Investigation on the Properties and on the Photo-Oxidation Behaviour of Polypropylene/Fumed Silica Nanocomposites

Abstract

This work investigates the effects of very small amounts of fumed silica on the morphology and on the rheological and mechanical behaviour of polypropylene nanocomposites and on their photo-oxidation behaviour. Polypropylene nanocomposites were prepared using a twin-screw corotating extruder with 0, 1 and 2 wt/wt% of SiO2. Morphological, mechanical, thermomechanical and rheological properties were examined. It was found that the viscosity of the matrix is reduced by the presence of the silica nanoparticles, suggesting a poor adhesion between the two phases and probably some lubricating effect. On the contrary, the mechanical and, in particular, the thermomechanical properties of the matrix are considerably improved by the presence of the silica. In particular, elastic modulus and tensile strength increases remarkably, and this effect becomes more and more remarkable with an increasing temperature. As for the photo-oxidation behaviour, the presence of silica improves the photostability of the polypropylene matrix. This effect has been attributed to both the barrier to the oxygen and to the absorbance of the UV radiation from the silica nanoparticles. Finally, no significant effect of the silica nanoparticles has been put in evidence on the crystallisation behaviour of the polypropylene. As for the effect of the silica content, the difference in the properties of the two nanocomposites is relatively small and all the measured properties depend much less than linearly with its amount. This has been correlated with the reaggregation of the nanoparticles that, having a larger size, decrease the contact area between the matrix and the filler.

Recycling of Heterogeneous Mixed Waste Polymers through Reactive Mixing

“…In agreement with our previous works, [ 24 , 25 ] the contact area between matrix and dispersed particles was calculated by considering the surface area of each particle by the number of particles. In more detail, the contact area of each particle is proportional to its square diameter, as follows and the number of particles is as follows: where V ti is the total volume in the sample and V i is the volume of each individual particle present.…”

Developing Post-Consumer Recycled Flexible Polypropylene and Fumed Silica-Based Nanocomposites with Improved Processability and Thermal Stability

“…where ∆H 100 is the melting enthalpy of a whole crystalline polypropylene (207 J g −1 ) [16] and X PP is the mass fraction of the polymer in the sample. DSC analyses were carried out in duplicate.…”

“…According to our review, NS incorporation in PCPP, which is a more structurally complex polymer system, has not been reported. Nanocomposites based on NS have been prepared only using virgin PP [15,16]. Thus, further research is required towards a better understanding of the role of NS in PCPP's performance.…”

“…Properties of nanocomposites depend on the type of polymer, the polymer's molecular weight and grade, chemical structure, type and concentration of nanofiller, processing conditions and plastic conversion techniques, among others [11]. Studies on nanocomposites with NS have used virgin isotactic polypropylene processed by in situ polymerization, melt mixing, compression molding and hot-drawing, which are not the conventional industrial techniques for obtaining flexible packaging film, which is one of the mean applications of PP, and some differences in property variations have been found [15][16][17][18][19].…”

Enhancing Mechanical Properties of Graft-Type Nanocomposites Using Organically Modified SiO2 and Polypropylene Containing Reactive Methoxy Groups

“…Polypropylene (PP), one of the most abundant thermoplastics, has been employed for fabricating polymer nanocomposites using a wide variety of nanofillers [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. The hydrophobicity and chemical innerness of PP make uniform dispersion of nanoparticles challenging, for which various strategies have been reported.…”