An assembly strategy of polylactic acid (PLA)-SiO2 nanocomposites embedded in polypropylene (PP) matrix

Abstract

The aim of this work is to evaluate the effect of adding different amounts of SiO 2 nanoparticles (NPs) during the synthesis of polylactic acid (PLA) and polypropylene (PP) blends on the proccesability. The analysis was carried out in terms of the morphological, rheological and mechanical properties as well as their potential applications for packaging. To reach this goal, it was initially realized an optimization of sol–gel parameters to produce of SiO 2 NPs with a particle size <20 nm. Thereafter, different quantities of SiO 2 NPs (1, 2, 3, 5 wt.%) were incorporated into PLA matrix through melt mixing process to achieve pellets and finally, it was realized the polymer blend to produce PP 100-x (PLA-SiO 2 ) x nanocomposites (x = 5, 10 and 20 wt.%, of PLA-SiO 2 pellets). It was found that the addition of SiO 2 into PLA matrix improves the crystallinity percentage, from 10 to 77 %, depending on the SiO 2 quantity; however, it also restricts the movement of PLA chains favoring a viscous behavior. A high dispersion of PLA-SiO 2 systems into PP matrix was obtained in composites containing 1 wt.% of SiO 2 . The presence of inorganic nanostructures modified the dipole–dipole interaction between organic components affecting the microstructure and thermal stability (lower T d ). The observed interaction and high dispersion with low amounts of SiO 2 NPs (1 wt.%), led to improve the interfacial miscibility, which in turn enhanced the mechanical properties in the PP 90 (PLA-SiO 2 ) 10 nanocomposites, compared to PP and PLA. The results indicate that at the end of product shelf-life, this composition can promote a faster degradation in contrast with pure PP and PP-PLA composites.