Nanocomposites of layered silica nanoparticles (LSN) obtained by the sol-gel method, and commercial montmorillonite clay Cloisite ® 20A with polypropylene (PP) and Cloisite ® 30B with polyamide-6 (PA6) were prepared by melt blending in order to study their effects on barrier, mechanical properties, and thermal stability. Transmission electron microscopy (TEM) showed that all of the nanocomposites present agglomerated nanoparticles with some degree of individual particles. In barrier properties, LSN dramatically increased the oxygen and water vapor permeability of PP at low loadings (<5 wt %) due to the percolation effect. However, in PP and PA6 nanocomposites with clays, the permeability showed increases and decreases depending on the solubility of the permeating gases with the clays and the polymers. Tensile stress-strain tests otherwise showed that the nanocomposites with clays present an enhancement in the elastic modulus. Meanwhile, with the LSN, a decrease was found due to the formation of agglomerations and voids. Finally, thermogravimetric analysis under inert conditions showed the nanoparticles do not have a significant effect on the thermal stability of the nanocomposites. These results expose the relevance of the type of layered nanoparticle and polymer matrix on the barrier, mechanical, and thermal behaviors of the resulting nanocomposites.

Spherical silica nanoparticles with 20 and 100 nm diameters and organic‐template layered silica nanoparticles synthesized by the sol‐gel method were melt blended with a polypropylene (PP) matrix in order to study and quantify their effect on the oxygen and water vapor permeability and mechanical and thermal behavior. With regard to barrier properties, the spherical nanoparticles barely increased the oxygen permeability at low loads (≤10 wt%); meanwhile the layered nanoparticles dramatically increased it even at low loading (<5 wt%) probably due to the percolation effect. The changes in water vapor permeability were similar to those in oxygen permeability. The repulsive interaction between nanoparticles and PP forms interconnecting voids where the gas permeates. Tensile stress–strain tests showed that the composites present up to a 56% increase in the elastic modulus with spherical nanoparticles at 20 wt%, while layered nanoparticles show a decrease probably due to agglomerations and voids. Thermogravimetric analysis under inert conditions showed that the nanoparticles improved the PP thermal degradation process through the adsorption of volatile compounds on their surface, where the smaller spherical nanoparticles show the greatest stabilization. © 2015 Society of Chemical Industry

Polypropylene (PP) and polyamide‐6 (PA6) nanocomposites containing thermally reduced graphene oxide (TRGO), obtained either at 600°C (TRGO600) or 800°C (TRGO800), were prepared by melt mixing in order to study the effect of the thermal treatments on their barrier and mechanical properties. Transmission electron microscopy images of nanocomposites showed a relative good dispersion of TRGO in polymer matrices with some agglomerations. Differential scanning calorimetry analyses showed a slight reduction in crystallinity for both polymers in the presence of TRGO. The permeability to oxygen and water vapor was decreased in almost all nanocomposites due to a more tortuous path to gas permeation, being more evident for PP/TRGO800. Tensile stress–strain tests showed that all nanocomposites had higher elastic modulus, but PA6/TRGO600 nanocomposites showed better mechanical properties. These findings indicated that TRGO obtained at a higher temperature imparts better barrier and mechanical properties to PP, while TRGO obtained at a lower temperature imparts better barrier and mechanical properties to PA6. POLYM. COMPOS., 40:E1746–E1756, 2019. © 2018 Society of Plastics Engineers