Carbon nanofillers reinforced resin-filled polymer foams for high-impact applications

Polymer foams are used for shock absorption in packaging, structural and ballistic applications. Foams have very large surface area owing to the porous morphology, which facilitates effective distribution of impact energy and shock waves. Polyamide6 (PA6) is a thermoplastic polymer with good mechanical properties. Two separate routes used to produce PA6/PU composite foams. In the first one, PA6 syntactic foams with Polyurethane (PU) microspheres (15 to 20 vol%) were produced by simple melt-casting process. In the other method, foaming of PA6 was performed by heating in a closed mould using chemical blowing agent and then filling the porous network by liquid PU resin by vacuum impregnation. Specimen produced by this method had relatively lower impact strength than that of syntactic foams. Syntactic foams exhibited 12% higher impact strength than that of PU filled foams produced using blowing agent. Furthermore, carbon nanotubes (CNTs) can be used as reinforcements in the PU resin to improve the mechanical strength and thermal stability. Uniformly distributed CNTs form a bridged network in the matrix, aiding in better load distribution. The CNT-reinforced PU resin imparts better properties to the foamed composites compared to pure PU filled composites. It was found that synatactic PA6 foams produced by loading CNT reinforced PU microspheres showed around 12% improvement in impact strength compared to that of syntactic PA6 foams loaded with PU microspheres. These foamed composite may have applications in structural components, aerospace equipment, and protective apparel. (author)