Property manipulated polypropylene–iron nanocomposites with maleic anhydride polypropylene

Abstract

Magnetic polypropylene (PP) polymer nanocomposites (PNCs) were fabricated with the reinforcing core–shell Fe–Fe₂O₃ nanoparticles (NPs) synthesized by an in-situ thermal decomposition method. Maleic anhydride functionalized PP (M-PP) with two different molecular weights (M_n = 800, called LM-PP; M_n = 8000, called HM-PP) were found not only serving as surfactant to control the particle size, but also influencing the oxidation degree of the synthesized NPs. With regular PP only, the average nanoparticle size was 15.9 ± 2.2 nm. The NPs decreased to 10.6 ± 1.3 nm and 14.6 ± 2.7 nm in the presence of LM-PP and HM-PP, respectively. A surprisingly enhanced thermal stability by 117.6 °C in air was observed due to both the oxygen trapping effect of the NPs and the polymer–particle interaction. With only 2.4 wt% of M-PP in the PNCs, the complex viscosity was decreased by 86% at the frequency of 0.1 Hz. Enhanced saturated magnetization of the PNCs after introducing LM-PP indicated that the NPs were partially protected by the LM-PP shell and less dominated by the surface oxidation effects. The room temperature Mössbauer spectra analysis confirmed the oxidation degree of the NPs in each PNC and the molecular weight effect of M-PP on the restricted oxidation behavior of the NPs was studied as well. Both LM-PP and HM-PP change the crystalline fraction (X_c) of PP slightly (<1%) in the M-PP–PP blends. While in the PNCs, their contributions to the X_c of PP are significantly different from each other. Specifically, LM-PP increases the X_c of PP by 6.4% and HM-PP reduces the X_c by 10.1%. The electrical conductivity of these PNCs is also comparatively investigated.