Self-Activating Sprayable Resins for Sustainable Plating on Plastics

Plating on plastics (PoP) is a crucial process in current industrial practice. Indeed, PoP combines the advantages of polymers (low weight, reduced cost and flexibility) with those typical of metals (aesthetic appearance, wear resistance, high electrical or thermal conductivity and ferromagnetic behavior). For these reasons, PoP finds widespread use across numerous sectors, including the automotive industry, electronics, household goods manufacturing and fashion.

State-of-the-art PoP processes applied to ABS (the most commonly employed polymer), or to other plastic substrates, typically rely on materials that are either hazardous or limited in availability. In particular, the surface etching step necessary to improve metal–polymer adhesion typically involves highly toxic hexavalent chromium compounds. Furthermore, the activation step conventionally requires palladium, a scarce element classified by the European Union as a critical raw material.

Within the framework of the safe-and-sustainable-by-design (SSbD) strategy, the European FreeMe project seeks to remove both Cr(VI) and Pd from the PoP process, ensuring compliance with REACH regulations. In this context, the present study reports on the development of sprayable resin formulations containing appropriate metallic precursors. Owing to the incorporation of these precursors, the materials exhibit self-activating behavior, thereby eliminating the need for conventional etching and activation steps. The embedded precursor is subsequently reduced to its metallic form through immersion in a reducing solution, generating metallic nuclei that initiate the electroless deposition of NiP.

In addition to NiP, copper coatings can also be deposited via electroless plating using a similar approach, as demonstrated by selecting an appropriate metal precursor within the resin and a suitable plating bath. The resulting NiP and Cu layers are thoroughly characterized to assess their uniformity, morphology, phase composition, and adhesion. The resins described in the present study can be directly spray-coated onto ABS substrates, resulting in easy potential industrial implementation.