Effect of Compatibilizer on the Persistent Luminescence of Polypropylene/Strontium Aluminate Composites

There is a demand for long afterglow composites due to their potential applications in nighttime signal boards, sensors, and biomedical areas. In this study, Polypropylene (PP)/strontium aluminate-based composites [SrAl2O4:Eu2+/Dy3+ (SAO(1)) and Sr4Al14O25: Eu+2, Dy+3 (SAO(2))] with maleic anhydride grafted PP compatibilizer (PRIEX) were prepared, and their auto-glowing properties were examined. After UV excitation at 320 nm, the PP/5PRIEX/SAO(1) composites showed green emission at 520 nm, and blue emission was observed for PP/5PRIEX/SAO(2) around 495 nm. The intensity of phosphorescence emission and phosphorescence decay was found to be proportional to the filler content (SAO(1) and SAO(2)). The FTIR analysis excluded the copolymerization reaction between the SAO(1) and SAO(2) fillers and the PP matrix during the high-temperature melt mixing process. The SAO(1) and SAO(2) fillers decreased the overall crystallinity of the composites without affecting the T-m and T-c (melting and crystallization temperature) values. The thermal stability of the composites was slightly improved with the SAO(1) and SAO(2) fillers, as seen from the TGA curve. Due to the plasticizing effect of the compatibilizer and the agglomeration of the SAO(1) and SAO(2) fillers, the tensile modulus, tensile strength, and storage modulus of the composites was found to be decreased with an increase in the SAO(1) and SAO(2) content. The decreasing effect was more pronounced, especially with the bulk-sized SAO(2) filler.