Nano-Sized Titanium Dioxides as Photo-Catalysts in Degradation of Polyethylene and Polypropylene Packagings

In present, packaging plastics such as PE and PP have become a major environmental problem. Whileproduction of biodegradable plastics is still expensive, various photo-catalytic additives especiallytitanium dioxide have been used as pro-oxidants in order to make conventional packaging plasticsdegradable after working period. Various particle-sized titanium dioxides were thermally blended withPE and PP and casted into 80-micron thick films. During the processing period, nano-sized TiO2significantly induced auto-oxidation of the PE films only. The carbonyl formation in PP films showedthe opposite trend possibly due to other mechanical pathways. The films then were exposed under254nm and 366nm UV light mimicking solar light profile. In most cases, TiO2 catalyzed photodegradationoccurred under the shortwave UV-254nm irradiation several folds higher than under longwave UV irradiation. The carbonyl index of the nano-sized TiO2 (1%wt) blended PE films increasedcontinuously over irradiation period and their tensile strength reduced to 35-38% after 28 days up to 42days before total ruptured. The films have also lost weight about 11-15 % in 14 days. The nano-sizedTiO2 blended PP films showed a dramatic increasing of carbonyl index in the first few days and thencontinuously dropped as they become fragmented with in 2 weeks. This also caused PP films to loseweight by 22% in 42 days. This study also suggested that titanium dioxide nano-sized particle showedfavorable activity and results over the commercial micron-sized.