Effect of morphology on the permeability, mechanical and thermal properties of polypropylene/SiO₂ nanocomposites

Abstract

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

Effect of thermally reduced graphene oxides obtained at different temperatures on the barrier and mechanical properties of polypropylene/TRGO and polyamide‐6/TRGO nanocomposites

“…Then, the property was again reduced with respect to neat PP for 10 wt% of filler. According to the literature, although impenetrable nanosheets such as graphene can lead to an increase of the tortuosity, there are other factors that strongly affect the barrier properties of nanocomposites, such as the aspect ratio, dispersion and orientation of the nanofillers, the polymer/filler interface as well as the crystallinity of the polymer matrix [2,3,5,11,14,[35][36][37]. The higher oxygen permeation found in the PP/TRGO 600 nanocomposites can be explained by the presence of polar groups in TRGO 600 , as already discussed.…”

“…The higher oxygen permeation found in the PP/TRGO 600 nanocomposites can be explained by the presence of polar groups in TRGO 600 , as already discussed. The lower interaction among this filler and the non-polar PP did not contribute to a good dispersion of the filler in the matrix, forming agglomerates and allowing more free movement of the oxygen molecules through the polymer-filler interface [2,3,6,11,14]. It has been stated that permeability should decrease as crystallinity increases [6,35,36].…”

“…5b) showed a less pronounced decrease with higher loads of TRGO. This is probably due to high filler loads can result in agglomeration and this may also have a deleterious outcome on the barrier property, giving rise to new pathways for gas diffusion [2,3,[5][6][7]11,14,37]. It is important to mention that the changes in crystallinity cannot be responsible for the decrease in oxygen permeability since the crystallinity of all the PA6/TRGO nanocomposites was reduced.…”

“…7a), it was seen that the elastic modulus was always increased with the addition of TRGO. This result can be due to the introduction of rigid nanostructures into the less rigid polymer matrix [2,3,5,7,16,38,39]. The elastic modulus of PP/TRGO 800 nanocomposites increased up to 40% at 10 wt% of filler, while for PP/TRGO 600 nanocomposites modulus was risen up to 28% for the same filler load.…”

“…The high interest on polymer nanocomposites is based on the possibility of greatly enhancing the properties of a given polymeric matrix, as they combine the advantages of the organic phase (flexibility, ductility, processability, etc.) with the properties of the filler (rigidity, thermal stability, barrier properties, among others), usually with low amounts of the dispersed phase .…”