Melt-blown polypropylene with long chain branching characteristics was prepared by γ-radiation and melt blending

Under the global impact of the COVID-19 pandemic, the demand for melt-blown polypropylene (PP), a crucial material in the manufacture of protective equipment, has seen a significant surge. During the melt-blowing process, PP melts exhibit a sharp decline in viscosity and exhibit poor thermal aging properties. In this study, melt-blown PP composites were prepared through radiation and melt blending techniques. By adjusting the proportions of the constituents, an investigation was conducted into the melt flow rate, FTIR spectra, rheological behavior, crystallization characteristics, surface morphology, surface charge, dielectric properties, and aging properties of these composites. The melt flow rate analysis revealed that the irradiated composites meet the melt-blowing standard of 1500 cm³/10 min. Infrared analysis shows that the chemical crosslinking network is formed by oxidative degradation-grafting reaction in melt-blown PP modification. Rheological studies demonstrated that flake graphite - lignin (GNP-LS) interactions promote heterogeneous network formation in composites. Four models-phase angle versus complex modulus, complex viscosity versus complex modulus, Han's plot, and Cole-Cole plot-provided evidence that the melt structure of PP undergoes a 'liquid-to-solid' transition. Differential scanning calorimetry (DSC) results indicated that flake graphite exhibits heterogeneous nucleation effects. Scanning electron microscopy (SEM) and transmission electron microscope(TEM) analysis showed that the interaction between flake graphite and lignin enhances the compatibility of the blend system. Zeta potential and dielectric properties tests show that the electrochemical environmental adaptability of melt-blown PP can be controlled by the gradient addition of lignin and flake graphite. Additionally, a large number of hindered phenol structures in GNP and LS enhance aging resistance. Thermogravimetric analysis (TG) indicated that GNP increased PP's heat resistance. Oxidation induction analysis further demonstrated that the oxidation induction time can reach 99.29 min upon the addition of flake graphite.