Electroless Plating of PLA and PETG for 3D Printed Flexible Substrates

The FDM (fused deposition modelling) 3D printing technology has acquired increasing commercial importance in the last few years. Large scale manufactured devices are nowadays available at low cost and are able to reach performances similar to industrial prototyping machines. Considering this recent new technological evolution, the surface finishing researcher is invited to develop and optimize treatments suitable for tridimensional complex objects made with different polymeric materials. One of the most used polymers for FDM printing is PLA (polylactic acid) due to its dimensional stabily after cooling, a condition needed to avoid deformations during the printing process. PLA presents other desirable properties like biodegradability and good mechanical properties, as well as remarkable disadvantages like poor resistance to aggressive environments and low glass transition temperature. Recently PLA is being replaced in many 3D printing processes by PETG (polyethylene terephthalate glycol-modified), a polymer able to compensate the drawbacks of PLA (with the only main disadvantage of being not biodegradable). An important surface treatment that the objects printed with these two polymers may require is metallization, a process able to make conductive the surface and to give new functional and aesthetic properties to the polymer. Metallization of non-conductive materials can be achieved using techniques like PVD, but one of the most economical is electroless plating.

Starting from this consideration, the present work aims at testing the possibility of electroless NiP and Cu plating on PLA and PETG. The resulting films can be used as deposited or as adhesion layers for the deposition of other metals like decorative chromium. A convenient preparation of the surface must be performed in order to achieve good uniformity and cohesion with the polymeric substrate. Two etching processes, alkaline and acidic, are used to increase the roughness of the surface and permit a good adhesion of the electroless plated metals. The characterization of the pretreatment is therefore presented together with the activation process and the description of the properties of the coatings obtained. To conclude the work and to provide a future perspective the deposition on 3D printed prototypes is performed.