Study of amino-functionalized mesoporous silica nanoparticles (NH2-MSN) and polyamide-6 nanocomposites co-incorporated with NH2-MSN and organo-montmorillonite

Abstract

In this work, spherical mesoporous silica nanospheres (MSNs) functionalized by content-tunable amino groups were synthesized via a facile co-condensation method aided by both ionic and nonionic surfactants. 3-Aminopropyltrimethoxysilane (APTMS) was added to co-condense with tetraethyl orthosilicate in basic aqueous solution at varied concentration, obtaining different surface amino content. The influence of APTMS concentration on the morphology, pore structure and surface amino coverage of synthesized nanoparticles was systematically investigated. A decelerating trend of the “surface amino coverage” growing with increasing “APTMS concentration” was observed, indicating there is a maximum grafting limit for APTMS on the exterior MSN surface. For the first time, MSN containing amino group (NH2-MSN) was utilized as inorganic nanofiller in polyamide-6 (PA6) nanocomposites, prepared by incorporating NH2-MSN and organo-montmorillonite (OMMT) simultaneously in PA6 through melt compounding. Mechanical properties of PA6 nanocomposites were fully investigated at two widely varied strain-rates (quasi-static and high-speed). The PA6/NH2-MSN/OMMT ternary nanocomposite showed simultaneous improvement of tensile stiffness (Young’s modulus and maximum tensile stress) and ductility (elongation at break). PA6-MSN interface analysis indicated that the strong interfacial affinity (covalent binding) may confine the mobility of PA6 molecules along the tension axis and obstruct the growing/propagation of micro-cracks. However, the synergistic effect involving nanofillers of different shape (spherical NH2-MSN and platelet OMMT) was considered to play critical role for the uniquely improved tensile ductility of ternary nanocomposite.