Functionalized metal oxide particles with antioxidant as new carriers providing higher stability of polyolefin products

Abstract

The aim of this research was to expand the current state of knowledge regarding the impact of the use of inorganic metal oxides and HALS stabilizers on the aging and stabilization processes of polyolefin products. For this purpose, the influence of functionalized metal oxide particles with an antioxidant on the aging behavior of ethylene-norbornene copolymer (EN) was analyzed. Innovatively, Hostavin N321 stabilizer was deposited on metal oxide surfaces (SiO2, TiO2, ZnO, Fe3O4) by mechano-chemical modification using a planetary ball mill. Unmodified and functionalized metal oxides with antioxidant were introduced into the EN, and the resulting composites were subjected to accelerated thermal and UV aging tests for 400 h. All tested samples showed high resistance to the thermooxidation process, but much greater changes were observed as a result of their exposure to UV radiation. In the case of unmodified oxides, Fe3O4 was characterized by the highest anti-aging behavior, which allowed for almost complete preservation of the EN functional properties and this could be the reason that the effect of the modification performed for this oxide was not visible. However, the proposed stabilizer immobilization on SiO2, ZnO and TiO2 surfaces enabled obtaining more complex stabilizing systems with long-term effective anti-aging activity, in which first the metal oxide provided a preventive effect as a UV absorber, and then when 100% heat conversion was not achieved, Hostavin N321 inhibited degradation through reactions with free radicals. Silica particles provided the strongest interactions with HALS antioxidant and prevented its diffusion towards the EN surface even at elevated temperatures, thus leading to the highest UV stability. This novel approach not only opens new perspectives for the production of multifunctional hybrid materials with their practical applications, but also reduces the cost of the final product, which is particularly important from the point of view of designing polymer materials in industry.