Selective decomposition of hexabromocyclododecane in polystyrene and recyclability improvement of its polymeric component

Abstract

Selective flame retardant decomposition and polymer recycling in a polystyrene (PS) material containing hexabromocyclododecane (HBCD) were studied using a paint-type copper phthalocyanine modified TiO2 (CuPcTiO2)/polyethylene oxide (PEO) photocatalyst system with three kinds of hindered amine light stabilizer (HALS) loadings. They were performed using visible light irradiation and additional thermal hybrid treatments. Mobility of the HALS with lightest weight was highest and caused the bleeding from the matrix during the irradiation treatment, leading to a lower decomposition ratio and larger changes of dynamic mechanical properties of the recycled PS. On the other hand, the higher molecular weight HALS loadings provided the higher ratios and blocked the changes. In particular, the properties in the HALS loading with a dormant (TEMPO) bond were hardly changed by such hybrid treatment. The py-GC/MS spectra of the extraction residue showed that the HALS adequately worked depending on the treatment situation as radical scavenger and initiator. The tensile strength and strain at break values of the recycled PS kept 90% of the pristine one. In addition, there were no significant differences between the SEM images. The results showed that it had sufficient performance to be used as the post-consumer material.