In this study, we have investigated the fading behavior of biodegradable polymers colored with π conjugated monascus color pigment and the inhibition of the discoloring by addition of quercetin as a UV absorber. The colored biodegradable polymers without quercetin rapidly discolored under UV radiation. On the other hand, the polymers with quercetin maintain their color. We have also investigated the discoloring mechanism by MO calculation. The mechanism of the monascus color was estimated as follows. (1) Ring-opening of lactone. (2) Hydration of double bonds. (3) The formation of carbonyl group by cleavage of double bonds.
The thermoxidative stability of polypropylene (PP) nanocomposites was improved by introducing dendritic polymer to surfaces of SiO2 nanoparticles through stepwise anionic ring-opening polymerization of glycidol. The introduction of surface polyglycidol (PGL) was confirmed and quantified by infrared spectroscopy and thermogravimetric analysis. The influence of the PGL generation on the lifetime of PP/SiO2 nanocomposites was examined by chemiluminescence analyzer in terms of the oxidation induction time at 180°C. It was found that the dendritic structure of PGL led to remarkable enhancement of the induction time, which likely arose from an encapsulation of a stabilizer in the interior of the dendritic structure of PGL.