Enhanced strength and synergistic flame retardancy of PE-base nanocomposites with coating-modified palygorskite clay

Abstract

Polyethylene (PE) - base nanocomposites composed of high density polyethylene (HDPE) as matrix and coating-modified palygorskite clay (MAT) as functional filler and fire resistance was prepared by melt blending method. The MAT powder was prepared by solution heterogeneous precipitation method combined with spray drying processes. The microstructure observation shows that the particle size of the obtained MAT powder was concentrated and even. Both mechanical properties and thermal behaviors of the nanocomposites containing MAT were compared to those with commercial ceramic fillers (naming as S type flame retardants) at the same addition mass ratios level. The added MAT mass fractions in the composite were defined as 5 wt%, 10 wt%, 15 wt%, and 20 wt%, respectively. When the addition amount of MAT is 15 wt%, the impact toughness of MAT/HDPE composites approaches 13.41 kJ/m2, which is better than that with commercial fillers. The added fractions of MAT increases to 19.1 wt%, and the elongation at break of nanocomposite reaches 495%, which is much higher than that with S type flame retardants. The differential scanning calorimeter (DSC) test results show that MAT can enhance the melting point range of HDPE and improve the thermal stability of the composite. The LOI (limiting oxygen index) results confirm that MAT can effectively improve the flame retardancy of HDPE composites, and the LOI value increases with the MAT addition. The enhancement of mechanical and thermal properties of the PE-base composite is essentially originated from the uniform dispersion of MAT in polymer matrix and the strong interactions with inorganic – organic interface compatibility.