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

Abstract

Lightweight plastic foam materials can save resources and energy and reduce environmental pollution. However, these plastic components with large cell sizes present unsatisfactory mechanical properties. Here, we describe a successful strategy to fabricate lightweight and tough polypropylene/nucleating agent (PP/NA) composite foams with high cell density and small cell size by combining designed nanoparticles with intrinsic cavities as nucleating agents and chemical foam injection molding technologies. The influences of nucleating agents with different contents, morphologies, and process parameters on the cell morphology of pure PP and PP/NA foam samples were studied systematically. Owning to the effective increase of the number of nucleation sites by introducing SiO 2 nanoparticles with pits on the surface (NAC), the lightweight and tough PP/NAC composite foam that the addition amount of NAC of 1 wt % (PPC1) was prepared with a high cell density of 1.22 × 10 7 cells/cm 3 and a small cell size of 27.99 μm, which enhanced the tensile strength from 21.47 to 24.31 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 μm and the cell density reaches 3.01 × 10 7 cells/cm 3 , enhancing the tensile strength to 25.36 MPa and causing a 557.52% increase in the tensile toughness. Therefore, this work provided insights into fabrication of lightweight and tough PP/NA composite foams, which have great promise as structure materials for future use in many applications, such as automotive.

The Structure and Properties of Medical Disposable Protective Clothing Materials with Different Packaging and Models under γ Irradiation

“…Curve A irradiated at 30 kGy in air conditions had a T c of 107.86 °C, which was significantly lower than that of unirradiated PP in previous studies, indicating that the molecular weight of PP decreased after irradiation, [30] and the peak shape narrowed because crystallization integrity increased. Curve B under nitrogen packaging had increased Tc, ΔT, Ti, X c , and peak shape widened compared to curve A, indicating that the molecular weight of the protective clothing material was protected to a certain degree after nitrogen packaging, and the crystalline integrity was weakened due to the widened peak shape [31] . It was also found that there was a shoulder peak near 107 °C, indicating a complex crystallization process.…”

“…Curve B under nitrogen packaging had increased Tc, ΔT, Ti, X c , and peak shape widened compared to curve A, indicating that the molecular weight of the protective clothing material was protected to a certain degree after nitrogen packaging, and the crystalline integrity was weakened due to the widened peak shape. [31] It was also found that there was a shoulder peak near 107 °C, indicating a complex crystallization process. Curve C under vacuum packaging had significantly increased Tc, ΔT, Ti, X c , and peak shape widened compared to curves A and B under air and nitrogen conditions, indicating that the molecular weight degradation of the protective clothing material after vacuum packaging was less than that of air and nitrogen conditions, and the crystallization performance was further improved, but the crystalline integrity was further reduced.…”