolding is an advantageous technique for manufacturing PMH structures as it combines automation, a fast process, cost efficiency, and dimensional accuracy. This review presents a comprehensive discussion of recent advances reported in the literature concerning PMH structures fabricated by direct‐adhesion injection overmolding. Following a general introduction, the fundamentals of the injection overmolding technique are presented. Next, the potential of some metal surface preparation methods to ensure good adhesion, and thus outstanding mechanical performance in injection overmolded PMH structures is discussed. Correlations are then made between metal surface features, processing parameters, and the mechanical strength of injection overmolded polymer‐metal joints. Some applications of injection overmolded PMH structures are explored, and, lastly, the main conclusions and prospects on the use of injection overmolding are presented.

Development of polyamide 6‐graphene oxide nanocomposite and direct‐joining with aluminum alloy for lightweight engineering applications

“…The injection molding parameters were set as follows: barrel temperature of 240 C, mold temperature of 80 C, flow rate of 40 cm 3 s À1 , holding pressure of 600 bar for 15 s, and cooling time of 45 s. These conditions were programmed to ensure low viscosity of the molten polymer and compensate for the thermal shrinkage, which has proven to be crucial for polymer filling in laser-formed grooves in metal surfaces, thus providing good mechanical anchorage in injection ovemolded hybrid joints. 17 The cross sections of the joints were examined by optical microscopy using an Olympus LEXT OLS4100 instrument. Joints were cut, embedded in epoxy resin and polished before analysis.…”

“…In the direct-adhesion injection overmolding method, the metal substrate undergoes physical and/or chemical surface treatments that result in a larger interfacial area, leading to improved stress distribution and enhanced mechanical performance. [17][18][19] The direct-adhesion injection overmolding technique has been employed for joining polyamide and glassfiber-reinforced polyamide composites with surfacetextured lightweight aluminum-based alloys. [20][21][22][23] These studies identified mechanical interlocking as the main adhesion mechanism of these joints and demonstrated a clear correlation between the joining strength and the degree to which the polymer fills in the features of the metal surface.…”

“…In parallel, hybrid polyamide‐metal structures have aroused great interest for the replacement of metal parts, particularly in the transport industry, which is keen to reduce the weight of vehicles for fuel and energy consumption savings, thereby contributing to sustainability. The injection overmolding technique offers great advantages in polymer‐metal assembly, as it allows the molding of the polymer component and joining with the metal part in a single step, through a fast, precise, efficient, and automated process 17–19 . The joining of the polymer to the metal part is typically accomplished with form‐fit elements, resulting in an uneven stress distribution that may potentially compromise the mechanical performance of hybrid structures.…”

“…The joining of the polymer to the metal part is typically accomplished with form‐fit elements, resulting in an uneven stress distribution that may potentially compromise the mechanical performance of hybrid structures. In the direct‐adhesion injection overmolding method, the metal substrate undergoes physical and/or chemical surface treatments that result in a larger interfacial area, leading to improved stress distribution and enhanced mechanical performance 17–19 . The direct‐adhesion injection overmolding technique has been employed for joining polyamide and glass‐fiber‐reinforced polyamide composites with surface‐textured lightweight aluminum‐based alloys 20–23 .…”

Investigation on using graphite filler for 3D printing of flexible electrically conductive polymer by extrusion‐based additive manufacturing

“…The most frequent materials added to enhance the electrical conductivity of polymers are graphene and carbon nanotubes 10 . Other fillers like graphite powder, 11 ZnO, 12 and metal powder 13 fillers can be employed to increase electrical and thermal conductivity of the polymer composite.…”