Fe-Ni alloy/polyamide 6 nanocomposites: effect of nanocrystalline metal particles on the mechanical and physical properties of the polymer

The focus of this study is to explore the potential use of Fe₄₀Ni₆₀/Polyamide 6 (PA6) nanocomposites in engineering applications by providing understanding of how the nanocrystalline (nc) metallic particles are altering physical properties of the polymer and the corresponding reinforcing mechanisms. This is the first study using nc Fe-Ni alloy, which has unique various properties, as a filler for polymers. nc Fe₄₀Ni₆₀ particles were chemically synthesized. The composites with various nanofiller loadings were made by compounding the materials, either by melt mixing (MM) or via solution mixing (SM), and injection molding. The results show that SM composites have remarkable mechanical and thermomechanical properties, but MM ones exhibit deteriorated properties. In addition, morphological and crystalline structure analyses indicate that there is good interfacial interaction between nanofiller and polymer only in SM composites. This is because the ferromagnetism of Fe-Ni alloy could be only overcome by intensive compounding. It is concluded that there are four competing factors determining the overall performance of SM composites: i) degree of agglomeration and particle distribution within PA6 matrix and physical structural changes that occurred in PA6 due to presence of alloy particles including ii) crystallinity; iii) ratio of γ-form to α-form crystals; and iv) Glass transition temperature (Tg) of PA6. Overall, compared to other conventional nanoreinforcements for PA6, nc Fe-Ni alloy shows great promise and can lead to a new class of metal-polymer nanocomposites.