Influence of Modified SiO2 Nanoparticles on the Photostability of Recycled HDPE.

Silica nanoparticles (SiO₂) were synthesized and organically modified with hexadecyltrimethoxysilane (Mod-SiO₂) to enhance their interaction with polymer. Composites from recycled high-density polyethylene (HDPE) were obtained by a melt blending method in the presence of SiO₂. The properties and photostability of the new materials were studied, as well as evaluating the effect of the content and modification of nanoparticles. Before irradiation, the microhardness of HDPE/SiO₂ and HDPE/Mod-SiO₂ increased ca. 65% after incorporating 5 wt% of SiO₂ and Mod-SiO₂ into HDPE, independent of the nanoparticle modification. After irradiation, the microhardness increased for HDPE and HDPE/SiO₂, which could be related to the increased degree of crystallinity of the polymers after photodegradation. In addition, nanocomposites with modified nanoparticles (HDPE/Mod-SiO₂) presented higher storage modulus (E′) and loss modulus (E″) than neat HDPE and HDPE/SiO₂. In general, the HDPE/SiO₂ and HDPE/Mod-SiO₂ nanocomposites showed lower degradation, evidenced by lower values of carbonyl index (CI) and chemiluminescence emission (CL), and higher M - v values when compared with the neat HDPE after irradiation, especially when 3 wt% of SiO₂ was incorporated into HDPE. Also, the good dispersion of modified SiO₂ within recycled HDPE could improve its mechanical properties and provide stability to photodegradation. [ABSTRACT FROM AUTHOR]