Reinforcement of PLA With a Novel One-Dimensional Magnesium-Based Hybrid Filler: Achieving Superior Mechanical and Flame Retardant Properties

Abstract

Polylactic acid (PLA) exhibits excellent biocompatibility and degradability but suffers from brittleness, low toughness, and flammability. In this study, a novel one-dimensional magnesium-based inorganic/organic hybrid flame retardant filler was synthesized by grafting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) onto magnesium sulfate (MOS) whiskers modified with vinyltrimethoxysilane (VTMS), which can be melt-blended into PLA to enhance its flame retardancy and mechanical properties. This article uses x-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), thermogravimetric analysis-derivative thermogravimetry (TG-DTG), and mechanical analysis. The flame retardancy of PLA significantly improves with the increase of DOPO-MOS/PLA filler content, and its combustion grade increases from FH-3 to FH-1, while the melt dripping decreases. Carbon layer analysis indicates that the flame retardant effect is attributed to condensation and gas-phase suppression. At a lower addition level, specifically when the amount is 2 parts per hundred resin weight (phr), the optimal impact strength reaches 8.22 kJ/m², and the optimal bending strength reaches 10.91 MPa. Furthermore, the whiskers increased the crystallinity of PLA, reaching a maximum relative crystallinity of 35.23%. This article provides a reference for exploring new organic/inorganic flame retardant additives.