Hybrid nanocomposites with ultra-low filling content by nano-coating fragmentation

In the current study, a new technique for the manufacturing of polymer nanocomposites (PNCs) with ultra-low filling content (<0.05 wt%) is presented. Specifically, this method has been validated through the production of polypropylene (PP) nanocomposites with Ag nanoparticles. The presented method first consisted in a metal nano-film deposition on PP pellet substrates by a physical vapor deposition (PVD) sputtering equipment. Subsequently, a percentage of the coated pellet was mixed to uncoated ones via an injection molding machine to produce the PNC in a single step. Different mixing percentages of coated PP pellet to the uncoated ones were studied. As a result, the fragmentation of the nano-coating of the particles occurs during mixing, due to the action of the shear forces, thus the nanoparticles are directly produced within the polymer matrix. The fabricated PNCs were evaluated with thermal, thermomechanical, and mechanical tests in order to assess property changes compared to neat PP. The preliminary visual analysis already highlights the presence of the Ag nano-filler through a chromatic change. The surface properties also undergo slight variations due to the presence of the filler, which was also confirmed by DSC and DMA analysis of the molded samples. Moreover, microscopic observations of nanocomposites showed the presence of distributed silver nanoparticles and thermographic analyses demonstrated a significant increase in the thermal diffusivity of the 0.05 wt% nanofilled sample compared to the unfilled one.