A study on the dispersion, preparation, characterization and photo-degradation of polypropylene traced with rare earth oxides

Abstract

This research work deals with the effect of rare earth oxides on the PP matrix with respect to the thermal and mechanical properties and to the photo-degradation under UV irradiation exposure. The rare earth oxides are used as tracers for the identification of polymer materials, in order to have an economically efficient recycling and high speed automatic sorting of plastic wastes. The addition of 0.1 wt% of such particles of a micrometric size has a minor effect on the mechanical and thermal properties of the traced materials, as well as on the photo-degradation of the polymer after UV irradiation exposure. For 1 wt% tracer content, before UV irradiation treatment, the melting and crystallization temperatures as well as the thermal stability of the PP matrix are slightly increased, whereas the elongation at break decreases from 10 to 50% for a cross-head speed of 250 mm/min. However, the addition of 1 wt% of CeO2 improves the photo-degradation resistance of the PP matrix to UV exposure due to the UV light screening effects offered by these particles. The SEM images together with the results obtained from image processing show a homogenous dispersion of tracers in the PP matrix.This research work deals with the effect of rare earth oxides on the PP matrix with respect to the thermal and mechanical properties and to the photo-degradation under UV irradiation exposure. The rare earth oxides are used as tracers for the identification of polymer materials, in order to have an economically efficient recycling and high speed automatic sorting of plastic wastes. The addition of 0.1 wt% of such particles of a micrometric size has a minor effect on the mechanical and thermal properties of the traced materials, as well as on the photo-degradation of the polymer after UV irradiation exposure. For 1 wt% tracer content, before UV irradiation treatment, the melting and crystallization temperatures as well as the thermal stability of the PP matrix are slightly increased, whereas the elongation at break decreases from 10 to 50% for a cross-head speed of 250 mm/min. However, the addition of 1 wt% of CeO2 improves the photo-degradation resistance of the PP matrix to UV exposure due to the UV light screening effects offered by these particles. The SEM images together with the results obtained from image processing show a homogenous dispersion of tracers in the PP matrix

Photodegradation of a polypropylene filled with lanthanide complexes

“…Furthermore, the mechanism of photo degradation of UV-BMU133 without or with T2 or T3 tracer after irradiation is identical and no additional peak appears when adding tracers. These findings are in good agreement with those observed by Bezati et al [27] for PP samples containing rare earth particles exposed to UV irradiation. Similar stabilization effect is observed for metal oxides by several authors [25,26] .…”

“…The decrease in melting temperature can also be due to oxidative reactions on the crystal surface that increase the surface free energy of the crystals [15,34] . Similar trends were observed by Bezati et al [27] and Rabello and White [16] in previous studies. From Table 1, it can also be noted that the cristallinity (X c ) of BMU133 is increased upon UV irradiation.…”

“…Such an effect is expected because the photo-degradation causes chain scissions resulting in the formation of more freed segments [16,23] . This contributes to a drop off of molecular weight of materials and consequently leads to a decrease of the melting temperature [27] . The decrease in melting temperature can also be due to oxidative reactions on the crystal surface that increase the surface free energy of the crystals [15,34] .…”

“…However, Tmax of the UV irradiated BMU133/T3, BMU133/T2 are slightly increased compared to UV-BMU133. This can be ascribed to the protective effect offered by tracer particles due to their UV-screening properties inducing a good thermal stability of the traced polymers towards ultraviolet radiations [27] . For visualization purposes, the TGA curves of UV-BMU133 and UV-BMU133-T3-0.1 after irradiation treatment are depicted in Figure 4.…”

“…Despite several researches focused on the study of the photo-degradation of polymers filled with nanosilica, zinc oxide, carbon black, MMT, etc only few studies deal with polymers containing rare earth oxides [24][25][26] . Recently, Bezati et al [27] have shown that the addition of 1 wt% of cerium oxide nanoparticles improves the photo-degradation resistance of PP matrix to UV exposure due to the light screening effects offered by these particles.…”