Lightweight and Tough Polypropylene/Silica Nanoparticle Composite Foam Nucleated from Nanoparticles with Intrinsic Cavities for Plastic Structural Components

Lightweight plastic foam materialscan save resourcesand energyand reduce environmental pollution. However, these plastic componentswith large cell sizes present unsatisfactory mechanical properties.Here, we describe a successful strategy to fabricate lightweight andtough polypropylene/nucleating agent (PP/NA) composite foams withhigh cell density and small cell size by combining designed nanoparticleswith intrinsic cavities as nucleating agents and chemical foam injectionmolding technologies. The influences of nucleating agents with differentcontents, morphologies, and process parameters on the cell morphologyof pure PP and PP/NA foam samples were studied systematically. Owningto the effective increase of the number of nucleation sites by introducingSiO(2) nanoparticles with pits on the surface (NAC), thelightweight and tough PP/NAC composite foam that the addition amountof NAC of 1 wt % (PPC1) was prepared with a high cell density of 1.22x 10(7) cells/cm(3) and a small cell size of27.99 & mu;m, which enhanced the tensile strength from 21.47 to24.31 MPa and caused a 356.06% increase in tensile toughness. Furthermore,the effects of packing time on the foaming behavior of PPC1 were studied.When packing time is 5 s, the average cell size is 17.01 & mu;mand the cell density reaches 3.01 x 10(7) cells/cm(3), enhancing the tensile strength to 25.36 MPa and causinga 557.52% increase in the tensile toughness. Therefore, this workprovided insights into fabrication of lightweight and tough PP/NAcomposite foams, which have great promise as structure materials forfuture use in many applications, such as automotive.