Fabrication of nanoprotrusion surface structured silica nanofibers for the improvement of the toughening of polypropylene

Abstract

The toughening of semi-crystalline polymers with inorganic nanofiller is very important in the practical applications of such polymers. In this study, we successfully fabricated the surface attaching silica nanoparticles of silica nanofibers (SiO₂@SNFs) from the calcination of electrospun poly(vinyl pyrrolidone)/tetraethyl orthosilicate/silica nanoparticle (PVP/TEOS/SiO₂) nanofibers for the toughening of polypropylene (PP). The SiO₂@SNFs had a nanoprotrusion structured surface, and the degree of surface nanoprotrusion of the silica nanofibers (SNF) can be adjusted via the incorporated SiO₂ nanoparticle content of the SiO₂@SNFs. The effects of the SiO₂ content of the SiO₂@SNFs on the crystallization behavior, relative β-form crystal content, and mechanical properties of PP were investigated with polarized optical microscopy, X-ray diffraction and notched Izod impact test methods. By comparison with SNF, the SiO₂@SNFs showed greater improvements in the impact strength and heterogeneous crystal nucleation of PP at the same loading content of filler. The impact strength of PP/SiO₂@SNFs at a loading of 2 wt% of SiO₂@SNFs with 9 phr (SiO₂/TEOS = 9/100) of SiO₂ nanoparticles was improved by about 1.9 and 1.4 times that of neat PP and PP/SNFs composite (2 wt% of SNFs), respectively. However, the crystallinity, relative β-form crystal content, and tensile strength of PP/SiO₂@SNFs were almost independent of the SiO₂ nanoparticle content of the SiO₂@SNFs. Our results demonstrated that these nanoprotrusion surface structured silica nanofibers can be used as a novel nanofiller for improving the toughening of PP.