New Reactor Granule Technology for Highly Filled Nanocomposites: Effective Flame Retardation of Polypropylene/Magnesium Hydroxide Nanocomposites

A novel additive-free reactor granule technology is reported for the fabrication of polyolefin-based nanocomposites, which involves in situ generation of nanoparticles with unprecedented dispersion even at high filler loadings. Polypropylene reactor powder obtained by catalyzed propylene polymerization is first impregnated with magnesium ethoxide (Mg(OEt)(2)) solution. After the solvent drying and pre-hydrolysis, the powder is melt mixed to convert partially hydrolyzed Mg(OEt)(2) into magnesium hydroxide (Mg(OH)(2)). Thus, prepared PP/Mg(OH)(2) composites exhibit uniform dispersion of the in situ formed Mg(OH)(2) nanoparticles even at a high filler loading (e.g., 20wt%) without the use of dispersants, which is unexpected for the combination of hydrophilic filler and hydrophobic matrices. The obtained nanocomposites significantly improve the flame retardancy at a filler loading much lower than those for conventional composites.