Effect of particle diameter on the permeability of polypropylene/SiO2 nanocomposites

In this contribution the permeation behaviour of polypropylene composites containing silica nanospheres of different diameters is reported. The composite materials were produced by melt compounding polypropylene with silica nanospheres, with diameters ranging from 12 to 150 nm, produced using standard sol–gel methods. The permeability of O2, N2 and H2O through the materials was tested. The results indicate that the addition of nanospheres with diameters of ≥30 nm results in an increase in the O2 and N2 permeability and is directly proportional to the nanosphere diameter. In the case of the water vapour transmission rate, it was found that there is also an increase, but the effect is inversely related with the nanospheres diameter. Incorporation of spheres with a diameter of 12 nm produces a decrease in the permeability of polypropylene composites in all instances, due to its formation of aggregates in composites.