Novel Recycling System of Polystyrene Water Debris with Polymer Photocatalyst and Thermal Treatment

A poly(styrene-block-acrylic acid) containing TiO2 gel (PS-b-PAA/TiO2) polymer photocatalyst had the same density as PS and could provoke photocatalytic activity to PS particles in water. It showed photocatalytic activity to a PS containing a N-H type hindered amine light stabilizer (PS/LA-77) in water under the UV irradiation. The molecular weight decrease was ca. 10%, showing that a weaker light source and different kind of hindered amine light stabilizer (HALS) should be employed. The phthalocyanine modified photocatalyst had the activity under visible light irradiation. In addition, a N-OR type HALS (LA-81) loading worked as radical scavenger, showing that the PS autoxidation was certainly controlled. After the 144 h irradiation, the molecular weight was drastically decreased with the increases of heating temperature and time. When the heat treatment was performed by the enclosed sample with the aluminum foil, the molecular weight change behavior was considerably different between the PS and PS/LA-81. The difference was due to the chain scission mechanism. The intra-alkyl radical production in PS chain allowed controlling molecular weight by the heat treatment.

Automated summary

The poly(styrene-block-acrylic acid) containing TiO2 gel polymer photocatalyst showed photocatalytic activity to PS particles in water, with molecular weight decrease and the use of different hindered amine light stabilizers. Phthalocyanine modified photocatalyst was active under visible light irradiation, and a N-OR type HALS (LA-81) acted as radical scavenger to control PS autoxidation. The heat treatment affected molecular weight through chain scission mechanism, with differences observed between PS and PS/LA-81 due to intra-alkyl radical production.